xref: /linux/kernel/sched/fair.c (revision 37744feebc086908fd89760650f458ab19071750)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
4  *
5  *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
6  *
7  *  Interactivity improvements by Mike Galbraith
8  *  (C) 2007 Mike Galbraith <efault@gmx.de>
9  *
10  *  Various enhancements by Dmitry Adamushko.
11  *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
12  *
13  *  Group scheduling enhancements by Srivatsa Vaddagiri
14  *  Copyright IBM Corporation, 2007
15  *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
16  *
17  *  Scaled math optimizations by Thomas Gleixner
18  *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
19  *
20  *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
21  *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
22  */
23 #include "sched.h"
24 
25 #include <trace/events/sched.h>
26 
27 /*
28  * Targeted preemption latency for CPU-bound tasks:
29  *
30  * NOTE: this latency value is not the same as the concept of
31  * 'timeslice length' - timeslices in CFS are of variable length
32  * and have no persistent notion like in traditional, time-slice
33  * based scheduling concepts.
34  *
35  * (to see the precise effective timeslice length of your workload,
36  *  run vmstat and monitor the context-switches (cs) field)
37  *
38  * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
39  */
40 unsigned int sysctl_sched_latency			= 6000000ULL;
41 static unsigned int normalized_sysctl_sched_latency	= 6000000ULL;
42 
43 /*
44  * The initial- and re-scaling of tunables is configurable
45  *
46  * Options are:
47  *
48  *   SCHED_TUNABLESCALING_NONE - unscaled, always *1
49  *   SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
50  *   SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
51  *
52  * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
53  */
54 enum sched_tunable_scaling sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
55 
56 /*
57  * Minimal preemption granularity for CPU-bound tasks:
58  *
59  * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
60  */
61 unsigned int sysctl_sched_min_granularity			= 750000ULL;
62 static unsigned int normalized_sysctl_sched_min_granularity	= 750000ULL;
63 
64 /*
65  * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
66  */
67 static unsigned int sched_nr_latency = 8;
68 
69 /*
70  * After fork, child runs first. If set to 0 (default) then
71  * parent will (try to) run first.
72  */
73 unsigned int sysctl_sched_child_runs_first __read_mostly;
74 
75 /*
76  * SCHED_OTHER wake-up granularity.
77  *
78  * This option delays the preemption effects of decoupled workloads
79  * and reduces their over-scheduling. Synchronous workloads will still
80  * have immediate wakeup/sleep latencies.
81  *
82  * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
83  */
84 unsigned int sysctl_sched_wakeup_granularity			= 1000000UL;
85 static unsigned int normalized_sysctl_sched_wakeup_granularity	= 1000000UL;
86 
87 const_debug unsigned int sysctl_sched_migration_cost	= 500000UL;
88 
89 int sched_thermal_decay_shift;
90 static int __init setup_sched_thermal_decay_shift(char *str)
91 {
92 	int _shift = 0;
93 
94 	if (kstrtoint(str, 0, &_shift))
95 		pr_warn("Unable to set scheduler thermal pressure decay shift parameter\n");
96 
97 	sched_thermal_decay_shift = clamp(_shift, 0, 10);
98 	return 1;
99 }
100 __setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift);
101 
102 #ifdef CONFIG_SMP
103 /*
104  * For asym packing, by default the lower numbered CPU has higher priority.
105  */
106 int __weak arch_asym_cpu_priority(int cpu)
107 {
108 	return -cpu;
109 }
110 
111 /*
112  * The margin used when comparing utilization with CPU capacity.
113  *
114  * (default: ~20%)
115  */
116 #define fits_capacity(cap, max)	((cap) * 1280 < (max) * 1024)
117 
118 #endif
119 
120 #ifdef CONFIG_CFS_BANDWIDTH
121 /*
122  * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
123  * each time a cfs_rq requests quota.
124  *
125  * Note: in the case that the slice exceeds the runtime remaining (either due
126  * to consumption or the quota being specified to be smaller than the slice)
127  * we will always only issue the remaining available time.
128  *
129  * (default: 5 msec, units: microseconds)
130  */
131 unsigned int sysctl_sched_cfs_bandwidth_slice		= 5000UL;
132 #endif
133 
134 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
135 {
136 	lw->weight += inc;
137 	lw->inv_weight = 0;
138 }
139 
140 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
141 {
142 	lw->weight -= dec;
143 	lw->inv_weight = 0;
144 }
145 
146 static inline void update_load_set(struct load_weight *lw, unsigned long w)
147 {
148 	lw->weight = w;
149 	lw->inv_weight = 0;
150 }
151 
152 /*
153  * Increase the granularity value when there are more CPUs,
154  * because with more CPUs the 'effective latency' as visible
155  * to users decreases. But the relationship is not linear,
156  * so pick a second-best guess by going with the log2 of the
157  * number of CPUs.
158  *
159  * This idea comes from the SD scheduler of Con Kolivas:
160  */
161 static unsigned int get_update_sysctl_factor(void)
162 {
163 	unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
164 	unsigned int factor;
165 
166 	switch (sysctl_sched_tunable_scaling) {
167 	case SCHED_TUNABLESCALING_NONE:
168 		factor = 1;
169 		break;
170 	case SCHED_TUNABLESCALING_LINEAR:
171 		factor = cpus;
172 		break;
173 	case SCHED_TUNABLESCALING_LOG:
174 	default:
175 		factor = 1 + ilog2(cpus);
176 		break;
177 	}
178 
179 	return factor;
180 }
181 
182 static void update_sysctl(void)
183 {
184 	unsigned int factor = get_update_sysctl_factor();
185 
186 #define SET_SYSCTL(name) \
187 	(sysctl_##name = (factor) * normalized_sysctl_##name)
188 	SET_SYSCTL(sched_min_granularity);
189 	SET_SYSCTL(sched_latency);
190 	SET_SYSCTL(sched_wakeup_granularity);
191 #undef SET_SYSCTL
192 }
193 
194 void sched_init_granularity(void)
195 {
196 	update_sysctl();
197 }
198 
199 #define WMULT_CONST	(~0U)
200 #define WMULT_SHIFT	32
201 
202 static void __update_inv_weight(struct load_weight *lw)
203 {
204 	unsigned long w;
205 
206 	if (likely(lw->inv_weight))
207 		return;
208 
209 	w = scale_load_down(lw->weight);
210 
211 	if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
212 		lw->inv_weight = 1;
213 	else if (unlikely(!w))
214 		lw->inv_weight = WMULT_CONST;
215 	else
216 		lw->inv_weight = WMULT_CONST / w;
217 }
218 
219 /*
220  * delta_exec * weight / lw.weight
221  *   OR
222  * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
223  *
224  * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
225  * we're guaranteed shift stays positive because inv_weight is guaranteed to
226  * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
227  *
228  * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
229  * weight/lw.weight <= 1, and therefore our shift will also be positive.
230  */
231 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
232 {
233 	u64 fact = scale_load_down(weight);
234 	int shift = WMULT_SHIFT;
235 
236 	__update_inv_weight(lw);
237 
238 	if (unlikely(fact >> 32)) {
239 		while (fact >> 32) {
240 			fact >>= 1;
241 			shift--;
242 		}
243 	}
244 
245 	fact = mul_u32_u32(fact, lw->inv_weight);
246 
247 	while (fact >> 32) {
248 		fact >>= 1;
249 		shift--;
250 	}
251 
252 	return mul_u64_u32_shr(delta_exec, fact, shift);
253 }
254 
255 
256 const struct sched_class fair_sched_class;
257 
258 /**************************************************************
259  * CFS operations on generic schedulable entities:
260  */
261 
262 #ifdef CONFIG_FAIR_GROUP_SCHED
263 static inline struct task_struct *task_of(struct sched_entity *se)
264 {
265 	SCHED_WARN_ON(!entity_is_task(se));
266 	return container_of(se, struct task_struct, se);
267 }
268 
269 /* Walk up scheduling entities hierarchy */
270 #define for_each_sched_entity(se) \
271 		for (; se; se = se->parent)
272 
273 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
274 {
275 	return p->se.cfs_rq;
276 }
277 
278 /* runqueue on which this entity is (to be) queued */
279 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
280 {
281 	return se->cfs_rq;
282 }
283 
284 /* runqueue "owned" by this group */
285 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
286 {
287 	return grp->my_q;
288 }
289 
290 static inline void cfs_rq_tg_path(struct cfs_rq *cfs_rq, char *path, int len)
291 {
292 	if (!path)
293 		return;
294 
295 	if (cfs_rq && task_group_is_autogroup(cfs_rq->tg))
296 		autogroup_path(cfs_rq->tg, path, len);
297 	else if (cfs_rq && cfs_rq->tg->css.cgroup)
298 		cgroup_path(cfs_rq->tg->css.cgroup, path, len);
299 	else
300 		strlcpy(path, "(null)", len);
301 }
302 
303 static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
304 {
305 	struct rq *rq = rq_of(cfs_rq);
306 	int cpu = cpu_of(rq);
307 
308 	if (cfs_rq->on_list)
309 		return rq->tmp_alone_branch == &rq->leaf_cfs_rq_list;
310 
311 	cfs_rq->on_list = 1;
312 
313 	/*
314 	 * Ensure we either appear before our parent (if already
315 	 * enqueued) or force our parent to appear after us when it is
316 	 * enqueued. The fact that we always enqueue bottom-up
317 	 * reduces this to two cases and a special case for the root
318 	 * cfs_rq. Furthermore, it also means that we will always reset
319 	 * tmp_alone_branch either when the branch is connected
320 	 * to a tree or when we reach the top of the tree
321 	 */
322 	if (cfs_rq->tg->parent &&
323 	    cfs_rq->tg->parent->cfs_rq[cpu]->on_list) {
324 		/*
325 		 * If parent is already on the list, we add the child
326 		 * just before. Thanks to circular linked property of
327 		 * the list, this means to put the child at the tail
328 		 * of the list that starts by parent.
329 		 */
330 		list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
331 			&(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list));
332 		/*
333 		 * The branch is now connected to its tree so we can
334 		 * reset tmp_alone_branch to the beginning of the
335 		 * list.
336 		 */
337 		rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
338 		return true;
339 	}
340 
341 	if (!cfs_rq->tg->parent) {
342 		/*
343 		 * cfs rq without parent should be put
344 		 * at the tail of the list.
345 		 */
346 		list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
347 			&rq->leaf_cfs_rq_list);
348 		/*
349 		 * We have reach the top of a tree so we can reset
350 		 * tmp_alone_branch to the beginning of the list.
351 		 */
352 		rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
353 		return true;
354 	}
355 
356 	/*
357 	 * The parent has not already been added so we want to
358 	 * make sure that it will be put after us.
359 	 * tmp_alone_branch points to the begin of the branch
360 	 * where we will add parent.
361 	 */
362 	list_add_rcu(&cfs_rq->leaf_cfs_rq_list, rq->tmp_alone_branch);
363 	/*
364 	 * update tmp_alone_branch to points to the new begin
365 	 * of the branch
366 	 */
367 	rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list;
368 	return false;
369 }
370 
371 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
372 {
373 	if (cfs_rq->on_list) {
374 		struct rq *rq = rq_of(cfs_rq);
375 
376 		/*
377 		 * With cfs_rq being unthrottled/throttled during an enqueue,
378 		 * it can happen the tmp_alone_branch points the a leaf that
379 		 * we finally want to del. In this case, tmp_alone_branch moves
380 		 * to the prev element but it will point to rq->leaf_cfs_rq_list
381 		 * at the end of the enqueue.
382 		 */
383 		if (rq->tmp_alone_branch == &cfs_rq->leaf_cfs_rq_list)
384 			rq->tmp_alone_branch = cfs_rq->leaf_cfs_rq_list.prev;
385 
386 		list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
387 		cfs_rq->on_list = 0;
388 	}
389 }
390 
391 static inline void assert_list_leaf_cfs_rq(struct rq *rq)
392 {
393 	SCHED_WARN_ON(rq->tmp_alone_branch != &rq->leaf_cfs_rq_list);
394 }
395 
396 /* Iterate thr' all leaf cfs_rq's on a runqueue */
397 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos)			\
398 	list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list,	\
399 				 leaf_cfs_rq_list)
400 
401 /* Do the two (enqueued) entities belong to the same group ? */
402 static inline struct cfs_rq *
403 is_same_group(struct sched_entity *se, struct sched_entity *pse)
404 {
405 	if (se->cfs_rq == pse->cfs_rq)
406 		return se->cfs_rq;
407 
408 	return NULL;
409 }
410 
411 static inline struct sched_entity *parent_entity(struct sched_entity *se)
412 {
413 	return se->parent;
414 }
415 
416 static void
417 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
418 {
419 	int se_depth, pse_depth;
420 
421 	/*
422 	 * preemption test can be made between sibling entities who are in the
423 	 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
424 	 * both tasks until we find their ancestors who are siblings of common
425 	 * parent.
426 	 */
427 
428 	/* First walk up until both entities are at same depth */
429 	se_depth = (*se)->depth;
430 	pse_depth = (*pse)->depth;
431 
432 	while (se_depth > pse_depth) {
433 		se_depth--;
434 		*se = parent_entity(*se);
435 	}
436 
437 	while (pse_depth > se_depth) {
438 		pse_depth--;
439 		*pse = parent_entity(*pse);
440 	}
441 
442 	while (!is_same_group(*se, *pse)) {
443 		*se = parent_entity(*se);
444 		*pse = parent_entity(*pse);
445 	}
446 }
447 
448 #else	/* !CONFIG_FAIR_GROUP_SCHED */
449 
450 static inline struct task_struct *task_of(struct sched_entity *se)
451 {
452 	return container_of(se, struct task_struct, se);
453 }
454 
455 #define for_each_sched_entity(se) \
456 		for (; se; se = NULL)
457 
458 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
459 {
460 	return &task_rq(p)->cfs;
461 }
462 
463 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
464 {
465 	struct task_struct *p = task_of(se);
466 	struct rq *rq = task_rq(p);
467 
468 	return &rq->cfs;
469 }
470 
471 /* runqueue "owned" by this group */
472 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
473 {
474 	return NULL;
475 }
476 
477 static inline void cfs_rq_tg_path(struct cfs_rq *cfs_rq, char *path, int len)
478 {
479 	if (path)
480 		strlcpy(path, "(null)", len);
481 }
482 
483 static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
484 {
485 	return true;
486 }
487 
488 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
489 {
490 }
491 
492 static inline void assert_list_leaf_cfs_rq(struct rq *rq)
493 {
494 }
495 
496 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos)	\
497 		for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
498 
499 static inline struct sched_entity *parent_entity(struct sched_entity *se)
500 {
501 	return NULL;
502 }
503 
504 static inline void
505 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
506 {
507 }
508 
509 #endif	/* CONFIG_FAIR_GROUP_SCHED */
510 
511 static __always_inline
512 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
513 
514 /**************************************************************
515  * Scheduling class tree data structure manipulation methods:
516  */
517 
518 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
519 {
520 	s64 delta = (s64)(vruntime - max_vruntime);
521 	if (delta > 0)
522 		max_vruntime = vruntime;
523 
524 	return max_vruntime;
525 }
526 
527 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
528 {
529 	s64 delta = (s64)(vruntime - min_vruntime);
530 	if (delta < 0)
531 		min_vruntime = vruntime;
532 
533 	return min_vruntime;
534 }
535 
536 static inline int entity_before(struct sched_entity *a,
537 				struct sched_entity *b)
538 {
539 	return (s64)(a->vruntime - b->vruntime) < 0;
540 }
541 
542 static void update_min_vruntime(struct cfs_rq *cfs_rq)
543 {
544 	struct sched_entity *curr = cfs_rq->curr;
545 	struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);
546 
547 	u64 vruntime = cfs_rq->min_vruntime;
548 
549 	if (curr) {
550 		if (curr->on_rq)
551 			vruntime = curr->vruntime;
552 		else
553 			curr = NULL;
554 	}
555 
556 	if (leftmost) { /* non-empty tree */
557 		struct sched_entity *se;
558 		se = rb_entry(leftmost, struct sched_entity, run_node);
559 
560 		if (!curr)
561 			vruntime = se->vruntime;
562 		else
563 			vruntime = min_vruntime(vruntime, se->vruntime);
564 	}
565 
566 	/* ensure we never gain time by being placed backwards. */
567 	cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
568 #ifndef CONFIG_64BIT
569 	smp_wmb();
570 	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
571 #endif
572 }
573 
574 /*
575  * Enqueue an entity into the rb-tree:
576  */
577 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
578 {
579 	struct rb_node **link = &cfs_rq->tasks_timeline.rb_root.rb_node;
580 	struct rb_node *parent = NULL;
581 	struct sched_entity *entry;
582 	bool leftmost = true;
583 
584 	/*
585 	 * Find the right place in the rbtree:
586 	 */
587 	while (*link) {
588 		parent = *link;
589 		entry = rb_entry(parent, struct sched_entity, run_node);
590 		/*
591 		 * We dont care about collisions. Nodes with
592 		 * the same key stay together.
593 		 */
594 		if (entity_before(se, entry)) {
595 			link = &parent->rb_left;
596 		} else {
597 			link = &parent->rb_right;
598 			leftmost = false;
599 		}
600 	}
601 
602 	rb_link_node(&se->run_node, parent, link);
603 	rb_insert_color_cached(&se->run_node,
604 			       &cfs_rq->tasks_timeline, leftmost);
605 }
606 
607 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
608 {
609 	rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
610 }
611 
612 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
613 {
614 	struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline);
615 
616 	if (!left)
617 		return NULL;
618 
619 	return rb_entry(left, struct sched_entity, run_node);
620 }
621 
622 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
623 {
624 	struct rb_node *next = rb_next(&se->run_node);
625 
626 	if (!next)
627 		return NULL;
628 
629 	return rb_entry(next, struct sched_entity, run_node);
630 }
631 
632 #ifdef CONFIG_SCHED_DEBUG
633 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
634 {
635 	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
636 
637 	if (!last)
638 		return NULL;
639 
640 	return rb_entry(last, struct sched_entity, run_node);
641 }
642 
643 /**************************************************************
644  * Scheduling class statistics methods:
645  */
646 
647 int sched_proc_update_handler(struct ctl_table *table, int write,
648 		void __user *buffer, size_t *lenp,
649 		loff_t *ppos)
650 {
651 	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
652 	unsigned int factor = get_update_sysctl_factor();
653 
654 	if (ret || !write)
655 		return ret;
656 
657 	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
658 					sysctl_sched_min_granularity);
659 
660 #define WRT_SYSCTL(name) \
661 	(normalized_sysctl_##name = sysctl_##name / (factor))
662 	WRT_SYSCTL(sched_min_granularity);
663 	WRT_SYSCTL(sched_latency);
664 	WRT_SYSCTL(sched_wakeup_granularity);
665 #undef WRT_SYSCTL
666 
667 	return 0;
668 }
669 #endif
670 
671 /*
672  * delta /= w
673  */
674 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
675 {
676 	if (unlikely(se->load.weight != NICE_0_LOAD))
677 		delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
678 
679 	return delta;
680 }
681 
682 /*
683  * The idea is to set a period in which each task runs once.
684  *
685  * When there are too many tasks (sched_nr_latency) we have to stretch
686  * this period because otherwise the slices get too small.
687  *
688  * p = (nr <= nl) ? l : l*nr/nl
689  */
690 static u64 __sched_period(unsigned long nr_running)
691 {
692 	if (unlikely(nr_running > sched_nr_latency))
693 		return nr_running * sysctl_sched_min_granularity;
694 	else
695 		return sysctl_sched_latency;
696 }
697 
698 /*
699  * We calculate the wall-time slice from the period by taking a part
700  * proportional to the weight.
701  *
702  * s = p*P[w/rw]
703  */
704 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
705 {
706 	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
707 
708 	for_each_sched_entity(se) {
709 		struct load_weight *load;
710 		struct load_weight lw;
711 
712 		cfs_rq = cfs_rq_of(se);
713 		load = &cfs_rq->load;
714 
715 		if (unlikely(!se->on_rq)) {
716 			lw = cfs_rq->load;
717 
718 			update_load_add(&lw, se->load.weight);
719 			load = &lw;
720 		}
721 		slice = __calc_delta(slice, se->load.weight, load);
722 	}
723 	return slice;
724 }
725 
726 /*
727  * We calculate the vruntime slice of a to-be-inserted task.
728  *
729  * vs = s/w
730  */
731 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
732 {
733 	return calc_delta_fair(sched_slice(cfs_rq, se), se);
734 }
735 
736 #include "pelt.h"
737 #ifdef CONFIG_SMP
738 
739 static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
740 static unsigned long task_h_load(struct task_struct *p);
741 static unsigned long capacity_of(int cpu);
742 
743 /* Give new sched_entity start runnable values to heavy its load in infant time */
744 void init_entity_runnable_average(struct sched_entity *se)
745 {
746 	struct sched_avg *sa = &se->avg;
747 
748 	memset(sa, 0, sizeof(*sa));
749 
750 	/*
751 	 * Tasks are initialized with full load to be seen as heavy tasks until
752 	 * they get a chance to stabilize to their real load level.
753 	 * Group entities are initialized with zero load to reflect the fact that
754 	 * nothing has been attached to the task group yet.
755 	 */
756 	if (entity_is_task(se))
757 		sa->load_avg = scale_load_down(se->load.weight);
758 
759 	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
760 }
761 
762 static void attach_entity_cfs_rq(struct sched_entity *se);
763 
764 /*
765  * With new tasks being created, their initial util_avgs are extrapolated
766  * based on the cfs_rq's current util_avg:
767  *
768  *   util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
769  *
770  * However, in many cases, the above util_avg does not give a desired
771  * value. Moreover, the sum of the util_avgs may be divergent, such
772  * as when the series is a harmonic series.
773  *
774  * To solve this problem, we also cap the util_avg of successive tasks to
775  * only 1/2 of the left utilization budget:
776  *
777  *   util_avg_cap = (cpu_scale - cfs_rq->avg.util_avg) / 2^n
778  *
779  * where n denotes the nth task and cpu_scale the CPU capacity.
780  *
781  * For example, for a CPU with 1024 of capacity, a simplest series from
782  * the beginning would be like:
783  *
784  *  task  util_avg: 512, 256, 128,  64,  32,   16,    8, ...
785  * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
786  *
787  * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
788  * if util_avg > util_avg_cap.
789  */
790 void post_init_entity_util_avg(struct task_struct *p)
791 {
792 	struct sched_entity *se = &p->se;
793 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
794 	struct sched_avg *sa = &se->avg;
795 	long cpu_scale = arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq)));
796 	long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2;
797 
798 	if (cap > 0) {
799 		if (cfs_rq->avg.util_avg != 0) {
800 			sa->util_avg  = cfs_rq->avg.util_avg * se->load.weight;
801 			sa->util_avg /= (cfs_rq->avg.load_avg + 1);
802 
803 			if (sa->util_avg > cap)
804 				sa->util_avg = cap;
805 		} else {
806 			sa->util_avg = cap;
807 		}
808 	}
809 
810 	sa->runnable_avg = cpu_scale;
811 
812 	if (p->sched_class != &fair_sched_class) {
813 		/*
814 		 * For !fair tasks do:
815 		 *
816 		update_cfs_rq_load_avg(now, cfs_rq);
817 		attach_entity_load_avg(cfs_rq, se);
818 		switched_from_fair(rq, p);
819 		 *
820 		 * such that the next switched_to_fair() has the
821 		 * expected state.
822 		 */
823 		se->avg.last_update_time = cfs_rq_clock_pelt(cfs_rq);
824 		return;
825 	}
826 
827 	attach_entity_cfs_rq(se);
828 }
829 
830 #else /* !CONFIG_SMP */
831 void init_entity_runnable_average(struct sched_entity *se)
832 {
833 }
834 void post_init_entity_util_avg(struct task_struct *p)
835 {
836 }
837 static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
838 {
839 }
840 #endif /* CONFIG_SMP */
841 
842 /*
843  * Update the current task's runtime statistics.
844  */
845 static void update_curr(struct cfs_rq *cfs_rq)
846 {
847 	struct sched_entity *curr = cfs_rq->curr;
848 	u64 now = rq_clock_task(rq_of(cfs_rq));
849 	u64 delta_exec;
850 
851 	if (unlikely(!curr))
852 		return;
853 
854 	delta_exec = now - curr->exec_start;
855 	if (unlikely((s64)delta_exec <= 0))
856 		return;
857 
858 	curr->exec_start = now;
859 
860 	schedstat_set(curr->statistics.exec_max,
861 		      max(delta_exec, curr->statistics.exec_max));
862 
863 	curr->sum_exec_runtime += delta_exec;
864 	schedstat_add(cfs_rq->exec_clock, delta_exec);
865 
866 	curr->vruntime += calc_delta_fair(delta_exec, curr);
867 	update_min_vruntime(cfs_rq);
868 
869 	if (entity_is_task(curr)) {
870 		struct task_struct *curtask = task_of(curr);
871 
872 		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
873 		cgroup_account_cputime(curtask, delta_exec);
874 		account_group_exec_runtime(curtask, delta_exec);
875 	}
876 
877 	account_cfs_rq_runtime(cfs_rq, delta_exec);
878 }
879 
880 static void update_curr_fair(struct rq *rq)
881 {
882 	update_curr(cfs_rq_of(&rq->curr->se));
883 }
884 
885 static inline void
886 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
887 {
888 	u64 wait_start, prev_wait_start;
889 
890 	if (!schedstat_enabled())
891 		return;
892 
893 	wait_start = rq_clock(rq_of(cfs_rq));
894 	prev_wait_start = schedstat_val(se->statistics.wait_start);
895 
896 	if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
897 	    likely(wait_start > prev_wait_start))
898 		wait_start -= prev_wait_start;
899 
900 	__schedstat_set(se->statistics.wait_start, wait_start);
901 }
902 
903 static inline void
904 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
905 {
906 	struct task_struct *p;
907 	u64 delta;
908 
909 	if (!schedstat_enabled())
910 		return;
911 
912 	delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
913 
914 	if (entity_is_task(se)) {
915 		p = task_of(se);
916 		if (task_on_rq_migrating(p)) {
917 			/*
918 			 * Preserve migrating task's wait time so wait_start
919 			 * time stamp can be adjusted to accumulate wait time
920 			 * prior to migration.
921 			 */
922 			__schedstat_set(se->statistics.wait_start, delta);
923 			return;
924 		}
925 		trace_sched_stat_wait(p, delta);
926 	}
927 
928 	__schedstat_set(se->statistics.wait_max,
929 		      max(schedstat_val(se->statistics.wait_max), delta));
930 	__schedstat_inc(se->statistics.wait_count);
931 	__schedstat_add(se->statistics.wait_sum, delta);
932 	__schedstat_set(se->statistics.wait_start, 0);
933 }
934 
935 static inline void
936 update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
937 {
938 	struct task_struct *tsk = NULL;
939 	u64 sleep_start, block_start;
940 
941 	if (!schedstat_enabled())
942 		return;
943 
944 	sleep_start = schedstat_val(se->statistics.sleep_start);
945 	block_start = schedstat_val(se->statistics.block_start);
946 
947 	if (entity_is_task(se))
948 		tsk = task_of(se);
949 
950 	if (sleep_start) {
951 		u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
952 
953 		if ((s64)delta < 0)
954 			delta = 0;
955 
956 		if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
957 			__schedstat_set(se->statistics.sleep_max, delta);
958 
959 		__schedstat_set(se->statistics.sleep_start, 0);
960 		__schedstat_add(se->statistics.sum_sleep_runtime, delta);
961 
962 		if (tsk) {
963 			account_scheduler_latency(tsk, delta >> 10, 1);
964 			trace_sched_stat_sleep(tsk, delta);
965 		}
966 	}
967 	if (block_start) {
968 		u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
969 
970 		if ((s64)delta < 0)
971 			delta = 0;
972 
973 		if (unlikely(delta > schedstat_val(se->statistics.block_max)))
974 			__schedstat_set(se->statistics.block_max, delta);
975 
976 		__schedstat_set(se->statistics.block_start, 0);
977 		__schedstat_add(se->statistics.sum_sleep_runtime, delta);
978 
979 		if (tsk) {
980 			if (tsk->in_iowait) {
981 				__schedstat_add(se->statistics.iowait_sum, delta);
982 				__schedstat_inc(se->statistics.iowait_count);
983 				trace_sched_stat_iowait(tsk, delta);
984 			}
985 
986 			trace_sched_stat_blocked(tsk, delta);
987 
988 			/*
989 			 * Blocking time is in units of nanosecs, so shift by
990 			 * 20 to get a milliseconds-range estimation of the
991 			 * amount of time that the task spent sleeping:
992 			 */
993 			if (unlikely(prof_on == SLEEP_PROFILING)) {
994 				profile_hits(SLEEP_PROFILING,
995 						(void *)get_wchan(tsk),
996 						delta >> 20);
997 			}
998 			account_scheduler_latency(tsk, delta >> 10, 0);
999 		}
1000 	}
1001 }
1002 
1003 /*
1004  * Task is being enqueued - update stats:
1005  */
1006 static inline void
1007 update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1008 {
1009 	if (!schedstat_enabled())
1010 		return;
1011 
1012 	/*
1013 	 * Are we enqueueing a waiting task? (for current tasks
1014 	 * a dequeue/enqueue event is a NOP)
1015 	 */
1016 	if (se != cfs_rq->curr)
1017 		update_stats_wait_start(cfs_rq, se);
1018 
1019 	if (flags & ENQUEUE_WAKEUP)
1020 		update_stats_enqueue_sleeper(cfs_rq, se);
1021 }
1022 
1023 static inline void
1024 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1025 {
1026 
1027 	if (!schedstat_enabled())
1028 		return;
1029 
1030 	/*
1031 	 * Mark the end of the wait period if dequeueing a
1032 	 * waiting task:
1033 	 */
1034 	if (se != cfs_rq->curr)
1035 		update_stats_wait_end(cfs_rq, se);
1036 
1037 	if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
1038 		struct task_struct *tsk = task_of(se);
1039 
1040 		if (tsk->state & TASK_INTERRUPTIBLE)
1041 			__schedstat_set(se->statistics.sleep_start,
1042 				      rq_clock(rq_of(cfs_rq)));
1043 		if (tsk->state & TASK_UNINTERRUPTIBLE)
1044 			__schedstat_set(se->statistics.block_start,
1045 				      rq_clock(rq_of(cfs_rq)));
1046 	}
1047 }
1048 
1049 /*
1050  * We are picking a new current task - update its stats:
1051  */
1052 static inline void
1053 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
1054 {
1055 	/*
1056 	 * We are starting a new run period:
1057 	 */
1058 	se->exec_start = rq_clock_task(rq_of(cfs_rq));
1059 }
1060 
1061 /**************************************************
1062  * Scheduling class queueing methods:
1063  */
1064 
1065 #ifdef CONFIG_NUMA_BALANCING
1066 /*
1067  * Approximate time to scan a full NUMA task in ms. The task scan period is
1068  * calculated based on the tasks virtual memory size and
1069  * numa_balancing_scan_size.
1070  */
1071 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
1072 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1073 
1074 /* Portion of address space to scan in MB */
1075 unsigned int sysctl_numa_balancing_scan_size = 256;
1076 
1077 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
1078 unsigned int sysctl_numa_balancing_scan_delay = 1000;
1079 
1080 struct numa_group {
1081 	refcount_t refcount;
1082 
1083 	spinlock_t lock; /* nr_tasks, tasks */
1084 	int nr_tasks;
1085 	pid_t gid;
1086 	int active_nodes;
1087 
1088 	struct rcu_head rcu;
1089 	unsigned long total_faults;
1090 	unsigned long max_faults_cpu;
1091 	/*
1092 	 * Faults_cpu is used to decide whether memory should move
1093 	 * towards the CPU. As a consequence, these stats are weighted
1094 	 * more by CPU use than by memory faults.
1095 	 */
1096 	unsigned long *faults_cpu;
1097 	unsigned long faults[0];
1098 };
1099 
1100 /*
1101  * For functions that can be called in multiple contexts that permit reading
1102  * ->numa_group (see struct task_struct for locking rules).
1103  */
1104 static struct numa_group *deref_task_numa_group(struct task_struct *p)
1105 {
1106 	return rcu_dereference_check(p->numa_group, p == current ||
1107 		(lockdep_is_held(&task_rq(p)->lock) && !READ_ONCE(p->on_cpu)));
1108 }
1109 
1110 static struct numa_group *deref_curr_numa_group(struct task_struct *p)
1111 {
1112 	return rcu_dereference_protected(p->numa_group, p == current);
1113 }
1114 
1115 static inline unsigned long group_faults_priv(struct numa_group *ng);
1116 static inline unsigned long group_faults_shared(struct numa_group *ng);
1117 
1118 static unsigned int task_nr_scan_windows(struct task_struct *p)
1119 {
1120 	unsigned long rss = 0;
1121 	unsigned long nr_scan_pages;
1122 
1123 	/*
1124 	 * Calculations based on RSS as non-present and empty pages are skipped
1125 	 * by the PTE scanner and NUMA hinting faults should be trapped based
1126 	 * on resident pages
1127 	 */
1128 	nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
1129 	rss = get_mm_rss(p->mm);
1130 	if (!rss)
1131 		rss = nr_scan_pages;
1132 
1133 	rss = round_up(rss, nr_scan_pages);
1134 	return rss / nr_scan_pages;
1135 }
1136 
1137 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
1138 #define MAX_SCAN_WINDOW 2560
1139 
1140 static unsigned int task_scan_min(struct task_struct *p)
1141 {
1142 	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1143 	unsigned int scan, floor;
1144 	unsigned int windows = 1;
1145 
1146 	if (scan_size < MAX_SCAN_WINDOW)
1147 		windows = MAX_SCAN_WINDOW / scan_size;
1148 	floor = 1000 / windows;
1149 
1150 	scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
1151 	return max_t(unsigned int, floor, scan);
1152 }
1153 
1154 static unsigned int task_scan_start(struct task_struct *p)
1155 {
1156 	unsigned long smin = task_scan_min(p);
1157 	unsigned long period = smin;
1158 	struct numa_group *ng;
1159 
1160 	/* Scale the maximum scan period with the amount of shared memory. */
1161 	rcu_read_lock();
1162 	ng = rcu_dereference(p->numa_group);
1163 	if (ng) {
1164 		unsigned long shared = group_faults_shared(ng);
1165 		unsigned long private = group_faults_priv(ng);
1166 
1167 		period *= refcount_read(&ng->refcount);
1168 		period *= shared + 1;
1169 		period /= private + shared + 1;
1170 	}
1171 	rcu_read_unlock();
1172 
1173 	return max(smin, period);
1174 }
1175 
1176 static unsigned int task_scan_max(struct task_struct *p)
1177 {
1178 	unsigned long smin = task_scan_min(p);
1179 	unsigned long smax;
1180 	struct numa_group *ng;
1181 
1182 	/* Watch for min being lower than max due to floor calculations */
1183 	smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
1184 
1185 	/* Scale the maximum scan period with the amount of shared memory. */
1186 	ng = deref_curr_numa_group(p);
1187 	if (ng) {
1188 		unsigned long shared = group_faults_shared(ng);
1189 		unsigned long private = group_faults_priv(ng);
1190 		unsigned long period = smax;
1191 
1192 		period *= refcount_read(&ng->refcount);
1193 		period *= shared + 1;
1194 		period /= private + shared + 1;
1195 
1196 		smax = max(smax, period);
1197 	}
1198 
1199 	return max(smin, smax);
1200 }
1201 
1202 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
1203 {
1204 	rq->nr_numa_running += (p->numa_preferred_nid != NUMA_NO_NODE);
1205 	rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
1206 }
1207 
1208 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
1209 {
1210 	rq->nr_numa_running -= (p->numa_preferred_nid != NUMA_NO_NODE);
1211 	rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
1212 }
1213 
1214 /* Shared or private faults. */
1215 #define NR_NUMA_HINT_FAULT_TYPES 2
1216 
1217 /* Memory and CPU locality */
1218 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
1219 
1220 /* Averaged statistics, and temporary buffers. */
1221 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
1222 
1223 pid_t task_numa_group_id(struct task_struct *p)
1224 {
1225 	struct numa_group *ng;
1226 	pid_t gid = 0;
1227 
1228 	rcu_read_lock();
1229 	ng = rcu_dereference(p->numa_group);
1230 	if (ng)
1231 		gid = ng->gid;
1232 	rcu_read_unlock();
1233 
1234 	return gid;
1235 }
1236 
1237 /*
1238  * The averaged statistics, shared & private, memory & CPU,
1239  * occupy the first half of the array. The second half of the
1240  * array is for current counters, which are averaged into the
1241  * first set by task_numa_placement.
1242  */
1243 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
1244 {
1245 	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1246 }
1247 
1248 static inline unsigned long task_faults(struct task_struct *p, int nid)
1249 {
1250 	if (!p->numa_faults)
1251 		return 0;
1252 
1253 	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1254 		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1255 }
1256 
1257 static inline unsigned long group_faults(struct task_struct *p, int nid)
1258 {
1259 	struct numa_group *ng = deref_task_numa_group(p);
1260 
1261 	if (!ng)
1262 		return 0;
1263 
1264 	return ng->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1265 		ng->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1266 }
1267 
1268 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
1269 {
1270 	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
1271 		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1272 }
1273 
1274 static inline unsigned long group_faults_priv(struct numa_group *ng)
1275 {
1276 	unsigned long faults = 0;
1277 	int node;
1278 
1279 	for_each_online_node(node) {
1280 		faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
1281 	}
1282 
1283 	return faults;
1284 }
1285 
1286 static inline unsigned long group_faults_shared(struct numa_group *ng)
1287 {
1288 	unsigned long faults = 0;
1289 	int node;
1290 
1291 	for_each_online_node(node) {
1292 		faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)];
1293 	}
1294 
1295 	return faults;
1296 }
1297 
1298 /*
1299  * A node triggering more than 1/3 as many NUMA faults as the maximum is
1300  * considered part of a numa group's pseudo-interleaving set. Migrations
1301  * between these nodes are slowed down, to allow things to settle down.
1302  */
1303 #define ACTIVE_NODE_FRACTION 3
1304 
1305 static bool numa_is_active_node(int nid, struct numa_group *ng)
1306 {
1307 	return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
1308 }
1309 
1310 /* Handle placement on systems where not all nodes are directly connected. */
1311 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
1312 					int maxdist, bool task)
1313 {
1314 	unsigned long score = 0;
1315 	int node;
1316 
1317 	/*
1318 	 * All nodes are directly connected, and the same distance
1319 	 * from each other. No need for fancy placement algorithms.
1320 	 */
1321 	if (sched_numa_topology_type == NUMA_DIRECT)
1322 		return 0;
1323 
1324 	/*
1325 	 * This code is called for each node, introducing N^2 complexity,
1326 	 * which should be ok given the number of nodes rarely exceeds 8.
1327 	 */
1328 	for_each_online_node(node) {
1329 		unsigned long faults;
1330 		int dist = node_distance(nid, node);
1331 
1332 		/*
1333 		 * The furthest away nodes in the system are not interesting
1334 		 * for placement; nid was already counted.
1335 		 */
1336 		if (dist == sched_max_numa_distance || node == nid)
1337 			continue;
1338 
1339 		/*
1340 		 * On systems with a backplane NUMA topology, compare groups
1341 		 * of nodes, and move tasks towards the group with the most
1342 		 * memory accesses. When comparing two nodes at distance
1343 		 * "hoplimit", only nodes closer by than "hoplimit" are part
1344 		 * of each group. Skip other nodes.
1345 		 */
1346 		if (sched_numa_topology_type == NUMA_BACKPLANE &&
1347 					dist >= maxdist)
1348 			continue;
1349 
1350 		/* Add up the faults from nearby nodes. */
1351 		if (task)
1352 			faults = task_faults(p, node);
1353 		else
1354 			faults = group_faults(p, node);
1355 
1356 		/*
1357 		 * On systems with a glueless mesh NUMA topology, there are
1358 		 * no fixed "groups of nodes". Instead, nodes that are not
1359 		 * directly connected bounce traffic through intermediate
1360 		 * nodes; a numa_group can occupy any set of nodes.
1361 		 * The further away a node is, the less the faults count.
1362 		 * This seems to result in good task placement.
1363 		 */
1364 		if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1365 			faults *= (sched_max_numa_distance - dist);
1366 			faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1367 		}
1368 
1369 		score += faults;
1370 	}
1371 
1372 	return score;
1373 }
1374 
1375 /*
1376  * These return the fraction of accesses done by a particular task, or
1377  * task group, on a particular numa node.  The group weight is given a
1378  * larger multiplier, in order to group tasks together that are almost
1379  * evenly spread out between numa nodes.
1380  */
1381 static inline unsigned long task_weight(struct task_struct *p, int nid,
1382 					int dist)
1383 {
1384 	unsigned long faults, total_faults;
1385 
1386 	if (!p->numa_faults)
1387 		return 0;
1388 
1389 	total_faults = p->total_numa_faults;
1390 
1391 	if (!total_faults)
1392 		return 0;
1393 
1394 	faults = task_faults(p, nid);
1395 	faults += score_nearby_nodes(p, nid, dist, true);
1396 
1397 	return 1000 * faults / total_faults;
1398 }
1399 
1400 static inline unsigned long group_weight(struct task_struct *p, int nid,
1401 					 int dist)
1402 {
1403 	struct numa_group *ng = deref_task_numa_group(p);
1404 	unsigned long faults, total_faults;
1405 
1406 	if (!ng)
1407 		return 0;
1408 
1409 	total_faults = ng->total_faults;
1410 
1411 	if (!total_faults)
1412 		return 0;
1413 
1414 	faults = group_faults(p, nid);
1415 	faults += score_nearby_nodes(p, nid, dist, false);
1416 
1417 	return 1000 * faults / total_faults;
1418 }
1419 
1420 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1421 				int src_nid, int dst_cpu)
1422 {
1423 	struct numa_group *ng = deref_curr_numa_group(p);
1424 	int dst_nid = cpu_to_node(dst_cpu);
1425 	int last_cpupid, this_cpupid;
1426 
1427 	this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1428 	last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1429 
1430 	/*
1431 	 * Allow first faults or private faults to migrate immediately early in
1432 	 * the lifetime of a task. The magic number 4 is based on waiting for
1433 	 * two full passes of the "multi-stage node selection" test that is
1434 	 * executed below.
1435 	 */
1436 	if ((p->numa_preferred_nid == NUMA_NO_NODE || p->numa_scan_seq <= 4) &&
1437 	    (cpupid_pid_unset(last_cpupid) || cpupid_match_pid(p, last_cpupid)))
1438 		return true;
1439 
1440 	/*
1441 	 * Multi-stage node selection is used in conjunction with a periodic
1442 	 * migration fault to build a temporal task<->page relation. By using
1443 	 * a two-stage filter we remove short/unlikely relations.
1444 	 *
1445 	 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1446 	 * a task's usage of a particular page (n_p) per total usage of this
1447 	 * page (n_t) (in a given time-span) to a probability.
1448 	 *
1449 	 * Our periodic faults will sample this probability and getting the
1450 	 * same result twice in a row, given these samples are fully
1451 	 * independent, is then given by P(n)^2, provided our sample period
1452 	 * is sufficiently short compared to the usage pattern.
1453 	 *
1454 	 * This quadric squishes small probabilities, making it less likely we
1455 	 * act on an unlikely task<->page relation.
1456 	 */
1457 	if (!cpupid_pid_unset(last_cpupid) &&
1458 				cpupid_to_nid(last_cpupid) != dst_nid)
1459 		return false;
1460 
1461 	/* Always allow migrate on private faults */
1462 	if (cpupid_match_pid(p, last_cpupid))
1463 		return true;
1464 
1465 	/* A shared fault, but p->numa_group has not been set up yet. */
1466 	if (!ng)
1467 		return true;
1468 
1469 	/*
1470 	 * Destination node is much more heavily used than the source
1471 	 * node? Allow migration.
1472 	 */
1473 	if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
1474 					ACTIVE_NODE_FRACTION)
1475 		return true;
1476 
1477 	/*
1478 	 * Distribute memory according to CPU & memory use on each node,
1479 	 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1480 	 *
1481 	 * faults_cpu(dst)   3   faults_cpu(src)
1482 	 * --------------- * - > ---------------
1483 	 * faults_mem(dst)   4   faults_mem(src)
1484 	 */
1485 	return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
1486 	       group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1487 }
1488 
1489 /*
1490  * 'numa_type' describes the node at the moment of load balancing.
1491  */
1492 enum numa_type {
1493 	/* The node has spare capacity that can be used to run more tasks.  */
1494 	node_has_spare = 0,
1495 	/*
1496 	 * The node is fully used and the tasks don't compete for more CPU
1497 	 * cycles. Nevertheless, some tasks might wait before running.
1498 	 */
1499 	node_fully_busy,
1500 	/*
1501 	 * The node is overloaded and can't provide expected CPU cycles to all
1502 	 * tasks.
1503 	 */
1504 	node_overloaded
1505 };
1506 
1507 /* Cached statistics for all CPUs within a node */
1508 struct numa_stats {
1509 	unsigned long load;
1510 	unsigned long util;
1511 	/* Total compute capacity of CPUs on a node */
1512 	unsigned long compute_capacity;
1513 	unsigned int nr_running;
1514 	unsigned int weight;
1515 	enum numa_type node_type;
1516 	int idle_cpu;
1517 };
1518 
1519 static inline bool is_core_idle(int cpu)
1520 {
1521 #ifdef CONFIG_SCHED_SMT
1522 	int sibling;
1523 
1524 	for_each_cpu(sibling, cpu_smt_mask(cpu)) {
1525 		if (cpu == sibling)
1526 			continue;
1527 
1528 		if (!idle_cpu(cpu))
1529 			return false;
1530 	}
1531 #endif
1532 
1533 	return true;
1534 }
1535 
1536 struct task_numa_env {
1537 	struct task_struct *p;
1538 
1539 	int src_cpu, src_nid;
1540 	int dst_cpu, dst_nid;
1541 
1542 	struct numa_stats src_stats, dst_stats;
1543 
1544 	int imbalance_pct;
1545 	int dist;
1546 
1547 	struct task_struct *best_task;
1548 	long best_imp;
1549 	int best_cpu;
1550 };
1551 
1552 static unsigned long cpu_load(struct rq *rq);
1553 static unsigned long cpu_util(int cpu);
1554 static inline long adjust_numa_imbalance(int imbalance, int src_nr_running);
1555 
1556 static inline enum
1557 numa_type numa_classify(unsigned int imbalance_pct,
1558 			 struct numa_stats *ns)
1559 {
1560 	if ((ns->nr_running > ns->weight) &&
1561 	    ((ns->compute_capacity * 100) < (ns->util * imbalance_pct)))
1562 		return node_overloaded;
1563 
1564 	if ((ns->nr_running < ns->weight) ||
1565 	    ((ns->compute_capacity * 100) > (ns->util * imbalance_pct)))
1566 		return node_has_spare;
1567 
1568 	return node_fully_busy;
1569 }
1570 
1571 #ifdef CONFIG_SCHED_SMT
1572 /* Forward declarations of select_idle_sibling helpers */
1573 static inline bool test_idle_cores(int cpu, bool def);
1574 static inline int numa_idle_core(int idle_core, int cpu)
1575 {
1576 	if (!static_branch_likely(&sched_smt_present) ||
1577 	    idle_core >= 0 || !test_idle_cores(cpu, false))
1578 		return idle_core;
1579 
1580 	/*
1581 	 * Prefer cores instead of packing HT siblings
1582 	 * and triggering future load balancing.
1583 	 */
1584 	if (is_core_idle(cpu))
1585 		idle_core = cpu;
1586 
1587 	return idle_core;
1588 }
1589 #else
1590 static inline int numa_idle_core(int idle_core, int cpu)
1591 {
1592 	return idle_core;
1593 }
1594 #endif
1595 
1596 /*
1597  * Gather all necessary information to make NUMA balancing placement
1598  * decisions that are compatible with standard load balancer. This
1599  * borrows code and logic from update_sg_lb_stats but sharing a
1600  * common implementation is impractical.
