xref: /freebsd/sys/kern/sched_ule.c (revision 9336e0699bda8a301cd2bfa37106b6ec5e32012e)
1 /*-
2  * Copyright (c) 2002-2007, Jeffrey Roberson <jeff@freebsd.org>
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice unmodified, this list of conditions, and the following
10  *    disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25  */
26 
27 /*
28  * This file implements the ULE scheduler.  ULE supports independent CPU
29  * run queues and fine grain locking.  It has superior interactive
30  * performance under load even on uni-processor systems.
31  *
32  * etymology:
33  *   ULE is the last three letters in schedule.  It owes its name to a
34  * generic user created for a scheduling system by Paul Mikesell at
35  * Isilon Systems and a general lack of creativity on the part of the author.
36  */
37 
38 #include <sys/cdefs.h>
39 __FBSDID("$FreeBSD$");
40 
41 #include "opt_hwpmc_hooks.h"
42 #include "opt_sched.h"
43 
44 #include <sys/param.h>
45 #include <sys/systm.h>
46 #include <sys/kdb.h>
47 #include <sys/kernel.h>
48 #include <sys/ktr.h>
49 #include <sys/lock.h>
50 #include <sys/mutex.h>
51 #include <sys/proc.h>
52 #include <sys/resource.h>
53 #include <sys/resourcevar.h>
54 #include <sys/sched.h>
55 #include <sys/smp.h>
56 #include <sys/sx.h>
57 #include <sys/sysctl.h>
58 #include <sys/sysproto.h>
59 #include <sys/turnstile.h>
60 #include <sys/umtx.h>
61 #include <sys/vmmeter.h>
62 #ifdef KTRACE
63 #include <sys/uio.h>
64 #include <sys/ktrace.h>
65 #endif
66 
67 #ifdef HWPMC_HOOKS
68 #include <sys/pmckern.h>
69 #endif
70 
71 #include <machine/cpu.h>
72 #include <machine/smp.h>
73 
74 #if !defined(__i386__) && !defined(__amd64__) && !defined(__powerpc__) && !defined(__arm__)
75 #error "This architecture is not currently compatible with ULE"
76 #endif
77 
78 #define	KTR_ULE	0
79 
80 /*
81  * Thread scheduler specific section.  All fields are protected
82  * by the thread lock.
83  */
84 struct td_sched {
85 	TAILQ_ENTRY(td_sched) ts_procq;	/* Run queue. */
86 	struct thread	*ts_thread;	/* Active associated thread. */
87 	struct runq	*ts_runq;	/* Run-queue we're queued on. */
88 	short		ts_flags;	/* TSF_* flags. */
89 	u_char		ts_rqindex;	/* Run queue index. */
90 	u_char		ts_cpu;		/* CPU that we have affinity for. */
91 	int		ts_slice;	/* Ticks of slice remaining. */
92 	u_int		ts_slptime;	/* Number of ticks we vol. slept */
93 	u_int		ts_runtime;	/* Number of ticks we were running */
94 	/* The following variables are only used for pctcpu calculation */
95 	int		ts_ltick;	/* Last tick that we were running on */
96 	int		ts_ftick;	/* First tick that we were running on */
97 	int		ts_ticks;	/* Tick count */
98 #ifdef SMP
99 	int		ts_rltick;	/* Real last tick, for affinity. */
100 #endif
101 };
102 /* flags kept in ts_flags */
103 #define	TSF_BOUND	0x0001		/* Thread can not migrate. */
104 #define	TSF_XFERABLE	0x0002		/* Thread was added as transferable. */
105 
106 static struct td_sched td_sched0;
107 
108 /*
109  * Cpu percentage computation macros and defines.
110  *
111  * SCHED_TICK_SECS:	Number of seconds to average the cpu usage across.
112  * SCHED_TICK_TARG:	Number of hz ticks to average the cpu usage across.
113  * SCHED_TICK_MAX:	Maximum number of ticks before scaling back.
114  * SCHED_TICK_SHIFT:	Shift factor to avoid rounding away results.
115  * SCHED_TICK_HZ:	Compute the number of hz ticks for a given ticks count.
116  * SCHED_TICK_TOTAL:	Gives the amount of time we've been recording ticks.