1601  */
1602 static void update_numa_stats(struct task_numa_env *env,
1603 			      struct numa_stats *ns, int nid,
1604 			      bool find_idle)
1605 {
1606 	int cpu, idle_core = -1;
1607 
1608 	memset(ns, 0, sizeof(*ns));
1609 	ns->idle_cpu = -1;
1610 
1611 	rcu_read_lock();
1612 	for_each_cpu(cpu, cpumask_of_node(nid)) {
1613 		struct rq *rq = cpu_rq(cpu);
1614 
1615 		ns->load += cpu_load(rq);
1616 		ns->util += cpu_util(cpu);
1617 		ns->nr_running += rq->cfs.h_nr_running;
1618 		ns->compute_capacity += capacity_of(cpu);
1619 
1620 		if (find_idle && !rq->nr_running && idle_cpu(cpu)) {
1621 			if (READ_ONCE(rq->numa_migrate_on) ||
1622 			    !cpumask_test_cpu(cpu, env->p->cpus_ptr))
1623 				continue;
1624 
1625 			if (ns->idle_cpu == -1)
1626 				ns->idle_cpu = cpu;
1627 
1628 			idle_core = numa_idle_core(idle_core, cpu);
1629 		}
1630 	}
1631 	rcu_read_unlock();
1632 
1633 	ns->weight = cpumask_weight(cpumask_of_node(nid));
1634 
1635 	ns->node_type = numa_classify(env->imbalance_pct, ns);
1636 
1637 	if (idle_core >= 0)
1638 		ns->idle_cpu = idle_core;
1639 }
1640 
1641 static void task_numa_assign(struct task_numa_env *env,
1642 			     struct task_struct *p, long imp)
1643 {
1644 	struct rq *rq = cpu_rq(env->dst_cpu);
1645 
1646 	/* Check if run-queue part of active NUMA balance. */
1647 	if (env->best_cpu != env->dst_cpu && xchg(&rq->numa_migrate_on, 1)) {
1648 		int cpu;
1649 		int start = env->dst_cpu;
1650 
1651 		/* Find alternative idle CPU. */
1652 		for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start) {
1653 			if (cpu == env->best_cpu || !idle_cpu(cpu) ||
1654 			    !cpumask_test_cpu(cpu, env->p->cpus_ptr)) {
1655 				continue;
1656 			}
1657 
1658 			env->dst_cpu = cpu;
1659 			rq = cpu_rq(env->dst_cpu);
1660 			if (!xchg(&rq->numa_migrate_on, 1))
1661 				goto assign;
1662 		}
1663 
1664 		/* Failed to find an alternative idle CPU */
1665 		return;
1666 	}
1667 
1668 assign:
1669 	/*
1670 	 * Clear previous best_cpu/rq numa-migrate flag, since task now
1671 	 * found a better CPU to move/swap.
1672 	 */
1673 	if (env->best_cpu != -1 && env->best_cpu != env->dst_cpu) {
1674 		rq = cpu_rq(env->best_cpu);
1675 		WRITE_ONCE(rq->numa_migrate_on, 0);
1676 	}
1677 
1678 	if (env->best_task)
1679 		put_task_struct(env->best_task);
1680 	if (p)
1681 		get_task_struct(p);
1682 
1683 	env->best_task = p;
1684 	env->best_imp = imp;
1685 	env->best_cpu = env->dst_cpu;
1686 }
1687 
1688 static bool load_too_imbalanced(long src_load, long dst_load,
1689 				struct task_numa_env *env)
1690 {
1691 	long imb, old_imb;
1692 	long orig_src_load, orig_dst_load;
1693 	long src_capacity, dst_capacity;
1694 
1695 	/*
1696 	 * The load is corrected for the CPU capacity available on each node.
1697 	 *
1698 	 * src_load        dst_load
1699 	 * ------------ vs ---------
1700 	 * src_capacity    dst_capacity
1701 	 */
1702 	src_capacity = env->src_stats.compute_capacity;
1703 	dst_capacity = env->dst_stats.compute_capacity;
1704 
1705 	imb = abs(dst_load * src_capacity - src_load * dst_capacity);
1706 
1707 	orig_src_load = env->src_stats.load;
1708 	orig_dst_load = env->dst_stats.load;
1709 
1710 	old_imb = abs(orig_dst_load * src_capacity - orig_src_load * dst_capacity);
1711 
1712 	/* Would this change make things worse? */
1713 	return (imb > old_imb);
1714 }
1715 
1716 /*
1717  * Maximum NUMA importance can be 1998 (2*999);
1718  * SMALLIMP @ 30 would be close to 1998/64.
1719  * Used to deter task migration.
1720  */
1721 #define SMALLIMP	30
1722 
1723 /*
1724  * This checks if the overall compute and NUMA accesses of the system would
1725  * be improved if the source tasks was migrated to the target dst_cpu taking
1726  * into account that it might be best if task running on the dst_cpu should
1727  * be exchanged with the source task
1728  */
1729 static bool task_numa_compare(struct task_numa_env *env,
1730 			      long taskimp, long groupimp, bool maymove)
1731 {
1732 	struct numa_group *cur_ng, *p_ng = deref_curr_numa_group(env->p);
1733 	struct rq *dst_rq = cpu_rq(env->dst_cpu);
1734 	long imp = p_ng ? groupimp : taskimp;
1735 	struct task_struct *cur;
1736 	long src_load, dst_load;
1737 	int dist = env->dist;
1738 	long moveimp = imp;
1739 	long load;
1740 	bool stopsearch = false;
1741 
1742 	if (READ_ONCE(dst_rq->numa_migrate_on))
1743 		return false;
1744 
1745 	rcu_read_lock();
1746 	cur = rcu_dereference(dst_rq->curr);
1747 	if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1748 		cur = NULL;
1749 
1750 	/*
1751 	 * Because we have preemption enabled we can get migrated around and
1752 	 * end try selecting ourselves (current == env->p) as a swap candidate.
1753 	 */
1754 	if (cur == env->p) {
1755 		stopsearch = true;
1756 		goto unlock;
1757 	}
1758 
1759 	if (!cur) {
1760 		if (maymove && moveimp >= env->best_imp)
1761 			goto assign;
1762 		else
1763 			goto unlock;
1764 	}
1765 
1766 	/* Skip this swap candidate if cannot move to the source cpu. */
1767 	if (!cpumask_test_cpu(env->src_cpu, cur->cpus_ptr))
1768 		goto unlock;
1769 
1770 	/*
1771 	 * Skip this swap candidate if it is not moving to its preferred
1772 	 * node and the best task is.
1773 	 */
1774 	if (env->best_task &&
1775 	    env->best_task->numa_preferred_nid == env->src_nid &&
1776 	    cur->numa_preferred_nid != env->src_nid) {
1777 		goto unlock;
1778 	}
1779 
1780 	/*
1781 	 * "imp" is the fault differential for the source task between the
1782 	 * source and destination node. Calculate the total differential for
1783 	 * the source task and potential destination task. The more negative
1784 	 * the value is, the more remote accesses that would be expected to
1785 	 * be incurred if the tasks were swapped.
1786 	 *
1787 	 * If dst and source tasks are in the same NUMA group, or not
1788 	 * in any group then look only at task weights.
1789 	 */
1790 	cur_ng = rcu_dereference(cur->numa_group);
1791 	if (cur_ng == p_ng) {
1792 		imp = taskimp + task_weight(cur, env->src_nid, dist) -
1793 		      task_weight(cur, env->dst_nid, dist);
1794 		/*
1795 		 * Add some hysteresis to prevent swapping the
1796 		 * tasks within a group over tiny differences.
1797 		 */
1798 		if (cur_ng)
1799 			imp -= imp / 16;
1800 	} else {
1801 		/*
1802 		 * Compare the group weights. If a task is all by itself
1803 		 * (not part of a group), use the task weight instead.
1804 		 */
1805 		if (cur_ng && p_ng)
1806 			imp += group_weight(cur, env->src_nid, dist) -
1807 			       group_weight(cur, env->dst_nid, dist);
1808 		else
1809 			imp += task_weight(cur, env->src_nid, dist) -
1810 			       task_weight(cur, env->dst_nid, dist);
1811 	}
1812 
1813 	/* Discourage picking a task already on its preferred node */
1814 	if (cur->numa_preferred_nid == env->dst_nid)
1815 		imp -= imp / 16;
1816 
1817 	/*
1818 	 * Encourage picking a task that moves to its preferred node.
1819 	 * This potentially makes imp larger than it's maximum of
1820 	 * 1998 (see SMALLIMP and task_weight for why) but in this
1821 	 * case, it does not matter.
1822 	 */
1823 	if (cur->numa_preferred_nid == env->src_nid)
1824 		imp += imp / 8;
1825 
1826 	if (maymove && moveimp > imp && moveimp > env->best_imp) {
1827 		imp = moveimp;
1828 		cur = NULL;
1829 		goto assign;
1830 	}
1831 
1832 	/*
1833 	 * Prefer swapping with a task moving to its preferred node over a
1834 	 * task that is not.
1835 	 */
1836 	if (env->best_task && cur->numa_preferred_nid == env->src_nid &&
1837 	    env->best_task->numa_preferred_nid != env->src_nid) {
1838 		goto assign;
1839 	}
1840 
1841 	/*
1842 	 * If the NUMA importance is less than SMALLIMP,
1843 	 * task migration might only result in ping pong
1844 	 * of tasks and also hurt performance due to cache
1845 	 * misses.
1846 	 */
1847 	if (imp < SMALLIMP || imp <= env->best_imp + SMALLIMP / 2)
1848 		goto unlock;
1849 
1850 	/*
1851 	 * In the overloaded case, try and keep the load balanced.
1852 	 */
1853 	load = task_h_load(env->p) - task_h_load(cur);
1854 	if (!load)
1855 		goto assign;
1856 
1857 	dst_load = env->dst_stats.load + load;
1858 	src_load = env->src_stats.load - load;
1859 
1860 	if (load_too_imbalanced(src_load, dst_load, env))
1861 		goto unlock;
1862 
1863 assign:
1864 	/* Evaluate an idle CPU for a task numa move. */
1865 	if (!cur) {
1866 		int cpu = env->dst_stats.idle_cpu;
1867 
1868 		/* Nothing cached so current CPU went idle since the search. */
1869 		if (cpu < 0)
1870 			cpu = env->dst_cpu;
1871 
1872 		/*
1873 		 * If the CPU is no longer truly idle and the previous best CPU
1874 		 * is, keep using it.
1875 		 */
1876 		if (!idle_cpu(cpu) && env->best_cpu >= 0 &&
1877 		    idle_cpu(env->best_cpu)) {
1878 			cpu = env->best_cpu;
1879 		}
1880 
1881 		env->dst_cpu = cpu;
1882 	}
1883 
1884 	task_numa_assign(env, cur, imp);
1885 
1886 	/*
1887 	 * If a move to idle is allowed because there is capacity or load
1888 	 * balance improves then stop the search. While a better swap
1889 	 * candidate may exist, a search is not free.
1890 	 */
1891 	if (maymove && !cur && env->best_cpu >= 0 && idle_cpu(env->best_cpu))
1892 		stopsearch = true;
1893 
1894 	/*
1895 	 * If a swap candidate must be identified and the current best task
1896 	 * moves its preferred node then stop the search.
1897 	 */
1898 	if (!maymove && env->best_task &&
1899 	    env->best_task->numa_preferred_nid == env->src_nid) {
1900 		stopsearch = true;
1901 	}
1902 unlock:
1903 	rcu_read_unlock();
1904 
1905 	return stopsearch;
1906 }
1907 
1908 static void task_numa_find_cpu(struct task_numa_env *env,
1909 				long taskimp, long groupimp)
1910 {
1911 	bool maymove = false;
1912 	int cpu;
1913 
1914 	/*
1915 	 * If dst node has spare capacity, then check if there is an
1916 	 * imbalance that would be overruled by the load balancer.
1917 	 */
1918 	if (env->dst_stats.node_type == node_has_spare) {
1919 		unsigned int imbalance;
1920 		int src_running, dst_running;
1921 
1922 		/*
1923 		 * Would movement cause an imbalance? Note that if src has
1924 		 * more running tasks that the imbalance is ignored as the
1925 		 * move improves the imbalance from the perspective of the
1926 		 * CPU load balancer.
1927 		 * */
1928 		src_running = env->src_stats.nr_running - 1;
1929 		dst_running = env->dst_stats.nr_running + 1;
1930 		imbalance = max(0, dst_running - src_running);
1931 		imbalance = adjust_numa_imbalance(imbalance, src_running);
1932 
1933 		/* Use idle CPU if there is no imbalance */
1934 		if (!imbalance) {
1935 			maymove = true;
1936 			if (env->dst_stats.idle_cpu >= 0) {
1937 				env->dst_cpu = env->dst_stats.idle_cpu;
1938 				task_numa_assign(env, NULL, 0);
1939 				return;
1940 			}
1941 		}
1942 	} else {
1943 		long src_load, dst_load, load;
1944 		/*
1945 		 * If the improvement from just moving env->p direction is better
1946 		 * than swapping tasks around, check if a move is possible.
1947 		 */
1948 		load = task_h_load(env->p);
1949 		dst_load = env->dst_stats.load + load;
1950 		src_load = env->src_stats.load - load;
1951 		maymove = !load_too_imbalanced(src_load, dst_load, env);
1952 	}
1953 
1954 	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1955 		/* Skip this CPU if the source task cannot migrate */
1956 		if (!cpumask_test_cpu(cpu, env->p->cpus_ptr))
1957 			continue;
1958 
1959 		env->dst_cpu = cpu;
1960 		if (task_numa_compare(env, taskimp, groupimp, maymove))
1961 			break;
1962 	}
1963 }
1964 
1965 static int task_numa_migrate(struct task_struct *p)
1966 {
1967 	struct task_numa_env env = {
1968 		.p = p,
1969 
1970 		.src_cpu = task_cpu(p),
1971 		.src_nid = task_node(p),
1972 
1973 		.imbalance_pct = 112,
1974 
1975 		.best_task = NULL,
1976 		.best_imp = 0,
1977 		.best_cpu = -1,
1978 	};
1979 	unsigned long taskweight, groupweight;
1980 	struct sched_domain *sd;
1981 	long taskimp, groupimp;
1982 	struct numa_group *ng;
1983 	struct rq *best_rq;
1984 	int nid, ret, dist;
1985 
1986 	/*
1987 	 * Pick the lowest SD_NUMA domain, as that would have the smallest
1988 	 * imbalance and would be the first to start moving tasks about.
1989 	 *
1990 	 * And we want to avoid any moving of tasks about, as that would create
1991 	 * random movement of tasks -- counter the numa conditions we're trying
1992 	 * to satisfy here.
1993 	 */
1994 	rcu_read_lock();
1995 	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1996 	if (sd)
1997 		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1998 	rcu_read_unlock();
1999 
2000 	/*
2001 	 * Cpusets can break the scheduler domain tree into smaller
2002 	 * balance domains, some of which do not cross NUMA boundaries.
2003 	 * Tasks that are "trapped" in such domains cannot be migrated
2004 	 * elsewhere, so there is no point in (re)trying.
2005 	 */
2006 	if (unlikely(!sd)) {
2007 		sched_setnuma(p, task_node(p));
2008 		return -EINVAL;
2009 	}
2010 
2011 	env.dst_nid = p->numa_preferred_nid;
2012 	dist = env.dist = node_distance(env.src_nid, env.dst_nid);
2013 	taskweight = task_weight(p, env.src_nid, dist);
2014 	groupweight = group_weight(p, env.src_nid, dist);
2015 	update_numa_stats(&env, &env.src_stats, env.src_nid, false);
2016 	taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
2017 	groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
2018 	update_numa_stats(&env, &env.dst_stats, env.dst_nid, true);
2019 
2020 	/* Try to find a spot on the preferred nid. */
2021 	task_numa_find_cpu(&env, taskimp, groupimp);
2022 
2023 	/*
2024 	 * Look at other nodes in these cases:
2025 	 * - there is no space available on the preferred_nid
2026 	 * - the task is part of a numa_group that is interleaved across
2027 	 *   multiple NUMA nodes; in order to better consolidate the group,
2028 	 *   we need to check other locations.
2029 	 */
2030 	ng = deref_curr_numa_group(p);
2031 	if (env.best_cpu == -1 || (ng && ng->active_nodes > 1)) {
2032 		for_each_online_node(nid) {
2033 			if (nid == env.src_nid || nid == p->numa_preferred_nid)
2034 				continue;
2035 
2036 			dist = node_distance(env.src_nid, env.dst_nid);
2037 			if (sched_numa_topology_type == NUMA_BACKPLANE &&
2038 						dist != env.dist) {
2039 				taskweight = task_weight(p, env.src_nid, dist);
2040 				groupweight = group_weight(p, env.src_nid, dist);
2041 			}
2042 
2043 			/* Only consider nodes where both task and groups benefit */
2044 			taskimp = task_weight(p, nid, dist) - taskweight;
2045 			groupimp = group_weight(p, nid, dist) - groupweight;
2046 			if (taskimp < 0 && groupimp < 0)
2047 				continue;
2048 
2049 			env.dist = dist;
2050 			env.dst_nid = nid;
2051 			update_numa_stats(&env, &env.dst_stats, env.dst_nid, true);
2052 			task_numa_find_cpu(&env, taskimp, groupimp);
2053 		}
2054 	}
2055 
2056 	/*
2057 	 * If the task is part of a workload that spans multiple NUMA nodes,
2058 	 * and is migrating into one of the workload's active nodes, remember
2059 	 * this node as the task's preferred numa node, so the workload can
2060 	 * settle down.
2061 	 * A task that migrated to a second choice node will be better off
2062 	 * trying for a better one later. Do not set the preferred node here.
2063 	 */
2064 	if (ng) {
2065 		if (env.best_cpu == -1)
2066 			nid = env.src_nid;
2067 		else
2068 			nid = cpu_to_node(env.best_cpu);
2069 
2070 		if (nid != p->numa_preferred_nid)
2071 			sched_setnuma(p, nid);
2072 	}
2073 
2074 	/* No better CPU than the current one was found. */
2075 	if (env.best_cpu == -1) {
2076 		trace_sched_stick_numa(p, env.src_cpu, NULL, -1);
2077 		return -EAGAIN;
2078 	}
2079 
2080 	best_rq = cpu_rq(env.best_cpu);
2081 	if (env.best_task == NULL) {
2082 		ret = migrate_task_to(p, env.best_cpu);
2083 		WRITE_ONCE(best_rq->numa_migrate_on, 0);
2084 		if (ret != 0)
2085 			trace_sched_stick_numa(p, env.src_cpu, NULL, env.best_cpu);
2086 		return ret;
2087 	}
2088 
2089 	ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu);
2090 	WRITE_ONCE(best_rq->numa_migrate_on, 0);
2091 
2092 	if (ret != 0)
2093 		trace_sched_stick_numa(p, env.src_cpu, env.best_task, env.best_cpu);
2094 	put_task_struct(env.best_task);
2095 	return ret;
2096 }
2097 
2098 /* Attempt to migrate a task to a CPU on the preferred node. */
2099 static void numa_migrate_preferred(struct task_struct *p)
2100 {
2101 	unsigned long interval = HZ;
2102 
2103 	/* This task has no NUMA fault statistics yet */
2104 	if (unlikely(p->numa_preferred_nid == NUMA_NO_NODE || !p->numa_faults))
2105 		return;
2106 
2107 	/* Periodically retry migrating the task to the preferred node */
2108 	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
2109 	p->numa_migrate_retry = jiffies + interval;
2110 
2111 	/* Success if task is already running on preferred CPU */
2112 	if (task_node(p) == p->numa_preferred_nid)
2113 		return;
2114 
2115 	/* Otherwise, try migrate to a CPU on the preferred node */
2116 	task_numa_migrate(p);
2117 }
2118 
2119 /*
2120  * Find out how many nodes on the workload is actively running on. Do this by
2121  * tracking the nodes from which NUMA hinting faults are triggered. This can
2122  * be different from the set of nodes where the workload's memory is currently
2123  * located.
2124  */
2125 static void numa_group_count_active_nodes(struct numa_group *numa_group)
2126 {
2127 	unsigned long faults, max_faults = 0;
2128 	int nid, active_nodes = 0;
2129 
2130 	for_each_online_node(nid) {
2131 		faults = group_faults_cpu(numa_group, nid);
2132 		if (faults > max_faults)
2133 			max_faults = faults;
2134 	}
2135 
2136 	for_each_online_node(nid) {
2137 		faults = group_faults_cpu(numa_group, nid);
2138 		if (faults * ACTIVE_NODE_FRACTION > max_faults)
2139 			active_nodes++;
2140 	}
2141 
2142 	numa_group->max_faults_cpu = max_faults;
2143 	numa_group->active_nodes = active_nodes;
2144 }
2145 
2146 /*
2147  * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
2148  * increments. The more local the fault statistics are, the higher the scan
2149  * period will be for the next scan window. If local/(local+remote) ratio is
2150  * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
2151  * the scan period will decrease. Aim for 70% local accesses.
2152  */
2153 #define NUMA_PERIOD_SLOTS 10
2154 #define NUMA_PERIOD_THRESHOLD 7
2155 
2156 /*
2157  * Increase the scan period (slow down scanning) if the majority of
2158  * our memory is already on our local node, or if the majority of
2159  * the page accesses are shared with other processes.
2160  * Otherwise, decrease the scan period.
2161  */
2162 static void update_task_scan_period(struct task_struct *p,
2163 			unsigned long shared, unsigned long private)
2164 {
2165 	unsigned int period_slot;
2166 	int lr_ratio, ps_ratio;
2167 	int diff;
2168 
2169 	unsigned long remote = p->numa_faults_locality[0];
2170 	unsigned long local = p->numa_faults_locality[1];
2171 
2172 	/*
2173 	 * If there were no record hinting faults then either the task is
2174 	 * completely idle or all activity is areas that are not of interest
2175 	 * to automatic numa balancing. Related to that, if there were failed
2176 	 * migration then it implies we are migrating too quickly or the local
2177 	 * node is overloaded. In either case, scan slower
2178 	 */
2179 	if (local + shared == 0 || p->numa_faults_locality[2]) {
2180 		p->numa_scan_period = min(p->numa_scan_period_max,
2181 			p->numa_scan_period << 1);
2182 
2183 		p->mm->numa_next_scan = jiffies +
2184 			msecs_to_jiffies(p->numa_scan_period);
2185 
2186 		return;
2187 	}
2188 
2189 	/*
2190 	 * Prepare to scale scan period relative to the current period.
2191 	 *	 == NUMA_PERIOD_THRESHOLD scan period stays the same
2192 	 *       <  NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
2193 	 *	 >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
2194 	 */
2195 	period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
2196 	lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
2197 	ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);
2198 
2199 	if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
2200 		/*
2201 		 * Most memory accesses are local. There is no need to
2202 		 * do fast NUMA scanning, since memory is already local.
2203 		 */
2204 		int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
2205 		if (!slot)
2206 			slot = 1;
2207 		diff = slot * period_slot;
2208 	} else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
2209 		/*
2210 		 * Most memory accesses are shared with other tasks.
2211 		 * There is no point in continuing fast NUMA scanning,
2212 		 * since other tasks may just move the memory elsewhere.
2213 		 */
2214 		int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
2215 		if (!slot)
2216 			slot = 1;
2217 		diff = slot * period_slot;
2218 	} else {
2219 		/*
2220 		 * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
2221 		 * yet they are not on the local NUMA node. Speed up
2222 		 * NUMA scanning to get the memory moved over.
2223 		 */
2224 		int ratio = max(lr_ratio, ps_ratio);
2225 		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
2226 	}
2227 
2228 	p->numa_scan_period = clamp(p->numa_scan_period + diff,
2229 			task_scan_min(p), task_scan_max(p));
2230 	memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2231 }
2232 
2233 /*
2234  * Get the fraction of time the task has been running since the last
2235  * NUMA placement cycle. The scheduler keeps similar statistics, but
2236  * decays those on a 32ms period, which is orders of magnitude off
2237  * from the dozens-of-seconds NUMA balancing period. Use the scheduler
2238  * stats only if the task is so new there are no NUMA statistics yet.
2239  */
2240 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
2241 {
2242 	u64 runtime, delta, now;
2243 	/* Use the start of this time slice to avoid calculations. */
2244 	now = p->se.exec_start;
2245 	runtime = p->se.sum_exec_runtime;
2246 
2247 	if (p->last_task_numa_placement) {
2248 		delta = runtime - p->last_sum_exec_runtime;
2249 		*period = now - p->last_task_numa_placement;
2250 
2251 		/* Avoid time going backwards, prevent potential divide error: */
2252 		if (unlikely((s64)*period < 0))
2253 			*period = 0;
2254 	} else {
2255 		delta = p->se.avg.load_sum;
2256 		*period = LOAD_AVG_MAX;
2257 	}
2258 
2259 	p->last_sum_exec_runtime = runtime;
2260 	p->last_task_numa_placement = now;
2261 
2262 	return delta;
2263 }
2264 
2265 /*
2266  * Determine the preferred nid for a task in a numa_group. This needs to
2267  * be done in a way that produces consistent results with group_weight,
2268  * otherwise workloads might not converge.
2269  */
2270 static int preferred_group_nid(struct task_struct *p, int nid)
2271 {
2272 	nodemask_t nodes;
2273 	int dist;
2274 
2275 	/* Direct connections between all NUMA nodes. */
2276 	if (sched_numa_topology_type == NUMA_DIRECT)
2277 		return nid;
2278 
2279 	/*
2280 	 * On a system with glueless mesh NUMA topology, group_weight
2281 	 * scores nodes according to the number of NUMA hinting faults on
2282 	 * both the node itself, and on nearby nodes.
2283 	 */
2284 	if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
2285 		unsigned long score, max_score = 0;
2286 		int node, max_node = nid;
2287 
2288 		dist = sched_max_numa_distance;
2289 
2290 		for_each_online_node(node) {
2291 			score = group_weight(p, node, dist);
2292 			if (score > max_score) {
2293 				max_score = score;
2294 				max_node = node;
2295 			}
2296 		}
2297 		return max_node;
2298 	}
2299 
2300 	/*
2301 	 * Finding the preferred nid in a system with NUMA backplane
2302 	 * interconnect topology is more involved. The goal is to locate
2303 	 * tasks from numa_groups near each other in the system, and
2304 	 * untangle workloads from different sides of the system. This requires
2305 	 * searching down the hierarchy of node groups, recursively searching
2306 	 * inside the highest scoring group of nodes. The nodemask tricks
2307 	 * keep the complexity of the search down.
2308 	 */
2309 	nodes = node_online_map;
2310 	for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
2311 		unsigned long max_faults = 0;
2312 		nodemask_t max_group = NODE_MASK_NONE;
2313 		int a, b;
2314 
2315 		/* Are there nodes at this distance from each other? */
2316 		if (!find_numa_distance(dist))
2317 			continue;
2318 
2319 		for_each_node_mask(a, nodes) {
2320 			unsigned long faults = 0;
2321 			nodemask_t this_group;
2322 			nodes_clear(this_group);
2323 
2324 			/* Sum group's NUMA faults; includes a==b case. */
2325 			for_each_node_mask(b, nodes) {
2326 				if (node_distance(a, b) < dist) {
2327 					faults += group_faults(p, b);
2328 					node_set(b, this_group);
2329 					node_clear(b, nodes);
2330 				}
2331 			}
2332 
2333 			/* Remember the top group. */
2334 			if (faults > max_faults) {
2335 				max_faults = faults;
2336 				max_group = this_group;
2337 				/*
2338 				 * subtle: at the smallest distance there is
2339 				 * just one node left in each "group", the
2340 				 * winner is the preferred nid.
2341 				 */
2342 				nid = a;
2343 			}
2344 		}
2345 		/* Next round, evaluate the nodes within max_group. */
2346 		if (!max_faults)
2347 			break;
2348 		nodes = max_group;
2349 	}
2350 	return nid;
2351 }
2352 
2353 static void task_numa_placement(struct task_struct *p)
2354 {
2355 	int seq, nid, max_nid = NUMA_NO_NODE;
2356 	unsigned long max_faults = 0;
2357 	unsigned long fault_types[2] = { 0, 0 };
2358 	unsigned long total_faults;
2359 	u64 runtime, period;
2360 	spinlock_t *group_lock = NULL;
2361 	struct numa_group *ng;
2362 
2363 	/*
2364 	 * The p->mm->numa_scan_seq field gets updated without
2365 	 * exclusive access. Use READ_ONCE() here to ensure
2366 	 * that the field is read in a single access:
2367 	 */
2368 	seq = READ_ONCE(p->mm->numa_scan_seq);
2369 	if (p->numa_scan_seq == seq)
2370 		return;
2371 	p->numa_scan_seq = seq;
2372 	p->numa_scan_period_max = task_scan_max(p);
2373 
2374 	total_faults = p->numa_faults_locality[0] +
2375 		       p->numa_faults_locality[1];
2376 	runtime = numa_get_avg_runtime(p, &period);
2377 
2378 	/* If the task is part of a group prevent parallel updates to group stats */
2379 	ng = deref_curr_numa_group(p);
2380 	if (ng) {
2381 		group_lock = &ng->lock;
2382 		spin_lock_irq(group_lock);
2383 	}
2384 
2385 	/* Find the node with the highest number of faults */
2386 	for_each_online_node(nid) {
2387 		/* Keep track of the offsets in numa_faults array */
2388 		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2389 		unsigned long faults = 0, group_faults = 0;
2390 		int priv;
2391 
2392 		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2393 			long diff, f_diff, f_weight;
2394 
2395 			mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
2396 			membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
2397 			cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
2398 			cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
2399 
2400 			/* Decay existing window, copy faults since last scan */
2401 			diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
2402 			fault_types[priv] += p->numa_faults[membuf_idx];
2403 			p->numa_faults[membuf_idx] = 0;
2404 
2405 			/*
2406 			 * Normalize the faults_from, so all tasks in a group
2407 			 * count according to CPU use, instead of by the raw
2408 			 * number of faults. Tasks with little runtime have
2409 			 * little over-all impact on throughput, and thus their
2410 			 * faults are less important.
2411 			 */
2412 			f_weight = div64_u64(runtime << 16, period + 1);
2413 			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2414 				   (total_faults + 1);
2415 			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
2416 			p->numa_faults[cpubuf_idx] = 0;
2417 
2418 			p->numa_faults[mem_idx] += diff;
2419 			p->numa_faults[cpu_idx] += f_diff;
2420 			faults += p->numa_faults[mem_idx];
2421 			p->total_numa_faults += diff;
2422 			if (ng) {
2423 				/*
2424 				 * safe because we can only change our own group
2425 				 *
2426 				 * mem_idx represents the offset for a given
2427 				 * nid and priv in a specific region because it
2428 				 * is at the beginning of the numa_faults array.
2429 				 */
2430 				ng->faults[mem_idx] += diff;
2431 				ng->faults_cpu[mem_idx] += f_diff;
2432 				ng->total_faults += diff;
2433 				group_faults += ng->faults[mem_idx];
2434 			}
2435 		}
2436 
2437 		if (!ng) {
2438 			if (faults > max_faults) {
2439 				max_faults = faults;
2440 				max_nid = nid;
2441 			}
2442 		} else if (group_faults > max_faults) {
2443 			max_faults = group_faults;
2444 			max_nid = nid;
2445 		}
2446 	}
2447 
2448 	if (ng) {
2449 		numa_group_count_active_nodes(ng);
2450 		spin_unlock_irq(group_lock);
2451 		max_nid = preferred_group_nid(p, max_nid);
2452 	}
2453 
2454 	if (max_faults) {
2455 		/* Set the new preferred node */
2456 		if (max_nid != p->numa_preferred_nid)
2457 			sched_setnuma(p, max_nid);
2458 	}
2459 
2460 	update_task_scan_period(p, fault_types[0], fault_types[1]);
2461 }
2462 
2463 static inline int get_numa_group(struct numa_group *grp)
2464 {
2465 	return refcount_inc_not_zero(&grp->refcount);
2466 }
2467 
2468 static inline void put_numa_group(struct numa_group *grp)
2469 {
2470 	if (refcount_dec_and_test(&grp->refcount))
2471 		kfree_rcu(grp, rcu);
2472 }
2473 
2474 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
2475 			int *priv)
2476 {
2477 	struct numa_group *grp, *my_grp;
2478 	struct task_struct *tsk;
2479 	bool join = false;
2480 	int cpu = cpupid_to_cpu(cpupid);
2481 	int i;
2482 
2483 	if (unlikely(!deref_curr_numa_group(p))) {
2484 		unsigned int size = sizeof(struct numa_group) +
2485 				    4*nr_node_ids*sizeof(unsigned long);
2486 
2487 		grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
2488 		if (!grp)
2489 			return;
2490 
2491 		refcount_set(&grp->refcount, 1);
2492 		grp->active_nodes = 1;
2493 		grp->max_faults_cpu = 0;
2494 		spin_lock_init(&grp->lock);
2495 		grp->gid = p->pid;
2496 		/* Second half of the array tracks nids where faults happen */
2497 		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
2498 						nr_node_ids;
2499 
2500 		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2501 			grp->faults[i] = p->numa_faults[i];
2502 
2503 		grp->total_faults = p->total_numa_faults;
2504 
2505 		grp->nr_tasks++;
2506 		rcu_assign_pointer(p->numa_group, grp);
2507 	}
2508 
2509 	rcu_read_lock();
2510 	tsk = READ_ONCE(cpu_rq(cpu)->curr);
2511 
2512 	if (!cpupid_match_pid(tsk, cpupid))
2513 		goto no_join;
2514 
2515 	grp = rcu_dereference(tsk->numa_group);
2516 	if (!grp)
2517 		goto no_join;
2518 
2519 	my_grp = deref_curr_numa_group(p);
2520 	if (grp == my_grp)
2521 		goto no_join;
2522 
2523 	/*
2524 	 * Only join the other group if its bigger; if we're the bigger group,
2525 	 * the other task will join us.
2526 	 */
2527 	if (my_grp->nr_tasks > grp->nr_tasks)
2528 		goto no_join;
2529 
2530 	/*
2531 	 * Tie-break on the grp address.
2532 	 */
2533 	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2534 		goto no_join;
2535 
2536 	/* Always join threads in the same process. */
2537 	if (tsk->mm == current->mm)
2538 		join = true;
2539 
2540 	/* Simple filter to avoid false positives due to PID collisions */
2541 	if (flags & TNF_SHARED)
2542 		join = true;
2543 
2544 	/* Update priv based on whether false sharing was detected */
2545 	*priv = !join;
2546 
2547 	if (join && !get_numa_group(grp))
2548 		goto no_join;
2549 
2550 	rcu_read_unlock();
2551 
2552 	if (!join)
2553 		return;
2554 
2555 	BUG_ON(irqs_disabled());
2556 	double_lock_irq(&my_grp->lock, &grp->lock);
2557 
2558 	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2559 		my_grp->faults[i] -= p->numa_faults[i];
2560 		grp->faults[i] += p->numa_faults[i];
2561 	}
2562 	my_grp->total_faults -= p->total_numa_faults;
2563 	grp->total_faults += p->total_numa_faults;
2564 
2565 	my_grp->nr_tasks--;
2566 	grp->nr_tasks++;
2567 
2568 	spin_unlock(&my_grp->lock);
2569 	spin_unlock_irq(&grp->lock);
2570 
2571 	rcu_assign_pointer(p->numa_group, grp);
2572 
2573 	put_numa_group(my_grp);
2574 	return;
2575 
2576 no_join:
2577 	rcu_read_unlock();
2578 	return;
2579 }
2580 
2581 /*
2582  * Get rid of NUMA staticstics associated with a task (either current or dead).
2583  * If @final is set, the task is dead and has reached refcount zero, so we can
2584  * safely free all relevant data structures. Otherwise, there might be
2585  * concurrent reads from places like load balancing and procfs, and we should
2586  * reset the data back to default state without freeing ->numa_faults.
2587  */
2588 void task_numa_free(struct task_struct *p, bool final)
2589 {
2590 	/* safe: p either is current or is being freed by current */
2591 	struct numa_group *grp = rcu_dereference_raw(p->numa_group);
2592 	unsigned long *numa_faults = p->numa_faults;
2593 	unsigned long flags;
2594 	int i;
2595 
2596 	if (!numa_faults)
2597 		return;
2598 
2599 	if (grp) {
2600 		spin_lock_irqsave(&grp->lock, flags);
2601 		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2602 			grp->faults[i] -= p->numa_faults[i];
2603 		grp->total_faults -= p->total_numa_faults;
2604 
2605 		grp->nr_tasks--;
2606 		spin_unlock_irqrestore(&grp->lock, flags);
2607 		RCU_INIT_POINTER(p->numa_group, NULL);
2608 		put_numa_group(grp);
2609 	}
2610 
2611 	if (final) {
2612 		p->numa_faults = NULL;
2613 		kfree(numa_faults);
2614 	} else {
2615 		p->total_numa_faults = 0;
2616 		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2617 			numa_faults[i] = 0;
2618 	}
2619 }
2620 
2621 /*
2622  * Got a PROT_NONE fault for a page on @node.
2623  */
2624 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2625 {
2626 	struct task_struct *p = current;
2627 	bool migrated = flags & TNF_MIGRATED;
2628 	int cpu_node = task_node(current);
2629 	int local = !!(flags & TNF_FAULT_LOCAL);
2630 	struct numa_group *ng;
2631 	int priv;
2632 
2633 	if (!static_branch_likely(&sched_numa_balancing))
2634 		return;
2635 
2636 	/* for example, ksmd faulting in a user's mm */
2637 	if (!p->mm)
2638 		return;
2639 
2640 	/* Allocate buffer to track faults on a per-node basis */
2641 	if (unlikely(!p->numa_faults)) {
2642 		int size = sizeof(*p->numa_faults) *
2643 			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2644 
2645 		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2646 		if (!p->numa_faults)
2647 			return;
2648 
2649 		p->total_numa_faults = 0;
2650 		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2651 	}
2652 
2653 	/*
2654 	 * First accesses are treated as private, otherwise consider accesses
2655 	 * to be private if the accessing pid has not changed
2656 	 */
2657 	if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2658 		priv = 1;
2659 	} else {
2660 		priv = cpupid_match_pid(p, last_cpupid);
2661 		if (!priv && !(flags & TNF_NO_GROUP))
2662 			task_numa_group(p, last_cpupid, flags, &priv);
2663 	}
2664 
2665 	/*
2666 	 * If a workload spans multiple NUMA nodes, a shared fault that
2667 	 * occurs wholly within the set of nodes that the workload is
2668 	 * actively using should be counted as local. This allows the
2669 	 * scan rate to slow down when a workload has settled down.
2670 	 */
2671 	ng = deref_curr_numa_group(p);
2672 	if (!priv && !local && ng && ng->active_nodes > 1 &&
2673 				numa_is_active_node(cpu_node, ng) &&
2674 				numa_is_active_node(mem_node, ng))
2675 		local = 1;
2676 
2677 	/*
2678 	 * Retry to migrate task to preferred node periodically, in case it
2679 	 * previously failed, or the scheduler moved us.
2680 	 */
2681 	if (time_after(jiffies, p->numa_migrate_retry)) {
2682 		task_numa_placement(p);
2683 		numa_migrate_preferred(p);
2684 	}
2685 
2686 	if (migrated)
2687 		p->numa_pages_migrated += pages;
2688 	if (flags & TNF_MIGRATE_FAIL)
2689 		p->numa_faults_locality[2] += pages;
2690 
2691 	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2692 	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2693 	p->numa_faults_locality[local] += pages;
2694 }
2695 
2696 static void reset_ptenuma_scan(struct task_struct *p)
2697 {
2698 	/*
2699 	 * We only did a read acquisition of the mmap sem, so
2700 	 * p->mm->numa_scan_seq is written to without exclusive access
2701 	 * and the update is not guaranteed to be atomic. That's not
2702 	 * much of an issue though, since this is just used for
2703 	 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2704 	 * expensive, to avoid any form of compiler optimizations:
2705 	 */
2706 	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2707 	p->mm->numa_scan_offset = 0;
2708 }
2709 
2710 /*
2711  * The expensive part of numa migration is done from task_work context.
2712  * Triggered from task_tick_numa().
2713  */
2714 static void task_numa_work(struct callback_head *work)
2715 {
2716 	unsigned long migrate, next_scan, now = jiffies;
2717 	struct task_struct *p = current;
2718 	struct mm_struct *mm = p->mm;
2719 	u64 runtime = p->se.sum_exec_runtime;
2720 	struct vm_area_struct *vma;
2721 	unsigned long start, end;
2722 	unsigned long nr_pte_updates = 0;
2723 	long pages, virtpages;
2724 
2725 	SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2726 
2727 	work->next = work;
2728 	/*
2729 	 * Who cares about NUMA placement when they're dying.
2730 	 *
2731 	 * NOTE: make sure not to dereference p->mm before this check,
2732 	 * exit_task_work() happens _after_ exit_mm() so we could be called
2733 	 * without p->mm even though we still had it when we enqueued this
2734 	 * work.
2735 	 */
2736 	if (p->flags & PF_EXITING)
2737 		return;
2738 
2739 	if (!mm->numa_next_scan) {
2740 		mm->numa_next_scan = now +
2741 			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2742 	}
2743 
2744 	/*
2745 	 * Enforce maximal scan/migration frequency..
2746 	 */
2747 	migrate = mm->numa_next_scan;
2748 	if (time_before(now, migrate))
2749 		return;
2750 
2751 	if (p->numa_scan_period == 0) {
2752 		p->numa_scan_period_max = task_scan_max(p);
2753 		p->numa_scan_period = task_scan_start(p);
2754 	}
2755 
2756 	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2757 	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2758 		return;
2759 
2760 	/*
2761 	 * Delay this task enough that another task of this mm will likely win
2762 	 * the next time around.
2763 	 */
2764 	p->node_stamp += 2 * TICK_NSEC;
2765 
2766 	start = mm->numa_scan_offset;
2767 	pages = sysctl_numa_balancing_scan_size;
2768 	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2769 	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2770 	if (!pages)
2771 		return;
2772 
2773 
2774 	if (!down_read_trylock(&mm->mmap_sem))
2775 		return;
2776 	vma = find_vma(mm, start);
2777 	if (!vma) {
2778 		reset_ptenuma_scan(p);
2779 		start = 0;
2780 		vma = mm->mmap;
2781 	}
2782 	for (; vma; vma = vma->vm_next) {
2783 		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2784 			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2785 			continue;
2786 		}
2787 
2788 		/*
2789 		 * Shared library pages mapped by multiple processes are not
2790 		 * migrated as it is expected they are cache replicated. Avoid
2791 		 * hinting faults in read-only file-backed mappings or the vdso
2792 		 * as migrating the pages will be of marginal benefit.
2793 		 */
2794 		if (!vma->vm_mm ||
2795 		    (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2796 			continue;
2797 
2798 		/*
2799 		 * Skip inaccessible VMAs to avoid any confusion between
2800 		 * PROT_NONE and NUMA hinting ptes
2801 		 */
2802 		if (!vma_is_accessible(vma))
2803 			continue;
2804 
2805 		do {
2806 			start = max(start, vma->vm_start);
2807 			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2808 			end = min(end, vma->vm_end);
2809 			nr_pte_updates = change_prot_numa(vma, start, end);
2810 
2811 			/*
2812 			 * Try to scan sysctl_numa_balancing_size worth of
2813 			 * hpages that have at least one present PTE that
2814 			 * is not already pte-numa. If the VMA contains
2815 			 * areas that are unused or already full of prot_numa
2816 			 * PTEs, scan up to virtpages, to skip through those
2817 			 * areas faster.
2818 			 */
2819 			if (nr_pte_updates)
2820 				pages -= (end - start) >> PAGE_SHIFT;
2821 			virtpages -= (end - start) >> PAGE_SHIFT;
2822 
2823 			start = end;
2824 			if (pages <= 0 || virtpages <= 0)
2825 				goto out;
2826 
2827 			cond_resched();
2828 		} while (end != vma->vm_end);
2829 	}
2830 
2831 out:
2832 	/*
2833 	 * It is possible to reach the end of the VMA list but the last few
2834 	 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2835 	 * would find the !migratable VMA on the next scan but not reset the
2836 	 * scanner to the start so check it now.
2837 	 */
2838 	if (vma)
2839 		mm->numa_scan_offset = start;
2840 	else
2841 		reset_ptenuma_scan(p);
2842 	up_read(&mm->mmap_sem);
2843 
2844 	/*
2845 	 * Make sure tasks use at least 32x as much time to run other code
2846 	 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2847 	 * Usually update_task_scan_period slows down scanning enough; on an
2848 	 * overloaded system we need to limit overhead on a per task basis.
2849 	 */
2850 	if (unlikely(p->se.sum_exec_runtime != runtime)) {
2851 		u64 diff = p->se.sum_exec_runtime - runtime;
2852 		p->node_stamp += 32 * diff;
2853 	}
2854 }
2855 
2856 void init_numa_balancing(unsigned long clone_flags, struct task_struct *p)
2857 {
2858 	int mm_users = 0;
2859 	struct mm_struct *mm = p->mm;
2860 
2861 	if (mm) {
2862 		mm_users = atomic_read(&mm->mm_users);
2863 		if (mm_users == 1) {
2864 			mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2865 			mm->numa_scan_seq = 0;
2866 		}
2867 	}
2868 	p->node_stamp			= 0;
2869 	p->numa_scan_seq		= mm ? mm->numa_scan_seq : 0;
2870 	p->numa_scan_period		= sysctl_numa_balancing_scan_delay;
2871 	/* Protect against double add, see task_tick_numa and task_numa_work */
2872 	p->numa_work.next		= &p->numa_work;
2873 	p->numa_faults			= NULL;
2874 	RCU_INIT_POINTER(p->numa_group, NULL);
2875 	p->last_task_numa_placement	= 0;
2876 	p->last_sum_exec_runtime	= 0;
2877 
2878 	init_task_work(&p->numa_work, task_numa_work);
2879 
2880 	/* New address space, reset the preferred nid */
2881 	if (!(clone_flags & CLONE_VM)) {
2882 		p->numa_preferred_nid = NUMA_NO_NODE;
2883 		return;
2884 	}
2885 
2886 	/*
2887 	 * New thread, keep existing numa_preferred_nid which should be copied
2888 	 * already by arch_dup_task_struct but stagger when scans start.
2889 	 */
2890 	if (mm) {
2891 		unsigned int delay;
2892 
2893 		delay = min_t(unsigned int, task_scan_max(current),
2894 			current->numa_scan_period * mm_users * NSEC_PER_MSEC);
2895 		delay += 2 * TICK_NSEC;
2896 		p->node_stamp = delay;
2897 	}
2898 }
2899 
2900 /*
2901  * Drive the periodic memory faults..
2902  */
2903 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2904 {
2905 	struct callback_head *work = &curr->numa_work;
2906 	u64 period, now;
2907 
2908 	/*
2909 	 * We don't care about NUMA placement if we don't have memory.
2910 	 */
2911 	if ((curr->flags & (PF_EXITING | PF_KTHREAD)) || work->next != work)
2912 		return;
2913 
2914 	/*
2915 	 * Using runtime rather than walltime has the dual advantage that
2916 	 * we (mostly) drive the selection from busy threads and that the
2917 	 * task needs to have done some actual work before we bother with
2918 	 * NUMA placement.
2919 	 */
2920 	now = curr->se.sum_exec_runtime;
2921 	period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2922 
2923 	if (now > curr->node_stamp + period) {
2924 		if (!curr->node_stamp)
2925 			curr->numa_scan_period = task_scan_start(curr);
2926 		curr->node_stamp += period;
2927 
2928 		if (!time_before(jiffies, curr->mm->numa_next_scan))
2929 			task_work_add(curr, work, true);
2930 	}
2931 }
2932 
2933 static void update_scan_period(struct task_struct *p, int new_cpu)
2934 {
2935 	int src_nid = cpu_to_node(task_cpu(p));
2936 	int dst_nid = cpu_to_node(new_cpu);
2937 
2938 	if (!static_branch_likely(&sched_numa_balancing))
2939 		return;
2940 
2941 	if (!p->mm || !p->numa_faults || (p->flags & PF_EXITING))
2942 		return;
2943 
2944 	if (src_nid == dst_nid)
2945 		return;
2946 
2947 	/*
2948 	 * Allow resets if faults have been trapped before one scan
2949 	 * has completed. This is most likely due to a new task that
2950 	 * is pulled cross-node due to wakeups or load balancing.
2951 	 */
2952 	if (p->numa_scan_seq) {
2953 		/*
2954 		 * Avoid scan adjustments if moving to the preferred
2955 		 * node or if the task was not previously running on
2956 		 * the preferred node.
2957 		 */
2958 		if (dst_nid == p->numa_preferred_nid ||
2959 		    (p->numa_preferred_nid != NUMA_NO_NODE &&
2960 			src_nid != p->numa_preferred_nid))
2961 			return;
2962 	}
2963 
2964 	p->numa_scan_period = task_scan_start(p);
2965 }
2966 
2967 #else
2968 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2969 {
2970 }
2971 
2972 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2973 {
2974 }
2975 
2976 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2977 {
2978 }
2979 
2980 static inline void update_scan_period(struct task_struct *p, int new_cpu)
2981 {
2982 }
2983 
2984 #endif /* CONFIG_NUMA_BALANCING */
2985 
2986 static void
2987 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2988 {
2989 	update_load_add(&cfs_rq->load, se->load.weight);
2990 #ifdef CONFIG_SMP
2991 	if (entity_is_task(se)) {
2992 		struct rq *rq = rq_of(cfs_rq);
2993 
2994 		account_numa_enqueue(rq, task_of(se));
2995 		list_add(&se->group_node, &rq->cfs_tasks);
2996 	}
2997 #endif
2998 	cfs_rq->nr_running++;
2999 }
3000 
3001 static void
3002 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
3003 {
3004 	update_load_sub(&cfs_rq->load, se->load.weight);
3005 #ifdef CONFIG_SMP
3006 	if (entity_is_task(se)) {
3007 		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
3008 		list_del_init(&se->group_node);
3009 	}
3010 #endif
3011 	cfs_rq->nr_running--;
3012 }
3013 
3014 /*
3015  * Signed add and clamp on underflow.
3016  *
3017  * Explicitly do a load-store to ensure the intermediate value never hits
3018  * memory. This allows lockless observations without ever seeing the negative
3019  * values.
3020  */
3021 #define add_positive(_ptr, _val) do {                           \
3022 	typeof(_ptr) ptr = (_ptr);                              \
3023 	typeof(_val) val = (_val);                              \
3024 	typeof(*ptr) res, var = READ_ONCE(*ptr);                \
3025 								\
3026 	res = var + val;                                        \
3027 								\
3028 	if (val < 0 && res > var)                               \
3029 		res = 0;                                        \
3030 								\
3031 	WRITE_ONCE(*ptr, res);                                  \
3032 } while (0)
3033 
3034 /*
3035  * Unsigned subtract and clamp on underflow.
3036  *
3037  * Explicitly do a load-store to ensure the intermediate value never hits
3038  * memory. This allows lockless observations without ever seeing the negative
3039  * values.
3040  */
3041 #define sub_positive(_ptr, _val) do {				\
3042 	typeof(_ptr) ptr = (_ptr);				\
3043 	typeof(*ptr) val = (_val);				\
3044 	typeof(*ptr) res, var = READ_ONCE(*ptr);		\
3045 	res = var - val;					\
3046 	if (res > var)						\
3047 		res = 0;					\
3048 	WRITE_ONCE(*ptr, res);					\
3049 } while (0)
3050 
3051 /*
3052  * Remove and clamp on negative, from a local variable.
3053  *
3054  * A variant of sub_positive(), which does not use explicit load-store
3055  * and is thus optimized for local variable updates.
3056  */
3057 #define lsub_positive(_ptr, _val) do {				\
3058 	typeof(_ptr) ptr = (_ptr);				\
3059 	*ptr -= min_t(typeof(*ptr), *ptr, _val);		\
3060 } while (0)
3061 
3062 #ifdef CONFIG_SMP
3063 static inline void
3064 enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3065 {
3066 	cfs_rq->avg.load_avg += se->avg.load_avg;
3067 	cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
3068 }
3069 
3070 static inline void
3071 dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3072 {
3073 	sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
3074 	sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum);
3075 }
3076 #else
3077 static inline void
3078 enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
3079 static inline void
3080 dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
3081 #endif
3082 
3083 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
3084 			    unsigned long weight)
3085 {
3086 	if (se->on_rq) {
3087 		/* commit outstanding execution time */
3088 		if (cfs_rq->curr == se)
3089 			update_curr(cfs_rq);
3090 		account_entity_dequeue(cfs_rq, se);
3091 	}
3092 	dequeue_load_avg(cfs_rq, se);
3093 
3094 	update_load_set(&se->load, weight);
3095 
3096 #ifdef CONFIG_SMP
3097 	do {
3098 		u32 divider = LOAD_AVG_MAX - 1024 + se->avg.period_contrib;
3099 
3100 		se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider);
3101 	} while (0);
3102 #endif
3103 
3104 	enqueue_load_avg(cfs_rq, se);
3105 	if (se->on_rq)
3106 		account_entity_enqueue(cfs_rq, se);
3107 
3108 }
3109 
3110 void reweight_task(struct task_struct *p, int prio)
3111 {
3112 	struct sched_entity *se = &p->se;
3113 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
3114 	struct load_weight *load = &se->load;
3115 	unsigned long weight = scale_load(sched_prio_to_weight[prio]);
3116 
3117 	reweight_entity(cfs_rq, se, weight);
3118 	load->inv_weight = sched_prio_to_wmult[prio];
3119 }
3120 
3121 #ifdef CONFIG_FAIR_GROUP_SCHED
3122 #ifdef CONFIG_SMP
3123 /*
3124  * All this does is approximate the hierarchical proportion which includes that
3125  * global sum we all love to hate.
3126  *
3127  * That is, the weight of a group entity, is the proportional share of the
3128  * group weight based on the group runqueue weights. That is:
3129  *
3130  *                     tg->weight * grq->load.weight
3131  *   ge->load.weight = -----------------------------               (1)
3132  *			  \Sum grq->load.weight
3133  *
3134  * Now, because computing that sum is prohibitively expensive to compute (been
3135  * there, done that) we approximate it with this average stuff. The average
3136  * moves slower and therefore the approximation is cheaper and more stable.
3137  *
3138  * So instead of the above, we substitute:
3139  *
3140  *   grq->load.weight -> grq->avg.load_avg                         (2)
3141  *
3142  * which yields the following:
3143  *
3144  *                     tg->weight * grq->avg.load_avg
3145  *   ge->load.weight = ------------------------------              (3)
3146  *				tg->load_avg
3147  *
3148  * Where: tg->load_avg ~= \Sum grq->avg.load_avg
3149  *
3150  * That is shares_avg, and it is right (given the approximation (2)).
3151  *
3152  * The problem with it is that because the average is slow -- it was designed
3153  * to be exactly that of course -- this leads to transients in boundary
3154  * conditions. In specific, the case where the group was idle and we start the
3155  * one task. It takes time for our CPU's grq->avg.load_avg to build up,
3156  * yielding bad latency etc..
3157  *
3158  * Now, in that special case (1) reduces to:
3159  *
3160  *                     tg->weight * grq->load.weight
3161  *   ge->load.weight = ----------------------------- = tg->weight   (4)
3162  *			    grp->load.weight
3163  *
3164  * That is, the sum collapses because all other CPUs are idle; the UP scenario.
3165  *
3166  * So what we do is modify our approximation (3) to approach (4) in the (near)
3167  * UP case, like:
3168  *
3169  *   ge->load.weight =
3170  *
3171  *              tg->weight * grq->load.weight
3172  *     ---------------------------------------------------         (5)
3173  *     tg->load_avg - grq->avg.load_avg + grq->load.weight
3174  *
3175  * But because grq->load.weight can drop to 0, resulting in a divide by zero,
3176  * we need to use grq->avg.load_avg as its lower bound, which then gives:
3177  *
3178  *
3179  *                     tg->weight * grq->load.weight
3180  *   ge->load.weight = -----------------------------		   (6)
3181  *				tg_load_avg'
3182  *
3183  * Where:
3184  *
3185  *   tg_load_avg' = tg->load_avg - grq->avg.load_avg +
3186  *                  max(grq->load.weight, grq->avg.load_avg)
3187  *
3188  * And that is shares_weight and is icky. In the (near) UP case it approaches
3189  * (4) while in the normal case it approaches (3). It consistently
3190  * overestimates the ge->load.weight and therefore:
3191  *
3192  *   \Sum ge->load.weight >= tg->weight
3193  *
3194  * hence icky!
3195  */
3196 static long calc_group_shares(struct cfs_rq *cfs_rq)
3197 {
3198 	long tg_weight, tg_shares, load, shares;
3199 	struct task_group *tg = cfs_rq->tg;
3200 
3201 	tg_shares = READ_ONCE(tg->shares);
3202 
3203 	load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
3204 
3205 	tg_weight = atomic_long_read(&tg->load_avg);
3206 
3207 	/* Ensure tg_weight >= load */
3208 	tg_weight -= cfs_rq->tg_load_avg_contrib;
3209 	tg_weight += load;
3210 
3211 	shares = (tg_shares * load);
3212 	if (tg_weight)
3213 		shares /= tg_weight;
3214 
3215 	/*
3216 	 * MIN_SHARES has to be unscaled here to support per-CPU partitioning
3217 	 * of a group with small tg->shares value. It is a floor value which is
3218 	 * assigned as a minimum load.weight to the sched_entity representing
3219 	 * the group on a CPU.
3220 	 *
3221 	 * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
3222 	 * on an 8-core system with 8 tasks each runnable on one CPU shares has
3223 	 * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
3224 	 * case no task is runnable on a CPU MIN_SHARES=2 should be returned
3225 	 * instead of 0.
3226 	 */
3227 	return clamp_t(long, shares, MIN_SHARES, tg_shares);
3228 }
3229 #endif /* CONFIG_SMP */
3230 
3231 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
3232 
3233 /*
3234  * Recomputes the group entity based on the current state of its group
3235  * runqueue.
3236  */
3237 static void update_cfs_group(struct sched_entity *se)
3238 {
3239 	struct cfs_rq *gcfs_rq = group_cfs_rq(se);
3240 	long shares;
3241 
3242 	if (!gcfs_rq)
3243 		return;
3244 
3245 	if (throttled_hierarchy(gcfs_rq))
3246 		return;
3247 
3248 #ifndef CONFIG_SMP
3249 	shares = READ_ONCE(gcfs_rq->tg->shares);
3250 
3251 	if (likely(se->load.weight == shares))
3252 		return;
3253 #else
3254 	shares   = calc_group_shares(gcfs_rq);
3255 #endif
3256 
3257 	reweight_entity(cfs_rq_of(se), se, shares);
3258 }
3259 
3260 #else /* CONFIG_FAIR_GROUP_SCHED */
3261 static inline void update_cfs_group(struct sched_entity *se)
3262 {
3263 }
3264 #endif /* CONFIG_FAIR_GROUP_SCHED */
3265 
3266 static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
3267 {
3268 	struct rq *rq = rq_of(cfs_rq);
3269 
3270 	if (&rq->cfs == cfs_rq) {
3271 		/*
3272 		 * There are a few boundary cases this might miss but it should
3273 		 * get called often enough that that should (hopefully) not be
3274 		 * a real problem.
3275 		 *
3276 		 * It will not get called when we go idle, because the idle
3277 		 * thread is a different class (!fair), nor will the utilization
3278 		 * number include things like RT tasks.
3279 		 *
3280 		 * As is, the util number is not freq-invariant (we'd have to
3281 		 * implement arch_scale_freq_capacity() for that).
3282 		 *
3283 		 * See cpu_util().
3284 		 */
3285 		cpufreq_update_util(rq, flags);
3286 	}
3287 }
3288 
3289 #ifdef CONFIG_SMP
3290 #ifdef CONFIG_FAIR_GROUP_SCHED
3291 /**
3292  * update_tg_load_avg - update the tg's load avg
3293  * @cfs_rq: the cfs_rq whose avg changed
3294  * @force: update regardless of how small the difference
3295  *
3296  * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
3297  * However, because tg->load_avg is a global value there are performance
3298  * considerations.
3299  *
3300  * In order to avoid having to look at the other cfs_rq's, we use a
3301  * differential update where we store the last value we propagated. This in
3302  * turn allows skipping updates if the differential is 'small'.
3303  *
3304  * Updating tg's load_avg is necessary before update_cfs_share().
3305  */
3306 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
3307 {
3308 	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
3309 
3310 	/*
3311 	 * No need to update load_avg for root_task_group as it is not used.
3312 	 */
3313 	if (cfs_rq->tg == &root_task_group)
3314 		return;
3315 
3316 	if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
3317 		atomic_long_add(delta, &cfs_rq->tg->load_avg);
3318 		cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
3319 	}
3320 }
3321 
3322 /*
3323  * Called within set_task_rq() right before setting a task's CPU. The
3324  * caller only guarantees p->pi_lock is held; no other assumptions,
3325  * including the state of rq->lock, should be made.
3326  */
3327 void set_task_rq_fair(struct sched_entity *se,
3328 		      struct cfs_rq *prev, struct cfs_rq *next)
3329 {
3330 	u64 p_last_update_time;
3331 	u64 n_last_update_time;
3332 
3333 	if (!sched_feat(ATTACH_AGE_LOAD))
3334 		return;
3335 
3336 	/*
3337 	 * We are supposed to update the task to "current" time, then its up to
3338 	 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
3339 	 * getting what current time is, so simply throw away the out-of-date
3340 	 * time. This will result in the wakee task is less decayed, but giving
3341 	 * the wakee more load sounds not bad.
3342 	 */
3343 	if (!(se->avg.last_update_time && prev))
3344 		return;
3345 
3346 #ifndef CONFIG_64BIT
3347 	{
3348 		u64 p_last_update_time_copy;
3349 		u64 n_last_update_time_copy;
3350 
3351 		do {
3352 			p_last_update_time_copy = prev->load_last_update_time_copy;
3353 			n_last_update_time_copy = next->load_last_update_time_copy;
3354 
3355 			smp_rmb();
3356 
3357 			p_last_update_time = prev->avg.last_update_time;
3358 			n_last_update_time = next->avg.last_update_time;
3359 
3360 		} while (p_last_update_time != p_last_update_time_copy ||
3361 			 n_last_update_time != n_last_update_time_copy);
3362 	}
3363 #else
3364 	p_last_update_time = prev->avg.last_update_time;
3365 	n_last_update_time = next->avg.last_update_time;
3366 #endif
3367 	__update_load_avg_blocked_se(p_last_update_time, se);
3368 	se->avg.last_update_time = n_last_update_time;
3369 }
3370 
3371 
3372 /*
3373  * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
3374  * propagate its contribution. The key to this propagation is the invariant
3375  * that for each group:
3376  *
3377  *   ge->avg == grq->avg						(1)
3378  *
3379  * _IFF_ we look at the pure running and runnable sums. Because they
3380  * represent the very same entity, just at different points in the hierarchy.
3381  *
3382  * Per the above update_tg_cfs_util() and update_tg_cfs_runnable() are trivial
3383  * and simply copies the running/runnable sum over (but still wrong, because
3384  * the group entity and group rq do not have their PELT windows aligned).
3385  *
3386  * However, update_tg_cfs_load() is more complex. So we have:
3387  *
3388  *   ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg		(2)
3389  *
3390  * And since, like util, the runnable part should be directly transferable,
3391  * the following would _appear_ to be the straight forward approach:
3392  *
3393  *   grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg	(3)
3394  *
3395  * And per (1) we have:
3396  *
3397  *   ge->avg.runnable_avg == grq->avg.runnable_avg
3398  *
3399  * Which gives:
3400  *
3401  *                      ge->load.weight * grq->avg.load_avg
3402  *   ge->avg.load_avg = -----------------------------------		(4)
3403  *                               grq->load.weight
3404  *
3405  * Except that is wrong!
3406  *
3407  * Because while for entities historical weight is not important and we
3408  * really only care about our future and therefore can consider a pure
3409  * runnable sum, runqueues can NOT do this.
3410  *
3411  * We specifically want runqueues to have a load_avg that includes
3412  * historical weights. Those represent the blocked load, the load we expect
3413  * to (shortly) return to us. This only works by keeping the weights as
3414  * integral part of the sum. We therefore cannot decompose as per (3).
3415  *
3416  * Another reason this doesn't work is that runnable isn't a 0-sum entity.
3417  * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
3418  * rq itself is runnable anywhere between 2/3 and 1 depending on how the
3419  * runnable section of these tasks overlap (or not). If they were to perfectly
3420  * align the rq as a whole would be runnable 2/3 of the time. If however we
3421  * always have at least 1 runnable task, the rq as a whole is always runnable.
3422  *
3423  * So we'll have to approximate.. :/
3424  *
3425  * Given the constraint:
3426  *
3427  *   ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
3428  *
3429  * We can construct a rule that adds runnable to a rq by assuming minimal
3430  * overlap.
3431  *
3432  * On removal, we'll assume each task is equally runnable; which yields:
3433  *
3434  *   grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
3435  *
3436  * XXX: only do this for the part of runnable > running ?
3437  *
3438  */
3439 
3440 static inline void
3441 update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3442 {
3443 	long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;
3444 
3445 	/* Nothing to update */
3446 	if (!delta)
3447 		return;
3448 
3449 	/*
3450 	 * The relation between sum and avg is:
3451 	 *
3452 	 *   LOAD_AVG_MAX - 1024 + sa->period_contrib
3453 	 *
3454 	 * however, the PELT windows are not aligned between grq and gse.
3455 	 */
3456 
3457 	/* Set new sched_entity's utilization */
3458 	se->avg.util_avg = gcfs_rq->avg.util_avg;
3459 	se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX;
3460 
3461 	/* Update parent cfs_rq utilization */
3462 	add_positive(&cfs_rq->avg.util_avg, delta);
3463 	cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX;
3464 }
3465 
3466 static inline void
3467 update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3468 {
3469 	long delta = gcfs_rq->avg.runnable_avg - se->avg.runnable_avg;
3470 
3471 	/* Nothing to update */
3472 	if (!delta)
3473 		return;
3474 
3475 	/*
3476 	 * The relation between sum and avg is:
3477 	 *
3478 	 *   LOAD_AVG_MAX - 1024 + sa->period_contrib
3479 	 *
3480 	 * however, the PELT windows are not aligned between grq and gse.
3481 	 */
3482 
3483 	/* Set new sched_entity's runnable */
3484 	se->avg.runnable_avg = gcfs_rq->avg.runnable_avg;
3485 	se->avg.runnable_sum = se->avg.runnable_avg * LOAD_AVG_MAX;
3486 
3487 	/* Update parent cfs_rq runnable */
3488 	add_positive(&cfs_rq->avg.runnable_avg, delta);
3489 	cfs_rq->avg.runnable_sum = cfs_rq->avg.runnable_avg * LOAD_AVG_MAX;
3490 }
3491 
3492 static inline void
3493 update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3494 {
3495 	long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
3496 	unsigned long load_avg;
3497 	u64 load_sum = 0;
3498 	s64 delta_sum;
3499 
3500 	if (!runnable_sum)
3501 		return;
3502 
3503 	gcfs_rq->prop_runnable_sum = 0;
3504 
3505 	if (runnable_sum >= 0) {
3506 		/*
3507 		 * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
3508 		 * the CPU is saturated running == runnable.
3509 		 */
3510 		runnable_sum += se->avg.load_sum;
3511 		runnable_sum = min(runnable_sum, (long)LOAD_AVG_MAX);
3512 	} else {
3513 		/*
3514 		 * Estimate the new unweighted runnable_sum of the gcfs_rq by
3515 		 * assuming all tasks are equally runnable.
3516 		 */
3517 		if (scale_load_down(gcfs_rq->load.weight)) {
3518 			load_sum = div_s64(gcfs_rq->avg.load_sum,
3519 				scale_load_down(gcfs_rq->load.weight));
3520 		}
3521 
3522 		/* But make sure to not inflate se's runnable */
3523 		runnable_sum = min(se->avg.load_sum, load_sum);
3524 	}
3525 
3526 	/*
3527 	 * runnable_sum can't be lower than running_sum
3528 	 * Rescale running sum to be in the same range as runnable sum
3529 	 * running_sum is in [0 : LOAD_AVG_MAX <<  SCHED_CAPACITY_SHIFT]
3530 	 * runnable_sum is in [0 : LOAD_AVG_MAX]
3531 	 */
3532 	running_sum = se->avg.util_sum >> SCHED_CAPACITY_SHIFT;
3533 	runnable_sum = max(runnable_sum, running_sum);
3534 
3535 	load_sum = (s64)se_weight(se) * runnable_sum;
3536 	load_avg = div_s64(load_sum, LOAD_AVG_MAX);
3537 
3538 	delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
3539 	delta_avg = load_avg - se->avg.load_avg;
3540 
3541 	se->avg.load_sum = runnable_sum;
3542 	se->avg.load_avg = load_avg;
3543 	add_positive(&cfs_rq->avg.load_avg, delta_avg);
3544 	add_positive(&cfs_rq->avg.load_sum, delta_sum);
3545 }
3546 
3547 static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
3548 {
3549 	cfs_rq->propagate = 1;
3550 	cfs_rq->prop_runnable_sum += runnable_sum;
3551 }
3552 
3553 /* Update task and its cfs_rq load average */
3554 static inline int propagate_entity_load_avg(struct sched_entity *se)
3555 {
3556 	struct cfs_rq *cfs_rq, *gcfs_rq;
3557 
3558 	if (entity_is_task(se))
3559 		return 0;
3560 
3561 	gcfs_rq = group_cfs_rq(se);
3562 	if (!gcfs_rq->propagate)
3563 		return 0;
3564 
3565 	gcfs_rq->propagate = 0;
3566 
3567 	cfs_rq = cfs_rq_of(se);
3568 
3569 	add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
3570 
3571 	update_tg_cfs_util(cfs_rq, se, gcfs_rq);
3572 	update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
3573 	update_tg_cfs_load(cfs_rq, se, gcfs_rq);
3574 
3575 	trace_pelt_cfs_tp(cfs_rq);
3576 	trace_pelt_se_tp(se);
3577 
3578 	return 1;
3579 }
3580 
3581 /*
3582  * Check if we need to update the load and the utilization of a blocked
3583  * group_entity:
3584  */
3585 static inline bool skip_blocked_update(struct sched_entity *se)
3586 {
3587 	struct cfs_rq *gcfs_rq = group_cfs_rq(se);
3588 
3589 	/*
3590 	 * If sched_entity still have not zero load or utilization, we have to
3591 	 * decay it:
3592 	 */
3593 	if (se->avg.load_avg || se->avg.util_avg)
3594 		return false;
3595 
3596 	/*
3597 	 * If there is a pending propagation, we have to update the load and
3598 	 * the utilization of the sched_entity:
3599 	 */
3600 	if (gcfs_rq->propagate)
3601 		return false;
3602 
3603 	/*
3604 	 * Otherwise, the load and the utilization of the sched_entity is
3605 	 * already zero and there is no pending propagation, so it will be a
3606 	 * waste of time to try to decay it:
3607 	 */
3608 	return true;
3609 }
3610 
3611 #else /* CONFIG_FAIR_GROUP_SCHED */
3612 
3613 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
3614 
3615 static inline int propagate_entity_load_avg(struct sched_entity *se)
3616 {
3617 	return 0;
3618 }
3619 
3620 static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
3621 
3622 #endif /* CONFIG_FAIR_GROUP_SCHED */
3623 
3624 /**
3625  * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
3626  * @now: current time, as per cfs_rq_clock_pelt()
3627  * @cfs_rq: cfs_rq to update
3628  *
3629  * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
3630  * avg. The immediate corollary is that all (fair) tasks must be attached, see
3631  * post_init_entity_util_avg().
3632  *
3633  * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
3634  *
3635  * Returns true if the load decayed or we removed load.
3636  *
3637  * Since both these conditions indicate a changed cfs_rq->avg.load we should
3638  * call update_tg_load_avg() when this function returns true.
3639  */
3640 static inline int
3641 update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3642 {
3643 	unsigned long removed_load = 0, removed_util = 0, removed_runnable = 0;
3644 	struct sched_avg *sa = &cfs_rq->avg;
3645 	int decayed = 0;
3646 
3647 	if (cfs_rq->removed.nr) {
3648 		unsigned long r;
3649 		u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
3650 
3651 		raw_spin_lock(&cfs_rq->removed.lock);
3652 		swap(cfs_rq->removed.util_avg, removed_util);
3653 		swap(cfs_rq->removed.load_avg, removed_load);
3654 		swap(cfs_rq->removed.runnable_avg, removed_runnable);
3655 		cfs_rq->removed.nr = 0;
3656 		raw_spin_unlock(&cfs_rq->removed.lock);
3657 
3658 		r = removed_load;
3659 		sub_positive(&sa->load_avg, r);
3660 		sub_positive(&sa->load_sum, r * divider);
3661 
3662 		r = removed_util;
3663 		sub_positive(&sa->util_avg, r);
3664 		sub_positive(&sa->util_sum, r * divider);
3665 
3666 		r = removed_runnable;
3667 		sub_positive(&sa->runnable_avg, r);
3668 		sub_positive(&sa->runnable_sum, r * divider);
3669 
3670 		/*
3671 		 * removed_runnable is the unweighted version of removed_load so we
3672 		 * can use it to estimate removed_load_sum.
3673 		 */
3674 		add_tg_cfs_propagate(cfs_rq,
3675 			-(long)(removed_runnable * divider) >> SCHED_CAPACITY_SHIFT);
3676 
3677 		decayed = 1;
3678 	}
3679 
3680 	decayed |= __update_load_avg_cfs_rq(now, cfs_rq);
3681 
3682 #ifndef CONFIG_64BIT
3683 	smp_wmb();
3684 	cfs_rq->load_last_update_time_copy = sa->last_update_time;
3685 #endif
3686 
3687 	return decayed;
3688 }
3689 
3690 /**
3691  * attach_entity_load_avg - attach this entity to its cfs_rq load avg
3692  * @cfs_rq: cfs_rq to attach to
3693  * @se: sched_entity to attach
3694  *
3695  * Must call update_cfs_rq_load_avg() before this, since we rely on
3696  * cfs_rq->avg.last_update_time being current.
3697  */
3698 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3699 {
3700 	u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib;
3701 
3702 	/*
3703 	 * When we attach the @se to the @cfs_rq, we must align the decay
3704 	 * window because without that, really weird and wonderful things can
3705 	 * happen.
3706 	 *
3707 	 * XXX illustrate
3708 	 */
3709 	se->avg.last_update_time = cfs_rq->avg.last_update_time;
3710 	se->avg.period_contrib = cfs_rq->avg.period_contrib;
3711 
3712 	/*
3713 	 * Hell(o) Nasty stuff.. we need to recompute _sum based on the new
3714 	 * period_contrib. This isn't strictly correct, but since we're
3715 	 * entirely outside of the PELT hierarchy, nobody cares if we truncate
3716 	 * _sum a little.
3717 	 */
3718 	se->avg.util_sum = se->avg.util_avg * divider;
3719 
3720 	se->avg.runnable_sum = se->avg.runnable_avg * divider;
3721 
3722 	se->avg.load_sum = divider;
3723 	if (se_weight(se)) {
3724 		se->avg.load_sum =
3725 			div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se));
3726 	}
3727 
3728 	enqueue_load_avg(cfs_rq, se);
3729 	cfs_rq->avg.util_avg += se->avg.util_avg;
3730 	cfs_rq->avg.util_sum += se->avg.util_sum;
3731 	cfs_rq->avg.runnable_avg += se->avg.runnable_avg;
3732 	cfs_rq->avg.runnable_sum += se->avg.runnable_sum;
3733 
3734 	add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
3735 
3736 	cfs_rq_util_change(cfs_rq, 0);
3737 
3738 	trace_pelt_cfs_tp(cfs_rq);
3739 }
3740 
3741 /**
3742  * detach_entity_load_avg - detach this entity from its cfs_rq load avg
3743  * @cfs_rq: cfs_rq to detach from
3744  * @se: sched_entity to detach
3745  *
3746  * Must call update_cfs_rq_load_avg() before this, since we rely on
3747  * cfs_rq->avg.last_update_time being current.
3748  */
3749 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3750 {
3751 	dequeue_load_avg(cfs_rq, se);
3752 	sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
3753 	sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3754 	sub_positive(&cfs_rq->avg.runnable_avg, se->avg.runnable_avg);
3755 	sub_positive(&cfs_rq->avg.runnable_sum, se->avg.runnable_sum);
3756 
3757 	add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
3758 
3759 	cfs_rq_util_change(cfs_rq, 0);
3760 
3761 	trace_pelt_cfs_tp(cfs_rq);
3762 }
3763 
3764 /*
3765  * Optional action to be done while updating the load average
3766  */
3767 #define UPDATE_TG	0x1
3768 #define SKIP_AGE_LOAD	0x2
3769 #define DO_ATTACH	0x4
3770 
3771 /* Update task and its cfs_rq load average */
3772 static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3773 {
3774 	u64 now = cfs_rq_clock_pelt(cfs_rq);
3775 	int decayed;
3776 
3777 	/*
3778 	 * Track task load average for carrying it to new CPU after migrated, and
3779 	 * track group sched_entity load average for task_h_load calc in migration
3780 	 */
3781 	if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
3782 		__update_load_avg_se(now, cfs_rq, se);
3783 
3784 	decayed  = update_cfs_rq_load_avg(now, cfs_rq);
3785 	decayed |= propagate_entity_load_avg(se);
3786 
3787 	if (!se->avg.last_update_time && (flags & DO_ATTACH)) {
3788 
3789 		/*
3790 		 * DO_ATTACH means we're here from enqueue_entity().
3791 		 * !last_update_time means we've passed through
3792 		 * migrate_task_rq_fair() indicating we migrated.
3793 		 *
3794 		 * IOW we're enqueueing a task on a new CPU.
3795 		 */
3796 		attach_entity_load_avg(cfs_rq, se);
3797 		update_tg_load_avg(cfs_rq, 0);
3798 
3799 	} else if (decayed) {
3800 		cfs_rq_util_change(cfs_rq, 0);
3801 
3802 		if (flags & UPDATE_TG)
3803 			update_tg_load_avg(cfs_rq, 0);
3804 	}
3805 }
3806 
3807 #ifndef CONFIG_64BIT
3808 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3809 {
3810 	u64 last_update_time_copy;
3811 	u64 last_update_time;
3812 
3813 	do {
3814 		last_update_time_copy = cfs_rq->load_last_update_time_copy;
3815 		smp_rmb();
3816 		last_update_time = cfs_rq->avg.last_update_time;
3817 	} while (last_update_time != last_update_time_copy);
3818 
3819 	return last_update_time;
3820 }
3821 #else
3822 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3823 {
3824 	return cfs_rq->avg.last_update_time;
3825 }
3826 #endif
3827 
3828 /*
3829  * Synchronize entity load avg of dequeued entity without locking
3830  * the previous rq.
3831  */
3832 static void sync_entity_load_avg(struct sched_entity *se)
3833 {
3834 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
3835 	u64 last_update_time;
3836 
3837 	last_update_time = cfs_rq_last_update_time(cfs_rq);
3838 	__update_load_avg_blocked_se(last_update_time, se);
3839 }
3840 
3841 /*
3842  * Task first catches up with cfs_rq, and then subtract
3843  * itself from the cfs_rq (task must be off the queue now).
3844  */
3845 static void remove_entity_load_avg(struct sched_entity *se)
3846 {
3847 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
3848 	unsigned long flags;
3849 
3850 	/*
3851 	 * tasks cannot exit without having gone through wake_up_new_task() ->
3852 	 * post_init_entity_util_avg() which will have added things to the
3853 	 * cfs_rq, so we can remove unconditionally.
3854 	 */
3855 
3856 	sync_entity_load_avg(se);
3857 
3858 	raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
3859 	++cfs_rq->removed.nr;
3860 	cfs_rq->removed.util_avg	+= se->avg.util_avg;
3861 	cfs_rq->removed.load_avg	+= se->avg.load_avg;
3862 	cfs_rq->removed.runnable_avg	+= se->avg.runnable_avg;
3863 	raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
3864 }
3865 
3866 static inline unsigned long cfs_rq_runnable_avg(struct cfs_rq *cfs_rq)
3867 {
3868 	return cfs_rq->avg.runnable_avg;
3869 }
3870 
3871 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
3872 {
3873 	return cfs_rq->avg.load_avg;
3874 }
3875 
3876 static inline unsigned long task_util(struct task_struct *p)
3877 {
3878 	return READ_ONCE(p->se.avg.util_avg);
3879 }
3880 
3881 static inline unsigned long _task_util_est(struct task_struct *p)
3882 {
3883 	struct util_est ue = READ_ONCE(p->se.avg.util_est);
3884 
3885 	return (max(ue.ewma, ue.enqueued) | UTIL_AVG_UNCHANGED);
3886 }
3887 
3888 static inline unsigned long task_util_est(struct task_struct *p)
3889 {
3890 	return max(task_util(p), _task_util_est(p));
3891 }
3892 
3893 #ifdef CONFIG_UCLAMP_TASK
3894 static inline unsigned long uclamp_task_util(struct task_struct *p)
3895 {
3896 	return clamp(task_util_est(p),
3897 		     uclamp_eff_value(p, UCLAMP_MIN),
3898 		     uclamp_eff_value(p, UCLAMP_MAX));
3899 }
3900 #else
3901 static inline unsigned long uclamp_task_util(struct task_struct *p)
3902 {
3903 	return task_util_est(p);
3904 }
3905 #endif
3906 
3907 static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
3908 				    struct task_struct *p)
3909 {
3910 	unsigned int enqueued;
3911 
3912 	if (!sched_feat(UTIL_EST))
3913 		return;
3914 
3915 	/* Update root cfs_rq's estimated utilization */
3916 	enqueued  = cfs_rq->avg.util_est.enqueued;
3917 	enqueued += _task_util_est(p);
3918 	WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
3919 }
3920 
3921 /*
3922  * Check if a (signed) value is within a specified (unsigned) margin,
3923  * based on the observation that:
3924  *
3925  *     abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
3926  *
3927  * NOTE: this only works when value + maring < INT_MAX.
3928  */
3929 static inline bool within_margin(int value, int margin)
3930 {
3931 	return ((unsigned int)(value + margin - 1) < (2 * margin - 1));
3932 }
3933 
3934 static void
3935 util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
3936 {
3937 	long last_ewma_diff;
3938 	struct util_est ue;
3939 	int cpu;
3940 
3941 	if (!sched_feat(UTIL_EST))
3942 		return;
3943 
3944 	/* Update root cfs_rq's estimated utilization */
3945 	ue.enqueued  = cfs_rq->avg.util_est.enqueued;
3946 	ue.enqueued -= min_t(unsigned int, ue.enqueued, _task_util_est(p));
3947 	WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued);
3948 
3949 	/*
3950 	 * Skip update of task's estimated utilization when the task has not
3951 	 * yet completed an activation, e.g. being migrated.
3952 	 */
3953 	if (!task_sleep)
3954 		return;
3955 
3956 	/*
3957 	 * If the PELT values haven't changed since enqueue time,
3958 	 * skip the util_est update.
3959 	 */
3960 	ue = p->se.avg.util_est;
3961 	if (ue.enqueued & UTIL_AVG_UNCHANGED)
3962 		return;
3963 
3964 	/*
3965 	 * Reset EWMA on utilization increases, the moving average is used only
3966 	 * to smooth utilization decreases.
3967 	 */
3968 	ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED);
3969 	if (sched_feat(UTIL_EST_FASTUP)) {
3970 		if (ue.ewma < ue.enqueued) {
3971 			ue.ewma = ue.enqueued;
3972 			goto done;
3973 		}
3974 	}
3975 
3976 	/*
3977 	 * Skip update of task's estimated utilization when its EWMA is
3978 	 * already ~1% close to its last activation value.
3979 	 */
3980 	last_ewma_diff = ue.enqueued - ue.ewma;
3981 	if (within_margin(last_ewma_diff, (SCHED_CAPACITY_SCALE / 100)))
3982 		return;
3983 
3984 	/*
3985 	 * To avoid overestimation of actual task utilization, skip updates if
3986 	 * we cannot grant there is idle time in this CPU.
3987 	 */
3988 	cpu = cpu_of(rq_of(cfs_rq));
3989 	if (task_util(p) > capacity_orig_of(cpu))
3990 		return;
3991 
3992 	/*
3993 	 * Update Task's estimated utilization
3994 	 *
3995 	 * When *p completes an activation we can consolidate another sample
3996 	 * of the task size. This is done by storing the current PELT value
3997 	 * as ue.enqueued and by using this value to update the Exponential
3998 	 * Weighted Moving Average (EWMA):
3999 	 *
4000 	 *  ewma(t) = w *  task_util(p) + (1-w) * ewma(t-1)
4001 	 *          = w *  task_util(p) +         ewma(t-1)  - w * ewma(t-1)
4002 	 *          = w * (task_util(p) -         ewma(t-1)) +     ewma(t-1)
4003 	 *          = w * (      last_ewma_diff            ) +     ewma(t-1)
4004 	 *          = w * (last_ewma_diff  +  ewma(t-1) / w)
4005 	 *
4006 	 * Where 'w' is the weight of new samples, which is configured to be
4007 	 * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
4008 	 */
4009 	ue.ewma <<= UTIL_EST_WEIGHT_SHIFT;
4010 	ue.ewma  += last_ewma_diff;
4011 	ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
4012 done:
4013 	WRITE_ONCE(p->se.avg.util_est, ue);
4014 }
4015 
4016 static inline int task_fits_capacity(struct task_struct *p, long capacity)
4017 {
4018 	return fits_capacity(uclamp_task_util(p), capacity);
4019 }
4020 
4021 static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
4022 {
4023 	if (!static_branch_unlikely(&sched_asym_cpucapacity))
4024 		return;
4025 
4026 	if (!p) {
4027 		rq->misfit_task_load = 0;
4028 		return;
4029 	}
4030 
4031 	if (task_fits_capacity(p, capacity_of(cpu_of(rq)))) {
4032 		rq->misfit_task_load = 0;
4033 		return;
4034 	}
4035 
4036 	rq->misfit_task_load = task_h_load(p);
4037 }
4038 
4039 #else /* CONFIG_SMP */
4040 
4041 #define UPDATE_TG	0x0
4042 #define SKIP_AGE_LOAD	0x0
4043 #define DO_ATTACH	0x0
4044 
4045 static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
4046 {
4047 	cfs_rq_util_change(cfs_rq, 0);
4048 }
4049 
4050 static inline void remove_entity_load_avg(struct sched_entity *se) {}
4051 
4052 static inline void
4053 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
4054 static inline void
4055 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
4056 
4057 static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
4058 {
4059 	return 0;
4060 }
4061 
4062 static inline void
4063 util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
4064 
4065 static inline void
4066 util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p,
4067 		 bool task_sleep) {}
4068 static inline void update_misfit_status(struct task_struct *p, struct rq *rq) {}
4069 
4070 #endif /* CONFIG_SMP */
4071 
4072 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
4073 {
4074 #ifdef CONFIG_SCHED_DEBUG
4075 	s64 d = se->vruntime - cfs_rq->min_vruntime;
4076 
4077 	if (d < 0)
4078 		d = -d;
4079 
4080 	if (d > 3*sysctl_sched_latency)
4081 		schedstat_inc(cfs_rq->nr_spread_over);
4082 #endif
4083 }
4084 
4085 static void
4086 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
4087 {
4088 	u64 vruntime = cfs_rq->min_vruntime;
4089 
4090 	/*
4091 	 * The 'current' period is already promised to the current tasks,
4092 	 * however the extra weight of the new task will slow them down a
4093 	 * little, place the new task so that it fits in the slot that
4094 	 * stays open at the end.
4095 	 */
4096 	if (initial && sched_feat(START_DEBIT))
4097 		vruntime += sched_vslice(cfs_rq, se);
4098 
4099 	/* sleeps up to a single latency don't count. */
4100 	if (!initial) {
4101 		unsigned long thresh = sysctl_sched_latency;
4102 
4103 		/*
4104 		 * Halve their sleep time's effect, to allow
4105 		 * for a gentler effect of sleepers:
4106 		 */
4107 		if (sched_feat(GENTLE_FAIR_SLEEPERS))
4108 			thresh >>= 1;
4109 
4110 		vruntime -= thresh;
4111 	}
4112 
4113 	/* ensure we never gain time by being placed backwards. */
4114 	se->vruntime = max_vruntime(se->vruntime, vruntime);
4115 }
4116 
4117 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
4118 
4119 static inline void check_schedstat_required(void)
4120 {
4121 #ifdef CONFIG_SCHEDSTATS
4122 	if (schedstat_enabled())
4123 		return;
4124 
4125 	/* Force schedstat enabled if a dependent tracepoint is active */
4126 	if (trace_sched_stat_wait_enabled()    ||
4127 			trace_sched_stat_sleep_enabled()   ||
4128 			trace_sched_stat_iowait_enabled()  ||
4129 			trace_sched_stat_blocked_enabled() ||
4130 			trace_sched_stat_runtime_enabled())  {
4131 		printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
4132 			     "stat_blocked and stat_runtime require the "
4133 			     "kernel parameter schedstats=enable or "
4134 			     "kernel.sched_schedstats=1\n");
4135 	}
4136 #endif
4137 }
4138 
4139 static inline bool cfs_bandwidth_used(void);
4140 
4141 /*
4142  * MIGRATION
4143  *
4144  *	dequeue
4145  *	  update_curr()
4146  *	    update_min_vruntime()
4147  *	  vruntime -= min_vruntime
4148  *
4149  *	enqueue
4150  *	  update_curr()
4151  *	    update_min_vruntime()
4152  *	  vruntime += min_vruntime
4153  *
4154  * this way the vruntime transition between RQs is done when both
4155  * min_vruntime are up-to-date.
4156  *
4157  * WAKEUP (remote)
4158  *
4159  *	->migrate_task_rq_fair() (p->state == TASK_WAKING)
4160  *	  vruntime -= min_vruntime
4161  *
4162  *	enqueue
4163  *	  update_curr()
4164  *	    update_min_vruntime()
4165  *	  vruntime += min_vruntime
4166  *
4167  * this way we don't have the most up-to-date min_vruntime on the originating
4168  * CPU and an up-to-date min_vruntime on the destination CPU.
4169  */
4170 
4171 static void
4172 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4173 {
4174 	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
4175 	bool curr = cfs_rq->curr == se;
4176 
4177 	/*
4178 	 * If we're the current task, we must renormalise before calling
4179 	 * update_curr().
4180 	 */
4181 	if (renorm && curr)
4182 		se->vruntime += cfs_rq->min_vruntime;
4183 
4184 	update_curr(cfs_rq);
4185 
4186 	/*
4187 	 * Otherwise, renormalise after, such that we're placed at the current
4188 	 * moment in time, instead of some random moment in the past. Being
4189 	 * placed in the past could significantly boost this task to the
4190 	 * fairness detriment of existing tasks.
4191 	 */
4192 	if (renorm && !curr)
4193 		se->vruntime += cfs_rq->min_vruntime;
4194 
4195 	/*
4196 	 * When enqueuing a sched_entity, we must:
4197 	 *   - Update loads to have both entity and cfs_rq synced with now.
4198 	 *   - Add its load to cfs_rq->runnable_avg
4199 	 *   - For group_entity, update its weight to reflect the new share of
4200 	 *     its group cfs_rq
4201 	 *   - Add its new weight to cfs_rq->load.weight
4202 	 */
4203 	update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
4204 	se_update_runnable(se);
4205 	update_cfs_group(se);
4206 	account_entity_enqueue(cfs_rq, se);
4207 
4208 	if (flags & ENQUEUE_WAKEUP)
4209 		place_entity(cfs_rq, se, 0);
4210 
4211 	check_schedstat_required();
4212 	update_stats_enqueue(cfs_rq, se, flags);
4213 	check_spread(cfs_rq, se);
4214 	if (!curr)
4215 		__enqueue_entity(cfs_rq, se);
4216 	se->on_rq = 1;
4217 
4218 	/*
4219 	 * When bandwidth control is enabled, cfs might have been removed
4220 	 * because of a parent been throttled but cfs->nr_running > 1. Try to
4221 	 * add it unconditionnally.
4222 	 */
4223 	if (cfs_rq->nr_running == 1 || cfs_bandwidth_used())
4224 		list_add_leaf_cfs_rq(cfs_rq);
4225 
4226 	if (cfs_rq->nr_running == 1)
4227 		check_enqueue_throttle(cfs_rq);
4228 }
4229 
4230 static void __clear_buddies_last(struct sched_entity *se)
4231 {
4232 	for_each_sched_entity(se) {
4233 		struct cfs_rq *cfs_rq = cfs_rq_of(se);
4234 		if (cfs_rq->last != se)
4235 			break;
4236 
4237 		cfs_rq->last = NULL;
4238 	}
4239 }
4240 
4241 static void __clear_buddies_next(struct sched_entity *se)
4242 {
4243 	for_each_sched_entity(se) {
4244 		struct cfs_rq *cfs_rq = cfs_rq_of(se);
4245 		if (cfs_rq->next != se)
4246 			break;
4247 
4248 		cfs_rq->next = NULL;
4249 	}
4250 }
4251 
4252 static void __clear_buddies_skip(struct sched_entity *se)
4253 {
4254 	for_each_sched_entity(se) {
4255 		struct cfs_rq *cfs_rq = cfs_rq_of(se);
4256 		if (cfs_rq->skip != se)
4257 			break;
4258 
4259 		cfs_rq->skip = NULL;
4260 	}
4261 }
4262 
4263 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
4264 {
4265 	if (cfs_rq->last == se)
4266 		__clear_buddies_last(se);
4267 
4268 	if (cfs_rq->next == se)
4269 		__clear_buddies_next(se);
4270 
4271 	if (cfs_rq->skip == se)
4272 		__clear_buddies_skip(se);
4273 }
4274 
4275 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4276 
4277 static void
4278 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4279 {
4280 	/*
4281 	 * Update run-time statistics of the 'current'.
4282 	 */
4283 	update_curr(cfs_rq);
4284 
4285 	/*
4286 	 * When dequeuing a sched_entity, we must:
4287 	 *   - Update loads to have both entity and cfs_rq synced with now.
4288 	 *   - Subtract its load from the cfs_rq->runnable_avg.
4289 	 *   - Subtract its previous weight from cfs_rq->load.weight.
4290 	 *   - For group entity, update its weight to reflect the new share
4291 	 *     of its group cfs_rq.
4292 	 */
4293 	update_load_avg(cfs_rq, se, UPDATE_TG);
4294 	se_update_runnable(se);
4295 
4296 	update_stats_dequeue(cfs_rq, se, flags);
4297 
4298 	clear_buddies(cfs_rq, se);
4299 
4300 	if (se != cfs_rq->curr)
4301 		__dequeue_entity(cfs_rq, se);
4302 	se->on_rq = 0;
4303 	account_entity_dequeue(cfs_rq, se);
4304 
4305 	/*
4306 	 * Normalize after update_curr(); which will also have moved
4307 	 * min_vruntime if @se is the one holding it back. But before doing
4308 	 * update_min_vruntime() again, which will discount @se's position and
4309 	 * can move min_vruntime forward still more.
4310 	 */
4311 	if (!(flags & DEQUEUE_SLEEP))
4312 		se->vruntime -= cfs_rq->min_vruntime;
4313 
4314 	/* return excess runtime on last dequeue */
4315 	return_cfs_rq_runtime(cfs_rq);
4316 
4317 	update_cfs_group(se);
4318 
4319 	/*
4320 	 * Now advance min_vruntime if @se was the entity holding it back,
4321 	 * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
4322 	 * put back on, and if we advance min_vruntime, we'll be placed back
4323 	 * further than we started -- ie. we'll be penalized.
4324 	 */
4325 	if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
4326 		update_min_vruntime(cfs_rq);
4327 }
4328 
4329 /*
4330  * Preempt the current task with a newly woken task if needed:
4331  */
4332 static void
4333 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4334 {
4335 	unsigned long ideal_runtime, delta_exec;
4336 	struct sched_entity *se;
4337 	s64 delta;
4338 
4339 	ideal_runtime = sched_slice(cfs_rq, curr);
4340 	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
4341 	if (delta_exec > ideal_runtime) {
4342 		resched_curr(rq_of(cfs_rq));
4343 		/*
4344 		 * The current task ran long enough, ensure it doesn't get
4345 		 * re-elected due to buddy favours.
4346 		 */
4347 		clear_buddies(cfs_rq, curr);
4348 		return;
4349 	}
4350 
4351 	/*
4352 	 * Ensure that a task that missed wakeup preemption by a
4353 	 * narrow margin doesn't have to wait for a full slice.
4354 	 * This also mitigates buddy induced latencies under load.
4355 	 */
4356 	if (delta_exec < sysctl_sched_min_granularity)
4357 		return;
4358 
4359 	se = __pick_first_entity(cfs_rq);
4360 	delta = curr->vruntime - se->vruntime;
4361 
4362 	if (delta < 0)
4363 		return;
4364 
4365 	if (delta > ideal_runtime)
4366 		resched_curr(rq_of(cfs_rq));
4367 }
4368 
4369 static void
4370 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
4371 {
4372 	/* 'current' is not kept within the tree. */
4373 	if (se->on_rq) {
4374 		/*
4375 		 * Any task has to be enqueued before it get to execute on
4376 		 * a CPU. So account for the time it spent waiting on the
4377 		 * runqueue.
4378 		 */
4379 		update_stats_wait_end(cfs_rq, se);
4380 		__dequeue_entity(cfs_rq, se);
4381 		update_load_avg(cfs_rq, se, UPDATE_TG);
4382 	}
4383 
4384 	update_stats_curr_start(cfs_rq, se);
4385 	cfs_rq->curr = se;
4386 
4387 	/*
4388 	 * Track our maximum slice length, if the CPU's load is at
4389 	 * least twice that of our own weight (i.e. dont track it
4390 	 * when there are only lesser-weight tasks around):
4391 	 */
4392 	if (schedstat_enabled() &&
4393 	    rq_of(cfs_rq)->cfs.load.weight >= 2*se->load.weight) {
4394 		schedstat_set(se->statistics.slice_max,
4395 			max((u64)schedstat_val(se->statistics.slice_max),
4396 			    se->sum_exec_runtime - se->prev_sum_exec_runtime));
4397 	}
4398 
4399 	se->prev_sum_exec_runtime = se->sum_exec_runtime;
4400 }
4401 
4402 static int
4403 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
4404 
4405 /*
4406  * Pick the next process, keeping these things in mind, in this order:
4407  * 1) keep things fair between processes/task groups
4408  * 2) pick the "next" process, since someone really wants that to run
4409  * 3) pick the "last" process, for cache locality
4410  * 4) do not run the "skip" process, if something else is available
4411  */
4412 static struct sched_entity *
4413 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4414 {
4415 	struct sched_entity *left = __pick_first_entity(cfs_rq);
4416 	struct sched_entity *se;
4417 
4418 	/*
4419 	 * If curr is set we have to see if its left of the leftmost entity
4420 	 * still in the tree, provided there was anything in the tree at all.
4421 	 */
4422 	if (!left || (curr && entity_before(curr, left)))
4423 		left = curr;
4424 
4425 	se = left; /* ideally we run the leftmost entity */
4426 
4427 	/*
4428 	 * Avoid running the skip buddy, if running something else can
4429 	 * be done without getting too unfair.
4430 	 */
4431 	if (cfs_rq->skip == se) {
4432 		struct sched_entity *second;
4433 
4434 		if (se == curr) {
4435 			second = __pick_first_entity(cfs_rq);
4436 		} else {
4437 			second = __pick_next_entity(se);
4438 			if (!second || (curr && entity_before(curr, second)))
4439 				second = curr;
4440 		}
4441 
4442 		if (second && wakeup_preempt_entity(second, left) < 1)
4443 			se = second;
4444 	}
4445 
4446 	/*
4447 	 * Prefer last buddy, try to return the CPU to a preempted task.
4448 	 */
4449 	if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
4450 		se = cfs_rq->last;
4451 
4452 	/*
4453 	 * Someone really wants this to run. If it's not unfair, run it.
4454 	 */
4455 	if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
4456 		se = cfs_rq->next;
4457 
4458 	clear_buddies(cfs_rq, se);
4459 
4460 	return se;
4461 }
4462 
4463 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4464 
4465 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
4466 {
4467 	/*
4468 	 * If still on the runqueue then deactivate_task()
4469 	 * was not called and update_curr() has to be done:
4470 	 */
4471 	if (prev->on_rq)
4472 		update_curr(cfs_rq);
4473 
4474 	/* throttle cfs_rqs exceeding runtime */
4475 	check_cfs_rq_runtime(cfs_rq);
4476 
4477 	check_spread(cfs_rq, prev);
4478 
4479 	if (prev->on_rq) {
4480 		update_stats_wait_start(cfs_rq, prev);
4481 		/* Put 'current' back into the tree. */
4482 		__enqueue_entity(cfs_rq, prev);
4483 		/* in !on_rq case, update occurred at dequeue */
4484 		update_load_avg(cfs_rq, prev, 0);
4485 	}
4486 	cfs_rq->curr = NULL;
4487 }
4488 
4489 static void
4490 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
4491 {
4492 	/*
4493 	 * Update run-time statistics of the 'current'.
4494 	 */
4495 	update_curr(cfs_rq);
4496 
4497 	/*
4498 	 * Ensure that runnable average is periodically updated.
4499 	 */
4500 	update_load_avg(cfs_rq, curr, UPDATE_TG);
4501 	update_cfs_group(curr);
4502 
4503 #ifdef CONFIG_SCHED_HRTICK
4504 	/*
4505 	 * queued ticks are scheduled to match the slice, so don't bother
4506 	 * validating it and just reschedule.
4507 	 */
4508 	if (queued) {
4509 		resched_curr(rq_of(cfs_rq));
4510 		return;
4511 	}
4512 	/*
4513 	 * don't let the period tick interfere with the hrtick preemption
4514 	 */
4515 	if (!sched_feat(DOUBLE_TICK) &&
4516 			hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
4517 		return;
4518 #endif
4519 
4520 	if (cfs_rq->nr_running > 1)
4521 		check_preempt_tick(cfs_rq, curr);
4522 }
4523 
4524 
4525 /**************************************************
4526  * CFS bandwidth control machinery
4527  */
4528 
4529 #ifdef CONFIG_CFS_BANDWIDTH
4530 
4531 #ifdef CONFIG_JUMP_LABEL
4532 static struct static_key __cfs_bandwidth_used;
4533 
4534 static inline bool cfs_bandwidth_used(void)
4535 {
4536 	return static_key_false(&__cfs_bandwidth_used);
4537 }
4538 
4539 void cfs_bandwidth_usage_inc(void)
4540 {
4541 	static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
4542 }
4543 
4544 void cfs_bandwidth_usage_dec(void)
4545 {
4546 	static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
4547 }
4548 #else /* CONFIG_JUMP_LABEL */
4549 static bool cfs_bandwidth_used(void)
4550 {
4551 	return true;
4552 }
4553 
4554 void cfs_bandwidth_usage_inc(void) {}
4555 void cfs_bandwidth_usage_dec(void) {}
4556 #endif /* CONFIG_JUMP_LABEL */
4557 
4558 /*
4559  * default period for cfs group bandwidth.
4560  * default: 0.1s, units: nanoseconds
4561  */
4562 static inline u64 default_cfs_period(void)
4563 {
4564 	return 100000000ULL;
4565 }
4566 
4567 static inline u64 sched_cfs_bandwidth_slice(void)
4568 {
4569 	return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
4570 }
4571 
4572 /*
4573  * Replenish runtime according to assigned quota. We use sched_clock_cpu
4574  * directly instead of rq->clock to avoid adding additional synchronization
4575  * around rq->lock.
4576  *
4577  * requires cfs_b->lock
4578  */
4579 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
4580 {
4581 	if (cfs_b->quota != RUNTIME_INF)
4582 		cfs_b->runtime = cfs_b->quota;
4583 }
4584 
4585 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4586 {
4587 	return &tg->cfs_bandwidth;
4588 }
4589 
4590 /* returns 0 on failure to allocate runtime */
4591 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4592 {
4593 	struct task_group *tg = cfs_rq->tg;
4594 	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
4595 	u64 amount = 0, min_amount;
4596 
4597 	/* note: this is a positive sum as runtime_remaining <= 0 */
4598 	min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
4599 
4600 	raw_spin_lock(&cfs_b->lock);
4601 	if (cfs_b->quota == RUNTIME_INF)
4602 		amount = min_amount;
4603 	else {
4604 		start_cfs_bandwidth(cfs_b);
4605 
4606 		if (cfs_b->runtime > 0) {
4607 			amount = min(cfs_b->runtime, min_amount);
4608 			cfs_b->runtime -= amount;
4609 			cfs_b->idle = 0;
4610 		}
4611 	}
4612 	raw_spin_unlock(&cfs_b->lock);
4613 
4614 	cfs_rq->runtime_remaining += amount;
4615 
4616 	return cfs_rq->runtime_remaining > 0;
4617 }
4618 
4619 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4620 {
4621 	/* dock delta_exec before expiring quota (as it could span periods) */
4622 	cfs_rq->runtime_remaining -= delta_exec;
4623 
4624 	if (likely(cfs_rq->runtime_remaining > 0))
4625 		return;
4626 
4627 	if (cfs_rq->throttled)
4628 		return;
4629 	/*
4630 	 * if we're unable to extend our runtime we resched so that the active
4631 	 * hierarchy can be throttled
4632 	 */
4633 	if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
4634 		resched_curr(rq_of(cfs_rq));
4635 }
4636 
4637 static __always_inline
4638 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4639 {
4640 	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4641 		return;
4642 
4643 	__account_cfs_rq_runtime(cfs_rq, delta_exec);
4644 }
4645 
4646 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4647 {
4648 	return cfs_bandwidth_used() && cfs_rq->throttled;
4649 }
4650 
4651 /* check whether cfs_rq, or any parent, is throttled */
4652 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4653 {
4654 	return cfs_bandwidth_used() && cfs_rq->throttle_count;
4655 }
4656 
4657 /*
4658  * Ensure that neither of the group entities corresponding to src_cpu or
4659  * dest_cpu are members of a throttled hierarchy when performing group
4660  * load-balance operations.
4661  */
4662 static inline int throttled_lb_pair(struct task_group *tg,
4663 				    int src_cpu, int dest_cpu)
4664 {
4665 	struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
4666 
4667 	src_cfs_rq = tg->cfs_rq[src_cpu];
4668 	dest_cfs_rq = tg->cfs_rq[dest_cpu];
4669 
4670 	return throttled_hierarchy(src_cfs_rq) ||
4671 	       throttled_hierarchy(dest_cfs_rq);
4672 }
4673 
4674 static int tg_unthrottle_up(struct task_group *tg, void *data)
4675 {
4676 	struct rq *rq = data;
4677 	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4678 
4679 	cfs_rq->throttle_count--;
4680 	if (!cfs_rq->throttle_count) {
4681 		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4682 					     cfs_rq->throttled_clock_task;
4683 
4684 		/* Add cfs_rq with already running entity in the list */
4685 		if (cfs_rq->nr_running >= 1)
4686 			list_add_leaf_cfs_rq(cfs_rq);
4687 	}
4688 
4689 	return 0;
4690 }
4691 
4692 static int tg_throttle_down(struct task_group *tg, void *data)
4693 {
4694 	struct rq *rq = data;
4695 	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4696 
4697 	/* group is entering throttled state, stop time */
4698 	if (!cfs_rq->throttle_count) {
4699 		cfs_rq->throttled_clock_task = rq_clock_task(rq);
4700 		list_del_leaf_cfs_rq(cfs_rq);
4701 	}
4702 	cfs_rq->throttle_count++;
4703 
4704 	return 0;
4705 }
4706 
4707 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
4708 {
4709 	struct rq *rq = rq_of(cfs_rq);
4710 	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4711 	struct sched_entity *se;
4712 	long task_delta, idle_task_delta, dequeue = 1;
4713 	bool empty;
4714 
4715 	se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
4716 
4717 	/* freeze hierarchy runnable averages while throttled */
4718 	rcu_read_lock();
4719 	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
4720 	rcu_read_unlock();
4721 
4722 	task_delta = cfs_rq->h_nr_running;
4723 	idle_task_delta = cfs_rq->idle_h_nr_running;
4724 	for_each_sched_entity(se) {
4725 		struct cfs_rq *qcfs_rq = cfs_rq_of(se);
4726 		/* throttled entity or throttle-on-deactivate */
4727 		if (!se->on_rq)
4728 			break;
4729 
4730 		if (dequeue) {
4731 			dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
4732 		} else {
4733 			update_load_avg(qcfs_rq, se, 0);
4734 			se_update_runnable(se);
4735 		}
4736 
4737 		qcfs_rq->h_nr_running -= task_delta;
4738 		qcfs_rq->idle_h_nr_running -= idle_task_delta;
4739 
4740 		if (qcfs_rq->load.weight)
4741 			dequeue = 0;
4742 	}
4743 
4744 	if (!se)
4745 		sub_nr_running(rq, task_delta);
4746 
4747 	cfs_rq->throttled = 1;
4748 	cfs_rq->throttled_clock = rq_clock(rq);
4749 	raw_spin_lock(&cfs_b->lock);
4750 	empty = list_empty(&cfs_b->throttled_cfs_rq);
4751 
4752 	/*
4753 	 * Add to the _head_ of the list, so that an already-started
4754 	 * distribute_cfs_runtime will not see us. If disribute_cfs_runtime is
4755 	 * not running add to the tail so that later runqueues don't get starved.
4756 	 */
4757 	if (cfs_b->distribute_running)
4758 		list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
4759 	else
4760 		list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
4761 
4762 	/*
4763 	 * If we're the first throttled task, make sure the bandwidth
4764 	 * timer is running.
4765 	 */
4766 	if (empty)
4767 		start_cfs_bandwidth(cfs_b);
4768 
4769 	raw_spin_unlock(&cfs_b->lock);
4770 }
4771 
4772 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4773 {
4774 	struct rq *rq = rq_of(cfs_rq);
4775 	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4776 	struct sched_entity *se;
4777 	long task_delta, idle_task_delta;
4778 
4779 	se = cfs_rq->tg->se[cpu_of(rq)];
4780 
4781 	cfs_rq->throttled = 0;
4782 
4783 	update_rq_clock(rq);
4784 
4785 	raw_spin_lock(&cfs_b->lock);
4786 	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4787 	list_del_rcu(&cfs_rq->throttled_list);
4788 	raw_spin_unlock(&cfs_b->lock);
4789 
4790 	/* update hierarchical throttle state */
4791 	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
4792 
4793 	if (!cfs_rq->load.weight)
4794 		return;
4795 
4796 	task_delta = cfs_rq->h_nr_running;
4797 	idle_task_delta = cfs_rq->idle_h_nr_running;
4798 	for_each_sched_entity(se) {
4799 		if (se->on_rq)
4800 			break;
4801 		cfs_rq = cfs_rq_of(se);
4802 		enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
4803 
4804 		cfs_rq->h_nr_running += task_delta;
4805 		cfs_rq->idle_h_nr_running += idle_task_delta;
4806 
4807 		/* end evaluation on encountering a throttled cfs_rq */
4808 		if (cfs_rq_throttled(cfs_rq))
4809 			goto unthrottle_throttle;
4810 	}
4811 
4812 	for_each_sched_entity(se) {
4813 		cfs_rq = cfs_rq_of(se);
4814 
4815 		update_load_avg(cfs_rq, se, UPDATE_TG);
4816 		se_update_runnable(se);
4817 
4818 		cfs_rq->h_nr_running += task_delta;
4819 		cfs_rq->idle_h_nr_running += idle_task_delta;
4820 
4821 
4822 		/* end evaluation on encountering a throttled cfs_rq */
4823 		if (cfs_rq_throttled(cfs_rq))
4824 			goto unthrottle_throttle;
4825 
4826 		/*
4827 		 * One parent has been throttled and cfs_rq removed from the
4828 		 * list. Add it back to not break the leaf list.
4829 		 */
4830 		if (throttled_hierarchy(cfs_rq))
4831 			list_add_leaf_cfs_rq(cfs_rq);
4832 	}
4833 
4834 	/* At this point se is NULL and we are at root level*/
4835 	add_nr_running(rq, task_delta);
4836 
4837 unthrottle_throttle:
4838 	/*
4839 	 * The cfs_rq_throttled() breaks in the above iteration can result in
4840 	 * incomplete leaf list maintenance, resulting in triggering the
4841 	 * assertion below.
4842 	 */
4843 	for_each_sched_entity(se) {
4844 		cfs_rq = cfs_rq_of(se);
4845 
4846 		if (list_add_leaf_cfs_rq(cfs_rq))
4847 			break;
4848 	}
4849 
4850 	assert_list_leaf_cfs_rq(rq);
4851 
4852 	/* Determine whether we need to wake up potentially idle CPU: */
4853 	if (rq->curr == rq->idle && rq->cfs.nr_running)
4854 		resched_curr(rq);
4855 }
4856 
4857 static void distribute_cfs_runtime(struct cfs_bandwidth *cfs_b)
4858 {
4859 	struct cfs_rq *cfs_rq;
4860 	u64 runtime, remaining = 1;
4861 
4862 	rcu_read_lock();
4863 	list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
4864 				throttled_list) {
4865 		struct rq *rq = rq_of(cfs_rq);
4866 		struct rq_flags rf;
4867 
4868 		rq_lock_irqsave(rq, &rf);
4869 		if (!cfs_rq_throttled(cfs_rq))
4870 			goto next;
4871 
4872 		/* By the above check, this should never be true */
4873 		SCHED_WARN_ON(cfs_rq->runtime_remaining > 0);
4874 
4875 		raw_spin_lock(&cfs_b->lock);
4876 		runtime = -cfs_rq->runtime_remaining + 1;
4877 		if (runtime > cfs_b->runtime)
4878 			runtime = cfs_b->runtime;
4879 		cfs_b->runtime -= runtime;
4880 		remaining = cfs_b->runtime;
4881 		raw_spin_unlock(&cfs_b->lock);
4882 
4883 		cfs_rq->runtime_remaining += runtime;
4884 
4885 		/* we check whether we're throttled above */
4886 		if (cfs_rq->runtime_remaining > 0)
4887 			unthrottle_cfs_rq(cfs_rq);
4888 
4889 next:
4890 		rq_unlock_irqrestore(rq, &rf);
4891 
4892 		if (!remaining)
4893 			break;
4894 	}
4895 	rcu_read_unlock();
4896 }
4897 
4898 /*
4899  * Responsible for refilling a task_group's bandwidth and unthrottling its
4900  * cfs_rqs as appropriate. If there has been no activity within the last
4901  * period the timer is deactivated until scheduling resumes; cfs_b->idle is
4902  * used to track this state.
4903  */
4904 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags)
4905 {
4906 	int throttled;
4907 
4908 	/* no need to continue the timer with no bandwidth constraint */
4909 	if (cfs_b->quota == RUNTIME_INF)
4910 		goto out_deactivate;
4911 
4912 	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4913 	cfs_b->nr_periods += overrun;
4914 
4915 	/*
4916 	 * idle depends on !throttled (for the case of a large deficit), and if
4917 	 * we're going inactive then everything else can be deferred
4918 	 */
4919 	if (cfs_b->idle && !throttled)
4920 		goto out_deactivate;
4921 
4922 	__refill_cfs_bandwidth_runtime(cfs_b);
4923 
4924 	if (!throttled) {
4925 		/* mark as potentially idle for the upcoming period */
4926 		cfs_b->idle = 1;
4927 		return 0;
4928 	}
4929 
4930 	/* account preceding periods in which throttling occurred */
4931 	cfs_b->nr_throttled += overrun;
4932 
4933 	/*
4934 	 * This check is repeated as we release cfs_b->lock while we unthrottle.
4935 	 */
4936 	while (throttled && cfs_b->runtime > 0 && !cfs_b->distribute_running) {
4937 		cfs_b->distribute_running = 1;
4938 		raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
4939 		/* we can't nest cfs_b->lock while distributing bandwidth */
4940 		distribute_cfs_runtime(cfs_b);
4941 		raw_spin_lock_irqsave(&cfs_b->lock, flags);
4942 
4943 		cfs_b->distribute_running = 0;
4944 		throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4945 	}
4946 
4947 	/*
4948 	 * While we are ensured activity in the period following an
4949 	 * unthrottle, this also covers the case in which the new bandwidth is
4950 	 * insufficient to cover the existing bandwidth deficit.  (Forcing the
4951 	 * timer to remain active while there are any throttled entities.)
4952 	 */
4953 	cfs_b->idle = 0;
4954 
4955 	return 0;
4956 
4957 out_deactivate:
4958 	return 1;
4959 }
4960 
4961 /* a cfs_rq won't donate quota below this amount */
4962 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
4963 /* minimum remaining period time to redistribute slack quota */
4964 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
4965 /* how long we wait to gather additional slack before distributing */
4966 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
4967 
4968 /*
4969  * Are we near the end of the current quota period?
4970  *
4971  * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4972  * hrtimer base being cleared by hrtimer_start. In the case of
4973  * migrate_hrtimers, base is never cleared, so we are fine.
4974  */
4975 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
4976 {
4977 	struct hrtimer *refresh_timer = &cfs_b->period_timer;
4978 	u64 remaining;
4979 
4980 	/* if the call-back is running a quota refresh is already occurring */
4981 	if (hrtimer_callback_running(refresh_timer))
4982 		return 1;
4983 
4984 	/* is a quota refresh about to occur? */
4985 	remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
4986 	if (remaining < min_expire)
4987 		return 1;
4988 
4989 	return 0;
4990 }
4991 
4992 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
4993 {
4994 	u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
4995 
4996 	/* if there's a quota refresh soon don't bother with slack */
4997 	if (runtime_refresh_within(cfs_b, min_left))
4998 		return;
4999 
5000 	/* don't push forwards an existing deferred unthrottle */
5001 	if (cfs_b->slack_started)
5002 		return;
5003 	cfs_b->slack_started = true;
5004 
5005 	hrtimer_start(&cfs_b->slack_timer,
5006 			ns_to_ktime(cfs_bandwidth_slack_period),
5007 			HRTIMER_MODE_REL);
5008 }
5009 
5010 /* we know any runtime found here is valid as update_curr() precedes return */
5011 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5012 {
5013 	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
5014 	s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
5015 
5016 	if (slack_runtime <= 0)
5017 		return;
5018 
5019 	raw_spin_lock(&cfs_b->lock);
5020 	if (cfs_b->quota != RUNTIME_INF) {
5021 		cfs_b->runtime += slack_runtime;
5022 
5023 		/* we are under rq->lock, defer unthrottling using a timer */
5024 		if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
5025 		    !list_empty(&cfs_b->throttled_cfs_rq))
5026 			start_cfs_slack_bandwidth(cfs_b);
5027 	}
5028 	raw_spin_unlock(&cfs_b->lock);
5029 
5030 	/* even if it's not valid for return we don't want to try again */
5031 	cfs_rq->runtime_remaining -= slack_runtime;
5032 }
5033 
5034 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5035 {
5036 	if (!cfs_bandwidth_used())
5037 		return;
5038 
5039 	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
5040 		return;
5041 
5042 	__return_cfs_rq_runtime(cfs_rq);
5043 }
5044 
5045 /*
5046  * This is done with a timer (instead of inline with bandwidth return) since
5047  * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
5048  */
5049 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
5050 {
5051 	u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
5052 	unsigned long flags;
5053 
5054 	/* confirm we're still not at a refresh boundary */
5055 	raw_spin_lock_irqsave(&cfs_b->lock, flags);
5056 	cfs_b->slack_started = false;
5057 	if (cfs_b->distribute_running) {
5058 		raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5059 		return;
5060 	}
5061 
5062 	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
5063 		raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5064 		return;
5065 	}
5066 
5067 	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
5068 		runtime = cfs_b->runtime;
5069 
5070 	if (runtime)
5071 		cfs_b->distribute_running = 1;
5072 
5073 	raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5074 
5075 	if (!runtime)
5076 		return;
5077 
5078 	distribute_cfs_runtime(cfs_b);
5079 
5080 	raw_spin_lock_irqsave(&cfs_b->lock, flags);
5081 	cfs_b->distribute_running = 0;
5082 	raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5083 }
5084 
5085 /*
5086  * When a group wakes up we want to make sure that its quota is not already
5087  * expired/exceeded, otherwise it may be allowed to steal additional ticks of
5088  * runtime as update_curr() throttling can not not trigger until it's on-rq.
5089  */
5090 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
5091 {
5092 	if (!cfs_bandwidth_used())
5093 		return;
5094 
5095 	/* an active group must be handled by the update_curr()->put() path */
5096 	if (!cfs_rq->runtime_enabled || cfs_rq->curr)
5097 		return;
5098 
5099 	/* ensure the group is not already throttled */
5100 	if (cfs_rq_throttled(cfs_rq))
5101 		return;
5102 
5103 	/* update runtime allocation */
5104 	account_cfs_rq_runtime(cfs_rq, 0);
5105 	if (cfs_rq->runtime_remaining <= 0)
5106 		throttle_cfs_rq(cfs_rq);
5107 }
5108 
5109 static void sync_throttle(struct task_group *tg, int cpu)
5110 {
5111 	struct cfs_rq *pcfs_rq, *cfs_rq;
5112 
5113 	if (!cfs_bandwidth_used())
5114 		return;
5115 
5116 	if (!tg->parent)
5117 		return;
5118 
5119 	cfs_rq = tg->cfs_rq[cpu];
5120 	pcfs_rq = tg->parent->cfs_rq[cpu];
5121 
5122 	cfs_rq->throttle_count = pcfs_rq->throttle_count;
5123 	cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
5124 }
5125 
5126 /* conditionally throttle active cfs_rq's from put_prev_entity() */
5127 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5128 {
5129 	if (!cfs_bandwidth_used())
5130 		return false;
5131 
5132 	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
5133 		return false;
5134 
5135 	/*
5136 	 * it's possible for a throttled entity to be forced into a running
5137 	 * state (e.g. set_curr_task), in this case we're finished.
5138 	 */
5139 	if (cfs_rq_throttled(cfs_rq))
5140 		return true;
5141 
5142 	throttle_cfs_rq(cfs_rq);
5143 	return true;
5144 }
5145 
5146 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
5147 {
5148 	struct cfs_bandwidth *cfs_b =
5149 		container_of(timer, struct cfs_bandwidth, slack_timer);
5150 
5151 	do_sched_cfs_slack_timer(cfs_b);
5152 
5153 	return HRTIMER_NORESTART;
5154 }
5155 
5156 extern const u64 max_cfs_quota_period;
5157 
5158 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
5159 {
5160 	struct cfs_bandwidth *cfs_b =
5161 		container_of(timer, struct cfs_bandwidth, period_timer);
5162 	unsigned long flags;
5163 	int overrun;
5164 	int idle = 0;
5165 	int count = 0;
5166 
5167 	raw_spin_lock_irqsave(&cfs_b->lock, flags);
5168 	for (;;) {
5169 		overrun = hrtimer_forward_now(timer, cfs_b->period);
5170 		if (!overrun)
5171 			break;
5172 
5173 		if (++count > 3) {
5174 			u64 new, old = ktime_to_ns(cfs_b->period);
5175 
5176 			/*
5177 			 * Grow period by a factor of 2 to avoid losing precision.
5178 			 * Precision loss in the quota/period ratio can cause __cfs_schedulable
5179 			 * to fail.
5180 			 */
5181 			new = old * 2;
5182 			if (new < max_cfs_quota_period) {
5183 				cfs_b->period = ns_to_ktime(new);
5184 				cfs_b->quota *= 2;
5185 
5186 				pr_warn_ratelimited(
5187 	"cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n",
5188 					smp_processor_id(),
5189 					div_u64(new, NSEC_PER_USEC),
5190 					div_u64(cfs_b->quota, NSEC_PER_USEC));
5191 			} else {
5192 				pr_warn_ratelimited(
5193 	"cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n",
5194 					smp_processor_id(),
5195 					div_u64(old, NSEC_PER_USEC),
5196 					div_u64(cfs_b->quota, NSEC_PER_USEC));
5197 			}
5198 
5199 			/* reset count so we don't come right back in here */
5200 			count = 0;
5201 		}
5202 
5203 		idle = do_sched_cfs_period_timer(cfs_b, overrun, flags);
5204 	}
5205 	if (idle)
5206 		cfs_b->period_active = 0;
5207 	raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5208 
5209 	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
5210 }
5211 
5212 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5213 {
5214 	raw_spin_lock_init(&cfs_b->lock);
5215 	cfs_b->runtime = 0;
5216 	cfs_b->quota = RUNTIME_INF;
5217 	cfs_b->period = ns_to_ktime(default_cfs_period());
5218 
5219 	INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
5220 	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
5221 	cfs_b->period_timer.function = sched_cfs_period_timer;
5222 	hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
5223 	cfs_b->slack_timer.function = sched_cfs_slack_timer;
5224 	cfs_b->distribute_running = 0;
5225 	cfs_b->slack_started = false;
5226 }
5227 
5228 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5229 {
5230 	cfs_rq->runtime_enabled = 0;
5231 	INIT_LIST_HEAD(&cfs_rq->throttled_list);
5232 }
5233 
5234 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5235 {
5236 	lockdep_assert_held(&cfs_b->lock);
5237 
5238 	if (cfs_b->period_active)
5239 		return;
5240 
5241 	cfs_b->period_active = 1;
5242 	hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
5243 	hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
5244 }
5245 
5246 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5247 {
5248 	/* init_cfs_bandwidth() was not called */
5249 	if (!cfs_b->throttled_cfs_rq.next)
5250 		return;
5251 
5252 	hrtimer_cancel(&cfs_b->period_timer);
5253 	hrtimer_cancel(&cfs_b->slack_timer);
5254 }
5255 
5256 /*
5257  * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
5258  *
5259  * The race is harmless, since modifying bandwidth settings of unhooked group
5260  * bits doesn't do much.
5261  */
5262 
5263 /* cpu online calback */
5264 static void __maybe_unused update_runtime_enabled(struct rq *rq)
5265 {
5266 	struct task_group *tg;
5267 
5268 	lockdep_assert_held(&rq->lock);
5269 
5270 	rcu_read_lock();
5271 	list_for_each_entry_rcu(tg, &task_groups, list) {
5272 		struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
5273 		struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
5274 
5275 		raw_spin_lock(&cfs_b->lock);
5276 		cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
5277 		raw_spin_unlock(&cfs_b->lock);
5278 	}
5279 	rcu_read_unlock();
5280 }
5281 
5282 /* cpu offline callback */
5283 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
5284 {
5285 	struct task_group *tg;
5286 
5287 	lockdep_assert_held(&rq->lock);
5288 
5289 	rcu_read_lock();
5290 	list_for_each_entry_rcu(tg, &task_groups, list) {
5291 		struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
5292 
5293 		if (!cfs_rq->runtime_enabled)
5294 			continue;
5295 
5296 		/*
5297 		 * clock_task is not advancing so we just need to make sure
5298 		 * there's some valid quota amount
5299 		 */
5300 		cfs_rq->runtime_remaining = 1;
5301 		/*
5302 		 * Offline rq is schedulable till CPU is completely disabled
5303 		 * in take_cpu_down(), so we prevent new cfs throttling here.
5304 		 */
5305 		cfs_rq->runtime_enabled = 0;
5306 
5307 		if (cfs_rq_throttled(cfs_rq))
5308 			unthrottle_cfs_rq(cfs_rq);
5309 	}
5310 	rcu_read_unlock();
5311 }
5312 
5313 #else /* CONFIG_CFS_BANDWIDTH */
5314 
5315 static inline bool cfs_bandwidth_used(void)
5316 {
5317 	return false;
5318 }
5319 
5320 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
5321 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
5322 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
5323 static inline void sync_throttle(struct task_group *tg, int cpu) {}
5324 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5325 
5326 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
5327 {
5328 	return 0;
5329 }
5330 
5331 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
5332 {
5333 	return 0;
5334 }
5335 
5336 static inline int throttled_lb_pair(struct task_group *tg,
5337 				    int src_cpu, int dest_cpu)
5338 {
5339 	return 0;
5340 }
5341 
5342 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
5343 
5344 #ifdef CONFIG_FAIR_GROUP_SCHED
5345 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5346 #endif
5347 
5348 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
5349 {
5350 	return NULL;
5351 }
5352 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
5353 static inline void update_runtime_enabled(struct rq *rq) {}
5354 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
5355 
5356 #endif /* CONFIG_CFS_BANDWIDTH */
5357 
5358 /**************************************************
5359  * CFS operations on tasks:
5360  */
5361 
5362 #ifdef CONFIG_SCHED_HRTICK
5363 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
5364 {
5365 	struct sched_entity *se = &p->se;
5366 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
5367 
5368 	SCHED_WARN_ON(task_rq(p) != rq);
5369 
5370 	if (rq->cfs.h_nr_running > 1) {
5371 		u64 slice = sched_slice(cfs_rq, se);
5372 		u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
5373 		s64 delta = slice - ran;
5374 
5375 		if (delta < 0) {
5376 			if (rq->curr == p)
5377 				resched_curr(rq);
5378 			return;
5379 		}
5380 		hrtick_start(rq, delta);
5381 	}
5382 }
5383 
5384 /*
5385  * called from enqueue/dequeue and updates the hrtick when the
5386  * current task is from our class and nr_running is low enough
5387  * to matter.
5388  */
5389 static void hrtick_update(struct rq *rq)
5390 {
5391 	struct task_struct *curr = rq->curr;
5392 
5393 	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
5394 		return;
5395 
5396 	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
5397 		hrtick_start_fair(rq, curr);
5398 }
5399 #else /* !CONFIG_SCHED_HRTICK */
5400 static inline void
5401 hrtick_start_fair(struct rq *rq, struct task_struct *p)
5402 {
5403 }
5404 
5405 static inline void hrtick_update(struct rq *rq)
5406 {
5407 }
5408 #endif
5409 
5410 #ifdef CONFIG_SMP
5411 static inline unsigned long cpu_util(int cpu);
5412 
5413 static inline bool cpu_overutilized(int cpu)
5414 {
5415 	return !fits_capacity(cpu_util(cpu), capacity_of(cpu));
5416 }
5417 
5418 static inline void update_overutilized_status(struct rq *rq)
5419 {
5420 	if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu)) {
5421 		WRITE_ONCE(rq->rd->overutilized, SG_OVERUTILIZED);
5422 		trace_sched_overutilized_tp(rq->rd, SG_OVERUTILIZED);
5423 	}
5424 }
5425 #else
5426 static inline void update_overutilized_status(struct rq *rq) { }
5427 #endif
5428 
5429 /* Runqueue only has SCHED_IDLE tasks enqueued */
5430 static int sched_idle_rq(struct rq *rq)
5431 {
5432 	return unlikely(rq->nr_running == rq->cfs.idle_h_nr_running &&
5433 			rq->nr_running);
5434 }
5435 
5436 #ifdef CONFIG_SMP
5437 static int sched_idle_cpu(int cpu)
5438 {
5439 	return sched_idle_rq(cpu_rq(cpu));
5440 }
5441 #endif
5442 
5443 /*
5444  * The enqueue_task method is called before nr_running is
5445  * increased. Here we update the fair scheduling stats and
5446  * then put the task into the rbtree:
5447  */
5448 static void
5449 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5450 {
5451 	struct cfs_rq *cfs_rq;
5452 	struct sched_entity *se = &p->se;
5453 	int idle_h_nr_running = task_has_idle_policy(p);
5454 
5455 	/*
5456 	 * The code below (indirectly) updates schedutil which looks at
5457 	 * the cfs_rq utilization to select a frequency.
5458 	 * Let's add the task's estimated utilization to the cfs_rq's
5459 	 * estimated utilization, before we update schedutil.
5460 	 */
5461 	util_est_enqueue(&rq->cfs, p);
5462 
5463 	/*
5464 	 * If in_iowait is set, the code below may not trigger any cpufreq
5465 	 * utilization updates, so do it here explicitly with the IOWAIT flag
5466 	 * passed.
5467 	 */
5468 	if (p->in_iowait)
5469 		cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
5470 
5471 	for_each_sched_entity(se) {
5472 		if (se->on_rq)
5473 			break;
5474 		cfs_rq = cfs_rq_of(se);
5475 		enqueue_entity(cfs_rq, se, flags);
5476 
5477 		cfs_rq->h_nr_running++;
5478 		cfs_rq->idle_h_nr_running += idle_h_nr_running;
5479 
5480 		/* end evaluation on encountering a throttled cfs_rq */
5481 		if (cfs_rq_throttled(cfs_rq))
5482 			goto enqueue_throttle;
5483 
5484 		flags = ENQUEUE_WAKEUP;
5485 	}
5486 
5487 	for_each_sched_entity(se) {
5488 		cfs_rq = cfs_rq_of(se);
5489 
5490 		update_load_avg(cfs_rq, se, UPDATE_TG);
5491 		se_update_runnable(se);
5492 		update_cfs_group(se);
5493 
5494 		cfs_rq->h_nr_running++;
5495 		cfs_rq->idle_h_nr_running += idle_h_nr_running;
5496 
5497 		/* end evaluation on encountering a throttled cfs_rq */
5498 		if (cfs_rq_throttled(cfs_rq))
5499 			goto enqueue_throttle;
5500 
5501                /*
5502                 * One parent has been throttled and cfs_rq removed from the
5503                 * list. Add it back to not break the leaf list.
5504                 */
5505                if (throttled_hierarchy(cfs_rq))
5506                        list_add_leaf_cfs_rq(cfs_rq);
5507 	}
5508 
5509 enqueue_throttle:
5510 	if (!se) {
5511 		add_nr_running(rq, 1);
5512 		/*
5513 		 * Since new tasks are assigned an initial util_avg equal to
5514 		 * half of the spare capacity of their CPU, tiny tasks have the
5515 		 * ability to cross the overutilized threshold, which will
5516 		 * result in the load balancer ruining all the task placement
5517 		 * done by EAS. As a way to mitigate that effect, do not account
5518 		 * for the first enqueue operation of new tasks during the
5519 		 * overutilized flag detection.
5520 		 *
5521 		 * A better way of solving this problem would be to wait for
5522 		 * the PELT signals of tasks to converge before taking them
5523 		 * into account, but that is not straightforward to implement,
5524 		 * and the following generally works well enough in practice.
5525 		 */
5526 		if (flags & ENQUEUE_WAKEUP)
5527 			update_overutilized_status(rq);
5528 
5529 	}
5530 
5531 	if (cfs_bandwidth_used()) {
5532 		/*
5533 		 * When bandwidth control is enabled; the cfs_rq_throttled()
5534 		 * breaks in the above iteration can result in incomplete
5535 		 * leaf list maintenance, resulting in triggering the assertion
5536 		 * below.
5537 		 */
5538 		for_each_sched_entity(se) {
5539 			cfs_rq = cfs_rq_of(se);
5540 
5541 			if (list_add_leaf_cfs_rq(cfs_rq))
5542 				break;
5543 		}
5544 	}
5545 
5546 	assert_list_leaf_cfs_rq(rq);
5547 
5548 	hrtick_update(rq);
5549 }
5550 
5551 static void set_next_buddy(struct sched_entity *se);
5552 
5553 /*
5554  * The dequeue_task method is called before nr_running is
5555  * decreased. We remove the task from the rbtree and
5556  * update the fair scheduling stats:
5557  */
5558 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5559 {
5560 	struct cfs_rq *cfs_rq;
5561 	struct sched_entity *se = &p->se;
5562 	int task_sleep = flags & DEQUEUE_SLEEP;
5563 	int idle_h_nr_running = task_has_idle_policy(p);
5564 	bool was_sched_idle = sched_idle_rq(rq);
5565 
5566 	for_each_sched_entity(se) {
5567 		cfs_rq = cfs_rq_of(se);
5568 		dequeue_entity(cfs_rq, se, flags);
5569 
5570 		cfs_rq->h_nr_running--;
5571 		cfs_rq->idle_h_nr_running -= idle_h_nr_running;
5572 
5573 		/* end evaluation on encountering a throttled cfs_rq */
5574 		if (cfs_rq_throttled(cfs_rq))
5575 			goto dequeue_throttle;
5576 
5577 		/* Don't dequeue parent if it has other entities besides us */
5578 		if (cfs_rq->load.weight) {
5579 			/* Avoid re-evaluating load for this entity: */
5580 			se = parent_entity(se);
5581 			/*
5582 			 * Bias pick_next to pick a task from this cfs_rq, as
5583 			 * p is sleeping when it is within its sched_slice.
5584 			 */
5585 			if (task_sleep && se && !throttled_hierarchy(cfs_rq))
5586 				set_next_buddy(se);
5587 			break;
5588 		}
5589 		flags |= DEQUEUE_SLEEP;
5590 	}
5591 
5592 	for_each_sched_entity(se) {
5593 		cfs_rq = cfs_rq_of(se);
5594 
5595 		update_load_avg(cfs_rq, se, UPDATE_TG);
5596 		se_update_runnable(se);
5597 		update_cfs_group(se);
5598 
5599 		cfs_rq->h_nr_running--;
5600 		cfs_rq->idle_h_nr_running -= idle_h_nr_running;
5601 
5602 		/* end evaluation on encountering a throttled cfs_rq */
5603 		if (cfs_rq_throttled(cfs_rq))
5604 			goto dequeue_throttle;
5605 
5606 	}
5607 
5608 dequeue_throttle:
5609 	if (!se)
5610 		sub_nr_running(rq, 1);
5611 
5612 	/* balance early to pull high priority tasks */
5613 	if (unlikely(!was_sched_idle && sched_idle_rq(rq)))
5614 		rq->next_balance = jiffies;
5615 
5616 	util_est_dequeue(&rq->cfs, p, task_sleep);
5617 	hrtick_update(rq);
5618 }
5619 
5620 #ifdef CONFIG_SMP
5621 
5622 /* Working cpumask for: load_balance, load_balance_newidle. */
5623 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
5624 DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
5625 
5626 #ifdef CONFIG_NO_HZ_COMMON
5627 
5628 static struct {
5629 	cpumask_var_t idle_cpus_mask;
5630 	atomic_t nr_cpus;
5631 	int has_blocked;		/* Idle CPUS has blocked load */
5632 	unsigned long next_balance;     /* in jiffy units */
5633 	unsigned long next_blocked;	/* Next update of blocked load in jiffies */
5634 } nohz ____cacheline_aligned;
5635 
5636 #endif /* CONFIG_NO_HZ_COMMON */
5637 
5638 static unsigned long cpu_load(struct rq *rq)
5639 {
5640 	return cfs_rq_load_avg(&rq->cfs);
5641 }
5642 
5643 /*
5644  * cpu_load_without - compute CPU load without any contributions from *p
5645  * @cpu: the CPU which load is requested
5646  * @p: the task which load should be discounted
5647  *
5648  * The load of a CPU is defined by the load of tasks currently enqueued on that
5649  * CPU as well as tasks which are currently sleeping after an execution on that
5650  * CPU.
5651  *
5652  * This method returns the load of the specified CPU by discounting the load of
5653  * the specified task, whenever the task is currently contributing to the CPU
5654  * load.
5655  */
5656 static unsigned long cpu_load_without(struct rq *rq, struct task_struct *p)
5657 {
5658 	struct cfs_rq *cfs_rq;
5659 	unsigned int load;
5660 
5661 	/* Task has no contribution or is new */
5662 	if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
5663 		return cpu_load(rq);
5664 
5665 	cfs_rq = &rq->cfs;
5666 	load = READ_ONCE(cfs_rq->avg.load_avg);
5667 
5668 	/* Discount task's util from CPU's util */
5669 	lsub_positive(&load, task_h_load(p));
5670 
5671 	return load;
5672 }
5673 
5674 static unsigned long cpu_runnable(struct rq *rq)
5675 {
5676 	return cfs_rq_runnable_avg(&rq->cfs);
5677 }
5678 
5679 static unsigned long cpu_runnable_without(struct rq *rq, struct task_struct *p)
5680 {
5681 	struct cfs_rq *cfs_rq;
5682 	unsigned int runnable;
5683 
5684 	/* Task has no contribution or is new */
5685 	if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
5686 		return cpu_runnable(rq);
5687 
5688 	cfs_rq = &rq->cfs;
5689 	runnable = READ_ONCE(cfs_rq->avg.runnable_avg);
5690 
5691 	/* Discount task's runnable from CPU's runnable */
5692 	lsub_positive(&runnable, p->se.avg.runnable_avg);
5693 
5694 	return runnable;
5695 }
5696 
5697 static unsigned long capacity_of(int cpu)
5698 {
5699 	return cpu_rq(cpu)->cpu_capacity;
5700 }
5701 
5702 static void record_wakee(struct task_struct *p)
5703 {
5704 	/*
5705 	 * Only decay a single time; tasks that have less then 1 wakeup per
5706 	 * jiffy will not have built up many flips.
5707 	 */
5708 	if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
5709 		current->wakee_flips >>= 1;
5710 		current->wakee_flip_decay_ts = jiffies;
5711 	}
5712 
5713 	if (current->last_wakee != p) {
5714 		current->last_wakee = p;
5715 		current->wakee_flips++;
5716 	}
5717 }
5718 
5719 /*
5720  * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5721  *
5722  * A waker of many should wake a different task than the one last awakened
5723  * at a frequency roughly N times higher than one of its wakees.
5724  *
5725  * In order to determine whether we should let the load spread vs consolidating
5726  * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
5727  * partner, and a factor of lls_size higher frequency in the other.
5728  *
5729  * With both conditions met, we can be relatively sure that the relationship is
5730  * non-monogamous, with partner count exceeding socket size.
5731  *
5732  * Waker/wakee being client/server, worker/dispatcher, interrupt source or
5733  * whatever is irrelevant, spread criteria is apparent partner count exceeds
5734  * socket size.
5735  */
5736 static int wake_wide(struct task_struct *p)
5737 {
5738 	unsigned int master = current->wakee_flips;
5739 	unsigned int slave = p->wakee_flips;
5740 	int factor = this_cpu_read(sd_llc_size);
5741 
5742 	if (master < slave)
5743 		swap(master, slave);
5744 	if (slave < factor || master < slave * factor)
5745 		return 0;
5746 	return 1;
5747 }
5748 
5749 /*
5750  * The purpose of wake_affine() is to quickly determine on which CPU we can run
5751  * soonest. For the purpose of speed we only consider the waking and previous
5752  * CPU.
5753  *
5754  * wake_affine_idle() - only considers 'now', it check if the waking CPU is
5755  *			cache-affine and is (or	will be) idle.
5756  *
5757  * wake_affine_weight() - considers the weight to reflect the average
5758  *			  scheduling latency of the CPUs. This seems to work
5759  *			  for the overloaded case.
5760  */
5761 static int
5762 wake_affine_idle(int this_cpu, int prev_cpu, int sync)
5763 {
5764 	/*
5765 	 * If this_cpu is idle, it implies the wakeup is from interrupt
5766 	 * context. Only allow the move if cache is shared. Otherwise an
5767 	 * interrupt intensive workload could force all tasks onto one
5768 	 * node depending on the IO topology or IRQ affinity settings.
5769 	 *
5770 	 * If the prev_cpu is idle and cache affine then avoid a migration.
5771 	 * There is no guarantee that the cache hot data from an interrupt
5772 	 * is more important than cache hot data on the prev_cpu and from
5773 	 * a cpufreq perspective, it's better to have higher utilisation
5774 	 * on one CPU.
5775 	 */
5776 	if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
5777 		return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
5778 
5779 	if (sync && cpu_rq(this_cpu)->nr_running == 1)
5780 		return this_cpu;
5781 
5782 	return nr_cpumask_bits;
5783 }
5784 
5785 static int
5786 wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
5787 		   int this_cpu, int prev_cpu, int sync)
5788 {
5789 	s64 this_eff_load, prev_eff_load;
5790 	unsigned long task_load;
5791 
5792 	this_eff_load = cpu_load(cpu_rq(this_cpu));
5793 
5794 	if (sync) {
5795 		unsigned long current_load = task_h_load(current);
5796 
5797 		if (current_load > this_eff_load)
5798 			return this_cpu;
5799 
5800 		this_eff_load -= current_load;
5801 	}
5802 
5803 	task_load = task_h_load(p);
5804 
5805 	this_eff_load += task_load;
5806 	if (sched_feat(WA_BIAS))
5807 		this_eff_load *= 100;
5808 	this_eff_load *= capacity_of(prev_cpu);
5809 
5810 	prev_eff_load = cpu_load(cpu_rq(prev_cpu));
5811 	prev_eff_load -= task_load;
5812 	if (sched_feat(WA_BIAS))
5813 		prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
5814 	prev_eff_load *= capacity_of(this_cpu);
5815 
5816 	/*
5817 	 * If sync, adjust the weight of prev_eff_load such that if
5818 	 * prev_eff == this_eff that select_idle_sibling() will consider
5819 	 * stacking the wakee on top of the waker if no other CPU is
5820 	 * idle.
5821 	 */
5822 	if (sync)
5823 		prev_eff_load += 1;
5824 
5825 	return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
5826 }
5827 
5828 static int wake_affine(struct sched_domain *sd, struct task_struct *p,
5829 		       int this_cpu, int prev_cpu, int sync)
5830 {
5831 	int target = nr_cpumask_bits;
5832 
5833 	if (sched_feat(WA_IDLE))
5834 		target = wake_affine_idle(this_cpu, prev_cpu, sync);
5835 
5836 	if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
5837 		target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
5838 
5839 	schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5840 	if (target == nr_cpumask_bits)
5841 		return prev_cpu;
5842 
5843 	schedstat_inc(sd->ttwu_move_affine);
5844 	schedstat_inc(p->se.statistics.nr_wakeups_affine);
5845 	return target;
5846 }
5847 
5848 static struct sched_group *
5849 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5850 		  int this_cpu, int sd_flag);
5851 
5852 /*
5853  * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
5854  */
5855 static int
5856 find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5857 {
5858 	unsigned long load, min_load = ULONG_MAX;
5859 	unsigned int min_exit_latency = UINT_MAX;
5860 	u64 latest_idle_timestamp = 0;
5861 	int least_loaded_cpu = this_cpu;
5862 	int shallowest_idle_cpu = -1;
5863 	int i;
5864 
5865 	/* Check if we have any choice: */
5866 	if (group->group_weight == 1)
5867 		return cpumask_first(sched_group_span(group));
5868 
5869 	/* Traverse only the allowed CPUs */
5870 	for_each_cpu_and(i, sched_group_span(group), p->cpus_ptr) {
5871 		if (sched_idle_cpu(i))
5872 			return i;
5873 
5874 		if (available_idle_cpu(i)) {
5875 			struct rq *rq = cpu_rq(i);
5876 			struct cpuidle_state *idle = idle_get_state(rq);
5877 			if (idle && idle->exit_latency < min_exit_latency) {
5878 				/*
5879 				 * We give priority to a CPU whose idle state
5880 				 * has the smallest exit latency irrespective
5881 				 * of any idle timestamp.
5882 				 */
5883 				min_exit_latency = idle->exit_latency;
5884 				latest_idle_timestamp = rq->idle_stamp;
5885 				shallowest_idle_cpu = i;
5886 			} else if ((!idle || idle->exit_latency == min_exit_latency) &&
5887 				   rq->idle_stamp > latest_idle_timestamp) {
5888 				/*
5889 				 * If equal or no active idle state, then
5890 				 * the most recently idled CPU might have
5891 				 * a warmer cache.
5892 				 */
5893 				latest_idle_timestamp = rq->idle_stamp;
5894 				shallowest_idle_cpu = i;
5895 			}
5896 		} else if (shallowest_idle_cpu == -1) {
5897 			load = cpu_load(cpu_rq(i));
5898 			if (load < min_load) {
5899 				min_load = load;
5900 				least_loaded_cpu = i;
5901 			}
5902 		}
5903 	}
5904 
5905 	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5906 }
5907 
5908 static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
5909 				  int cpu, int prev_cpu, int sd_flag)
5910 {
5911 	int new_cpu = cpu;
5912 
5913 	if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr))
5914 		return prev_cpu;
5915 
5916 	/*
5917 	 * We need task's util for cpu_util_without, sync it up to
5918 	 * prev_cpu's last_update_time.
5919 	 */
5920 	if (!(sd_flag & SD_BALANCE_FORK))
5921 		sync_entity_load_avg(&p->se);
5922 
5923 	while (sd) {
5924 		struct sched_group *group;
5925 		struct sched_domain *tmp;
5926 		int weight;
5927 
5928 		if (!(sd->flags & sd_flag)) {
5929 			sd = sd->child;
5930 			continue;
5931 		}
5932 
5933 		group = find_idlest_group(sd, p, cpu, sd_flag);
5934 		if (!group) {
5935 			sd = sd->child;
5936 			continue;
5937 		}
5938 
5939 		new_cpu = find_idlest_group_cpu(group, p, cpu);
5940 		if (new_cpu == cpu) {
5941 			/* Now try balancing at a lower domain level of 'cpu': */
5942 			sd = sd->child;
5943 			continue;
5944 		}
5945 
5946 		/* Now try balancing at a lower domain level of 'new_cpu': */
5947 		cpu = new_cpu;
5948 		weight = sd->span_weight;
5949 		sd = NULL;
5950 		for_each_domain(cpu, tmp) {
5951 			if (weight <= tmp->span_weight)
5952 				break;
5953 			if (tmp->flags & sd_flag)
5954 				sd = tmp;
5955 		}
5956 	}
5957 
5958 	return new_cpu;
5959 }
5960 
5961 #ifdef CONFIG_SCHED_SMT
5962 DEFINE_STATIC_KEY_FALSE(sched_smt_present);
5963 EXPORT_SYMBOL_GPL(sched_smt_present);
5964 
5965 static inline void set_idle_cores(int cpu, int val)
5966 {
5967 	struct sched_domain_shared *sds;
5968 
5969 	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
5970 	if (sds)
5971 		WRITE_ONCE(sds->has_idle_cores, val);
5972 }
5973 
5974 static inline bool test_idle_cores(int cpu, bool def)
5975 {
5976 	struct sched_domain_shared *sds;
5977 
5978 	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
5979 	if (sds)
5980 		return READ_ONCE(sds->has_idle_cores);
5981 
5982 	return def;
5983 }
5984 
5985 /*
5986  * Scans the local SMT mask to see if the entire core is idle, and records this
5987  * information in sd_llc_shared->has_idle_cores.
5988  *
5989  * Since SMT siblings share all cache levels, inspecting this limited remote
5990  * state should be fairly cheap.
5991  */
5992 void __update_idle_core(struct rq *rq)
5993 {
5994 	int core = cpu_of(rq);
5995 	int cpu;
5996 
5997 	rcu_read_lock();
5998 	if (test_idle_cores(core, true))
5999 		goto unlock;
6000 
6001 	for_each_cpu(cpu, cpu_smt_mask(core)) {
6002 		if (cpu == core)
6003 			continue;
6004 
6005 		if (!available_idle_cpu(cpu))
6006 			goto unlock;
6007 	}
6008 
6009 	set_idle_cores(core, 1);
6010 unlock:
6011 	rcu_read_unlock();
6012 }
6013 
6014 /*
6015  * Scan the entire LLC domain for idle cores; this dynamically switches off if
6016  * there are no idle cores left in the system; tracked through
6017  * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
6018  */
6019 static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
6020 {
6021 	struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
6022 	int core, cpu;
6023 
6024 	if (!static_branch_likely(&sched_smt_present))
6025 		return -1;
6026 
6027 	if (!test_idle_cores(target, false))
6028 		return -1;
6029 
6030 	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
6031 
6032 	for_each_cpu_wrap(core, cpus, target) {
6033 		bool idle = true;
6034 
6035 		for_each_cpu(cpu, cpu_smt_mask(core)) {
6036 			if (!available_idle_cpu(cpu)) {
6037 				idle = false;
6038 				break;
6039 			}
6040 		}
6041 		cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
6042 
6043 		if (idle)
6044 			return core;
6045 	}
6046 
6047 	/*
6048 	 * Failed to find an idle core; stop looking for one.
6049 	 */
6050 	set_idle_cores(target, 0);
6051 
6052 	return -1;
6053 }
6054 
6055 /*
6056  * Scan the local SMT mask for idle CPUs.
6057  */
6058 static int select_idle_smt(struct task_struct *p, int target)
6059 {
6060 	int cpu;
6061 
6062 	if (!static_branch_likely(&sched_smt_present))
6063 		return -1;
6064 
6065 	for_each_cpu(cpu, cpu_smt_mask(target)) {
6066 		if (!cpumask_test_cpu(cpu, p->cpus_ptr))
6067 			continue;
6068 		if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
6069 			return cpu;
6070 	}
6071 
6072 	return -1;
6073 }
6074 
6075 #else /* CONFIG_SCHED_SMT */
6076 
6077 static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
6078 {
6079 	return -1;
6080 }
6081 
6082 static inline int select_idle_smt(struct task_struct *p, int target)
6083 {
6084 	return -1;
6085 }
6086 
6087 #endif /* CONFIG_SCHED_SMT */
6088 
6089 /*
6090  * Scan the LLC domain for idle CPUs; this is dynamically regulated by
6091  * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
6092  * average idle time for this rq (as found in rq->avg_idle).
6093  */
6094 static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
6095 {
6096 	struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
6097 	struct sched_domain *this_sd;
6098 	u64 avg_cost, avg_idle;
6099 	u64 time;
6100 	int this = smp_processor_id();
6101 	int cpu, nr = INT_MAX;
6102 
6103 	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
6104 	if (!this_sd)
6105 		return -1;
6106 
6107 	/*
6108 	 * Due to large variance we need a large fuzz factor; hackbench in
6109 	 * particularly is sensitive here.
6110 	 */
6111 	avg_idle = this_rq()->avg_idle / 512;
6112 	avg_cost = this_sd->avg_scan_cost + 1;
6113 
6114 	if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost)
6115 		return -1;
6116 
6117 	if (sched_feat(SIS_PROP)) {
6118 		u64 span_avg = sd->span_weight * avg_idle;
6119 		if (span_avg > 4*avg_cost)
6120 			nr = div_u64(span_avg, avg_cost);
6121 		else
6122 			nr = 4;
6123 	}
6124 
6125 	time = cpu_clock(this);
6126 
6127 	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
6128 
6129 	for_each_cpu_wrap(cpu, cpus, target) {
6130 		if (!--nr)
6131 			return -1;
6132 		if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
6133 			break;
6134 	}
6135 
6136 	time = cpu_clock(this) - time;
6137 	update_avg(&this_sd->avg_scan_cost, time);
6138 
6139 	return cpu;
6140 }
6141 
6142 /*
6143  * Scan the asym_capacity domain for idle CPUs; pick the first idle one on which
6144  * the task fits. If no CPU is big enough, but there are idle ones, try to
6145  * maximize capacity.
6146  */
6147 static int
6148 select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
6149 {
6150 	unsigned long best_cap = 0;
6151 	int cpu, best_cpu = -1;
6152 	struct cpumask *cpus;
6153 
6154 	sync_entity_load_avg(&p->se);
6155 
6156 	cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
6157 	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
6158 
6159 	for_each_cpu_wrap(cpu, cpus, target) {
6160 		unsigned long cpu_cap = capacity_of(cpu);
6161 
6162 		if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu))
6163 			continue;
6164 		if (task_fits_capacity(p, cpu_cap))
6165 			return cpu;
6166 
6167 		if (cpu_cap > best_cap) {
6168 			best_cap = cpu_cap;
6169 			best_cpu = cpu;
6170 		}
6171 	}
6172 
6173 	return best_cpu;
6174 }
6175 
6176 /*
6177  * Try and locate an idle core/thread in the LLC cache domain.
6178  */
6179 static int select_idle_sibling(struct task_struct *p, int prev, int target)
6180 {
6181 	struct sched_domain *sd;
6182 	int i, recent_used_cpu;
6183 
6184 	/*
6185 	 * For asymmetric CPU capacity systems, our domain of interest is
6186 	 * sd_asym_cpucapacity rather than sd_llc.
6187 	 */
6188 	if (static_branch_unlikely(&sched_asym_cpucapacity)) {
6189 		sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, target));
6190 		/*
6191 		 * On an asymmetric CPU capacity system where an exclusive
6192 		 * cpuset defines a symmetric island (i.e. one unique
6193 		 * capacity_orig value through the cpuset), the key will be set
6194 		 * but the CPUs within that cpuset will not have a domain with
6195 		 * SD_ASYM_CPUCAPACITY. These should follow the usual symmetric
6196 		 * capacity path.
6197 		 */
6198 		if (!sd)
6199 			goto symmetric;
6200 
6201 		i = select_idle_capacity(p, sd, target);
6202 		return ((unsigned)i < nr_cpumask_bits) ? i : target;
6203 	}
6204 
6205 symmetric:
6206 	if (available_idle_cpu(target) || sched_idle_cpu(target))
6207 		return target;
6208 
6209 	/*
6210 	 * If the previous CPU is cache affine and idle, don't be stupid:
6211 	 */
6212 	if (prev != target && cpus_share_cache(prev, target) &&
6213 	    (available_idle_cpu(prev) || sched_idle_cpu(prev)))
6214 		return prev;
6215 
6216 	/*
6217 	 * Allow a per-cpu kthread to stack with the wakee if the
6218 	 * kworker thread and the tasks previous CPUs are the same.
6219 	 * The assumption is that the wakee queued work for the
6220 	 * per-cpu kthread that is now complete and the wakeup is
6221 	 * essentially a sync wakeup. An obvious example of this
6222 	 * pattern is IO completions.
6223 	 */
6224 	if (is_per_cpu_kthread(current) &&
6225 	    prev == smp_processor_id() &&
6226 	    this_rq()->nr_running <= 1) {
6227 		return prev;
6228 	}
6229 
6230 	/* Check a recently used CPU as a potential idle candidate: */
6231 	recent_used_cpu = p->recent_used_cpu;
6232 	if (recent_used_cpu != prev &&
6233 	    recent_used_cpu != target &&
6234 	    cpus_share_cache(recent_used_cpu, target) &&
6235 	    (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) &&
6236 	    cpumask_test_cpu(p->recent_used_cpu, p->cpus_ptr)) {
6237 		/*
6238 		 * Replace recent_used_cpu with prev as it is a potential
6239 		 * candidate for the next wake:
6240 		 */
6241 		p->recent_used_cpu = prev;
6242 		return recent_used_cpu;
6243 	}
6244 
6245 	sd = rcu_dereference(per_cpu(sd_llc, target));
6246 	if (!sd)
6247 		return target;
6248 
6249 	i = select_idle_core(p, sd, target);
6250 	if ((unsigned)i < nr_cpumask_bits)
6251 		return i;
6252 
6253 	i = select_idle_cpu(p, sd, target);
6254 	if ((unsigned)i < nr_cpumask_bits)
6255 		return i;
6256 
6257 	i = select_idle_smt(p, target);
6258 	if ((unsigned)i < nr_cpumask_bits)
6259 		return i;
6260 
6261 	return target;
6262 }
6263 
6264 /**
6265  * Amount of capacity of a CPU that is (estimated to be) used by CFS tasks
6266  * @cpu: the CPU to get the utilization of
6267  *
6268  * The unit of the return value must be the one of capacity so we can compare
6269  * the utilization with the capacity of the CPU that is available for CFS task
6270  * (ie cpu_capacity).
6271  *
6272  * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
6273  * recent utilization of currently non-runnable tasks on a CPU. It represents
6274  * the amount of utilization of a CPU in the range [0..capacity_orig] where
6275  * capacity_orig is the cpu_capacity available at the highest frequency
6276  * (arch_scale_freq_capacity()).
6277  * The utilization of a CPU converges towards a sum equal to or less than the
6278  * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
6279  * the running time on this CPU scaled by capacity_curr.
6280  *
6281  * The estimated utilization of a CPU is defined to be the maximum between its
6282  * cfs_rq.avg.util_avg and the sum of the estimated utilization of the tasks
6283  * currently RUNNABLE on that CPU.
6284  * This allows to properly represent the expected utilization of a CPU which
6285  * has just got a big task running since a long sleep period. At the same time
6286  * however it preserves the benefits of the "blocked utilization" in
6287  * describing the potential for other tasks waking up on the same CPU.
6288  *
6289  * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
6290  * higher than capacity_orig because of unfortunate rounding in
6291  * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
6292  * the average stabilizes with the new running time. We need to check that the
6293  * utilization stays within the range of [0..capacity_orig] and cap it if
6294  * necessary. Without utilization capping, a group could be seen as overloaded
6295  * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
6296  * available capacity. We allow utilization to overshoot capacity_curr (but not
6297  * capacity_orig) as it useful for predicting the capacity required after task
6298  * migrations (scheduler-driven DVFS).
6299  *
6300  * Return: the (estimated) utilization for the specified CPU
6301  */
6302 static inline unsigned long cpu_util(int cpu)
6303 {
6304 	struct cfs_rq *cfs_rq;
6305 	unsigned int util;
6306 
6307 	cfs_rq = &cpu_rq(cpu)->cfs;
6308 	util = READ_ONCE(cfs_rq->avg.util_avg);
6309 
6310 	if (sched_feat(UTIL_EST))
6311 		util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued));
6312 
6313 	return min_t(unsigned long, util, capacity_orig_of(cpu));
6314 }
6315 
6316 /*
6317  * cpu_util_without: compute cpu utilization without any contributions from *p
6318  * @cpu: the CPU which utilization is requested
6319  * @p: the task which utilization should be discounted
6320  *
6321  * The utilization of a CPU is defined by the utilization of tasks currently
6322  * enqueued on that CPU as well as tasks which are currently sleeping after an
6323  * execution on that CPU.
6324  *
6325  * This method returns the utilization of the specified CPU by discounting the
6326  * utilization of the specified task, whenever the task is currently
6327  * contributing to the CPU utilization.
6328  */
6329 static unsigned long cpu_util_without(int cpu, struct task_struct *p)
6330 {
6331 	struct cfs_rq *cfs_rq;
6332 	unsigned int util;
6333 
6334 	/* Task has no contribution or is new */
6335 	if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
6336 		return cpu_util(cpu);
6337 
6338 	cfs_rq = &cpu_rq(cpu)->cfs;
6339 	util = READ_ONCE(cfs_rq->avg.util_avg);
6340 
6341 	/* Discount task's util from CPU's util */
6342 	lsub_positive(&util, task_util(p));
6343 
6344 	/*
6345 	 * Covered cases:
6346 	 *
6347 	 * a) if *p is the only task sleeping on this CPU, then:
6348 	 *      cpu_util (== task_util) > util_est (== 0)
6349 	 *    and thus we return:
6350 	 *      cpu_util_without = (cpu_util - task_util) = 0
6351 	 *
6352 	 * b) if other tasks are SLEEPING on this CPU, which is now exiting
6353 	 *    IDLE, then:
6354 	 *      cpu_util >= task_util
6355 	 *      cpu_util > util_est (== 0)
6356 	 *    and thus we discount *p's blocked utilization to return:
6357 	 *      cpu_util_without = (cpu_util - task_util) >= 0
6358 	 *
6359 	 * c) if other tasks are RUNNABLE on that CPU and
6360 	 *      util_est > cpu_util
6361 	 *    then we use util_est since it returns a more restrictive
6362 	 *    estimation of the spare capacity on that CPU, by just
6363 	 *    considering the expected utilization of tasks already
6364 	 *    runnable on that CPU.
6365 	 *
6366 	 * Cases a) and b) are covered by the above code, while case c) is
6367 	 * covered by the following code when estimated utilization is
6368 	 * enabled.
6369 	 */
6370 	if (sched_feat(UTIL_EST)) {
6371 		unsigned int estimated =
6372 			READ_ONCE(cfs_rq->avg.util_est.enqueued);
6373 
6374 		/*
6375 		 * Despite the following checks we still have a small window
6376 		 * for a possible race, when an execl's select_task_rq_fair()
6377 		 * races with LB's detach_task():
6378 		 *
6379 		 *   detach_task()
6380 		 *     p->on_rq = TASK_ON_RQ_MIGRATING;
6381 		 *     ---------------------------------- A
6382 		 *     deactivate_task()                   \
6383 		 *       dequeue_task()                     + RaceTime
6384 		 *         util_est_dequeue()              /
6385 		 *     ---------------------------------- B
6386 		 *
6387 		 * The additional check on "current == p" it's required to
6388 		 * properly fix the execl regression and it helps in further
6389 		 * reducing the chances for the above race.
6390 		 */
6391 		if (unlikely(task_on_rq_queued(p) || current == p))
6392 			lsub_positive(&estimated, _task_util_est(p));
6393 
6394 		util = max(util, estimated);
6395 	}
6396 
6397 	/*
6398 	 * Utilization (estimated) can exceed the CPU capacity, thus let's
6399 	 * clamp to the maximum CPU capacity to ensure consistency with
6400 	 * the cpu_util call.
6401 	 */
6402 	return min_t(unsigned long, util, capacity_orig_of(cpu));
6403 }
6404 
6405 /*
6406  * Predicts what cpu_util(@cpu) would return if @p was migrated (and enqueued)
6407  * to @dst_cpu.
6408  */
6409 static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
6410 {
6411 	struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs;
6412 	unsigned long util_est, util = READ_ONCE(cfs_rq->avg.util_avg);
6413 
6414 	/*
6415 	 * If @p migrates from @cpu to another, remove its contribution. Or,
6416 	 * if @p migrates from another CPU to @cpu, add its contribution. In
6417 	 * the other cases, @cpu is not impacted by the migration, so the
6418 	 * util_avg should already be correct.
6419 	 */
6420 	if (task_cpu(p) == cpu && dst_cpu != cpu)
6421 		sub_positive(&util, task_util(p));
6422 	else if (task_cpu(p) != cpu && dst_cpu == cpu)
6423 		util += task_util(p);
6424 
6425 	if (sched_feat(UTIL_EST)) {
6426 		util_est = READ_ONCE(cfs_rq->avg.util_est.enqueued);
6427 
6428 		/*
6429 		 * During wake-up, the task isn't enqueued yet and doesn't
6430 		 * appear in the cfs_rq->avg.util_est.enqueued of any rq,
6431 		 * so just add it (if needed) to "simulate" what will be
6432 		 * cpu_util() after the task has been enqueued.
6433 		 */
6434 		if (dst_cpu == cpu)
6435 			util_est += _task_util_est(p);
6436 
6437 		util = max(util, util_est);
6438 	}
6439 
6440 	return min(util, capacity_orig_of(cpu));
6441 }
6442 
6443 /*
6444  * compute_energy(): Estimates the energy that @pd would consume if @p was
6445  * migrated to @dst_cpu. compute_energy() predicts what will be the utilization
6446  * landscape of @pd's CPUs after the task migration, and uses the Energy Model
6447  * to compute what would be the energy if we decided to actually migrate that
6448  * task.
6449  */
6450 static long
6451 compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
6452 {
6453 	struct cpumask *pd_mask = perf_domain_span(pd);
6454 	unsigned long cpu_cap = arch_scale_cpu_capacity(cpumask_first(pd_mask));
6455 	unsigned long max_util = 0, sum_util = 0;
6456 	int cpu;
6457 
6458 	/*
6459 	 * The capacity state of CPUs of the current rd can be driven by CPUs
6460 	 * of another rd if they belong to the same pd. So, account for the
6461 	 * utilization of these CPUs too by masking pd with cpu_online_mask
6462 	 * instead of the rd span.
6463 	 *
6464 	 * If an entire pd is outside of the current rd, it will not appear in
6465 	 * its pd list and will not be accounted by compute_energy().
6466 	 */
6467 	for_each_cpu_and(cpu, pd_mask, cpu_online_mask) {
6468 		unsigned long cpu_util, util_cfs = cpu_util_next(cpu, p, dst_cpu);
6469 		struct task_struct *tsk = cpu == dst_cpu ? p : NULL;
6470 
6471 		/*
6472 		 * Busy time computation: utilization clamping is not
6473 		 * required since the ratio (sum_util / cpu_capacity)
6474 		 * is already enough to scale the EM reported power
6475 		 * consumption at the (eventually clamped) cpu_capacity.
6476 		 */
6477 		sum_util += schedutil_cpu_util(cpu, util_cfs, cpu_cap,
6478 					       ENERGY_UTIL, NULL);
6479 
6480 		/*
6481 		 * Performance domain frequency: utilization clamping
6482 		 * must be considered since it affects the selection
6483 		 * of the performance domain frequency.
6484 		 * NOTE: in case RT tasks are running, by default the
6485 		 * FREQUENCY_UTIL's utilization can be max OPP.
6486 		 */
6487 		cpu_util = schedutil_cpu_util(cpu, util_cfs, cpu_cap,
6488 					      FREQUENCY_UTIL, tsk);
6489 		max_util = max(max_util, cpu_util);
6490 	}
6491 
6492 	return em_pd_energy(pd->em_pd, max_util, sum_util);
6493 }
6494 
6495 /*
6496  * find_energy_efficient_cpu(): Find most energy-efficient target CPU for the
6497  * waking task. find_energy_efficient_cpu() looks for the CPU with maximum
6498  * spare capacity in each performance domain and uses it as a potential
6499  * candidate to execute the task. Then, it uses the Energy Model to figure
6500  * out which of the CPU candidates is the most energy-efficient.
6501  *
6502  * The rationale for this heuristic is as follows. In a performance domain,
6503  * all the most energy efficient CPU candidates (according to the Energy
6504  * Model) are those for which we'll request a low frequency. When there are
6505  * several CPUs for which the frequency request will be the same, we don't
6506  * have enough data to break the tie between them, because the Energy Model
6507  * only includes active power costs. With this model, if we assume that
6508  * frequency requests follow utilization (e.g. using schedutil), the CPU with
6509  * the maximum spare capacity in a performance domain is guaranteed to be among
6510  * the best candidates of the performance domain.
6511  *
6512  * In practice, it could be preferable from an energy standpoint to pack
6513  * small tasks on a CPU in order to let other CPUs go in deeper idle states,
6514  * but that could also hurt our chances to go cluster idle, and we have no
6515  * ways to tell with the current Energy Model if this is actually a good
6516  * idea or not. So, find_energy_efficient_cpu() basically favors
6517  * cluster-packing, and spreading inside a cluster. That should at least be
6518  * a good thing for latency, and this is consistent with the idea that most
6519  * of the energy savings of EAS come from the asymmetry of the system, and
6520  * not so much from breaking the tie between identical CPUs. That's also the
6521  * reason why EAS is enabled in the topology code only for systems where
6522  * SD_ASYM_CPUCAPACITY is set.
6523  *
6524  * NOTE: Forkees are not accepted in the energy-aware wake-up path because
6525  * they don't have any useful utilization data yet and it's not possible to
6526  * forecast their impact on energy consumption. Consequently, they will be
6527  * placed by find_idlest_cpu() on the least loaded CPU, which might turn out
6528  * to be energy-inefficient in some use-cases. The alternative would be to
6529  * bias new tasks towards specific types of CPUs first, or to try to infer
6530  * their util_avg from the parent task, but those heuristics could hurt
6531  * other use-cases too. So, until someone finds a better way to solve this,
6532  * let's keep things simple by re-using the existing slow path.
6533  */
6534 static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
6535 {
6536 	unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX;
6537 	struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
6538 	unsigned long cpu_cap, util, base_energy = 0;
6539 	int cpu, best_energy_cpu = prev_cpu;
6540 	struct sched_domain *sd;
6541 	struct perf_domain *pd;
6542 
6543 	rcu_read_lock();
6544 	pd = rcu_dereference(rd->pd);
6545 	if (!pd || READ_ONCE(rd->overutilized))
6546 		goto fail;
6547 
6548 	/*
6549 	 * Energy-aware wake-up happens on the lowest sched_domain starting
6550 	 * from sd_asym_cpucapacity spanning over this_cpu and prev_cpu.
6551 	 */
6552 	sd = rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity));
6553 	while (sd && !cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
6554 		sd = sd->parent;
6555 	if (!sd)
6556 		goto fail;
6557 
6558 	sync_entity_load_avg(&p->se);
6559 	if (!task_util_est(p))
6560 		goto unlock;
6561 
6562 	for (; pd; pd = pd->next) {
6563 		unsigned long cur_delta, spare_cap, max_spare_cap = 0;
6564 		unsigned long base_energy_pd;
6565 		int max_spare_cap_cpu = -1;
6566 
6567 		/* Compute the 'base' energy of the pd, without @p */
6568 		base_energy_pd = compute_energy(p, -1, pd);
6569 		base_energy += base_energy_pd;
6570 
6571 		for_each_cpu_and(cpu, perf_domain_span(pd), sched_domain_span(sd)) {
6572 			if (!cpumask_test_cpu(cpu, p->cpus_ptr))
6573 				continue;
6574 
6575 			util = cpu_util_next(cpu, p, cpu);
6576 			cpu_cap = capacity_of(cpu);
6577 			spare_cap = cpu_cap - util;
6578 
6579 			/*
6580 			 * Skip CPUs that cannot satisfy the capacity request.
6581 			 * IOW, placing the task there would make the CPU
6582 			 * overutilized. Take uclamp into account to see how
6583 			 * much capacity we can get out of the CPU; this is
6584 			 * aligned with schedutil_cpu_util().
6585 			 */
6586 			util = uclamp_rq_util_with(cpu_rq(cpu), util, p);
6587 			if (!fits_capacity(util, cpu_cap))
6588 				continue;
6589 
6590 			/* Always use prev_cpu as a candidate. */
6591 			if (cpu == prev_cpu) {
6592 				prev_delta = compute_energy(p, prev_cpu, pd);
6593 				prev_delta -= base_energy_pd;
6594 				best_delta = min(best_delta, prev_delta);
6595 			}
6596 
6597 			/*
6598 			 * Find the CPU with the maximum spare capacity in
6599 			 * the performance domain
6600 			 */
6601 			if (spare_cap > max_spare_cap) {
6602 				max_spare_cap = spare_cap;
6603 				max_spare_cap_cpu = cpu;
6604 			}
6605 		}
6606 
6607 		/* Evaluate the energy impact of using this CPU. */
6608 		if (max_spare_cap_cpu >= 0 && max_spare_cap_cpu != prev_cpu) {
6609 			cur_delta = compute_energy(p, max_spare_cap_cpu, pd);
6610 			cur_delta -= base_energy_pd;
6611 			if (cur_delta < best_delta) {
6612 				best_delta = cur_delta;
6613 				best_energy_cpu = max_spare_cap_cpu;
6614 			}
6615 		}
6616 	}
6617 unlock:
6618 	rcu_read_unlock();
6619 
6620 	/*
6621 	 * Pick the best CPU if prev_cpu cannot be used, or if it saves at
6622 	 * least 6% of the energy used by prev_cpu.
6623 	 */
6624 	if (prev_delta == ULONG_MAX)
6625 		return best_energy_cpu;
6626 
6627 	if ((prev_delta - best_delta) > ((prev_delta + base_energy) >> 4))
6628 		return best_energy_cpu;
6629 
6630 	return prev_cpu;
6631 
6632 fail:
6633 	rcu_read_unlock();
6634 
6635 	return -1;
6636 }
6637 
6638 /*
6639  * select_task_rq_fair: Select target runqueue for the waking task in domains
6640  * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
6641  * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
6642  *
6643  * Balances load by selecting the idlest CPU in the idlest group, or under
6644  * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
6645  *
6646  * Returns the target CPU number.
6647  *
6648  * preempt must be disabled.
6649  */
6650 static int
6651 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
6652 {
6653 	struct sched_domain *tmp, *sd = NULL;
6654 	int cpu = smp_processor_id();
6655 	int new_cpu = prev_cpu;
6656 	int want_affine = 0;
6657 	int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
6658 
6659 	if (sd_flag & SD_BALANCE_WAKE) {
6660 		record_wakee(p);
6661 
6662 		if (sched_energy_enabled()) {
6663 			new_cpu = find_energy_efficient_cpu(p, prev_cpu);
6664 			if (new_cpu >= 0)
6665 				return new_cpu;
6666 			new_cpu = prev_cpu;
6667 		}
6668 
6669 		want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, p->cpus_ptr);
6670 	}
6671 
6672 	rcu_read_lock();
6673 	for_each_domain(cpu, tmp) {
6674 		if (!(tmp->flags & SD_LOAD_BALANCE))
6675 			break;
6676 
6677 		/*
6678 		 * If both 'cpu' and 'prev_cpu' are part of this domain,
6679 		 * cpu is a valid SD_WAKE_AFFINE target.
6680 		 */
6681 		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
6682 		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
6683 			if (cpu != prev_cpu)
6684 				new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);
6685 
6686 			sd = NULL; /* Prefer wake_affine over balance flags */
6687 			break;
6688 		}
6689 
6690 		if (tmp->flags & sd_flag)
6691 			sd = tmp;
6692 		else if (!want_affine)
6693 			break;
6694 	}
6695 
6696 	if (unlikely(sd)) {
6697 		/* Slow path */
6698 		new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
6699 	} else if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
6700 		/* Fast path */
6701 
6702 		new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
6703 
6704 		if (want_affine)
6705 			current->recent_used_cpu = cpu;
6706 	}
6707 	rcu_read_unlock();
6708 
6709 	return new_cpu;
6710 }
6711 
6712 static void detach_entity_cfs_rq(struct sched_entity *se);
6713 
6714 /*
6715  * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
6716  * cfs_rq_of(p) references at time of call are still valid and identify the
6717  * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6718  */
6719 static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
6720 {
6721 	/*
6722 	 * As blocked tasks retain absolute vruntime the migration needs to
6723 	 * deal with this by subtracting the old and adding the new
6724 	 * min_vruntime -- the latter is done by enqueue_entity() when placing
6725 	 * the task on the new runqueue.
6726 	 */
6727 	if (p->state == TASK_WAKING) {
6728 		struct sched_entity *se = &p->se;
6729 		struct cfs_rq *cfs_rq = cfs_rq_of(se);
6730 		u64 min_vruntime;
6731 
6732 #ifndef CONFIG_64BIT
6733 		u64 min_vruntime_copy;
6734 
6735 		do {
6736 			min_vruntime_copy = cfs_rq->min_vruntime_copy;
6737 			smp_rmb();
6738 			min_vruntime = cfs_rq->min_vruntime;
6739 		} while (min_vruntime != min_vruntime_copy);
6740 #else
6741 		min_vruntime = cfs_rq->min_vruntime;
6742 #endif
6743 
6744 		se->vruntime -= min_vruntime;
6745 	}
6746 
6747 	if (p->on_rq == TASK_ON_RQ_MIGRATING) {
6748 		/*
6749 		 * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old'
6750 		 * rq->lock and can modify state directly.
6751 		 */
6752 		lockdep_assert_held(&task_rq(p)->lock);
6753 		detach_entity_cfs_rq(&p->se);
6754 
6755 	} else {
6756 		/*
6757 		 * We are supposed to update the task to "current" time, then
6758 		 * its up to date and ready to go to new CPU/cfs_rq. But we
6759 		 * have difficulty in getting what current time is, so simply
6760 		 * throw away the out-of-date time. This will result in the
6761 		 * wakee task is less decayed, but giving the wakee more load
6762 		 * sounds not bad.
6763 		 */
6764 		remove_entity_load_avg(&p->se);
6765 	}
6766 
6767 	/* Tell new CPU we are migrated */
6768 	p->se.avg.last_update_time = 0;
6769 
6770 	/* We have migrated, no longer consider this task hot */
6771 	p->se.exec_start = 0;
6772 
6773 	update_scan_period(p, new_cpu);
6774 }
6775 
6776 static void task_dead_fair(struct task_struct *p)
6777 {
6778 	remove_entity_load_avg(&p->se);
6779 }
6780 
6781 static int
6782 balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6783 {
6784 	if (rq->nr_running)
6785 		return 1;
6786 
6787 	return newidle_balance(rq, rf) != 0;
6788 }
6789 #endif /* CONFIG_SMP */
6790 
6791 static unsigned long wakeup_gran(struct sched_entity *se)
6792 {
6793 	unsigned long gran = sysctl_sched_wakeup_granularity;
6794 
6795 	/*
6796 	 * Since its curr running now, convert the gran from real-time
6797 	 * to virtual-time in his units.
6798 	 *
6799 	 * By using 'se' instead of 'curr' we penalize light tasks, so
6800 	 * they get preempted easier. That is, if 'se' < 'curr' then
6801 	 * the resulting gran will be larger, therefore penalizing the
6802 	 * lighter, if otoh 'se' > 'curr' then the resulting gran will
6803 	 * be smaller, again penalizing the lighter task.
6804 	 *
6805 	 * This is especially important for buddies when the leftmost
6806 	 * task is higher priority than the buddy.
6807 	 */
6808 	return calc_delta_fair(gran, se);
6809 }
6810 
6811 /*
6812  * Should 'se' preempt 'curr'.
6813  *
6814  *             |s1
6815  *        |s2
6816  *   |s3
6817  *         g
6818  *      |<--->|c
6819  *
6820  *  w(c, s1) = -1
6821  *  w(c, s2) =  0
6822  *  w(c, s3) =  1
6823  *
6824  */
6825 static int
6826 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
6827 {
6828 	s64 gran, vdiff = curr->vruntime - se->vruntime;
6829 
6830 	if (vdiff <= 0)
6831 		return -1;
6832 
6833 	gran = wakeup_gran(se);
6834 	if (vdiff > gran)
6835 		return 1;
6836 
6837 	return 0;
6838 }
6839 
6840 static void set_last_buddy(struct sched_entity *se)
6841 {
6842 	if (entity_is_task(se) && unlikely(task_has_idle_policy(task_of(se))))
6843 		return;
6844 
6845 	for_each_sched_entity(se) {
6846 		if (SCHED_WARN_ON(!se->on_rq))
6847 			return;
6848 		cfs_rq_of(se)->last = se;
6849 	}
6850 }
6851 
6852 static void set_next_buddy(struct sched_entity *se)
6853 {
6854 	if (entity_is_task(se) && unlikely(task_has_idle_policy(task_of(se))))
6855 		return;
6856 
6857 	for_each_sched_entity(se) {
6858 		if (SCHED_WARN_ON(!se->on_rq))
6859 			return;
6860 		cfs_rq_of(se)->next = se;
6861 	}
6862 }
6863 
6864 static void set_skip_buddy(struct sched_entity *se)
6865 {
6866 	for_each_sched_entity(se)
6867 		cfs_rq_of(se)->skip = se;
6868 }
6869 
6870 /*
6871  * Preempt the current task with a newly woken task if needed:
6872  */
6873 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
6874 {
6875 	struct task_struct *curr = rq->curr;
6876 	struct sched_entity *se = &curr->se, *pse = &p->se;
6877 	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6878 	int scale = cfs_rq->nr_running >= sched_nr_latency;
6879 	int next_buddy_marked = 0;
6880 
6881 	if (unlikely(se == pse))
6882 		return;
6883 
6884 	/*
6885 	 * This is possible from callers such as attach_tasks(), in which we
6886 	 * unconditionally check_prempt_curr() after an enqueue (which may have
6887 	 * lead to a throttle).  This both saves work and prevents false
6888 	 * next-buddy nomination below.
6889 	 */
6890 	if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
6891 		return;
6892 
6893 	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
6894 		set_next_buddy(pse);
6895 		next_buddy_marked = 1;
6896 	}
6897 
6898 	/*
6899 	 * We can come here with TIF_NEED_RESCHED already set from new task
6900 	 * wake up path.
6901 	 *
6902 	 * Note: this also catches the edge-case of curr being in a throttled
6903 	 * group (e.g. via set_curr_task), since update_curr() (in the
6904 	 * enqueue of curr) will have resulted in resched being set.  This
6905 	 * prevents us from potentially nominating it as a false LAST_BUDDY
6906 	 * below.
6907 	 */
6908 	if (test_tsk_need_resched(curr))
6909 		return;
6910 
6911 	/* Idle tasks are by definition preempted by non-idle tasks. */
6912 	if (unlikely(task_has_idle_policy(curr)) &&
6913 	    likely(!task_has_idle_policy(p)))
6914 		goto preempt;
6915 
6916 	/*
6917 	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
6918 	 * is driven by the tick):
6919 	 */
6920 	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
6921 		return;
6922 
6923 	find_matching_se(&se, &pse);
6924 	update_curr(cfs_rq_of(se));
6925 	BUG_ON(!pse);
6926 	if (wakeup_preempt_entity(se, pse) == 1) {
6927 		/*
6928 		 * Bias pick_next to pick the sched entity that is
6929 		 * triggering this preemption.
6930 		 */
6931 		if (!next_buddy_marked)
6932 			set_next_buddy(pse);
6933 		goto preempt;
6934 	}
6935 
6936 	return;
6937 
6938 preempt:
6939 	resched_curr(rq);
6940 	/*
6941 	 * Only set the backward buddy when the current task is still
6942 	 * on the rq. This can happen when a wakeup gets interleaved
6943 	 * with schedule on the ->pre_schedule() or idle_balance()
6944 	 * point, either of which can * drop the rq lock.
6945 	 *
6946 	 * Also, during early boot the idle thread is in the fair class,
6947 	 * for obvious reasons its a bad idea to schedule back to it.
6948 	 */
6949 	if (unlikely(!se->on_rq || curr == rq->idle))
6950 		return;
6951 
6952 	if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
6953 		set_last_buddy(se);
6954 }
6955 
6956 struct task_struct *
6957 pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6958 {
6959 	struct cfs_rq *cfs_rq = &rq->cfs;
6960 	struct sched_entity *se;
6961 	struct task_struct *p;
6962 	int new_tasks;
6963 
6964 again:
6965 	if (!sched_fair_runnable(rq))
6966 		goto idle;
6967 
6968 #ifdef CONFIG_FAIR_GROUP_SCHED
6969 	if (!prev || prev->sched_class != &fair_sched_class)
6970 		goto simple;
6971 
6972 	/*
6973 	 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
6974 	 * likely that a next task is from the same cgroup as the current.
6975 	 *
6976 	 * Therefore attempt to avoid putting and setting the entire cgroup
6977 	 * hierarchy, only change the part that actually changes.
6978 	 */
6979 
6980 	do {
6981 		struct sched_entity *curr = cfs_rq->curr;
6982 
6983 		/*
6984 		 * Since we got here without doing put_prev_entity() we also
6985 		 * have to consider cfs_rq->curr. If it is still a runnable
6986 		 * entity, update_curr() will update its vruntime, otherwise
6987 		 * forget we've ever seen it.
6988 		 */
6989 		if (curr) {
6990 			if (curr->on_rq)
6991 				update_curr(cfs_rq);
6992 			else
6993 				curr = NULL;
6994 
6995 			/*
6996 			 * This call to check_cfs_rq_runtime() will do the
6997 			 * throttle and dequeue its entity in the parent(s).
6998 			 * Therefore the nr_running test will indeed
6999 			 * be correct.
7000 			 */
7001 			if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
7002 				cfs_rq = &rq->cfs;
7003 
7004 				if (!cfs_rq->nr_running)
7005 					goto idle;
7006 
7007 				goto simple;
7008 			}
7009 		}
7010 
7011 		se = pick_next_entity(cfs_rq, curr);
7012 		cfs_rq = group_cfs_rq(se);
7013 	} while (cfs_rq);
7014 
7015 	p = task_of(se);
7016 
7017 	/*
7018 	 * Since we haven't yet done put_prev_entity and if the selected task
7019 	 * is a different task than we started out with, try and touch the
7020 	 * least amount of cfs_rqs.
7021 	 */
7022 	if (prev != p) {
7023 		struct sched_entity *pse = &prev->se;
7024 
7025 		while (!(cfs_rq = is_same_group(se, pse))) {
7026 			int se_depth = se->depth;
7027 			int pse_depth = pse->depth;
7028 
7029 			if (se_depth <= pse_depth) {
7030 				put_prev_entity(cfs_rq_of(pse), pse);
7031 				pse = parent_entity(pse);
7032 			}
7033 			if (se_depth >= pse_depth) {
7034 				set_next_entity(cfs_rq_of(se), se);
7035 				se = parent_entity(se);
7036 			}
7037 		}
7038 
7039 		put_prev_entity(cfs_rq, pse);
7040 		set_next_entity(cfs_rq, se);
7041 	}
7042 
7043 	goto done;
7044 simple:
7045 #endif
7046 	if (prev)
7047 		put_prev_task(rq, prev);
7048 
7049 	do {
7050 		se = pick_next_entity(cfs_rq, NULL);
7051 		set_next_entity(cfs_rq, se);
7052 		cfs_rq = group_cfs_rq(se);
7053 	} while (cfs_rq);
7054 
7055 	p = task_of(se);
7056 
7057 done: __maybe_unused;
7058 #ifdef CONFIG_SMP
7059 	/*
7060 	 * Move the next running task to the front of
7061 	 * the list, so our cfs_tasks list becomes MRU
7062 	 * one.
7063 	 */
7064 	list_move(&p->se.group_node, &rq->cfs_tasks);
7065 #endif
7066 
7067 	if (hrtick_enabled(rq))
7068 		hrtick_start_fair(rq, p);
7069 
7070 	update_misfit_status(p, rq);
7071 
7072 	return p;
7073 
7074 idle:
7075 	if (!rf)
7076 		return NULL;
7077 
7078 	new_tasks = newidle_balance(rq, rf);
7079 
7080 	/*
7081 	 * Because newidle_balance() releases (and re-acquires) rq->lock, it is
7082 	 * possible for any higher priority task to appear. In that case we
7083 	 * must re-start the pick_next_entity() loop.
7084 	 */
7085 	if (new_tasks < 0)
7086 		return RETRY_TASK;
7087 
7088 	if (new_tasks > 0)
7089 		goto again;
7090 
7091 	/*
7092 	 * rq is about to be idle, check if we need to update the
7093 	 * lost_idle_time of clock_pelt
7094 	 */
7095 	update_idle_rq_clock_pelt(rq);
7096 
7097 	return NULL;
7098 }
7099 
7100 static struct task_struct *__pick_next_task_fair(struct rq *rq)
7101 {
7102 	return pick_next_task_fair(rq, NULL, NULL);
7103 }
7104 
7105 /*
7106  * Account for a descheduled task:
7107  */
7108 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
7109 {
7110 	struct sched_entity *se = &prev->se;
7111 	struct cfs_rq *cfs_rq;
7112 
7113 	for_each_sched_entity(se) {
7114 		cfs_rq = cfs_rq_of(se);
7115 		put_prev_entity(cfs_rq, se);
7116 	}
7117 }
7118 
7119 /*
7120  * sched_yield() is very simple
7121  *
7122  * The magic of dealing with the ->skip buddy is in pick_next_entity.
7123  */
7124 static void yield_task_fair(struct rq *rq)
7125 {
7126 	struct task_struct *curr = rq->curr;
7127 	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
7128 	struct sched_entity *se = &curr->se;
7129 
7130 	/*
7131 	 * Are we the only task in the tree?
7132 	 */
7133 	if (unlikely(rq->nr_running == 1))
7134 		return;
7135 
7136 	clear_buddies(cfs_rq, se);
7137 
7138 	if (curr->policy != SCHED_BATCH) {
7139 		update_rq_clock(rq);
7140 		/*
7141 		 * Update run-time statistics of the 'current'.
7142 		 */
7143 		update_curr(cfs_rq);
7144 		/*
7145 		 * Tell update_rq_clock() that we've just updated,
7146 		 * so we don't do microscopic update in schedule()
7147 		 * and double the fastpath cost.
7148 		 */
7149 		rq_clock_skip_update(rq);
7150 	}
7151 
7152 	set_skip_buddy(se);
7153 }
7154 
7155 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
7156 {
7157 	struct sched_entity *se = &p->se;
7158 
7159 	/* throttled hierarchies are not runnable */
7160 	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
7161 		return false;
7162 
7163 	/* Tell the scheduler that we'd really like pse to run next. */
7164 	set_next_buddy(se);
7165 
7166 	yield_task_fair(rq);
7167 
7168 	return true;
7169 }
7170 
7171 #ifdef CONFIG_SMP
7172 /**************************************************
7173  * Fair scheduling class load-balancing methods.
7174  *
7175  * BASICS
7176  *
7177  * The purpose of load-balancing is to achieve the same basic fairness the
7178  * per-CPU scheduler provides, namely provide a proportional amount of compute
7179  * time to each task. This is expressed in the following equation:
7180  *
7181  *   W_i,n/P_i == W_j,n/P_j for all i,j                               (1)
7182  *
7183  * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
7184  * W_i,0 is defined as:
7185  *
7186  *   W_i,0 = \Sum_j w_i,j                                             (2)
7187  *
7188  * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
7189  * is derived from the nice value as per sched_prio_to_weight[].
7190  *
7191  * The weight average is an exponential decay average of the instantaneous
7192  * weight:
7193  *
7194  *   W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0               (3)
7195  *
7196  * C_i is the compute capacity of CPU i, typically it is the
7197  * fraction of 'recent' time available for SCHED_OTHER task execution. But it
7198  * can also include other factors [XXX].
7199  *
7200  * To achieve this balance we define a measure of imbalance which follows
7201  * directly from (1):
7202  *
7203  *   imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j }    (4)
7204  *
7205  * We them move tasks around to minimize the imbalance. In the continuous
7206  * function space it is obvious this converges, in the discrete case we get
7207  * a few fun cases generally called infeasible weight scenarios.
7208  *
7209  * [XXX expand on:
7210  *     - infeasible weights;
7211  *     - local vs global optima in the discrete case. ]
7212  *
7213  *
7214  * SCHED DOMAINS
7215  *
7216  * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
7217  * for all i,j solution, we create a tree of CPUs that follows the hardware
7218  * topology where each level pairs two lower groups (or better). This results
7219  * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
7220  * tree to only the first of the previous level and we decrease the frequency
7221  * of load-balance at each level inv. proportional to the number of CPUs in
7222  * the groups.
7223  *
7224  * This yields:
7225  *
7226  *     log_2 n     1     n
7227  *   \Sum       { --- * --- * 2^i } = O(n)                            (5)
7228  *     i = 0      2^i   2^i
7229  *                               `- size of each group
7230  *         |         |     `- number of CPUs doing load-balance
7231  *         |         `- freq
7232  *         `- sum over all levels
7233  *
7234  * Coupled with a limit on how many tasks we can migrate every balance pass,
7235  * this makes (5) the runtime complexity of the balancer.
7236  *
7237  * An important property here is that each CPU is still (indirectly) connected
7238  * to every other CPU in at most O(log n) steps:
7239  *
7240  * The adjacency matrix of the resulting graph is given by:
7241  *
7242  *             log_2 n
7243  *   A_i,j = \Union     (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1)  (6)
7244  *             k = 0
7245  *
7246  * And you'll find that:
7247  *
7248  *   A^(log_2 n)_i,j != 0  for all i,j                                (7)
7249  *
7250  * Showing there's indeed a path between every CPU in at most O(log n) steps.
7251  * The task movement gives a factor of O(m), giving a convergence complexity
7252  * of:
7253  *
7254  *   O(nm log n),  n := nr_cpus, m := nr_tasks                        (8)
7255  *
7256  *
7257  * WORK CONSERVING
7258  *
7259  * In order to avoid CPUs going idle while there's still work to do, new idle
7260  * balancing is more aggressive and has the newly idle CPU iterate up the domain
7261  * tree itself instead of relying on other CPUs to bring it work.
7262  *
7263  * This adds some complexity to both (5) and (8) but it reduces the total idle
7264  * time.
7265  *
7266  * [XXX more?]
7267  *
7268  *
7269  * CGROUPS
7270  *
7271  * Cgroups make a horror show out of (2), instead of a simple sum we get:
7272  *
7273  *                                s_k,i
7274  *   W_i,0 = \Sum_j \Prod_k w_k * -----                               (9)
7275  *                                 S_k
7276  *
7277  * Where
7278  *
7279  *   s_k,i = \Sum_j w_i,j,k  and  S_k = \Sum_i s_k,i                 (10)
7280  *
7281  * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
7282  *
7283  * The big problem is S_k, its a global sum needed to compute a local (W_i)
7284  * property.
7285  *
7286  * [XXX write more on how we solve this.. _after_ merging pjt's patches that
7287  *      rewrite all of this once again.]
7288  */
7289 
7290 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
7291 
7292 enum fbq_type { regular, remote, all };
7293 
7294 /*
7295  * 'group_type' describes the group of CPUs at the moment of load balancing.
7296  *
7297  * The enum is ordered by pulling priority, with the group with lowest priority
7298  * first so the group_type can simply be compared when selecting the busiest
7299  * group. See update_sd_pick_busiest().
7300  */
7301 enum group_type {
7302 	/* The group has spare capacity that can be used to run more tasks.  */
7303 	group_has_spare = 0,
7304 	/*
7305 	 * The group is fully used and the tasks don't compete for more CPU
7306 	 * cycles. Nevertheless, some tasks might wait before running.
7307 	 */
7308 	group_fully_busy,
7309 	/*
7310 	 * SD_ASYM_CPUCAPACITY only: One task doesn't fit with CPU's capacity
7311 	 * and must be migrated to a more powerful CPU.
7312 	 */
7313 	group_misfit_task,
7314 	/*
7315 	 * SD_ASYM_PACKING only: One local CPU with higher capacity is available,
7316 	 * and the task should be migrated to it instead of running on the
7317 	 * current CPU.
7318 	 */
7319 	group_asym_packing,
7320 	/*
7321 	 * The tasks' affinity constraints previously prevented the scheduler
7322 	 * from balancing the load across the system.
7323 	 */
7324 	group_imbalanced,
7325 	/*
7326 	 * The CPU is overloaded and can't provide expected CPU cycles to all
7327 	 * tasks.
7328 	 */
7329 	group_overloaded
7330 };
7331 
7332 enum migration_type {
7333 	migrate_load = 0,
7334 	migrate_util,
7335 	migrate_task,
7336 	migrate_misfit
7337 };
7338 
7339 #define LBF_ALL_PINNED	0x01
7340 #define LBF_NEED_BREAK	0x02
7341 #define LBF_DST_PINNED  0x04
7342 #define LBF_SOME_PINNED	0x08
7343 #define LBF_NOHZ_STATS	0x10
7344 #define LBF_NOHZ_AGAIN	0x20
7345 
7346 struct lb_env {
7347 	struct sched_domain	*sd;
7348 
7349 	struct rq		*src_rq;
7350 	int			src_cpu;
7351 
7352 	int			dst_cpu;
7353 	struct rq		*dst_rq;
7354 
7355 	struct cpumask		*dst_grpmask;
7356 	int			new_dst_cpu;
7357 	enum cpu_idle_type	idle;
7358 	long			imbalance;
7359 	/* The set of CPUs under consideration for load-balancing */
7360 	struct cpumask		*cpus;
7361 
7362 	unsigned int		flags;
7363 
7364 	unsigned int		loop;
7365 	unsigned int		loop_break;
7366 	unsigned int		loop_max;
7367 
7368 	enum fbq_type		fbq_type;
7369 	enum migration_type	migration_type;
7370 	struct list_head	tasks;
7371 };
7372 
7373 /*
7374  * Is this task likely cache-hot:
7375  */
7376 static int task_hot(struct task_struct *p, struct lb_env *env)
7377 {
7378 	s64 delta;
7379 
7380 	lockdep_assert_held(&env->src_rq->lock);
7381 
7382 	if (p->sched_class != &fair_sched_class)
7383 		return 0;
7384 
7385 	if (unlikely(task_has_idle_policy(p)))
7386 		return 0;
7387 
7388 	/*
7389 	 * Buddy candidates are cache hot:
7390 	 */
7391 	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
7392 			(&p->se == cfs_rq_of(&p->se)->next ||
7393 			 &p->se == cfs_rq_of(&p->se)->last))
7394 		return 1;
7395 
7396 	if (sysctl_sched_migration_cost == -1)
7397 		return 1;
7398 	if (sysctl_sched_migration_cost == 0)
7399 		return 0;
7400 
7401 	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
7402 
7403 	return delta < (s64)sysctl_sched_migration_cost;
7404 }
7405 
7406 #ifdef CONFIG_NUMA_BALANCING
7407 /*
7408  * Returns 1, if task migration degrades locality
7409  * Returns 0, if task migration improves locality i.e migration preferred.
7410  * Returns -1, if task migration is not affected by locality.
7411  */
7412 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
7413 {
7414 	struct numa_group *numa_group = rcu_dereference(p->numa_group);
7415 	unsigned long src_weight, dst_weight;
7416 	int src_nid, dst_nid, dist;
7417 
7418 	if (!static_branch_likely(&sched_numa_balancing))
7419 		return -1;
7420 
7421 	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
7422 		return -1;
7423 
7424 	src_nid = cpu_to_node(env->src_cpu);
7425 	dst_nid = cpu_to_node(env->dst_cpu);
7426 
7427 	if (src_nid == dst_nid)
7428 		return -1;
7429 
7430 	/* Migrating away from the preferred node is always bad. */
7431 	if (src_nid == p->numa_preferred_nid) {
7432 		if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
7433 			return 1;
7434 		else
7435 			return -1;
7436 	}
7437 
7438 	/* Encourage migration to the preferred node. */
7439 	if (dst_nid == p->numa_preferred_nid)
7440 		return 0;
7441 
7442 	/* Leaving a core idle is often worse than degrading locality. */
7443 	if (env->idle == CPU_IDLE)
7444 		return -1;
7445 
7446 	dist = node_distance(src_nid, dst_nid);
7447 	if (numa_group) {
7448 		src_weight = group_weight(p, src_nid, dist);
7449 		dst_weight = group_weight(p, dst_nid, dist);
7450 	} else {
7451 		src_weight = task_weight(p, src_nid, dist);
7452 		dst_weight = task_weight(p, dst_nid, dist);
7453 	}
7454 
7455 	return dst_weight < src_weight;
7456 }
7457 
7458 #else
7459 static inline int migrate_degrades_locality(struct task_struct *p,
7460 					     struct lb_env *env)
7461 {
7462 	return -1;
7463 }
7464 #endif
7465 
7466 /*
7467  * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
7468  */
7469 static
7470 int can_migrate_task(struct task_struct *p, struct lb_env *env)
7471 {
7472 	int tsk_cache_hot;
7473 
7474 	lockdep_assert_held(&env->src_rq->lock);
7475 
7476 	/*
7477 	 * We do not migrate tasks that are:
7478 	 * 1) throttled_lb_pair, or
7479 	 * 2) cannot be migrated to this CPU due to cpus_ptr, or
7480 	 * 3) running (obviously), or
7481 	 * 4) are cache-hot on their current CPU.
7482 	 */
7483 	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
7484 		return 0;
7485 
7486 	if (!cpumask_test_cpu(env->dst_cpu, p->cpus_ptr)) {
7487 		int cpu;
7488 
7489 		schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
7490 
7491 		env->flags |= LBF_SOME_PINNED;
7492 
7493 		/*
7494 		 * Remember if this task can be migrated to any other CPU in
7495 		 * our sched_group. We may want to revisit it if we couldn't
7496 		 * meet load balance goals by pulling other tasks on src_cpu.
7497 		 *
7498 		 * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
7499 		 * already computed one in current iteration.
7500 		 */
7501 		if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED))
7502 			return 0;
7503 
7504 		/* Prevent to re-select dst_cpu via env's CPUs: */
7505 		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
7506 			if (cpumask_test_cpu(cpu, p->cpus_ptr)) {
7507 				env->flags |= LBF_DST_PINNED;
7508 				env->new_dst_cpu = cpu;
7509 				break;
7510 			}
7511 		}
7512 
7513 		return 0;
7514 	}
7515 
7516 	/* Record that we found atleast one task that could run on dst_cpu */
7517 	env->flags &= ~LBF_ALL_PINNED;
7518 
7519 	if (task_running(env->src_rq, p)) {
7520 		schedstat_inc(p->se.statistics.nr_failed_migrations_running);
7521 		return 0;
7522 	}
7523 
7524 	/*
7525 	 * Aggressive migration if:
7526 	 * 1) destination numa is preferred
7527 	 * 2) task is cache cold, or
7528 	 * 3) too many balance attempts have failed.
7529 	 */
7530 	tsk_cache_hot = migrate_degrades_locality(p, env);
7531 	if (tsk_cache_hot == -1)
7532 		tsk_cache_hot = task_hot(p, env);
7533 
7534 	if (tsk_cache_hot <= 0 ||
7535 	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
7536 		if (tsk_cache_hot == 1) {
7537 			schedstat_inc(env->sd->lb_hot_gained[env->idle]);
7538 			schedstat_inc(p->se.statistics.nr_forced_migrations);
7539 		}
7540 		return 1;
7541 	}
7542 
7543 	schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
7544 	return 0;
7545 }
7546 
7547 /*
7548  * detach_task() -- detach the task for the migration specified in env
7549  */
7550 static void detach_task(struct task_struct *p, struct lb_env *env)
7551 {
7552 	lockdep_assert_held(&env->src_rq->lock);
7553 
7554 	deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
7555 	set_task_cpu(p, env->dst_cpu);
7556 }
7557 
7558 /*
7559  * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
7560  * part of active balancing operations within "domain".
7561  *
7562  * Returns a task if successful and NULL otherwise.
7563  */
7564 static struct task_struct *detach_one_task(struct lb_env *env)
7565 {
7566 	struct task_struct *p;
7567 
7568 	lockdep_assert_held(&env->src_rq->lock);
7569 
7570 	list_for_each_entry_reverse(p,
7571 			&env->src_rq->cfs_tasks, se.group_node) {
7572 		if (!can_migrate_task(p, env))
7573 			continue;
7574 
7575 		detach_task(p, env);
7576 
7577 		/*
7578 		 * Right now, this is only the second place where
7579 		 * lb_gained[env->idle] is updated (other is detach_tasks)
7580 		 * so we can safely collect stats here rather than
7581 		 * inside detach_tasks().
7582 		 */
7583 		schedstat_inc(env->sd->lb_gained[env->idle]);
7584 		return p;
7585 	}
7586 	return NULL;
7587 }
7588 
7589 static const unsigned int sched_nr_migrate_break = 32;
7590 
7591 /*
7592  * detach_tasks() -- tries to detach up to imbalance load/util/tasks from
7593  * busiest_rq, as part of a balancing operation within domain "sd".
7594  *
7595  * Returns number of detached tasks if successful and 0 otherwise.
7596  */
7597 static int detach_tasks(struct lb_env *env)
7598 {
7599 	struct list_head *tasks = &env->src_rq->cfs_tasks;
7600 	unsigned long util, load;
7601 	struct task_struct *p;
7602 	int detached = 0;
7603 
7604 	lockdep_assert_held(&env->src_rq->lock);
7605 
7606 	if (env->imbalance <= 0)
7607 		return 0;
7608 
7609 	while (!list_empty(tasks)) {
7610 		/*
7611 		 * We don't want to steal all, otherwise we may be treated likewise,
7612 		 * which could at worst lead to a livelock crash.
7613 		 */
7614 		if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
7615 			break;
7616 
7617 		p = list_last_entry(tasks, struct task_struct, se.group_node);
7618 
7619 		env->loop++;
7620 		/* We've more or less seen every task there is, call it quits */
7621 		if (env->loop > env->loop_max)
7622 			break;
7623 
7624 		/* take a breather every nr_migrate tasks */
7625 		if (env->loop > env->loop_break) {
7626 			env->loop_break += sched_nr_migrate_break;
7627 			env->flags |= LBF_NEED_BREAK;
7628 			break;
7629 		}
7630 
7631 		if (!can_migrate_task(p, env))
7632 			goto next;
7633 
7634 		switch (env->migration_type) {
7635 		case migrate_load:
7636 			load = task_h_load(p);
7637 
7638 			if (sched_feat(LB_MIN) &&
7639 			    load < 16 && !env->sd->nr_balance_failed)
7640 				goto next;
7641 
7642 			/*
7643 			 * Make sure that we don't migrate too much load.
7644 			 * Nevertheless, let relax the constraint if
7645 			 * scheduler fails to find a good waiting task to
7646 			 * migrate.
7647 			 */
7648 			if (load/2 > env->imbalance &&
7649 			    env->sd->nr_balance_failed <= env->sd->cache_nice_tries)
7650 				goto next;
7651 
7652 			env->imbalance -= load;
7653 			break;
7654 
7655 		case migrate_util:
7656 			util = task_util_est(p);
7657 
7658 			if (util > env->imbalance)
7659 				goto next;
7660 
7661 			env->imbalance -= util;
7662 			break;
7663 
7664 		case migrate_task:
7665 			env->imbalance--;
7666 			break;
7667 
7668 		case migrate_misfit:
7669 			/* This is not a misfit task */
7670 			if (task_fits_capacity(p, capacity_of(env->src_cpu)))
7671 				goto next;
7672 
7673 			env->imbalance = 0;
7674 			break;
7675 		}
7676 
7677 		detach_task(p, env);
7678 		list_add(&p->se.group_node, &env->tasks);
7679 
7680 		detached++;
7681 
7682 #ifdef CONFIG_PREEMPTION
7683 		/*
7684 		 * NEWIDLE balancing is a source of latency, so preemptible
7685 		 * kernels will stop after the first task is detached to minimize
7686 		 * the critical section.
7687 		 */
7688 		if (env->idle == CPU_NEWLY_IDLE)
7689 			break;
7690 #endif
7691 
7692 		/*
7693 		 * We only want to steal up to the prescribed amount of
7694 		 * load/util/tasks.
7695 		 */
7696 		if (env->imbalance <= 0)
7697 			break;
7698 
7699 		continue;
7700 next:
7701 		list_move(&p->se.group_node, tasks);
7702 	}
7703 
7704 	/*
7705 	 * Right now, this is one of only two places we collect this stat
7706 	 * so we can safely collect detach_one_task() stats here rather
7707 	 * than inside detach_one_task().
7708 	 */
7709 	schedstat_add(env->sd->lb_gained[env->idle], detached);
7710 
7711 	return detached;
7712 }
7713 
7714 /*
7715  * attach_task() -- attach the task detached by detach_task() to its new rq.
7716  */
7717 static void attach_task(struct rq *rq, struct task_struct *p)
7718 {
7719 	lockdep_assert_held(&rq->lock);
7720 
7721 	BUG_ON(task_rq(p) != rq);
7722 	activate_task(rq, p, ENQUEUE_NOCLOCK);
7723 	check_preempt_curr(rq, p, 0);
7724 }
7725 
7726 /*
7727  * attach_one_task() -- attaches the task returned from detach_one_task() to
7728  * its new rq.
7729  */
7730 static void attach_one_task(struct rq *rq, struct task_struct *p)
7731 {
7732 	struct rq_flags rf;
7733 
7734 	rq_lock(rq, &rf);
7735 	update_rq_clock(rq);
7736 	attach_task(rq, p);
7737 	rq_unlock(rq, &rf);
7738 }
7739 
7740 /*
7741  * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
7742  * new rq.
7743  */
7744 static void attach_tasks(struct lb_env *env)
7745 {
7746 	struct list_head *tasks = &env->tasks;
7747 	struct task_struct *p;
7748 	struct rq_flags rf;
7749 
7750 	rq_lock(env->dst_rq, &rf);
7751 	update_rq_clock(env->dst_rq);
7752 
7753 	while (!list_empty(tasks)) {
7754 		p = list_first_entry(tasks, struct task_struct, se.group_node);
7755 		list_del_init(&p->se.group_node);
7756 
7757 		attach_task(env->dst_rq, p);
7758 	}
7759 
7760 	rq_unlock(env->dst_rq, &rf);
7761 }
7762 
7763 #ifdef CONFIG_NO_HZ_COMMON
7764 static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
7765 {
7766 	if (cfs_rq->avg.load_avg)
7767 		return true;
7768 
7769 	if (cfs_rq->avg.util_avg)
7770 		return true;
7771 
7772 	return false;
7773 }
7774 
7775 static inline bool others_have_blocked(struct rq *rq)
7776 {
7777 	if (READ_ONCE(rq->avg_rt.util_avg))
7778 		return true;
7779 
7780 	if (READ_ONCE(rq->avg_dl.util_avg))
7781 		return true;
7782 
7783 	if (thermal_load_avg(rq))
7784 		return true;
7785 
7786 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
7787 	if (READ_ONCE(rq->avg_irq.util_avg))
7788 		return true;
7789 #endif
7790 
7791 	return false;
7792 }
7793 
7794 static inline void update_blocked_load_status(struct rq *rq, bool has_blocked)
7795 {
7796 	rq->last_blocked_load_update_tick = jiffies;
7797 
7798 	if (!has_blocked)
7799 		rq->has_blocked_load = 0;
7800 }
7801 #else
7802 static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq) { return false; }
7803 static inline bool others_have_blocked(struct rq *rq) { return false; }
7804 static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) {}
7805 #endif
7806 
7807 static bool __update_blocked_others(struct rq *rq, bool *done)
7808 {
7809 	const struct sched_class *curr_class;
7810 	u64 now = rq_clock_pelt(rq);
7811 	unsigned long thermal_pressure;
7812 	bool decayed;
7813 
7814 	/*
7815 	 * update_load_avg() can call cpufreq_update_util(). Make sure that RT,
7816 	 * DL and IRQ signals have been updated before updating CFS.
7817 	 */
7818 	curr_class = rq->curr->sched_class;
7819 
7820 	thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
7821 
7822 	decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
7823 		  update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
7824 		  update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure) |
7825 		  update_irq_load_avg(rq, 0);
7826 
7827 	if (others_have_blocked(rq))
7828 		*done = false;
7829 
7830 	return decayed;
7831 }
7832 
7833 #ifdef CONFIG_FAIR_GROUP_SCHED
7834 
7835 static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
7836 {
7837 	if (cfs_rq->load.weight)
7838 		return false;
7839 
7840 	if (cfs_rq->avg.load_sum)
7841 		return false;
7842 
7843 	if (cfs_rq->avg.util_sum)
7844 		return false;
7845 
7846 	if (cfs_rq->avg.runnable_sum)
7847 		return false;
7848 
7849 	return true;
7850 }
7851 
7852 static bool __update_blocked_fair(struct rq *rq, bool *done)
7853 {
7854 	struct cfs_rq *cfs_rq, *pos;
7855 	bool decayed = false;
7856 	int cpu = cpu_of(rq);
7857 
7858 	/*
7859 	 * Iterates the task_group tree in a bottom up fashion, see
7860 	 * list_add_leaf_cfs_rq() for details.
7861 	 */
7862 	for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
7863 		struct sched_entity *se;
7864 
7865 		if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq)) {
7866 			update_tg_load_avg(cfs_rq, 0);
7867 
7868 			if (cfs_rq == &rq->cfs)
7869 				decayed = true;
7870 		}
7871 
7872 		/* Propagate pending load changes to the parent, if any: */
7873 		se = cfs_rq->tg->se[cpu];
7874 		if (se && !skip_blocked_update(se))
7875 			update_load_avg(cfs_rq_of(se), se, 0);
7876 
7877 		/*
7878 		 * There can be a lot of idle CPU cgroups.  Don't let fully
7879 		 * decayed cfs_rqs linger on the list.
7880 		 */
7881 		if (cfs_rq_is_decayed(cfs_rq))
7882 			list_del_leaf_cfs_rq(cfs_rq);
7883 
7884 		/* Don't need periodic decay once load/util_avg are null */
7885 		if (cfs_rq_has_blocked(cfs_rq))
7886 			*done = false;
7887 	}
7888 
7889 	return decayed;
7890 }
7891 
7892 /*
7893  * Compute the hierarchical load factor for cfs_rq and all its ascendants.
7894  * This needs to be done in a top-down fashion because the load of a child
7895  * group is a fraction of its parents load.
7896  */
7897 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
7898 {
7899 	struct rq *rq = rq_of(cfs_rq);
7900 	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
7901 	unsigned long now = jiffies;
7902 	unsigned long load;
7903 
7904 	if (cfs_rq->last_h_load_update == now)
7905 		return;
7906 
7907 	WRITE_ONCE(cfs_rq->h_load_next, NULL);
7908 	for_each_sched_entity(se) {
7909 		cfs_rq = cfs_rq_of(se);
7910 		WRITE_ONCE(cfs_rq->h_load_next, se);
7911 		if (cfs_rq->last_h_load_update == now)
7912 			break;
7913 	}
7914 
7915 	if (!se) {
7916 		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
7917 		cfs_rq->last_h_load_update = now;
7918 	}
7919 
7920 	while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) {
7921 		load = cfs_rq->h_load;
7922 		load = div64_ul(load * se->avg.load_avg,
7923 			cfs_rq_load_avg(cfs_rq) + 1);
7924 		cfs_rq = group_cfs_rq(se);
7925 		cfs_rq->h_load = load;
7926 		cfs_rq->last_h_load_update = now;
7927 	}
7928 }
7929 
7930 static unsigned long task_h_load(struct task_struct *p)
7931 {
7932 	struct cfs_rq *cfs_rq = task_cfs_rq(p);
7933 
7934 	update_cfs_rq_h_load(cfs_rq);
7935 	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
7936 			cfs_rq_load_avg(cfs_rq) + 1);
7937 }
7938 #else
7939 static bool __update_blocked_fair(struct rq *rq, bool *done)
7940 {
7941 	struct cfs_rq *cfs_rq = &rq->cfs;
7942 	bool decayed;
7943 
7944 	decayed = update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq);
7945 	if (cfs_rq_has_blocked(cfs_rq))
7946 		*done = false;
7947 
7948 	return decayed;
7949 }
7950 
7951 static unsigned long task_h_load(struct task_struct *p)
7952 {
7953 	return p->se.avg.load_avg;
7954 }
7955 #endif
7956 
7957 static void update_blocked_averages(int cpu)
7958 {
7959 	bool decayed = false, done = true;
7960 	struct rq *rq = cpu_rq(cpu);
7961 	struct rq_flags rf;
7962 
7963 	rq_lock_irqsave(rq, &rf);
7964 	update_rq_clock(rq);
7965 
7966 	decayed |= __update_blocked_others(rq, &done);
7967 	decayed |= __update_blocked_fair(rq, &done);
7968 
7969 	update_blocked_load_status(rq, !done);
7970 	if (decayed)
7971 		cpufreq_update_util(rq, 0);
7972 	rq_unlock_irqrestore(rq, &rf);
7973 }
7974 
7975 /********** Helpers for find_busiest_group ************************/
7976 
7977 /*
7978  * sg_lb_stats - stats of a sched_group required for load_balancing
7979  */
7980 struct sg_lb_stats {
7981 	unsigned long avg_load; /*Avg load across the CPUs of the group */
7982 	unsigned long group_load; /* Total load over the CPUs of the group */
7983 	unsigned long group_capacity;
7984 	unsigned long group_util; /* Total utilization over the CPUs of the group */
7985 	unsigned long group_runnable; /* Total runnable time over the CPUs of the group */
7986 	unsigned int sum_nr_running; /* Nr of tasks running in the group */
7987 	unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */
7988 	unsigned int idle_cpus;
7989 	unsigned int group_weight;
7990 	enum group_type group_type;
7991 	unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */
7992 	unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */
7993 #ifdef CONFIG_NUMA_BALANCING
7994 	unsigned int nr_numa_running;
7995 	unsigned int nr_preferred_running;
7996 #endif
7997 };
7998 
7999 /*
8000  * sd_lb_stats - Structure to store the statistics of a sched_domain
8001  *		 during load balancing.
8002  */
8003 struct sd_lb_stats {
8004 	struct sched_group *busiest;	/* Busiest group in this sd */
8005 	struct sched_group *local;	/* Local group in this sd */
8006 	unsigned long total_load;	/* Total load of all groups in sd */
8007 	unsigned long total_capacity;	/* Total capacity of all groups in sd */
8008 	unsigned long avg_load;	/* Average load across all groups in sd */
8009 	unsigned int prefer_sibling; /* tasks should go to sibling first */
8010 
8011 	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
8012 	struct sg_lb_stats local_stat;	/* Statistics of the local group */
8013 };
8014 
8015 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
8016 {
8017 	/*
8018 	 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
8019 	 * local_stat because update_sg_lb_stats() does a full clear/assignment.
8020 	 * We must however set busiest_stat::group_type and
8021 	 * busiest_stat::idle_cpus to the worst busiest group because
8022 	 * update_sd_pick_busiest() reads these before assignment.
8023 	 */
8024 	*sds = (struct sd_lb_stats){
8025 		.busiest = NULL,
8026 		.local = NULL,
8027 		.total_load = 0UL,
8028 		.total_capacity = 0UL,
8029 		.busiest_stat = {
8030 			.idle_cpus = UINT_MAX,
8031 			.group_type = group_has_spare,
8032 		},
8033 	};
8034 }
8035 
8036 static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu)
8037 {
8038 	struct rq *rq = cpu_rq(cpu);
8039 	unsigned long max = arch_scale_cpu_capacity(cpu);
8040 	unsigned long used, free;
8041 	unsigned long irq;
8042 
8043 	irq = cpu_util_irq(rq);
8044 
8045 	if (unlikely(irq >= max))
8046 		return 1;
8047 
8048 	/*
8049 	 * avg_rt.util_avg and avg_dl.util_avg track binary signals
8050 	 * (running and not running) with weights 0 and 1024 respectively.
8051 	 * avg_thermal.load_avg tracks thermal pressure and the weighted
8052 	 * average uses the actual delta max capacity(load).
8053 	 */
8054 	used = READ_ONCE(rq->avg_rt.util_avg);
8055 	used += READ_ONCE(rq->avg_dl.util_avg);
8056 	used += thermal_load_avg(rq);
8057 
8058 	if (unlikely(used >= max))
8059 		return 1;
8060 
8061 	free = max - used;
8062 
8063 	return scale_irq_capacity(free, irq, max);
8064 }
8065 
8066 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
8067 {
8068 	unsigned long capacity = scale_rt_capacity(sd, cpu);
8069 	struct sched_group *sdg = sd->groups;
8070 
8071 	cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu);
8072 
8073 	if (!capacity)
8074 		capacity = 1;
8075 
8076 	cpu_rq(cpu)->cpu_capacity = capacity;
8077 	sdg->sgc->capacity = capacity;
8078 	sdg->sgc->min_capacity = capacity;
8079 	sdg->sgc->max_capacity = capacity;
8080 }
8081 
8082 void update_group_capacity(struct sched_domain *sd, int cpu)
8083 {
8084 	struct sched_domain *child = sd->child;
8085 	struct sched_group *group, *sdg = sd->groups;
8086 	unsigned long capacity, min_capacity, max_capacity;
8087 	unsigned long interval;
8088 
8089 	interval = msecs_to_jiffies(sd->balance_interval);
8090 	interval = clamp(interval, 1UL, max_load_balance_interval);
8091 	sdg->sgc->next_update = jiffies + interval;
8092 
8093 	if (!child) {
8094 		update_cpu_capacity(sd, cpu);
8095 		return;
8096 	}
8097 
8098 	capacity = 0;
8099 	min_capacity = ULONG_MAX;
8100 	max_capacity = 0;
8101 
8102 	if (child->flags & SD_OVERLAP) {
8103 		/*
8104 		 * SD_OVERLAP domains cannot assume that child groups
8105 		 * span the current group.
8106 		 */
8107 
8108 		for_each_cpu(cpu, sched_group_span(sdg)) {
8109 			unsigned long cpu_cap = capacity_of(cpu);
8110 
8111 			capacity += cpu_cap;
8112 			min_capacity = min(cpu_cap, min_capacity);
8113 			max_capacity = max(cpu_cap, max_capacity);
8114 		}
8115 	} else  {
8116 		/*
8117 		 * !SD_OVERLAP domains can assume that child groups
8118 		 * span the current group.
8119 		 */
8120 
8121 		group = child->groups;
8122 		do {
8123 			struct sched_group_capacity *sgc = group->sgc;
8124 
8125 			capacity += sgc->capacity;
8126 			min_capacity = min(sgc->min_capacity, min_capacity);
8127 			max_capacity = max(sgc->max_capacity, max_capacity);
8128 			group = group->next;
8129 		} while (group != child->groups);
8130 	}
8131 
8132 	sdg->sgc->capacity = capacity;
8133 	sdg->sgc->min_capacity = min_capacity;
8134 	sdg->sgc->max_capacity = max_capacity;
8135 }
8136 
8137 /*
8138  * Check whether the capacity of the rq has been noticeably reduced by side
8139  * activity. The imbalance_pct is used for the threshold.
8140  * Return true is the capacity is reduced
8141  */
8142 static inline int
8143 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
8144 {
8145 	return ((rq->cpu_capacity * sd->imbalance_pct) <
8146 				(rq->cpu_capacity_orig * 100));
8147 }
8148 
8149 /*
8150  * Check whether a rq has a misfit task and if it looks like we can actually
8151  * help that task: we can migrate the task to a CPU of higher capacity, or
8152  * the task's current CPU is heavily pressured.
8153  */
8154 static inline int check_misfit_status(struct rq *rq, struct sched_domain *sd)
8155 {
8156 	return rq->misfit_task_load &&
8157 		(rq->cpu_capacity_orig < rq->rd->max_cpu_capacity ||
8158 		 check_cpu_capacity(rq, sd));
8159 }
8160 
8161 /*
8162  * Group imbalance indicates (and tries to solve) the problem where balancing
8163  * groups is inadequate due to ->cpus_ptr constraints.
8164  *
8165  * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
8166  * cpumask covering 1 CPU of the first group and 3 CPUs of the second group.
8167  * Something like:
8168  *
8169  *	{ 0 1 2 3 } { 4 5 6 7 }
8170  *	        *     * * *
8171  *
8172  * If we were to balance group-wise we'd place two tasks in the first group and
8173  * two tasks in the second group. Clearly this is undesired as it will overload
8174  * cpu 3 and leave one of the CPUs in the second group unused.
8175  *
8176  * The current solution to this issue is detecting the skew in the first group
8177  * by noticing the lower domain failed to reach balance and had difficulty
8178  * moving tasks due to affinity constraints.
8179  *
8180  * When this is so detected; this group becomes a candidate for busiest; see
8181  * update_sd_pick_busiest(). And calculate_imbalance() and
8182  * find_busiest_group() avoid some of the usual balance conditions to allow it
8183  * to create an effective group imbalance.
8184  *
8185  * This is a somewhat tricky proposition since the next run might not find the
8186  * group imbalance and decide the groups need to be balanced again. A most
8187  * subtle and fragile situation.
8188  */
8189 
8190 static inline int sg_imbalanced(struct sched_group *group)
8191 {
8192 	return group->sgc->imbalance;
8193 }
8194 
8195 /*
8196  * group_has_capacity returns true if the group has spare capacity that could
8197  * be used by some tasks.
8198  * We consider that a group has spare capacity if the  * number of task is
8199  * smaller than the number of CPUs or if the utilization is lower than the
8200  * available capacity for CFS tasks.
8201  * For the latter, we use a threshold to stabilize the state, to take into
8202  * account the variance of the tasks' load and to return true if the available
8203  * capacity in meaningful for the load balancer.
8204  * As an example, an available capacity of 1% can appear but it doesn't make
8205  * any benefit for the load balance.
8206  */
8207 static inline bool
8208 group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
8209 {
8210 	if (sgs->sum_nr_running < sgs->group_weight)
8211 		return true;
8212 
8213 	if ((sgs->group_capacity * imbalance_pct) <
8214 			(sgs->group_runnable * 100))
8215 		return false;
8216 
8217 	if ((sgs->group_capacity * 100) >
8218 			(sgs->group_util * imbalance_pct))
8219 		return true;
8220 
8221 	return false;
8222 }
8223 
8224 /*
8225  *  group_is_overloaded returns true if the group has more tasks than it can
8226  *  handle.
8227  *  group_is_overloaded is not equals to !group_has_capacity because a group
8228  *  with the exact right number of tasks, has no more spare capacity but is not
8229  *  overloaded so both group_has_capacity and group_is_overloaded return
8230  *  false.
8231  */
8232 static inline bool
8233 group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
8234 {
8235 	if (sgs->sum_nr_running <= sgs->group_weight)
8236 		return false;
8237 
8238 	if ((sgs->group_capacity * 100) <
8239 			(sgs->group_util * imbalance_pct))
8240 		return true;
8241 
8242 	if ((sgs->group_capacity * imbalance_pct) <
8243 			(sgs->group_runnable * 100))
8244 		return true;
8245 
8246 	return false;
8247 }
8248 
8249 /*
8250  * group_smaller_min_cpu_capacity: Returns true if sched_group sg has smaller
8251  * per-CPU capacity than sched_group ref.
8252  */
8253 static inline bool
8254 group_smaller_min_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
8255 {
8256 	return fits_capacity(sg->sgc->min_capacity, ref->sgc->min_capacity);
8257 }
8258 
8259 /*
8260  * group_smaller_max_cpu_capacity: Returns true if sched_group sg has smaller
8261  * per-CPU capacity_orig than sched_group ref.
8262  */
8263 static inline bool
8264 group_smaller_max_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
8265 {
8266 	return fits_capacity(sg->sgc->max_capacity, ref->sgc->max_capacity);
8267 }
8268 
8269 static inline enum
8270 group_type group_classify(unsigned int imbalance_pct,
8271 			  struct sched_group *group,
8272 			  struct sg_lb_stats *sgs)
8273 {
8274 	if (group_is_overloaded(imbalance_pct, sgs))
8275 		return group_overloaded;
8276 
8277 	if (sg_imbalanced(group))
8278 		return group_imbalanced;
8279 
8280 	if (sgs->group_asym_packing)
8281 		return group_asym_packing;
8282 
8283 	if (sgs->group_misfit_task_load)
8284 		return group_misfit_task;
8285 
8286 	if (!group_has_capacity(imbalance_pct, sgs))
8287 		return group_fully_busy;
8288 
8289 	return group_has_spare;
8290 }
8291 
8292 static bool update_nohz_stats(struct rq *rq, bool force)
8293 {
8294 #ifdef CONFIG_NO_HZ_COMMON
8295 	unsigned int cpu = rq->cpu;
8296 
8297 	if (!rq->has_blocked_load)
8298 		return false;
8299 
8300 	if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
8301 		return false;
8302 
8303 	if (!force && !time_after(jiffies, rq->last_blocked_load_update_tick))
8304 		return true;
8305 
8306 	update_blocked_averages(cpu);
8307 
8308 	return rq->has_blocked_load;
8309 #else
8310 	return false;
8311 #endif
8312 }
8313 
8314 /**
8315  * update_sg_lb_stats - Update sched_group's statistics for load balancing.
8316  * @env: The load balancing environment.
8317  * @group: sched_group whose statistics are to be updated.
8318  * @sgs: variable to hold the statistics for this group.
8319  * @sg_status: Holds flag indicating the status of the sched_group
8320  */
8321 static inline void update_sg_lb_stats(struct lb_env *env,
8322 				      struct sched_group *group,
8323 				      struct sg_lb_stats *sgs,
8324 				      int *sg_status)
8325 {
8326 	int i, nr_running, local_group;
8327 
8328 	memset(sgs, 0, sizeof(*sgs));
8329 
8330 	local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(group));
8331 
8332 	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
8333 		struct rq *rq = cpu_rq(i);
8334 
8335 		if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq, false))
8336 			env->flags |= LBF_NOHZ_AGAIN;
8337 
8338 		sgs->group_load += cpu_load(rq);
8339 		sgs->group_util += cpu_util(i);
8340 		sgs->group_runnable += cpu_runnable(rq);
8341 		sgs->sum_h_nr_running += rq->cfs.h_nr_running;
8342 
8343 		nr_running = rq->nr_running;
8344 		sgs->sum_nr_running += nr_running;
8345 
8346 		if (nr_running > 1)
8347 			*sg_status |= SG_OVERLOAD;
8348 
8349 		if (cpu_overutilized(i))
8350 			*sg_status |= SG_OVERUTILIZED;
8351 
8352 #ifdef CONFIG_NUMA_BALANCING
8353 		sgs->nr_numa_running += rq->nr_numa_running;
8354 		sgs->nr_preferred_running += rq->nr_preferred_running;
8355 #endif
8356 		/*
8357 		 * No need to call idle_cpu() if nr_running is not 0
8358 		 */
8359 		if (!nr_running && idle_cpu(i)) {
8360 			sgs->idle_cpus++;
8361 			/* Idle cpu can't have misfit task */
8362 			continue;
8363 		}
8364 
8365 		if (local_group)
8366 			continue;
8367 
8368 		/* Check for a misfit task on the cpu */
8369 		if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
8370 		    sgs->group_misfit_task_load < rq->misfit_task_load) {
8371 			sgs->group_misfit_task_load = rq->misfit_task_load;
8372 			*sg_status |= SG_OVERLOAD;
8373 		}
8374 	}
8375 
8376 	/* Check if dst CPU is idle and preferred to this group */
8377 	if (env->sd->flags & SD_ASYM_PACKING &&
8378 	    env->idle != CPU_NOT_IDLE &&
8379 	    sgs->sum_h_nr_running &&
8380 	    sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu)) {
8381 		sgs->group_asym_packing = 1;
8382 	}
8383 
8384 	sgs->group_capacity = group->sgc->capacity;
8385 
8386 	sgs->group_weight = group->group_weight;
8387 
8388 	sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs);
8389 
8390 	/* Computing avg_load makes sense only when group is overloaded */
8391 	if (sgs->group_type == group_overloaded)
8392 		sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
8393 				sgs->group_capacity;
8394 }
8395 
8396 /**
8397  * update_sd_pick_busiest - return 1 on busiest group
8398  * @env: The load balancing environment.
8399  * @sds: sched_domain statistics
8400  * @sg: sched_group candidate to be checked for being the busiest
8401  * @sgs: sched_group statistics
8402  *
8403  * Determine if @sg is a busier group than the previously selected
8404  * busiest group.
8405  *
8406  * Return: %true if @sg is a busier group than the previously selected
8407  * busiest group. %false otherwise.
8408  */
8409 static bool update_sd_pick_busiest(struct lb_env *env,
8410 				   struct sd_lb_stats *sds,
8411 				   struct sched_group *sg,
8412 				   struct sg_lb_stats *sgs)
8413 {
8414 	struct sg_lb_stats *busiest = &sds->busiest_stat;
8415 
8416 	/* Make sure that there is at least one task to pull */
8417 	if (!sgs->sum_h_nr_running)
8418 		return false;
8419 
8420 	/*
8421 	 * Don't try to pull misfit tasks we can't help.
8422 	 * We can use max_capacity here as reduction in capacity on some
8423 	 * CPUs in the group should either be possible to resolve
8424 	 * internally or be covered by avg_load imbalance (eventually).
8425 	 */
8426 	if (sgs->group_type == group_misfit_task &&
8427 	    (!group_smaller_max_cpu_capacity(sg, sds->local) ||
8428 	     sds->local_stat.group_type != group_has_spare))
8429 		return false;
8430 
8431 	if (sgs->group_type > busiest->group_type)
8432 		return true;
8433 
8434 	if (sgs->group_type < busiest->group_type)
8435 		return false;
8436 
8437 	/*
8438 	 * The candidate and the current busiest group are the same type of
8439 	 * group. Let check which one is the busiest according to the type.
8440 	 */
8441 
8442 	switch (sgs->group_type) {
8443 	case group_overloaded:
8444 		/* Select the overloaded group with highest avg_load. */
8445 		if (sgs->avg_load <= busiest->avg_load)
8446 			return false;
8447 		break;
8448 
8449 	case group_imbalanced:
8450 		/*
8451 		 * Select the 1st imbalanced group as we don't have any way to
8452 		 * choose one more than another.
8453 		 */
8454 		return false;
8455 
8456 	case group_asym_packing:
8457 		/* Prefer to move from lowest priority CPU's work */
8458 		if (sched_asym_prefer(sg->asym_prefer_cpu, sds->busiest->asym_prefer_cpu))
8459 			return false;
8460 		break;
8461 
8462 	case group_misfit_task:
8463 		/*
8464 		 * If we have more than one misfit sg go with the biggest
8465 		 * misfit.
8466 		 */
8467 		if (sgs->group_misfit_task_load < busiest->group_misfit_task_load)
8468 			return false;
8469 		break;
8470 
8471 	case group_fully_busy:
8472 		/*
8473 		 * Select the fully busy group with highest avg_load. In
8474 		 * theory, there is no need to pull task from such kind of
8475 		 * group because tasks have all compute capacity that they need
8476 		 * but we can still improve the overall throughput by reducing
8477 		 * contention when accessing shared HW resources.
8478 		 *
8479 		 * XXX for now avg_load is not computed and always 0 so we
8480 		 * select the 1st one.
8481 		 */
8482 		if (sgs->avg_load <= busiest->avg_load)
8483 			return false;
8484 		break;
8485 
8486 	case group_has_spare:
8487 		/*
8488 		 * Select not overloaded group with lowest number of idle cpus
8489 		 * and highest number of running tasks. We could also compare
8490 		 * the spare capacity which is more stable but it can end up
8491 		 * that the group has less spare capacity but finally more idle
8492 		 * CPUs which means less opportunity to pull tasks.
8493 		 */
8494 		if (sgs->idle_cpus > busiest->idle_cpus)
8495 			return false;
8496 		else if ((sgs->idle_cpus == busiest->idle_cpus) &&
8497 			 (sgs->sum_nr_running <= busiest->sum_nr_running))
8498 			return false;
8499 
8500 		break;
8501 	}
8502 
8503 	/*
8504 	 * Candidate sg has no more than one task per CPU and has higher
8505 	 * per-CPU capacity. Migrating tasks to less capable CPUs may harm
8506 	 * throughput. Maximize throughput, power/energy consequences are not
8507 	 * considered.
8508 	 */
8509 	if ((env->sd->flags & SD_ASYM_CPUCAPACITY) &&
8510 	    (sgs->group_type <= group_fully_busy) &&
8511 	    (group_smaller_min_cpu_capacity(sds->local, sg)))
8512 		return false;
8513 
8514 	return true;
8515 }
8516 
8517 #ifdef CONFIG_NUMA_BALANCING
8518 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
8519 {
8520 	if (sgs->sum_h_nr_running > sgs->nr_numa_running)
8521 		return regular;
8522 	if (sgs->sum_h_nr_running > sgs->nr_preferred_running)
8523 		return remote;
8524 	return all;
8525 }
8526 
8527 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
8528 {
8529 	if (rq->nr_running > rq->nr_numa_running)
8530 		return regular;
8531 	if (rq->nr_running > rq->nr_preferred_running)
8532 		return remote;
8533 	return all;
8534 }
8535 #else
8536 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
8537 {
8538 	return all;
8539 }
8540 
8541 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
8542 {
8543 	return regular;
8544 }
8545 #endif /* CONFIG_NUMA_BALANCING */
8546 
8547 
8548 struct sg_lb_stats;
8549 
8550 /*
8551  * task_running_on_cpu - return 1 if @p is running on @cpu.
8552  */
8553 
8554 static unsigned int task_running_on_cpu(int cpu, struct task_struct *p)
8555 {
8556 	/* Task has no contribution or is new */
8557 	if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
8558 		return 0;
8559 
8560 	if (task_on_rq_queued(p))
8561 		return 1;
8562 
8563 	return 0;
8564 }
8565 
8566 /**
8567  * idle_cpu_without - would a given CPU be idle without p ?
8568  * @cpu: the processor on which idleness is tested.
8569  * @p: task which should be ignored.
8570  *
8571  * Return: 1 if the CPU would be idle. 0 otherwise.
8572  */
8573 static int idle_cpu_without(int cpu, struct task_struct *p)
8574 {
8575 	struct rq *rq = cpu_rq(cpu);
8576 
8577 	if (rq->curr != rq->idle && rq->curr != p)
8578 		return 0;
8579 
8580 	/*
8581 	 * rq->nr_running can't be used but an updated version without the
8582 	 * impact of p on cpu must be used instead. The updated nr_running
8583 	 * be computed and tested before calling idle_cpu_without().
8584 	 */
8585 
8586 #ifdef CONFIG_SMP
8587 	if (!llist_empty(&rq->wake_list))
8588 		return 0;
8589 #endif
8590 
8591 	return 1;
8592 }
8593 
8594 /*
8595  * update_sg_wakeup_stats - Update sched_group's statistics for wakeup.
8596  * @sd: The sched_domain level to look for idlest group.
8597  * @group: sched_group whose statistics are to be updated.
8598  * @sgs: variable to hold the statistics for this group.
8599  * @p: The task for which we look for the idlest group/CPU.
8600  */
8601 static inline void update_sg_wakeup_stats(struct sched_domain *sd,
8602 					  struct sched_group *group,
8603 					  struct sg_lb_stats *sgs,
8604 					  struct task_struct *p)
8605 {
8606 	int i, nr_running;
8607 
8608 	memset(sgs, 0, sizeof(*sgs));
8609 
8610 	for_each_cpu(i, sched_group_span(group)) {
8611 		struct rq *rq = cpu_rq(i);
8612 		unsigned int local;
8613 
8614 		sgs->group_load += cpu_load_without(rq, p);
8615 		sgs->group_util += cpu_util_without(i, p);
8616 		sgs->group_runnable += cpu_runnable_without(rq, p);
8617 		local = task_running_on_cpu(i, p);
8618 		sgs->sum_h_nr_running += rq->cfs.h_nr_running - local;
8619 
8620 		nr_running = rq->nr_running - local;
8621 		sgs->sum_nr_running += nr_running;
8622 
8623 		/*
8624 		 * No need to call idle_cpu_without() if nr_running is not 0
8625 		 */
8626 		if (!nr_running && idle_cpu_without(i, p))
8627 			sgs->idle_cpus++;
8628 
8629 	}
8630 
8631 	/* Check if task fits in the group */
8632 	if (sd->flags & SD_ASYM_CPUCAPACITY &&
8633 	    !task_fits_capacity(p, group->sgc->max_capacity)) {
8634 		sgs->group_misfit_task_load = 1;
8635 	}
8636 
8637 	sgs->group_capacity = group->sgc->capacity;
8638 
8639 	sgs->group_weight = group->group_weight;
8640 
8641 	sgs->group_type = group_classify(sd->imbalance_pct, group, sgs);
8642 
8643 	/*
8644 	 * Computing avg_load makes sense only when group is fully busy or
8645 	 * overloaded
8646 	 */
8647 	if (sgs->group_type == group_fully_busy ||
8648 		sgs->group_type == group_overloaded)
8649 		sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
8650 				sgs->group_capacity;
8651 }
8652 
8653 static bool update_pick_idlest(struct sched_group *idlest,
8654 			       struct sg_lb_stats *idlest_sgs,
8655 			       struct sched_group *group,
8656 			       struct sg_lb_stats *sgs)
8657 {
8658 	if (sgs->group_type < idlest_sgs->group_type)
8659 		return true;
8660 
8661 	if (sgs->group_type > idlest_sgs->group_type)
8662 		return false;
8663 
8664 	/*
8665 	 * The candidate and the current idlest group are the same type of
8666 	 * group. Let check which one is the idlest according to the type.
8667 	 */
8668 
8669 	switch (sgs->group_type) {
8670 	case group_overloaded:
8671 	case group_fully_busy:
8672 		/* Select the group with lowest avg_load. */
8673 		if (idlest_sgs->avg_load <= sgs->avg_load)
8674 			return false;
8675 		break;
8676 
8677 	case group_imbalanced:
8678 	case group_asym_packing:
8679 		/* Those types are not used in the slow wakeup path */
8680 		return false;
8681 
8682 	case group_misfit_task:
8683 		/* Select group with the highest max capacity */
8684 		if (idlest->sgc->max_capacity >= group->sgc->max_capacity)
8685 			return false;
8686 		break;
8687 
8688 	case group_has_spare:
8689 		/* Select group with most idle CPUs */
8690 		if (idlest_sgs->idle_cpus >= sgs->idle_cpus)
8691 			return false;
8692 		break;
8693 	}
8694 
8695 	return true;
8696 }
8697 
8698 /*
8699  * find_idlest_group() finds and returns the least busy CPU group within the
8700  * domain.
8701  *
8702  * Assumes p is allowed on at least one CPU in sd.
8703  */
8704 static struct sched_group *
8705 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
8706 		  int this_cpu, int sd_flag)
8707 {
8708 	struct sched_group *idlest = NULL, *local = NULL, *group = sd->groups;
8709 	struct sg_lb_stats local_sgs, tmp_sgs;
8710 	struct sg_lb_stats *sgs;
8711 	unsigned long imbalance;
8712 	struct sg_lb_stats idlest_sgs = {
8713 			.avg_load = UINT_MAX,
8714 			.group_type = group_overloaded,
8715 	};
8716 
8717 	imbalance = scale_load_down(NICE_0_LOAD) *
8718 				(sd->imbalance_pct-100) / 100;
8719 
8720 	do {
8721 		int local_group;
8722 
8723 		/* Skip over this group if it has no CPUs allowed */
8724 		if (!cpumask_intersects(sched_group_span(group),
8725 					p->cpus_ptr))
8726 			continue;
8727 
8728 		local_group = cpumask_test_cpu(this_cpu,
8729 					       sched_group_span(group));
8730 
8731 		if (local_group) {
8732 			sgs = &local_sgs;
8733 			local = group;
8734 		} else {
8735 			sgs = &tmp_sgs;
8736 		}
8737 
8738 		update_sg_wakeup_stats(sd, group, sgs, p);
8739 
8740 		if (!local_group && update_pick_idlest(idlest, &idlest_sgs, group, sgs)) {
8741 			idlest = group;
8742 			idlest_sgs = *sgs;
8743 		}
8744 
8745 	} while (group = group->next, group != sd->groups);
8746 
8747 
8748 	/* There is no idlest group to push tasks to */
8749 	if (!idlest)
8750 		return NULL;
8751 
8752 	/* The local group has been skipped because of CPU affinity */
8753 	if (!local)
8754 		return idlest;
8755 
8756 	/*
8757 	 * If the local group is idler than the selected idlest group
8758 	 * don't try and push the task.
8759 	 */
8760 	if (local_sgs.group_type < idlest_sgs.group_type)
8761 		return NULL;
8762 
8763 	/*
8764 	 * If the local group is busier than the selected idlest group
8765 	 * try and push the task.
8766 	 */
8767 	if (local_sgs.group_type > idlest_sgs.group_type)
8768 		return idlest;
8769 
8770 	switch (local_sgs.group_type) {
8771 	case group_overloaded:
8772 	case group_fully_busy:
8773 		/*
8774 		 * When comparing groups across NUMA domains, it's possible for
8775 		 * the local domain to be very lightly loaded relative to the
8776 		 * remote domains but "imbalance" skews the comparison making
8777 		 * remote CPUs look much more favourable. When considering
8778 		 * cross-domain, add imbalance to the load on the remote node
8779 		 * and consider staying local.
8780 		 */
8781 
8782 		if ((sd->flags & SD_NUMA) &&
8783 		    ((idlest_sgs.avg_load + imbalance) >= local_sgs.avg_load))
8784 			return NULL;
8785 
8786 		/*
8787 		 * If the local group is less loaded than the selected
8788 		 * idlest group don't try and push any tasks.
8789 		 */
8790 		if (idlest_sgs.avg_load >= (local_sgs.avg_load + imbalance))
8791 			return NULL;
8792 
8793 		if (100 * local_sgs.avg_load <= sd->imbalance_pct * idlest_sgs.avg_load)
8794 			return NULL;
8795 		break;
8796 
8797 	case group_imbalanced:
8798 	case group_asym_packing:
8799 		/* Those type are not used in the slow wakeup path */
8800 		return NULL;
8801 
8802 	case group_misfit_task:
8803 		/* Select group with the highest max capacity */
8804 		if (local->sgc->max_capacity >= idlest->sgc->max_capacity)
8805 			return NULL;
8806 		break;
8807 
8808 	case group_has_spare:
8809 		if (sd->flags & SD_NUMA) {
8810 #ifdef CONFIG_NUMA_BALANCING
8811 			int idlest_cpu;
8812 			/*
8813 			 * If there is spare capacity at NUMA, try to select
8814 			 * the preferred node
8815 			 */
8816 			if (cpu_to_node(this_cpu) == p->numa_preferred_nid)
8817 				return NULL;
8818 
8819 			idlest_cpu = cpumask_first(sched_group_span(idlest));
8820 			if (cpu_to_node(idlest_cpu) == p->numa_preferred_nid)
8821 				return idlest;
8822 #endif
8823 			/*
8824 			 * Otherwise, keep the task on this node to stay close
8825 			 * its wakeup source and improve locality. If there is
8826 			 * a real need of migration, periodic load balance will
8827 			 * take care of it.
8828 			 */
8829 			if (local_sgs.idle_cpus)
8830 				return NULL;
8831 		}
8832 
8833 		/*
8834 		 * Select group with highest number of idle CPUs. We could also
8835 		 * compare the utilization which is more stable but it can end
8836 		 * up that the group has less spare capacity but finally more
8837 		 * idle CPUs which means more opportunity to run task.
8838 		 */
8839 		if (local_sgs.idle_cpus >= idlest_sgs.idle_cpus)
8840 			return NULL;
8841 		break;
8842 	}
8843 
8844 	return idlest;
8845 }
8846 
8847 /**
8848  * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
8849  * @env: The load balancing environment.
8850  * @sds: variable to hold the statistics for this sched_domain.
8851  */
8852 
8853 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
8854 {
8855 	struct sched_domain *child = env->sd->child;
8856 	struct sched_group *sg = env->sd->groups;
8857 	struct sg_lb_stats *local = &sds->local_stat;
8858 	struct sg_lb_stats tmp_sgs;
8859 	int sg_status = 0;
8860 
8861 #ifdef CONFIG_NO_HZ_COMMON
8862 	if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked))
8863 		env->flags |= LBF_NOHZ_STATS;
8864 #endif
8865 
8866 	do {
8867 		struct sg_lb_stats *sgs = &tmp_sgs;
8868 		int local_group;
8869 
8870 		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
8871 		if (local_group) {
8872 			sds->local = sg;
8873 			sgs = local;
8874 
8875 			if (env->idle != CPU_NEWLY_IDLE ||
8876 			    time_after_eq(jiffies, sg->sgc->next_update))
8877 				update_group_capacity(env->sd, env->dst_cpu);
8878 		}
8879 
8880 		update_sg_lb_stats(env, sg, sgs, &sg_status);
8881 
8882 		if (local_group)
8883 			goto next_group;
8884 
8885 
8886 		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
8887 			sds->busiest = sg;
8888 			sds->busiest_stat = *sgs;
8889 		}
8890 
8891 next_group:
8892 		/* Now, start updating sd_lb_stats */
8893 		sds->total_load += sgs->group_load;
8894 		sds->total_capacity += sgs->group_capacity;
8895 
8896 		sg = sg->next;
8897 	} while (sg != env->sd->groups);
8898 
8899 	/* Tag domain that child domain prefers tasks go to siblings first */
8900 	sds->prefer_sibling = child && child->flags & SD_PREFER_SIBLING;
8901 
8902 #ifdef CONFIG_NO_HZ_COMMON
8903 	if ((env->flags & LBF_NOHZ_AGAIN) &&
8904 	    cpumask_subset(nohz.idle_cpus_mask, sched_domain_span(env->sd))) {
8905 
8906 		WRITE_ONCE(nohz.next_blocked,
8907 			   jiffies + msecs_to_jiffies(LOAD_AVG_PERIOD));
8908 	}
8909 #endif
8910 
8911 	if (env->sd->flags & SD_NUMA)
8912 		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
8913 
8914 	if (!env->sd->parent) {
8915 		struct root_domain *rd = env->dst_rq->rd;
8916 
8917 		/* update overload indicator if we are at root domain */
8918 		WRITE_ONCE(rd->overload, sg_status & SG_OVERLOAD);
8919 
8920 		/* Update over-utilization (tipping point, U >= 0) indicator */
8921 		WRITE_ONCE(rd->overutilized, sg_status & SG_OVERUTILIZED);
8922 		trace_sched_overutilized_tp(rd, sg_status & SG_OVERUTILIZED);
8923 	} else if (sg_status & SG_OVERUTILIZED) {
8924 		struct root_domain *rd = env->dst_rq->rd;
8925 
8926 		WRITE_ONCE(rd->overutilized, SG_OVERUTILIZED);
8927 		trace_sched_overutilized_tp(rd, SG_OVERUTILIZED);
8928 	}
8929 }
8930 
8931 static inline long adjust_numa_imbalance(int imbalance, int src_nr_running)
8932 {
8933 	unsigned int imbalance_min;
8934 
8935 	/*
8936 	 * Allow a small imbalance based on a simple pair of communicating
8937 	 * tasks that remain local when the source domain is almost idle.
8938 	 */
8939 	imbalance_min = 2;
8940 	if (src_nr_running <= imbalance_min)
8941 		return 0;
8942 
8943 	return imbalance;
8944 }
8945 
8946 /**
8947  * calculate_imbalance - Calculate the amount of imbalance present within the
8948  *			 groups of a given sched_domain during load balance.
8949  * @env: load balance environment
8950  * @sds: statistics of the sched_domain whose imbalance is to be calculated.
8951  */
8952 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8953 {
8954 	struct sg_lb_stats *local, *busiest;
8955 
8956 	local = &sds->local_stat;
8957 	busiest = &sds->busiest_stat;
8958 
8959 	if (busiest->group_type == group_misfit_task) {
8960 		/* Set imbalance to allow misfit tasks to be balanced. */
8961 		env->migration_type = migrate_misfit;
8962 		env->imbalance = 1;
8963 		return;
8964 	}
8965 
8966 	if (busiest->group_type == group_asym_packing) {
8967 		/*
8968 		 * In case of asym capacity, we will try to migrate all load to
8969 		 * the preferred CPU.
8970 		 */
8971 		env->migration_type = migrate_task;
8972 		env->imbalance = busiest->sum_h_nr_running;
8973 		return;
8974 	}
8975 
8976 	if (busiest->group_type == group_imbalanced) {
8977 		/*
8978 		 * In the group_imb case we cannot rely on group-wide averages
8979 		 * to ensure CPU-load equilibrium, try to move any task to fix
8980 		 * the imbalance. The next load balance will take care of
8981 		 * balancing back the system.
8982 		 */
8983 		env->migration_type = migrate_task;
8984 		env->imbalance = 1;
8985 		return;
8986 	}
8987 
8988 	/*
8989 	 * Try to use spare capacity of local group without overloading it or
8990 	 * emptying busiest.
8991 	 */
8992 	if (local->group_type == group_has_spare) {
8993 		if (busiest->group_type > group_fully_busy) {
8994 			/*
8995 			 * If busiest is overloaded, try to fill spare
8996 			 * capacity. This might end up creating spare capacity
8997 			 * in busiest or busiest still being overloaded but
8998 			 * there is no simple way to directly compute the
8999 			 * amount of load to migrate in order to balance the
9000 			 * system.
9001 			 */
9002 			env->migration_type = migrate_util;
9003 			env->imbalance = max(local->group_capacity, local->group_util) -
9004 					 local->group_util;
9005 
9006 			/*
9007 			 * In some cases, the group's utilization is max or even
9008 			 * higher than capacity because of migrations but the
9009 			 * local CPU is (newly) idle. There is at least one
9010 			 * waiting task in this overloaded busiest group. Let's
9011 			 * try to pull it.
9012 			 */
9013 			if (env->idle != CPU_NOT_IDLE && env->imbalance == 0) {
9014 				env->migration_type = migrate_task;
9015 				env->imbalance = 1;
9016 			}
9017 
9018 			return;
9019 		}
9020 
9021 		if (busiest->group_weight == 1 || sds->prefer_sibling) {
9022 			unsigned int nr_diff = busiest->sum_nr_running;
9023 			/*
9024 			 * When prefer sibling, evenly spread running tasks on
9025 			 * groups.
9026 			 */
9027 			env->migration_type = migrate_task;
9028 			lsub_positive(&nr_diff, local->sum_nr_running);
9029 			env->imbalance = nr_diff >> 1;
9030 		} else {
9031 
9032 			/*
9033 			 * If there is no overload, we just want to even the number of
9034 			 * idle cpus.
9035 			 */
9036 			env->migration_type = migrate_task;
9037 			env->imbalance = max_t(long, 0, (local->idle_cpus -
9038 						 busiest->idle_cpus) >> 1);
9039 		}
9040 
9041 		/* Consider allowing a small imbalance between NUMA groups */
9042 		if (env->sd->flags & SD_NUMA)
9043 			env->imbalance = adjust_numa_imbalance(env->imbalance,
9044 						busiest->sum_nr_running);
9045 
9046 		return;
9047 	}
9048 
9049 	/*
9050 	 * Local is fully busy but has to take more load to relieve the
9051 	 * busiest group
9052 	 */
9053 	if (local->group_type < group_overloaded) {
9054 		/*
9055 		 * Local will become overloaded so the avg_load metrics are
9056 		 * finally needed.
9057 		 */
9058 
9059 		local->avg_load = (local->group_load * SCHED_CAPACITY_SCALE) /
9060 				  local->group_capacity;
9061 
9062 		sds->avg_load = (sds->total_load * SCHED_CAPACITY_SCALE) /
9063 				sds->total_capacity;
9064 		/*
9065 		 * If the local group is more loaded than the selected
9066 		 * busiest group don't try to pull any tasks.
9067 		 */
9068 		if (local->avg_load >= busiest->avg_load) {
9069 			env->imbalance = 0;
9070 			return;
9071 		}
9072 	}
9073 
9074 	/*
9075 	 * Both group are or will become overloaded and we're trying to get all
9076 	 * the CPUs to the average_load, so we don't want to push ourselves
9077 	 * above the average load, nor do we wish to reduce the max loaded CPU
9078 	 * below the average load. At the same time, we also don't want to
9079 	 * reduce the group load below the group capacity. Thus we look for
9080 	 * the minimum possible imbalance.
9081 	 */
9082 	env->migration_type = migrate_load;
9083 	env->imbalance = min(
9084 		(busiest->avg_load - sds->avg_load) * busiest->group_capacity,
9085 		(sds->avg_load - local->avg_load) * local->group_capacity
9086 	) / SCHED_CAPACITY_SCALE;
9087 }
9088 
9089 /******* find_busiest_group() helpers end here *********************/
9090 
9091 /*
9092  * Decision matrix according to the local and busiest group type:
9093  *
9094  * busiest \ local has_spare fully_busy misfit asym imbalanced overloaded
9095  * has_spare        nr_idle   balanced   N/A    N/A  balanced   balanced
9096  * fully_busy       nr_idle   nr_idle    N/A    N/A  balanced   balanced
9097  * misfit_task      force     N/A        N/A    N/A  force      force
9098  * asym_packing     force     force      N/A    N/A  force      force
9099  * imbalanced       force     force      N/A    N/A  force      force
9100  * overloaded       force     force      N/A    N/A  force      avg_load
9101  *
9102  * N/A :      Not Applicable because already filtered while updating
9103  *            statistics.
9104  * balanced : The system is balanced for these 2 groups.
9105  * force :    Calculate the imbalance as load migration is probably needed.
9106  * avg_load : Only if imbalance is significant enough.
9107  * nr_idle :  dst_cpu is not busy and the number of idle CPUs is quite
9108  *            different in groups.
9109  */
9110 
9111 /**
9112  * find_busiest_group - Returns the busiest group within the sched_domain
9113  * if there is an imbalance.
9114  *
9115  * Also calculates the amount of runnable load which should be moved
9116  * to restore balance.
9117  *
9118  * @env: The load balancing environment.
9119  *
9120  * Return:	- The busiest group if imbalance exists.
9121  */
9122 static struct sched_group *find_busiest_group(struct lb_env *env)
9123 {
9124 	struct sg_lb_stats *local, *busiest;
9125 	struct sd_lb_stats sds;
9126 
9127 	init_sd_lb_stats(&sds);
9128 
9129 	/*
9130 	 * Compute the various statistics relevant for load balancing at
9131 	 * this level.
9132 	 */
9133 	update_sd_lb_stats(env, &sds);
9134 
9135 	if (sched_energy_enabled()) {
9136 		struct root_domain *rd = env->dst_rq->rd;
9137 
9138 		if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
9139 			goto out_balanced;
9140 	}
9141 
9142 	local = &sds.local_stat;
9143 	busiest = &sds.busiest_stat;
9144 
9145 	/* There is no busy sibling group to pull tasks from */
9146 	if (!sds.busiest)
9147 		goto out_balanced;
9148 
9149 	/* Misfit tasks should be dealt with regardless of the avg load */
9150 	if (busiest->group_type == group_misfit_task)
9151 		goto force_balance;
9152 
9153 	/* ASYM feature bypasses nice load balance check */
9154 	if (busiest->group_type == group_asym_packing)
9155 		goto force_balance;
9156 
9157 	/*
9158 	 * If the busiest group is imbalanced the below checks don't
9159 	 * work because they assume all things are equal, which typically
9160 	 * isn't true due to cpus_ptr constraints and the like.
9161 	 */
9162 	if (busiest->group_type == group_imbalanced)
9163 		goto force_balance;
9164 
9165 	/*
9166 	 * If the local group is busier than the selected busiest group
9167 	 * don't try and pull any tasks.
9168 	 */
9169 	if (local->group_type > busiest->group_type)
9170 		goto out_balanced;
9171 
9172 	/*
9173 	 * When groups are overloaded, use the avg_load to ensure fairness
9174 	 * between tasks.
9175 	 */
9176 	if (local->group_type == group_overloaded) {
9177 		/*
9178 		 * If the local group is more loaded than the selected
9179 		 * busiest group don't try to pull any tasks.
9180 		 */
9181 		if (local->avg_load >= busiest->avg_load)
9182 			goto out_balanced;
9183 
9184 		/* XXX broken for overlapping NUMA groups */
9185 		sds.avg_load = (sds.total_load * SCHED_CAPACITY_SCALE) /
9186 				sds.total_capacity;
9187 
9188 		/*
9189 		 * Don't pull any tasks if this group is already above the
9190 		 * domain average load.
9191 		 */
9192 		if (local->avg_load >= sds.avg_load)
9193 			goto out_balanced;
9194 
9195 		/*
9196 		 * If the busiest group is more loaded, use imbalance_pct to be
9197 		 * conservative.
9198 		 */
9199 		if (100 * busiest->avg_load <=
9200 				env->sd->imbalance_pct * local->avg_load)
9201 			goto out_balanced;
9202 	}
9203 
9204 	/* Try to move all excess tasks to child's sibling domain */
9205 	if (sds.prefer_sibling && local->group_type == group_has_spare &&
9206 	    busiest->sum_nr_running > local->sum_nr_running + 1)
9207 		goto force_balance;
9208 
9209 	if (busiest->group_type != group_overloaded) {
9210 		if (env->idle == CPU_NOT_IDLE)
9211 			/*
9212 			 * If the busiest group is not overloaded (and as a
9213 			 * result the local one too) but this CPU is already
9214 			 * busy, let another idle CPU try to pull task.
9215 			 */
9216 			goto out_balanced;
9217 
9218 		if (busiest->group_weight > 1 &&
9219 		    local->idle_cpus <= (busiest->idle_cpus + 1))
9220 			/*
9221 			 * If the busiest group is not overloaded
9222 			 * and there is no imbalance between this and busiest
9223 			 * group wrt idle CPUs, it is balanced. The imbalance
9224 			 * becomes significant if the diff is greater than 1
9225 			 * otherwise we might end up to just move the imbalance
9226 			 * on another group. Of course this applies only if
9227 			 * there is more than 1 CPU per group.
9228 			 */
9229 			goto out_balanced;
9230 
9231 		if (busiest->sum_h_nr_running == 1)
9232 			/*
9233 			 * busiest doesn't have any tasks waiting to run
9234 			 */
9235 			goto out_balanced;
9236 	}
9237 
9238 force_balance:
9239 	/* Looks like there is an imbalance. Compute it */
9240 	calculate_imbalance(env, &sds);
9241 	return env->imbalance ? sds.busiest : NULL;
9242 
9243 out_balanced:
9244 	env->imbalance = 0;
9245 	return NULL;
9246 }
9247 
9248 /*
9249  * find_busiest_queue - find the busiest runqueue among the CPUs in the group.
9250  */
9251 static struct rq *find_busiest_queue(struct lb_env *env,
9252 				     struct sched_group *group)
9253 {
9254 	struct rq *busiest = NULL, *rq;
9255 	unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1;
9256 	unsigned int busiest_nr = 0;
9257 	int i;
9258 
9259 	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
9260 		unsigned long capacity, load, util;
9261 		unsigned int nr_running;
9262 		enum fbq_type rt;
9263 
9264 		rq = cpu_rq(i);
9265 		rt = fbq_classify_rq(rq);
9266 
9267 		/*
9268 		 * We classify groups/runqueues into three groups:
9269 		 *  - regular: there are !numa tasks
9270 		 *  - remote:  there are numa tasks that run on the 'wrong' node
9271 		 *  - all:     there is no distinction
9272 		 *
9273 		 * In order to avoid migrating ideally placed numa tasks,
9274 		 * ignore those when there's better options.
9275 		 *
9276 		 * If we ignore the actual busiest queue to migrate another
9277 		 * task, the next balance pass can still reduce the busiest
9278 		 * queue by moving tasks around inside the node.
9279 		 *
9280 		 * If we cannot move enough load due to this classification
9281 		 * the next pass will adjust the group classification and
9282 		 * allow migration of more tasks.
9283 		 *
9284 		 * Both cases only affect the total convergence complexity.
9285 		 */
9286 		if (rt > env->fbq_type)
9287 			continue;
9288 
9289 		capacity = capacity_of(i);
9290 		nr_running = rq->cfs.h_nr_running;
9291 
9292 		/*
9293 		 * For ASYM_CPUCAPACITY domains, don't pick a CPU that could
9294 		 * eventually lead to active_balancing high->low capacity.
9295 		 * Higher per-CPU capacity is considered better than balancing
9296 		 * average load.
9297 		 */
9298 		if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
9299 		    capacity_of(env->dst_cpu) < capacity &&
9300 		    nr_running == 1)
9301 			continue;
9302 
9303 		switch (env->migration_type) {
9304 		case migrate_load:
9305 			/*
9306 			 * When comparing with load imbalance, use cpu_load()
9307 			 * which is not scaled with the CPU capacity.
9308 			 */
9309 			load = cpu_load(rq);
9310 
9311 			if (nr_running == 1 && load > env->imbalance &&
9312 			    !check_cpu_capacity(rq, env->sd))
9313 				break;
9314 
9315 			/*
9316 			 * For the load comparisons with the other CPUs,
9317 			 * consider the cpu_load() scaled with the CPU
9318 			 * capacity, so that the load can be moved away
9319 			 * from the CPU that is potentially running at a
9320 			 * lower capacity.
9321 			 *
9322 			 * Thus we're looking for max(load_i / capacity_i),
9323 			 * crosswise multiplication to rid ourselves of the
9324 			 * division works out to:
9325 			 * load_i * capacity_j > load_j * capacity_i;
9326 			 * where j is our previous maximum.
9327 			 */
9328 			if (load * busiest_capacity > busiest_load * capacity) {
9329 				busiest_load = load;
9330 				busiest_capacity = capacity;
9331 				busiest = rq;
9332 			}
9333 			break;
9334 
9335 		case migrate_util:
9336 			util = cpu_util(cpu_of(rq));
9337 
9338 			/*
9339 			 * Don't try to pull utilization from a CPU with one
9340 			 * running task. Whatever its utilization, we will fail
9341 			 * detach the task.
9342 			 */
9343 			if (nr_running <= 1)
9344 				continue;
9345 
9346 			if (busiest_util < util) {
9347 				busiest_util = util;
9348 				busiest = rq;
9349 			}
9350 			break;
9351 
9352 		case migrate_task:
9353 			if (busiest_nr < nr_running) {
9354 				busiest_nr = nr_running;
9355 				busiest = rq;
9356 			}
9357 			break;
9358 
9359 		case migrate_misfit:
9360 			/*
9361 			 * For ASYM_CPUCAPACITY domains with misfit tasks we
9362 			 * simply seek the "biggest" misfit task.
9363 			 */
9364 			if (rq->misfit_task_load > busiest_load) {
9365 				busiest_load = rq->misfit_task_load;
9366 				busiest = rq;
9367 			}
9368 
9369 			break;
9370 
9371 		}
9372 	}
9373 
9374 	return busiest;
9375 }
9376 
9377 /*
9378  * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
9379  * so long as it is large enough.
9380  */
9381 #define MAX_PINNED_INTERVAL	512
9382 
9383 static inline bool
9384 asym_active_balance(struct lb_env *env)
9385 {
9386 	/*
9387 	 * ASYM_PACKING needs to force migrate tasks from busy but
9388 	 * lower priority CPUs in order to pack all tasks in the
9389 	 * highest priority CPUs.
9390 	 */
9391 	return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&
9392 	       sched_asym_prefer(env->dst_cpu, env->src_cpu);
9393 }
9394 
9395 static inline bool
9396 voluntary_active_balance(struct lb_env *env)
9397 {
9398 	struct sched_domain *sd = env->sd;
9399 
9400 	if (asym_active_balance(env))
9401 		return 1;
9402 
9403 	/*
9404 	 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
9405 	 * It's worth migrating the task if the src_cpu's capacity is reduced
9406 	 * because of other sched_class or IRQs if more capacity stays
9407 	 * available on dst_cpu.
9408 	 */
9409 	if ((env->idle != CPU_NOT_IDLE) &&
9410 	    (env->src_rq->cfs.h_nr_running == 1)) {
9411 		if ((check_cpu_capacity(env->src_rq, sd)) &&
9412 		    (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
9413 			return 1;
9414 	}
9415 
9416 	if (env->migration_type == migrate_misfit)
9417 		return 1;
9418 
9419 	return 0;
9420 }
9421 
9422 static int need_active_balance(struct lb_env *env)
9423 {
9424 	struct sched_domain *sd = env->sd;
9425 
9426 	if (voluntary_active_balance(env))
9427 		return 1;
9428 
9429 	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
9430 }
9431 
9432 static int active_load_balance_cpu_stop(void *data);
9433 
9434 static int should_we_balance(struct lb_env *env)
9435 {
9436 	struct sched_group *sg = env->sd->groups;
9437 	int cpu, balance_cpu = -1;
9438 
9439 	/*
9440 	 * Ensure the balancing environment is consistent; can happen
9441 	 * when the softirq triggers 'during' hotplug.
9442 	 */
9443 	if (!cpumask_test_cpu(env->dst_cpu, env->cpus))
9444 		return 0;
9445 
9446 	/*
9447 	 * In the newly idle case, we will allow all the CPUs
9448 	 * to do the newly idle load balance.
9449 	 */
9450 	if (env->idle == CPU_NEWLY_IDLE)
9451 		return 1;
9452 
9453 	/* Try to find first idle CPU */
9454 	for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
9455 		if (!idle_cpu(cpu))
9456 			continue;
9457 
9458 		balance_cpu = cpu;
9459 		break;
9460 	}
9461 
9462 	if (balance_cpu == -1)
9463 		balance_cpu = group_balance_cpu(sg);
9464 
9465 	/*
9466 	 * First idle CPU or the first CPU(busiest) in this sched group
9467 	 * is eligible for doing load balancing at this and above domains.
9468 	 */
9469 	return balance_cpu == env->dst_cpu;
9470 }
9471 
9472 /*
9473  * Check this_cpu to ensure it is balanced within domain. Attempt to move
9474  * tasks if there is an imbalance.
9475  */
9476 static int load_balance(int this_cpu, struct rq *this_rq,
9477 			struct sched_domain *sd, enum cpu_idle_type idle,
9478 			int *continue_balancing)
9479 {
9480 	int ld_moved, cur_ld_moved, active_balance = 0;
9481 	struct sched_domain *sd_parent = sd->parent;
9482 	struct sched_group *group;
9483 	struct rq *busiest;
9484 	struct rq_flags rf;
9485 	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
9486 
9487 	struct lb_env env = {
9488 		.sd		= sd,
9489 		.dst_cpu	= this_cpu,
9490 		.dst_rq		= this_rq,
9491 		.dst_grpmask    = sched_group_span(sd->groups),
9492 		.idle		= idle,
9493 		.loop_break	= sched_nr_migrate_break,
9494 		.cpus		= cpus,
9495 		.fbq_type	= all,
9496 		.tasks		= LIST_HEAD_INIT(env.tasks),
9497 	};
9498 
9499 	cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
9500 
9501 	schedstat_inc(sd->lb_count[idle]);
9502 
9503 redo:
9504 	if (!should_we_balance(&env)) {
9505 		*continue_balancing = 0;
9506 		goto out_balanced;
9507 	}
9508 
9509 	group = find_busiest_group(&env);
9510 	if (!group) {
9511 		schedstat_inc(sd->lb_nobusyg[idle]);
9512 		goto out_balanced;
9513 	}
9514 
9515 	busiest = find_busiest_queue(&env, group);
9516 	if (!busiest) {
9517 		schedstat_inc(sd->lb_nobusyq[idle]);
9518 		goto out_balanced;
9519 	}
9520 
9521 	BUG_ON(busiest == env.dst_rq);
9522 
9523 	schedstat_add(sd->lb_imbalance[idle], env.imbalance);
9524 
9525 	env.src_cpu = busiest->cpu;
9526 	env.src_rq = busiest;
9527 
9528 	ld_moved = 0;
9529 	if (busiest->nr_running > 1) {
9530 		/*
9531 		 * Attempt to move tasks. If find_busiest_group has found
9532 		 * an imbalance but busiest->nr_running <= 1, the group is
9533 		 * still unbalanced. ld_moved simply stays zero, so it is
9534 		 * correctly treated as an imbalance.
9535 		 */
9536 		env.flags |= LBF_ALL_PINNED;
9537 		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
9538 
9539 more_balance:
9540 		rq_lock_irqsave(busiest, &rf);
9541 		update_rq_clock(busiest);
9542 
9543 		/*
9544 		 * cur_ld_moved - load moved in current iteration
9545 		 * ld_moved     - cumulative load moved across iterations
9546 		 */
9547 		cur_ld_moved = detach_tasks(&env);
9548 
9549 		/*
9550 		 * We've detached some tasks from busiest_rq. Every
9551 		 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
9552 		 * unlock busiest->lock, and we are able to be sure
9553 		 * that nobody can manipulate the tasks in parallel.
9554 		 * See task_rq_lock() family for the details.
9555 		 */
9556 
9557 		rq_unlock(busiest, &rf);
9558 
9559 		if (cur_ld_moved) {
9560 			attach_tasks(&env);
9561 			ld_moved += cur_ld_moved;
9562 		}
9563 
9564 		local_irq_restore(rf.flags);
9565 
9566 		if (env.flags & LBF_NEED_BREAK) {
9567 			env.flags &= ~LBF_NEED_BREAK;
9568 			goto more_balance;
9569 		}
9570 
9571 		/*
9572 		 * Revisit (affine) tasks on src_cpu that couldn't be moved to
9573 		 * us and move them to an alternate dst_cpu in our sched_group
9574 		 * where they can run. The upper limit on how many times we
9575 		 * iterate on same src_cpu is dependent on number of CPUs in our
9576 		 * sched_group.
9577 		 *
9578 		 * This changes load balance semantics a bit on who can move
9579 		 * load to a given_cpu. In addition to the given_cpu itself
9580 		 * (or a ilb_cpu acting on its behalf where given_cpu is
9581 		 * nohz-idle), we now have balance_cpu in a position to move
9582 		 * load to given_cpu. In rare situations, this may cause
9583 		 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
9584 		 * _independently_ and at _same_ time to move some load to
9585 		 * given_cpu) causing exceess load to be moved to given_cpu.
9586 		 * This however should not happen so much in practice and
9587 		 * moreover subsequent load balance cycles should correct the
9588 		 * excess load moved.
9589 		 */
9590 		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
9591 
9592 			/* Prevent to re-select dst_cpu via env's CPUs */
9593 			__cpumask_clear_cpu(env.dst_cpu, env.cpus);
9594 
9595 			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
9596 			env.dst_cpu	 = env.new_dst_cpu;
9597 			env.flags	&= ~LBF_DST_PINNED;
9598 			env.loop	 = 0;
9599 			env.loop_break	 = sched_nr_migrate_break;
9600 
9601 			/*
9602 			 * Go back to "more_balance" rather than "redo" since we
9603 			 * need to continue with same src_cpu.
9604 			 */
9605 			goto more_balance;
9606 		}
9607 
9608 		/*
9609 		 * We failed to reach balance because of affinity.
9610 		 */
9611 		if (sd_parent) {
9612 			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
9613 
9614 			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
9615 				*group_imbalance = 1;
9616 		}
9617 
9618 		/* All tasks on this runqueue were pinned by CPU affinity */
9619 		if (unlikely(env.flags & LBF_ALL_PINNED)) {
9620 			__cpumask_clear_cpu(cpu_of(busiest), cpus);
9621 			/*
9622 			 * Attempting to continue load balancing at the current
9623 			 * sched_domain level only makes sense if there are
9624 			 * active CPUs remaining as possible busiest CPUs to
9625 			 * pull load from which are not contained within the
9626 			 * destination group that is receiving any migrated
9627 			 * load.
9628 			 */
9629 			if (!cpumask_subset(cpus, env.dst_grpmask)) {
9630 				env.loop = 0;
9631 				env.loop_break = sched_nr_migrate_break;
9632 				goto redo;
9633 			}
9634 			goto out_all_pinned;
9635 		}
9636 	}
9637 
9638 	if (!ld_moved) {
9639 		schedstat_inc(sd->lb_failed[idle]);
9640 		/*
9641 		 * Increment the failure counter only on periodic balance.
9642 		 * We do not want newidle balance, which can be very
9643 		 * frequent, pollute the failure counter causing
9644 		 * excessive cache_hot migrations and active balances.
9645 		 */
9646 		if (idle != CPU_NEWLY_IDLE)
9647 			sd->nr_balance_failed++;
9648 
9649 		if (need_active_balance(&env)) {
9650 			unsigned long flags;
9651 
9652 			raw_spin_lock_irqsave(&busiest->lock, flags);
9653 
9654 			/*
9655 			 * Don't kick the active_load_balance_cpu_stop,
9656 			 * if the curr task on busiest CPU can't be
9657 			 * moved to this_cpu:
9658 			 */
9659 			if (!cpumask_test_cpu(this_cpu, busiest->curr->cpus_ptr)) {
9660 				raw_spin_unlock_irqrestore(&busiest->lock,
9661 							    flags);
9662 				env.flags |= LBF_ALL_PINNED;
9663 				goto out_one_pinned;
9664 			}
9665 
9666 			/*
9667 			 * ->active_balance synchronizes accesses to
9668 			 * ->active_balance_work.  Once set, it's cleared
9669 			 * only after active load balance is finished.
9670 			 */
9671 			if (!busiest->active_balance) {
9672 				busiest->active_balance = 1;
9673 				busiest->push_cpu = this_cpu;
9674 				active_balance = 1;
9675 			}
9676 			raw_spin_unlock_irqrestore(&busiest->lock, flags);
9677 
9678 			if (active_balance) {
9679 				stop_one_cpu_nowait(cpu_of(busiest),
9680 					active_load_balance_cpu_stop, busiest,
9681 					&busiest->active_balance_work);
9682 			}
9683 
9684 			/* We've kicked active balancing, force task migration. */
9685 			sd->nr_balance_failed = sd->cache_nice_tries+1;
9686 		}
9687 	} else
9688 		sd->nr_balance_failed = 0;
9689 
9690 	if (likely(!active_balance) || voluntary_active_balance(&env)) {
9691 		/* We were unbalanced, so reset the balancing interval */
9692 		sd->balance_interval = sd->min_interval;
9693 	} else {
9694 		/*
9695 		 * If we've begun active balancing, start to back off. This
9696 		 * case may not be covered by the all_pinned logic if there
9697 		 * is only 1 task on the busy runqueue (because we don't call
9698 		 * detach_tasks).
9699 		 */
9700 		if (sd->balance_interval < sd->max_interval)
9701 			sd->balance_interval *= 2;
9702 	}
9703 
9704 	goto out;
9705 
9706 out_balanced:
9707 	/*
9708 	 * We reach balance although we may have faced some affinity
9709 	 * constraints. Clear the imbalance flag only if other tasks got
9710 	 * a chance to move and fix the imbalance.
9711 	 */
9712 	if (sd_parent && !(env.flags & LBF_ALL_PINNED)) {
9713 		int *group_imbalance = &sd_parent->groups->sgc->imbalance;
9714 
9715 		if (*group_imbalance)
9716 			*group_imbalance = 0;
9717 	}
9718 
9719 out_all_pinned:
9720 	/*
9721 	 * We reach balance because all tasks are pinned at this level so
9722 	 * we can't migrate them. Let the imbalance flag set so parent level
9723 	 * can try to migrate them.
9724 	 */
9725 	schedstat_inc(sd->lb_balanced[idle]);
9726 
9727 	sd->nr_balance_failed = 0;
9728 
9729 out_one_pinned:
9730 	ld_moved = 0;
9731 
9732 	/*
9733 	 * newidle_balance() disregards balance intervals, so we could
9734 	 * repeatedly reach this code, which would lead to balance_interval
9735 	 * skyrocketting in a short amount of time. Skip the balance_interval
9736 	 * increase logic to avoid that.
9737 	 */
9738 	if (env.idle == CPU_NEWLY_IDLE)
9739 		goto out;
9740 
9741 	/* tune up the balancing interval */
9742 	if ((env.flags & LBF_ALL_PINNED &&
9743 	     sd->balance_interval < MAX_PINNED_INTERVAL) ||
9744 	    sd->balance_interval < sd->max_interval)
9745 		sd->balance_interval *= 2;
9746 out:
9747 	return ld_moved;
9748 }
9749 
9750 static inline unsigned long
9751 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
9752 {
9753 	unsigned long interval = sd->balance_interval;
9754 
9755 	if (cpu_busy)
9756 		interval *= sd->busy_factor;
9757 
9758 	/* scale ms to jiffies */
9759 	interval = msecs_to_jiffies(interval);
9760 	interval = clamp(interval, 1UL, max_load_balance_interval);
9761 
9762 	return interval;
9763 }
9764 
9765 static inline void
9766 update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
9767 {
9768 	unsigned long interval, next;
9769 
9770 	/* used by idle balance, so cpu_busy = 0 */
9771 	interval = get_sd_balance_interval(sd, 0);
9772 	next = sd->last_balance + interval;
9773 
9774 	if (time_after(*next_balance, next))
9775 		*next_balance = next;
9776 }
9777 
9778 /*
9779  * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
9780  * running tasks off the busiest CPU onto idle CPUs. It requires at
9781  * least 1 task to be running on each physical CPU where possible, and
9782  * avoids physical / logical imbalances.
9783  */
9784 static int active_load_balance_cpu_stop(void *data)
9785 {
9786 	struct rq *busiest_rq = data;
9787 	int busiest_cpu = cpu_of(busiest_rq);
9788 	int target_cpu = busiest_rq->push_cpu;
9789 	struct rq *target_rq = cpu_rq(target_cpu);
9790 	struct sched_domain *sd;
9791 	struct task_struct *p = NULL;
9792 	struct rq_flags rf;
9793 
9794 	rq_lock_irq(busiest_rq, &rf);
9795 	/*
9796 	 * Between queueing the stop-work and running it is a hole in which
9797 	 * CPUs can become inactive. We should not move tasks from or to
9798 	 * inactive CPUs.
9799 	 */
9800 	if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
9801 		goto out_unlock;
9802 
9803 	/* Make sure the requested CPU hasn't gone down in the meantime: */
9804 	if (unlikely(busiest_cpu != smp_processor_id() ||
9805 		     !busiest_rq->active_balance))
9806 		goto out_unlock;
9807 
9808 	/* Is there any task to move? */
9809 	if (busiest_rq->nr_running <= 1)
9810 		goto out_unlock;
9811 
9812 	/*
9813 	 * This condition is "impossible", if it occurs
9814 	 * we need to fix it. Originally reported by
9815 	 * Bjorn Helgaas on a 128-CPU setup.
9816 	 */
9817 	BUG_ON(busiest_rq == target_rq);
9818 
9819 	/* Search for an sd spanning us and the target CPU. */
9820 	rcu_read_lock();
9821 	for_each_domain(target_cpu, sd) {
9822 		if ((sd->flags & SD_LOAD_BALANCE) &&
9823 		    cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
9824 				break;
9825 	}
9826 
9827 	if (likely(sd)) {
9828 		struct lb_env env = {
9829 			.sd		= sd,
9830 			.dst_cpu	= target_cpu,
9831 			.dst_rq		= target_rq,
9832 			.src_cpu	= busiest_rq->cpu,
9833 			.src_rq		= busiest_rq,
9834 			.idle		= CPU_IDLE,
9835 			/*
9836 			 * can_migrate_task() doesn't need to compute new_dst_cpu
9837 			 * for active balancing. Since we have CPU_IDLE, but no
9838 			 * @dst_grpmask we need to make that test go away with lying
9839 			 * about DST_PINNED.
9840 			 */
9841 			.flags		= LBF_DST_PINNED,
9842 		};
9843 
9844 		schedstat_inc(sd->alb_count);
9845 		update_rq_clock(busiest_rq);
9846 
9847 		p = detach_one_task(&env);
9848 		if (p) {
9849 			schedstat_inc(sd->alb_pushed);
9850 			/* Active balancing done, reset the failure counter. */
9851 			sd->nr_balance_failed = 0;
9852 		} else {
9853 			schedstat_inc(sd->alb_failed);
9854 		}
9855 	}
9856 	rcu_read_unlock();
9857 out_unlock:
9858 	busiest_rq->active_balance = 0;
9859 	rq_unlock(busiest_rq, &rf);
9860 
9861 	if (p)
9862 		attach_one_task(target_rq, p);
9863 
9864 	local_irq_enable();
9865 
9866 	return 0;
9867 }
9868 
9869 static DEFINE_SPINLOCK(balancing);
9870 
9871 /*
9872  * Scale the max load_balance interval with the number of CPUs in the system.
9873  * This trades load-balance latency on larger machines for less cross talk.
9874  */
9875 void update_max_interval(void)
9876 {
9877 	max_load_balance_interval = HZ*num_online_cpus()/10;
9878 }
9879 
9880 /*
9881  * It checks each scheduling domain to see if it is due to be balanced,
9882  * and initiates a balancing operation if so.
9883  *
9884  * Balancing parameters are set up in init_sched_domains.
9885  */
9886 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
9887 {
9888 	int continue_balancing = 1;
9889 	int cpu = rq->cpu;
9890 	int busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
9891 	unsigned long interval;
9892 	struct sched_domain *sd;
9893 	/* Earliest time when we have to do rebalance again */
9894 	unsigned long next_balance = jiffies + 60*HZ;
9895 	int update_next_balance = 0;
9896 	int need_serialize, need_decay = 0;
9897 	u64 max_cost = 0;
9898 
9899 	rcu_read_lock();
9900 	for_each_domain(cpu, sd) {
9901 		/*
9902 		 * Decay the newidle max times here because this is a regular
9903 		 * visit to all the domains. Decay ~1% per second.
9904 		 */
9905 		if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
9906 			sd->max_newidle_lb_cost =
9907 				(sd->max_newidle_lb_cost * 253) / 256;
9908 			sd->next_decay_max_lb_cost = jiffies + HZ;
9909 			need_decay = 1;
9910 		}
9911 		max_cost += sd->max_newidle_lb_cost;
9912 
9913 		if (!(sd->flags & SD_LOAD_BALANCE))
9914 			continue;
9915 
9916 		/*
9917 		 * Stop the load balance at this level. There is another
9918 		 * CPU in our sched group which is doing load balancing more
9919 		 * actively.
9920 		 */
9921 		if (!continue_balancing) {
9922 			if (need_decay)
9923 				continue;
9924 			break;
9925 		}
9926 
9927 		interval = get_sd_balance_interval(sd, busy);
9928 
9929 		need_serialize = sd->flags & SD_SERIALIZE;
9930 		if (need_serialize) {
9931 			if (!spin_trylock(&balancing))
9932 				goto out;
9933 		}
9934 
9935 		if (time_after_eq(jiffies, sd->last_balance + interval)) {
9936 			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
9937 				/*
9938 				 * The LBF_DST_PINNED logic could have changed
9939 				 * env->dst_cpu, so we can't know our idle
9940 				 * state even if we migrated tasks. Update it.
9941 				 */
9942 				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
9943 				busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
9944 			}
9945 			sd->last_balance = jiffies;
9946 			interval = get_sd_balance_interval(sd, busy);
9947 		}
9948 		if (need_serialize)
9949 			spin_unlock(&balancing);
9950 out:
9951 		if (time_after(next_balance, sd->last_balance + interval)) {
9952 			next_balance = sd->last_balance + interval;
9953 			update_next_balance = 1;
9954 		}
9955 	}
9956 	if (need_decay) {
9957 		/*
9958 		 * Ensure the rq-wide value also decays but keep it at a
9959 		 * reasonable floor to avoid funnies with rq->avg_idle.
9960 		 */
9961 		rq->max_idle_balance_cost =
9962 			max((u64)sysctl_sched_migration_cost, max_cost);
9963 	}
9964 	rcu_read_unlock();
9965 
9966 	/*
9967 	 * next_balance will be updated only when there is a need.
9968 	 * When the cpu is attached to null domain for ex, it will not be
9969 	 * updated.
9970 	 */
9971 	if (likely(update_next_balance)) {
9972 		rq->next_balance = next_balance;
9973 
9974 #ifdef CONFIG_NO_HZ_COMMON
9975 		/*
9976 		 * If this CPU has been elected to perform the nohz idle
9977 		 * balance. Other idle CPUs have already rebalanced with
9978 		 * nohz_idle_balance() and nohz.next_balance has been
9979 		 * updated accordingly. This CPU is now running the idle load
9980 		 * balance for itself and we need to update the
9981 		 * nohz.next_balance accordingly.
9982 		 */
9983 		if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
9984 			nohz.next_balance = rq->next_balance;
9985 #endif
9986 	}
9987 }
9988 
9989 static inline int on_null_domain(struct rq *rq)
9990 {
9991 	return unlikely(!rcu_dereference_sched(rq->sd));
9992 }
9993 
9994 #ifdef CONFIG_NO_HZ_COMMON
9995 /*
9996  * idle load balancing details
9997  * - When one of the busy CPUs notice that there may be an idle rebalancing
9998  *   needed, they will kick the idle load balancer, which then does idle
9999  *   load balancing for all the idle CPUs.
10000  * - HK_FLAG_MISC CPUs are used for this task, because HK_FLAG_SCHED not set
10001  *   anywhere yet.
10002  */
10003 
10004 static inline int find_new_ilb(void)
10005 {
10006 	int ilb;
10007 
10008 	for_each_cpu_and(ilb, nohz.idle_cpus_mask,
10009 			      housekeeping_cpumask(HK_FLAG_MISC)) {
10010 		if (idle_cpu(ilb))
10011 			return ilb;
10012 	}
10013 
10014 	return nr_cpu_ids;
10015 }
10016 
10017 /*
10018  * Kick a CPU to do the nohz balancing, if it is time for it. We pick any
10019  * idle CPU in the HK_FLAG_MISC housekeeping set (if there is one).
10020  */
10021 static void kick_ilb(unsigned int flags)
10022 {
10023 	int ilb_cpu;
10024 
10025 	nohz.next_balance++;
10026 
10027 	ilb_cpu = find_new_ilb();
10028 
10029 	if (ilb_cpu >= nr_cpu_ids)
10030 		return;
10031 
10032 	flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
10033 	if (flags & NOHZ_KICK_MASK)
10034 		return;
10035 
10036 	/*
10037 	 * Use smp_send_reschedule() instead of resched_cpu().
10038 	 * This way we generate a sched IPI on the target CPU which
10039 	 * is idle. And the softirq performing nohz idle load balance
10040 	 * will be run before returning from the IPI.
10041 	 */
10042 	smp_send_reschedule(ilb_cpu);
10043 }
10044 
10045 /*
10046  * Current decision point for kicking the idle load balancer in the presence
10047  * of idle CPUs in the system.
10048  */
10049 static void nohz_balancer_kick(struct rq *rq)
10050 {
10051 	unsigned long now = jiffies;
10052 	struct sched_domain_shared *sds;
10053 	struct sched_domain *sd;
10054 	int nr_busy, i, cpu = rq->cpu;
10055 	unsigned int flags = 0;
10056 
10057 	if (unlikely(rq->idle_balance))
10058 		return;
10059 
10060 	/*
10061 	 * We may be recently in ticked or tickless idle mode. At the first
10062 	 * busy tick after returning from idle, we will update the busy stats.
10063 	 */
10064 	nohz_balance_exit_idle(rq);
10065 
10066 	/*
10067 	 * None are in tickless mode and hence no need for NOHZ idle load
10068 	 * balancing.
10069 	 */
10070 	if (likely(!atomic_read(&nohz.nr_cpus)))
10071 		return;
10072 
10073 	if (READ_ONCE(nohz.has_blocked) &&
10074 	    time_after(now, READ_ONCE(nohz.next_blocked)))
10075 		flags = NOHZ_STATS_KICK;
10076 
10077 	if (time_before(now, nohz.next_balance))
10078 		goto out;
10079 
10080 	if (rq->nr_running >= 2) {
10081 		flags = NOHZ_KICK_MASK;
10082 		goto out;
10083 	}
10084 
10085 	rcu_read_lock();
10086 
10087 	sd = rcu_dereference(rq->sd);
10088 	if (sd) {
10089 		/*
10090 		 * If there's a CFS task and the current CPU has reduced
10091 		 * capacity; kick the ILB to see if there's a better CPU to run
10092 		 * on.
10093 		 */
10094 		if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) {
10095 			flags = NOHZ_KICK_MASK;
10096 			goto unlock;
10097 		}
10098 	}
10099 
10100 	sd = rcu_dereference(per_cpu(sd_asym_packing, cpu));
10101 	if (sd) {
10102 		/*
10103 		 * When ASYM_PACKING; see if there's a more preferred CPU
10104 		 * currently idle; in which case, kick the ILB to move tasks
10105 		 * around.
10106 		 */
10107 		for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
10108 			if (sched_asym_prefer(i, cpu)) {
10109 				flags = NOHZ_KICK_MASK;
10110 				goto unlock;
10111 			}
10112 		}
10113 	}
10114 
10115 	sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu));
10116 	if (sd) {
10117 		/*
10118 		 * When ASYM_CPUCAPACITY; see if there's a higher capacity CPU
10119 		 * to run the misfit task on.
10120 		 */
10121 		if (check_misfit_status(rq, sd)) {
10122 			flags = NOHZ_KICK_MASK;
10123 			goto unlock;
10124 		}
10125 
10126 		/*
10127 		 * For asymmetric systems, we do not want to nicely balance
10128 		 * cache use, instead we want to embrace asymmetry and only
10129 		 * ensure tasks have enough CPU capacity.
10130 		 *
10131 		 * Skip the LLC logic because it's not relevant in that case.
10132 		 */
10133 		goto unlock;
10134 	}
10135 
10136 	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
10137 	if (sds) {
10138 		/*
10139 		 * If there is an imbalance between LLC domains (IOW we could
10140 		 * increase the overall cache use), we need some less-loaded LLC
10141 		 * domain to pull some load. Likewise, we may need to spread
10142 		 * load within the current LLC domain (e.g. packed SMT cores but
10143 		 * other CPUs are idle). We can't really know from here how busy
10144 		 * the others are - so just get a nohz balance going if it looks
10145 		 * like this LLC domain has tasks we could move.
10146 		 */
10147 		nr_busy = atomic_read(&sds->nr_busy_cpus);
10148 		if (nr_busy > 1) {
10149 			flags = NOHZ_KICK_MASK;
10150 			goto unlock;
10151 		}
10152 	}
10153 unlock:
10154 	rcu_read_unlock();
10155 out:
10156 	if (flags)
10157 		kick_ilb(flags);
10158 }
10159 
10160 static void set_cpu_sd_state_busy(int cpu)
10161 {
10162 	struct sched_domain *sd;
10163 
10164 	rcu_read_lock();
10165 	sd = rcu_dereference(per_cpu(sd_llc, cpu));
10166 
10167 	if (!sd || !sd->nohz_idle)
10168 		goto unlock;
10169 	sd->nohz_idle = 0;
10170 
10171 	atomic_inc(&sd->shared->nr_busy_cpus);
10172 unlock:
10173 	rcu_read_unlock();
10174 }
10175 
10176 void nohz_balance_exit_idle(struct rq *rq)
10177 {
10178 	SCHED_WARN_ON(rq != this_rq());
10179 
10180 	if (likely(!rq->nohz_tick_stopped))
10181 		return;
10182 
10183 	rq->nohz_tick_stopped = 0;
10184 	cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask);
10185 	atomic_dec(&nohz.nr_cpus);
10186 
10187 	set_cpu_sd_state_busy(rq->cpu);
10188 }
10189 
10190 static void set_cpu_sd_state_idle(int cpu)
10191 {
10192 	struct sched_domain *sd;
10193 
10194 	rcu_read_lock();
10195 	sd = rcu_dereference(per_cpu(sd_llc, cpu));
10196 
10197 	if (!sd || sd->nohz_idle)
10198 		goto unlock;
10199 	sd->nohz_idle = 1;
10200 
10201 	atomic_dec(&sd->shared->nr_busy_cpus);
10202 unlock:
10203 	rcu_read_unlock();
10204 }
10205 
10206 /*
10207  * This routine will record that the CPU is going idle with tick stopped.
10208  * This info will be used in performing idle load balancing in the future.
10209  */
10210 void nohz_balance_enter_idle(int cpu)
10211 {
10212 	struct rq *rq = cpu_rq(cpu);
10213 
10214 	SCHED_WARN_ON(cpu != smp_processor_id());
10215 
10216 	/* If this CPU is going down, then nothing needs to be done: */
10217 	if (!cpu_active(cpu))
10218 		return;
10219 
10220 	/* Spare idle load balancing on CPUs that don't want to be disturbed: */
10221 	if (!housekeeping_cpu(cpu, HK_FLAG_SCHED))
10222 		return;
10223 
10224 	/*
10225 	 * Can be set safely without rq->lock held
10226 	 * If a clear happens, it will have evaluated last additions because
10227 	 * rq->lock is held during the check and the clear
10228 	 */
10229 	rq->has_blocked_load = 1;
10230 
10231 	/*
10232 	 * The tick is still stopped but load could have been added in the
10233 	 * meantime. We set the nohz.has_blocked flag to trig a check of the
10234 	 * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
10235 	 * of nohz.has_blocked can only happen after checking the new load
10236 	 */
10237 	if (rq->nohz_tick_stopped)
10238 		goto out;
10239 
10240 	/* If we're a completely isolated CPU, we don't play: */
10241 	if (on_null_domain(rq))
10242 		return;
10243 
10244 	rq->nohz_tick_stopped = 1;
10245 
10246 	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
10247 	atomic_inc(&nohz.nr_cpus);
10248 
10249 	/*
10250 	 * Ensures that if nohz_idle_balance() fails to observe our
10251 	 * @idle_cpus_mask store, it must observe the @has_blocked
10252 	 * store.
10253 	 */
10254 	smp_mb__after_atomic();
10255 
10256 	set_cpu_sd_state_idle(cpu);
10257 
10258 out:
10259 	/*
10260 	 * Each time a cpu enter idle, we assume that it has blocked load and
10261 	 * enable the periodic update of the load of idle cpus
10262 	 */
10263 	WRITE_ONCE(nohz.has_blocked, 1);
10264 }
10265 
10266 /*
10267  * Internal function that runs load balance for all idle cpus. The load balance
10268  * can be a simple update of blocked load or a complete load balance with
10269  * tasks movement depending of flags.
10270  * The function returns false if the loop has stopped before running
10271  * through all idle CPUs.
10272  */
10273 static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
10274 			       enum cpu_idle_type idle)
10275 {
10276 	/* Earliest time when we have to do rebalance again */
10277 	unsigned long now = jiffies;
10278 	unsigned long next_balance = now + 60*HZ;
10279 	bool has_blocked_load = false;
10280 	int update_next_balance = 0;
10281 	int this_cpu = this_rq->cpu;
10282 	int balance_cpu;
10283 	int ret = false;
10284 	struct rq *rq;
10285 
10286 	SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
10287 
10288 	/*
10289 	 * We assume there will be no idle load after this update and clear
10290 	 * the has_blocked flag. If a cpu enters idle in the mean time, it will
10291 	 * set the has_blocked flag and trig another update of idle load.
10292 	 * Because a cpu that becomes idle, is added to idle_cpus_mask before
10293 	 * setting the flag, we are sure to not clear the state and not
10294 	 * check the load of an idle cpu.
10295 	 */
10296 	WRITE_ONCE(nohz.has_blocked, 0);
10297 
10298 	/*
10299 	 * Ensures that if we miss the CPU, we must see the has_blocked
10300 	 * store from nohz_balance_enter_idle().
10301 	 */
10302 	smp_mb();
10303 
10304 	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
10305 		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
10306 			continue;
10307 
10308 		/*
10309 		 * If this CPU gets work to do, stop the load balancing
10310 		 * work being done for other CPUs. Next load
10311 		 * balancing owner will pick it up.
10312 		 */
10313 		if (need_resched()) {
10314 			has_blocked_load = true;
10315 			goto abort;
10316 		}
10317 
10318 		rq = cpu_rq(balance_cpu);
10319 
10320 		has_blocked_load |= update_nohz_stats(rq, true);
10321 
10322 		/*
10323 		 * If time for next balance is due,
10324 		 * do the balance.
10325 		 */
10326 		if (time_after_eq(jiffies, rq->next_balance)) {
10327 			struct rq_flags rf;
10328 
10329 			rq_lock_irqsave(rq, &rf);
10330 			update_rq_clock(rq);
10331 			rq_unlock_irqrestore(rq, &rf);
10332 
10333 			if (flags & NOHZ_BALANCE_KICK)
10334 				rebalance_domains(rq, CPU_IDLE);
10335 		}
10336 
10337 		if (time_after(next_balance, rq->next_balance)) {
10338 			next_balance = rq->next_balance;
10339 			update_next_balance = 1;
10340 		}
10341 	}
10342 
10343 	/* Newly idle CPU doesn't need an update */
10344 	if (idle != CPU_NEWLY_IDLE) {
10345 		update_blocked_averages(this_cpu);
10346 		has_blocked_load |= this_rq->has_blocked_load;
10347 	}
10348 
10349 	if (flags & NOHZ_BALANCE_KICK)
10350 		rebalance_domains(this_rq, CPU_IDLE);
10351 
10352 	WRITE_ONCE(nohz.next_blocked,
10353 		now + msecs_to_jiffies(LOAD_AVG_PERIOD));
10354 
10355 	/* The full idle balance loop has been done */
10356 	ret = true;
10357 
10358 abort:
10359 	/* There is still blocked load, enable periodic update */
10360 	if (has_blocked_load)
10361 		WRITE_ONCE(nohz.has_blocked, 1);
10362 
10363 	/*
10364 	 * next_balance will be updated only when there is a need.
10365 	 * When the CPU is attached to null domain for ex, it will not be
10366 	 * updated.
10367 	 */
10368 	if (likely(update_next_balance))
10369 		nohz.next_balance = next_balance;
10370 
10371 	return ret;
10372 }
10373 
10374 /*
10375  * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
10376  * rebalancing for all the cpus for whom scheduler ticks are stopped.
10377  */
10378 static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
10379 {
10380 	int this_cpu = this_rq->cpu;
10381 	unsigned int flags;
10382 
10383 	if (!(atomic_read(nohz_flags(this_cpu)) & NOHZ_KICK_MASK))
10384 		return false;
10385 
10386 	if (idle != CPU_IDLE) {
10387 		atomic_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
10388 		return false;
10389 	}
10390 
10391 	/* could be _relaxed() */
10392 	flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
10393 	if (!(flags & NOHZ_KICK_MASK))
10394 		return false;
10395 
10396 	_nohz_idle_balance(this_rq, flags, idle);
10397 
10398 	return true;
10399 }
10400 
10401 static void nohz_newidle_balance(struct rq *this_rq)
10402 {
10403 	int this_cpu = this_rq->cpu;
10404 
10405 	/*
10406 	 * This CPU doesn't want to be disturbed by scheduler
10407 	 * housekeeping
10408 	 */
10409 	if (!housekeeping_cpu(this_cpu, HK_FLAG_SCHED))
10410 		return;
10411 
10412 	/* Will wake up very soon. No time for doing anything else*/
10413 	if (this_rq->avg_idle < sysctl_sched_migration_cost)
10414 		return;
10415 
10416 	/* Don't need to update blocked load of idle CPUs*/
10417 	if (!READ_ONCE(nohz.has_blocked) ||
10418 	    time_before(jiffies, READ_ONCE(nohz.next_blocked)))
10419 		return;
10420 
10421 	raw_spin_unlock(&this_rq->lock);
10422 	/*
10423 	 * This CPU is going to be idle and blocked load of idle CPUs
10424 	 * need to be updated. Run the ilb locally as it is a good
10425 	 * candidate for ilb instead of waking up another idle CPU.
10426 	 * Kick an normal ilb if we failed to do the update.
10427 	 */
10428 	if (!_nohz_idle_balance(this_rq, NOHZ_STATS_KICK, CPU_NEWLY_IDLE))
10429 		kick_ilb(NOHZ_STATS_KICK);
10430 	raw_spin_lock(&this_rq->lock);
10431 }
10432 
10433 #else /* !CONFIG_NO_HZ_COMMON */
10434 static inline void nohz_balancer_kick(struct rq *rq) { }
10435 
10436 static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
10437 {
10438 	return false;
10439 }
10440 
10441 static inline void nohz_newidle_balance(struct rq *this_rq) { }
10442 #endif /* CONFIG_NO_HZ_COMMON */
10443 
10444 /*
10445  * idle_balance is called by schedule() if this_cpu is about to become
10446  * idle. Attempts to pull tasks from other CPUs.
10447  *
10448  * Returns:
10449  *   < 0 - we released the lock and there are !fair tasks present
10450  *     0 - failed, no new tasks
10451  *   > 0 - success, new (fair) tasks present
10452  */
10453 int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
10454 {
10455 	unsigned long next_balance = jiffies + HZ;
10456 	int this_cpu = this_rq->cpu;
10457 	struct sched_domain *sd;
10458 	int pulled_task = 0;
10459 	u64 curr_cost = 0;
10460 
10461 	update_misfit_status(NULL, this_rq);
10462 	/*
10463 	 * We must set idle_stamp _before_ calling idle_balance(), such that we
10464 	 * measure the duration of idle_balance() as idle time.
10465 	 */
10466 	this_rq->idle_stamp = rq_clock(this_rq);
10467 
10468 	/*
10469 	 * Do not pull tasks towards !active CPUs...
10470 	 */
10471 	if (!cpu_active(this_cpu))
10472 		return 0;
10473 
10474 	/*
10475 	 * This is OK, because current is on_cpu, which avoids it being picked
10476 	 * for load-balance and preemption/IRQs are still disabled avoiding
10477 	 * further scheduler activity on it and we're being very careful to
10478 	 * re-start the picking loop.
10479 	 */
10480 	rq_unpin_lock(this_rq, rf);
10481 
10482 	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
10483 	    !READ_ONCE(this_rq->rd->overload)) {
10484 
10485 		rcu_read_lock();
10486 		sd = rcu_dereference_check_sched_domain(this_rq->sd);
10487 		if (sd)
10488 			update_next_balance(sd, &next_balance);
10489 		rcu_read_unlock();
10490 
10491 		nohz_newidle_balance(this_rq);
10492 
10493 		goto out;
10494 	}
10495 
10496 	raw_spin_unlock(&this_rq->lock);
10497 
10498 	update_blocked_averages(this_cpu);
10499 	rcu_read_lock();
10500 	for_each_domain(this_cpu, sd) {
10501 		int continue_balancing = 1;
10502 		u64 t0, domain_cost;
10503 
10504 		if (!(sd->flags & SD_LOAD_BALANCE))
10505 			continue;
10506 
10507 		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
10508 			update_next_balance(sd, &next_balance);
10509 			break;
10510 		}
10511 
10512 		if (sd->flags & SD_BALANCE_NEWIDLE) {
10513 			t0 = sched_clock_cpu(this_cpu);
10514 
10515 			pulled_task = load_balance(this_cpu, this_rq,
10516 						   sd, CPU_NEWLY_IDLE,
10517 						   &continue_balancing);
10518 
10519 			domain_cost = sched_clock_cpu(this_cpu) - t0;
10520 			if (domain_cost > sd->max_newidle_lb_cost)
10521 				sd->max_newidle_lb_cost = domain_cost;
10522 
10523 			curr_cost += domain_cost;
10524 		}
10525 
10526 		update_next_balance(sd, &next_balance);
10527 
10528 		/*
10529 		 * Stop searching for tasks to pull if there are
10530 		 * now runnable tasks on this rq.
10531 		 */
10532 		if (pulled_task || this_rq->nr_running > 0)
10533 			break;
10534 	}
10535 	rcu_read_unlock();
10536 
10537 	raw_spin_lock(&this_rq->lock);
10538 
10539 	if (curr_cost > this_rq->max_idle_balance_cost)
10540 		this_rq->max_idle_balance_cost = curr_cost;
10541 
10542 out:
10543 	/*
10544 	 * While browsing the domains, we released the rq lock, a task could
10545 	 * have been enqueued in the meantime. Since we're not going idle,
10546 	 * pretend we pulled a task.
10547 	 */
10548 	if (this_rq->cfs.h_nr_running && !pulled_task)
10549 		pulled_task = 1;
10550 
10551 	/* Move the next balance forward */
10552 	if (time_after(this_rq->next_balance, next_balance))
10553 		this_rq->next_balance = next_balance;
10554 
10555 	/* Is there a task of a high priority class? */
10556 	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
10557 		pulled_task = -1;
10558 
10559 	if (pulled_task)
10560 		this_rq->idle_stamp = 0;
10561 
10562 	rq_repin_lock(this_rq, rf);
10563 
10564 	return pulled_task;
10565 }
10566 
10567 /*
10568  * run_rebalance_domains is triggered when needed from the scheduler tick.
10569  * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
10570  */
10571 static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
10572 {
10573 	struct rq *this_rq = this_rq();
10574 	enum cpu_idle_type idle = this_rq->idle_balance ?
10575 						CPU_IDLE : CPU_NOT_IDLE;
10576 
10577 	/*
10578 	 * If this CPU has a pending nohz_balance_kick, then do the
10579 	 * balancing on behalf of the other idle CPUs whose ticks are
10580 	 * stopped. Do nohz_idle_balance *before* rebalance_domains to
10581 	 * give the idle CPUs a chance to load balance. Else we may
10582 	 * load balance only within the local sched_domain hierarchy
10583 	 * and abort nohz_idle_balance altogether if we pull some load.
10584 	 */
10585 	if (nohz_idle_balance(this_rq, idle))
10586 		return;
10587 
10588 	/* normal load balance */
10589 	update_blocked_averages(this_rq->cpu);
10590 	rebalance_domains(this_rq, idle);
10591 }
10592 
10593 /*
10594  * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
10595  */
10596 void trigger_load_balance(struct rq *rq)
10597 {
10598 	/* Don't need to rebalance while attached to NULL domain */
10599 	if (unlikely(on_null_domain(rq)))
10600 		return;
10601 
10602 	if (time_after_eq(jiffies, rq->next_balance))
10603 		raise_softirq(SCHED_SOFTIRQ);
10604 
10605 	nohz_balancer_kick(rq);
10606 }
10607 
10608 static void rq_online_fair(struct rq *rq)
10609 {
10610 	update_sysctl();
10611 
10612 	update_runtime_enabled(rq);
10613 }
10614 
10615 static void rq_offline_fair(struct rq *rq)
10616 {
10617 	update_sysctl();
10618 
10619 	/* Ensure any throttled groups are reachable by pick_next_task */
10620 	unthrottle_offline_cfs_rqs(rq);
10621 }
10622 
10623 #endif /* CONFIG_SMP */
10624 
10625 /*
10626  * scheduler tick hitting a task of our scheduling class.
10627  *
10628  * NOTE: This function can be called remotely by the tick offload that
10629  * goes along full dynticks. Therefore no local assumption can be made
10630  * and everything must be accessed through the @rq and @curr passed in
10631  * parameters.
10632  */
10633 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
10634 {
10635 	struct cfs_rq *cfs_rq;
10636 	struct sched_entity *se = &curr->se;
10637 
10638 	for_each_sched_entity(se) {
10639 		cfs_rq = cfs_rq_of(se);
10640 		entity_tick(cfs_rq, se, queued);
10641 	}
10642 
10643 	if (static_branch_unlikely(&sched_numa_balancing))
10644 		task_tick_numa(rq, curr);
10645 
10646 	update_misfit_status(curr, rq);
10647 	update_overutilized_status(task_rq(curr));
10648 }
10649 
10650 /*
10651  * called on fork with the child task as argument from the parent's context
10652  *  - child not yet on the tasklist
10653  *  - preemption disabled
10654  */
10655 static void task_fork_fair(struct task_struct *p)
10656 {
10657 	struct cfs_rq *cfs_rq;
10658 	struct sched_entity *se = &p->se, *curr;
10659 	struct rq *rq = this_rq();
10660 	struct rq_flags rf;
10661 
10662 	rq_lock(rq, &rf);
10663 	update_rq_clock(rq);
10664 
10665 	cfs_rq = task_cfs_rq(current);
10666 	curr = cfs_rq->curr;
10667 	if (curr) {
10668 		update_curr(cfs_rq);
10669 		se->vruntime = curr->vruntime;
10670 	}
10671 	place_entity(cfs_rq, se, 1);
10672 
10673 	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
10674 		/*
10675 		 * Upon rescheduling, sched_class::put_prev_task() will place
10676 		 * 'current' within the tree based on its new key value.
10677 		 */
10678 		swap(curr->vruntime, se->vruntime);
10679 		resched_curr(rq);
10680 	}
10681 
10682 	se->vruntime -= cfs_rq->min_vruntime;
10683 	rq_unlock(rq, &rf);
10684 }
10685 
10686 /*
10687  * Priority of the task has changed. Check to see if we preempt
10688  * the current task.
10689  */
10690 static void
10691 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
10692 {
10693 	if (!task_on_rq_queued(p))
10694 		return;
10695 
10696 	if (rq->cfs.nr_running == 1)
10697 		return;
10698 
10699 	/*
10700 	 * Reschedule if we are currently running on this runqueue and
10701 	 * our priority decreased, or if we are not currently running on
10702 	 * this runqueue and our priority is higher than the current's
10703 	 */
10704 	if (rq->curr == p) {
10705 		if (p->prio > oldprio)
10706 			resched_curr(rq);
10707 	} else
10708 		check_preempt_curr(rq, p, 0);
10709 }
10710 
10711 static inline bool vruntime_normalized(struct task_struct *p)
10712 {
10713 	struct sched_entity *se = &p->se;
10714 
10715 	/*
10716 	 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
10717 	 * the dequeue_entity(.flags=0) will already have normalized the
10718 	 * vruntime.
10719 	 */
10720 	if (p->on_rq)
10721 		return true;
10722 
10723 	/*
10724 	 * When !on_rq, vruntime of the task has usually NOT been normalized.
10725 	 * But there are some cases where it has already been normalized:
10726 	 *
10727 	 * - A forked child which is waiting for being woken up by
10728 	 *   wake_up_new_task().
10729 	 * - A task which has been woken up by try_to_wake_up() and
10730 	 *   waiting for actually being woken up by sched_ttwu_pending().
10731 	 */
10732 	if (!se->sum_exec_runtime ||
10733 	    (p->state == TASK_WAKING && p->sched_remote_wakeup))
10734 		return true;
10735 
10736 	return false;
10737 }
10738 
10739 #ifdef CONFIG_FAIR_GROUP_SCHED
10740 /*
10741  * Propagate the changes of the sched_entity across the tg tree to make it
10742  * visible to the root
10743  */
10744 static void propagate_entity_cfs_rq(struct sched_entity *se)
10745 {
10746 	struct cfs_rq *cfs_rq;
10747 
10748 	/* Start to propagate at parent */
10749 	se = se->parent;
10750 
10751 	for_each_sched_entity(se) {
10752 		cfs_rq = cfs_rq_of(se);
10753 
10754 		if (cfs_rq_throttled(cfs_rq))
10755 			break;
10756 
10757 		update_load_avg(cfs_rq, se, UPDATE_TG);
10758 	}
10759 }
10760 #else
10761 static void propagate_entity_cfs_rq(struct sched_entity *se) { }
10762 #endif
10763 
10764 static void detach_entity_cfs_rq(struct sched_entity *se)
10765 {
10766 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
10767 
10768 	/* Catch up with the cfs_rq and remove our load when we leave */
10769 	update_load_avg(cfs_rq, se, 0);
10770 	detach_entity_load_avg(cfs_rq, se);
10771 	update_tg_load_avg(cfs_rq, false);
10772 	propagate_entity_cfs_rq(se);
10773 }
10774 
10775 static void attach_entity_cfs_rq(struct sched_entity *se)
10776 {
10777 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
10778 
10779 #ifdef CONFIG_FAIR_GROUP_SCHED
10780 	/*
10781 	 * Since the real-depth could have been changed (only FAIR
10782 	 * class maintain depth value), reset depth properly.
10783 	 */
10784 	se->depth = se->parent ? se->parent->depth + 1 : 0;
10785 #endif
10786 
10787 	/* Synchronize entity with its cfs_rq */
10788 	update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
10789 	attach_entity_load_avg(cfs_rq, se);
10790 	update_tg_load_avg(cfs_rq, false);
10791 	propagate_entity_cfs_rq(se);
10792 }
10793 
10794 static void detach_task_cfs_rq(struct task_struct *p)
10795 {
10796 	struct sched_entity *se = &p->se;
10797 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
10798 
10799 	if (!vruntime_normalized(p)) {
10800 		/*
10801 		 * Fix up our vruntime so that the current sleep doesn't
10802 		 * cause 'unlimited' sleep bonus.
10803 		 */
10804 		place_entity(cfs_rq, se, 0);
10805 		se->vruntime -= cfs_rq->min_vruntime;
10806 	}
10807 
10808 	detach_entity_cfs_rq(se);
10809 }
10810 
10811 static void attach_task_cfs_rq(struct task_struct *p)
10812 {
10813 	struct sched_entity *se = &p->se;
10814 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
10815 
10816 	attach_entity_cfs_rq(se);
10817 
10818 	if (!vruntime_normalized(p))
10819 		se->vruntime += cfs_rq->min_vruntime;
10820 }
10821 
10822 static void switched_from_fair(struct rq *rq, struct task_struct *p)
10823 {
10824 	detach_task_cfs_rq(p);
10825 }
10826 
10827 static void switched_to_fair(struct rq *rq, struct task_struct *p)
10828 {
10829 	attach_task_cfs_rq(p);
10830 
10831 	if (task_on_rq_queued(p)) {
10832 		/*
10833 		 * We were most likely switched from sched_rt, so
10834 		 * kick off the schedule if running, otherwise just see
10835 		 * if we can still preempt the current task.
10836 		 */
10837 		if (rq->curr == p)
10838 			resched_curr(rq);
10839 		else
10840 			check_preempt_curr(rq, p, 0);
10841 	}
10842 }
10843 
10844 /* Account for a task changing its policy or group.
10845  *
10846  * This routine is mostly called to set cfs_rq->curr field when a task
10847  * migrates between groups/classes.
10848  */
10849 static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first)
10850 {
10851 	struct sched_entity *se = &p->se;
10852 
10853 #ifdef CONFIG_SMP
10854 	if (task_on_rq_queued(p)) {
10855 		/*
10856 		 * Move the next running task to the front of the list, so our
10857 		 * cfs_tasks list becomes MRU one.
10858 		 */
10859 		list_move(&se->group_node, &rq->cfs_tasks);
10860 	}
10861 #endif
10862 
10863 	for_each_sched_entity(se) {
10864 		struct cfs_rq *cfs_rq = cfs_rq_of(se);
10865 
10866 		set_next_entity(cfs_rq, se);
10867 		/* ensure bandwidth has been allocated on our new cfs_rq */
10868 		account_cfs_rq_runtime(cfs_rq, 0);
10869 	}
10870 }
10871 
10872 void init_cfs_rq(struct cfs_rq *cfs_rq)
10873 {
10874 	cfs_rq->tasks_timeline = RB_ROOT_CACHED;
10875 	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
10876 #ifndef CONFIG_64BIT
10877 	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
10878 #endif
10879 #ifdef CONFIG_SMP
10880 	raw_spin_lock_init(&cfs_rq->removed.lock);
10881 #endif
10882 }
10883 
10884 #ifdef CONFIG_FAIR_GROUP_SCHED
10885 static void task_set_group_fair(struct task_struct *p)
10886 {
10887 	struct sched_entity *se = &p->se;
10888 
10889 	set_task_rq(p, task_cpu(p));
10890 	se->depth = se->parent ? se->parent->depth + 1 : 0;
10891 }
10892 
10893 static void task_move_group_fair(struct task_struct *p)
10894 {
10895 	detach_task_cfs_rq(p);
10896 	set_task_rq(p, task_cpu(p));
10897 
10898 #ifdef CONFIG_SMP
10899 	/* Tell se's cfs_rq has been changed -- migrated */
10900 	p->se.avg.last_update_time = 0;
10901 #endif
10902 	attach_task_cfs_rq(p);
10903 }
10904 
10905 static void task_change_group_fair(struct task_struct *p, int type)
10906 {
10907 	switch (type) {
10908 	case TASK_SET_GROUP:
10909 		task_set_group_fair(p);
10910 		break;
10911 
10912 	case TASK_MOVE_GROUP:
10913 		task_move_group_fair(p);
10914 		break;
10915 	}
10916 }
10917 
10918 void free_fair_sched_group(struct task_group *tg)
10919 {
10920 	int i;
10921 
10922 	destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
10923 
10924 	for_each_possible_cpu(i) {
10925 		if (tg->cfs_rq)
10926 			kfree(tg->cfs_rq[i]);
10927 		if (tg->se)
10928 			kfree(tg->se[i]);
10929 	}
10930 
10931 	kfree(tg->cfs_rq);
10932 	kfree(tg->se);
10933 }
10934 
10935 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
10936 {
10937 	struct sched_entity *se;
10938 	struct cfs_rq *cfs_rq;
10939 	int i;
10940 
10941 	tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL);
10942 	if (!tg->cfs_rq)
10943 		goto err;
10944 	tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL);
10945 	if (!tg->se)
10946 		goto err;
10947 
10948 	tg->shares = NICE_0_LOAD;
10949 
10950 	init_cfs_bandwidth(tg_cfs_bandwidth(tg));
10951 
10952 	for_each_possible_cpu(i) {
10953 		cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
10954 				      GFP_KERNEL, cpu_to_node(i));
10955 		if (!cfs_rq)
10956 			goto err;
10957 
10958 		se = kzalloc_node(sizeof(struct sched_entity),
10959 				  GFP_KERNEL, cpu_to_node(i));
10960 		if (!se)
10961 			goto err_free_rq;
10962 
10963 		init_cfs_rq(cfs_rq);
10964 		init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
10965 		init_entity_runnable_average(se);
10966 	}
10967 
10968 	return 1;
10969 
10970 err_free_rq:
10971 	kfree(cfs_rq);
10972 err:
10973 	return 0;
10974 }
10975 
10976 void online_fair_sched_group(struct task_group *tg)
10977 {
10978 	struct sched_entity *se;
10979 	struct rq_flags rf;
10980 	struct rq *rq;
10981 	int i;
10982 
10983 	for_each_possible_cpu(i) {
10984 		rq = cpu_rq(i);
10985 		se = tg->se[i];
10986 		rq_lock_irq(rq, &rf);
10987 		update_rq_clock(rq);
10988 		attach_entity_cfs_rq(se);
10989 		sync_throttle(tg, i);
10990 		rq_unlock_irq(rq, &rf);
10991 	}
10992 }
10993 
10994 void unregister_fair_sched_group(struct task_group *tg)
10995 {
10996 	unsigned long flags;
10997 	struct rq *rq;
10998 	int cpu;
10999 
11000 	for_each_possible_cpu(cpu) {
11001 		if (tg->se[cpu])
11002 			remove_entity_load_avg(tg->se[cpu]);
11003 
11004 		/*
11005 		 * Only empty task groups can be destroyed; so we can speculatively
11006 		 * check on_list without danger of it being re-added.
11007 		 */
11008 		if (!tg->cfs_rq[cpu]->on_list)
11009 			continue;
11010 
11011 		rq = cpu_rq(cpu);
11012 
11013 		raw_spin_lock_irqsave(&rq->lock, flags);
11014 		list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
11015 		raw_spin_unlock_irqrestore(&rq->lock, flags);
11016 	}
11017 }
11018 
11019 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
11020 			struct sched_entity *se, int cpu,
11021 			struct sched_entity *parent)
11022 {
11023 	struct rq *rq = cpu_rq(cpu);
11024 
11025 	cfs_rq->tg = tg;
11026 	cfs_rq->rq = rq;
11027 	init_cfs_rq_runtime(cfs_rq);
11028 
11029 	tg->cfs_rq[cpu] = cfs_rq;
11030 	tg->se[cpu] = se;
11031 
11032 	/* se could be NULL for root_task_group */
11033 	if (!se)
11034 		return;
11035 
11036 	if (!parent) {
11037 		se->cfs_rq = &rq->cfs;
11038 		se->depth = 0;
11039 	} else {
11040 		se->cfs_rq = parent->my_q;
11041 		se->depth = parent->depth + 1;
11042 	}
11043 
11044 	se->my_q = cfs_rq;
11045 	/* guarantee group entities always have weight */
11046 	update_load_set(&se->load, NICE_0_LOAD);
11047 	se->parent = parent;
11048 }
11049 
11050 static DEFINE_MUTEX(shares_mutex);
11051 
11052 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
11053 {
11054 	int i;
11055 
11056 	/*
11057 	 * We can't change the weight of the root cgroup.
11058 	 */
11059 	if (!tg->se[0])
11060 		return -EINVAL;
11061 
11062 	shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
11063 
11064 	mutex_lock(&shares_mutex);
11065 	if (tg->shares == shares)
11066 		goto done;
11067 
11068 	tg->shares = shares;
11069 	for_each_possible_cpu(i) {
11070 		struct rq *rq = cpu_rq(i);
11071 		struct sched_entity *se = tg->se[i];
11072 		struct rq_flags rf;
11073 
11074 		/* Propagate contribution to hierarchy */
11075 		rq_lock_irqsave(rq, &rf);
11076 		update_rq_clock(rq);
11077 		for_each_sched_entity(se) {
11078 			update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
11079 			update_cfs_group(se);
11080 		}
11081 		rq_unlock_irqrestore(rq, &rf);
11082 	}
11083 
11084 done:
11085 	mutex_unlock(&shares_mutex);
11086 	return 0;
11087 }
11088 #else /* CONFIG_FAIR_GROUP_SCHED */
11089 
11090 void free_fair_sched_group(struct task_group *tg) { }
11091 
11092 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
11093 {
11094 	return 1;
11095 }
11096 
11097 void online_fair_sched_group(struct task_group *tg) { }
11098 
11099 void unregister_fair_sched_group(struct task_group *tg) { }
11100 
11101 #endif /* CONFIG_FAIR_GROUP_SCHED */
11102 
11103 
11104 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
11105 {
11106 	struct sched_entity *se = &task->se;
11107 	unsigned int rr_interval = 0;
11108 
11109 	/*
11110 	 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
11111 	 * idle runqueue:
11112 	 */
11113 	if (rq->cfs.load.weight)
11114 		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
11115 
11116 	return rr_interval;
11117 }
11118 
11119 /*
11120  * All the scheduling class methods:
11121  */
11122 const struct sched_class fair_sched_class = {
11123 	.next			= &idle_sched_class,
11124 	.enqueue_task		= enqueue_task_fair,
11125 	.dequeue_task		= dequeue_task_fair,
11126 	.yield_task		= yield_task_fair,
11127 	.yield_to_task		= yield_to_task_fair,
11128 
11129 	.check_preempt_curr	= check_preempt_wakeup,
11130 
11131 	.pick_next_task		= __pick_next_task_fair,
11132 	.put_prev_task		= put_prev_task_fair,
11133 	.set_next_task          = set_next_task_fair,
11134 
11135 #ifdef CONFIG_SMP
11136 	.balance		= balance_fair,
11137 	.select_task_rq		= select_task_rq_fair,
11138 	.migrate_task_rq	= migrate_task_rq_fair,
11139 
11140 	.rq_online		= rq_online_fair,
11141 	.rq_offline		= rq_offline_fair,
11142 
11143 	.task_dead		= task_dead_fair,
11144 	.set_cpus_allowed	= set_cpus_allowed_common,
11145 #endif
11146 
11147 	.task_tick		= task_tick_fair,
11148 	.task_fork		= task_fork_fair,
11149 
11150 	.prio_changed		= prio_changed_fair,
11151 	.switched_from		= switched_from_fair,
11152 	.switched_to		= switched_to_fair,
11153 
11154 	.get_rr_interval	= get_rr_interval_fair,
11155 
11156 	.update_curr		= update_curr_fair,
11157 
11158 #ifdef CONFIG_FAIR_GROUP_SCHED
11159 	.task_change_group	= task_change_group_fair,
11160 #endif
11161 
11162 #ifdef CONFIG_UCLAMP_TASK
11163 	.uclamp_enabled		= 1,
11164 #endif
11165 };
11166 
11167 #ifdef CONFIG_SCHED_DEBUG
11168 void print_cfs_stats(struct seq_file *m, int cpu)
11169 {
11170 	struct cfs_rq *cfs_rq, *pos;
11171 
11172 	rcu_read_lock();
11173 	for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos)
11174 		print_cfs_rq(m, cpu, cfs_rq);
11175 	rcu_read_unlock();
11176 }
11177 
11178 #ifdef CONFIG_NUMA_BALANCING
11179 void show_numa_stats(struct task_struct *p, struct seq_file *m)
11180 {
11181 	int node;
11182 	unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
11183 	struct numa_group *ng;
11184 
11185 	rcu_read_lock();
11186 	ng = rcu_dereference(p->numa_group);
11187 	for_each_online_node(node) {
11188 		if (p->numa_faults) {
11189 			tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
11190 			tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
11191 		}
11192 		if (ng) {
11193 			gsf = ng->faults[task_faults_idx(NUMA_MEM, node, 0)],
11194 			gpf = ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
11195 		}
11196 		print_numa_stats(m, node, tsf, tpf, gsf, gpf);
11197 	}
11198 	rcu_read_unlock();
11199 }
11200 #endif /* CONFIG_NUMA_BALANCING */
11201 #endif /* CONFIG_SCHED_DEBUG */
11202 
11203 __init void init_sched_fair_class(void)
11204 {
11205 #ifdef CONFIG_SMP
11206 	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
11207 
11208 #ifdef CONFIG_NO_HZ_COMMON
11209 	nohz.next_balance = jiffies;
11210 	nohz.next_blocked = jiffies;
11211 	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
11212 #endif
11213 #endif /* SMP */
11214 
11215 }
11216 
11217 /*
11218  * Helper functions to facilitate extracting info from tracepoints.
11219  */
11220 
11221 const struct sched_avg *sched_trace_cfs_rq_avg(struct cfs_rq *cfs_rq)
11222 {
11223 #ifdef CONFIG_SMP
11224 	return cfs_rq ? &cfs_rq->avg : NULL;
11225 #else
11226 	return NULL;
11227 #endif
11228 }
11229 EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_avg);
11230 
11231 char *sched_trace_cfs_rq_path(struct cfs_rq *cfs_rq, char *str, int len)
11232 {
11233 	if (!cfs_rq) {
11234 		if (str)
11235 			strlcpy(str, "(null)", len);
11236 		else
11237 			return NULL;
11238 	}
11239 
11240 	cfs_rq_tg_path(cfs_rq, str, len);
11241 	return str;
11242 }
11243 EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_path);
11244 
11245 int sched_trace_cfs_rq_cpu(struct cfs_rq *cfs_rq)
11246 {
11247 	return cfs_rq ? cpu_of(rq_of(cfs_rq)) : -1;
11248 }
11249 EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_cpu);
11250 
11251 const struct sched_avg *sched_trace_rq_avg_rt(struct rq *rq)
11252 {
11253 #ifdef CONFIG_SMP
11254 	return rq ? &rq->avg_rt : NULL;
11255 #else
11256 	return NULL;
11257 #endif
11258 }
11259 EXPORT_SYMBOL_GPL(sched_trace_rq_avg_rt);
11260 
11261 const struct sched_avg *sched_trace_rq_avg_dl(struct rq *rq)
11262 {
11263 #ifdef CONFIG_SMP
11264 	return rq ? &rq->avg_dl : NULL;
11265 #else
11266 	return NULL;
11267 #endif
11268 }
11269 EXPORT_SYMBOL_GPL(sched_trace_rq_avg_dl);
11270 
11271 const struct sched_avg *sched_trace_rq_avg_irq(struct rq *rq)
11272 {
11273 #if defined(CONFIG_SMP) && defined(CONFIG_HAVE_SCHED_AVG_IRQ)
11274 	return rq ? &rq->avg_irq : NULL;
11275 #else
11276 	return NULL;
11277 #endif
11278 }
11279 EXPORT_SYMBOL_GPL(sched_trace_rq_avg_irq);
11280 
11281 int sched_trace_rq_cpu(struct rq *rq)
11282 {
11283 	return rq ? cpu_of(rq) : -1;
11284 }
11285 EXPORT_SYMBOL_GPL(sched_trace_rq_cpu);
11286 
11287 const struct cpumask *sched_trace_rd_span(struct root_domain *rd)
11288 {
11289 #ifdef CONFIG_SMP
11290 	return rd ? rd->span : NULL;
11291 #else
11292 	return NULL;
11293 #endif
11294 }
11295 EXPORT_SYMBOL_GPL(sched_trace_rd_span);
11296