117  */
118 #define	SCHED_TICK_SECS		10
119 #define	SCHED_TICK_TARG		(hz * SCHED_TICK_SECS)
120 #define	SCHED_TICK_MAX		(SCHED_TICK_TARG + hz)
121 #define	SCHED_TICK_SHIFT	10
122 #define	SCHED_TICK_HZ(ts)	((ts)->ts_ticks >> SCHED_TICK_SHIFT)
123 #define	SCHED_TICK_TOTAL(ts)	(max((ts)->ts_ltick - (ts)->ts_ftick, hz))
124 
125 /*
126  * These macros determine priorities for non-interactive threads.  They are
127  * assigned a priority based on their recent cpu utilization as expressed
128  * by the ratio of ticks to the tick total.  NHALF priorities at the start
129  * and end of the MIN to MAX timeshare range are only reachable with negative
130  * or positive nice respectively.
131  *
132  * PRI_RANGE:	Priority range for utilization dependent priorities.
133  * PRI_NRESV:	Number of nice values.
134  * PRI_TICKS:	Compute a priority in PRI_RANGE from the ticks count and total.
135  * PRI_NICE:	Determines the part of the priority inherited from nice.
136  */
137 #define	SCHED_PRI_NRESV		(PRIO_MAX - PRIO_MIN)
138 #define	SCHED_PRI_NHALF		(SCHED_PRI_NRESV / 2)
139 #define	SCHED_PRI_MIN		(PRI_MIN_TIMESHARE + SCHED_PRI_NHALF)
140 #define	SCHED_PRI_MAX		(PRI_MAX_TIMESHARE - SCHED_PRI_NHALF)
141 #define	SCHED_PRI_RANGE		(SCHED_PRI_MAX - SCHED_PRI_MIN)
142 #define	SCHED_PRI_TICKS(ts)						\
143     (SCHED_TICK_HZ((ts)) /						\
144     (roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE))
145 #define	SCHED_PRI_NICE(nice)	(nice)
146 
147 /*
148  * These determine the interactivity of a process.  Interactivity differs from
149  * cpu utilization in that it expresses the voluntary time slept vs time ran
150  * while cpu utilization includes all time not running.  This more accurately
151  * models the intent of the thread.
152  *
153  * SLP_RUN_MAX:	Maximum amount of sleep time + run time we'll accumulate
154  *		before throttling back.
155  * SLP_RUN_FORK:	Maximum slp+run time to inherit at fork time.
156  * INTERACT_MAX:	Maximum interactivity value.  Smaller is better.
157  * INTERACT_THRESH:	Threshhold for placement on the current runq.
158  */
159 #define	SCHED_SLP_RUN_MAX	((hz * 5) << SCHED_TICK_SHIFT)
160 #define	SCHED_SLP_RUN_FORK	((hz / 2) << SCHED_TICK_SHIFT)
161 #define	SCHED_INTERACT_MAX	(100)
162 #define	SCHED_INTERACT_HALF	(SCHED_INTERACT_MAX / 2)
163 #define	SCHED_INTERACT_THRESH	(30)
164 
165 /*
166  * tickincr:		Converts a stathz tick into a hz domain scaled by
167  *			the shift factor.  Without the shift the error rate
168  *			due to rounding would be unacceptably high.
169  * realstathz:		stathz is sometimes 0 and run off of hz.
170  * sched_slice:		Runtime of each thread before rescheduling.
171  * preempt_thresh:	Priority threshold for preemption and remote IPIs.
172  */
173 static int sched_interact = SCHED_INTERACT_THRESH;
174 static int realstathz;
175 static int tickincr;
176 static int sched_slice;
177 #ifdef PREEMPTION
178 #ifdef FULL_PREEMPTION
179 static int preempt_thresh = PRI_MAX_IDLE;
180 #else
181 static int preempt_thresh = PRI_MIN_KERN;
182 #endif
183 #else
184 static int preempt_thresh = 0;
185 #endif
186 
187 /*
188  * tdq - per processor runqs and statistics.  All fields are protected by the
189  * tdq_lock.  The load and lowpri may be accessed without to avoid excess
190  * locking in sched_pickcpu();
191  */
192 struct tdq {
193 	struct mtx	*tdq_lock;		/* Pointer to group lock. */
194 	struct runq	tdq_realtime;		/* real-time run queue. */
195 	struct runq	tdq_timeshare;		/* timeshare run queue. */
196 	struct runq	tdq_idle;		/* Queue of IDLE threads. */
197 	int		tdq_load;		/* Aggregate load. */
198 	u_char		tdq_idx;		/* Current insert index. */
199 	u_char		tdq_ridx;		/* Current removal index. */
200 #ifdef SMP
201 	u_char		tdq_lowpri;		/* Lowest priority thread. */
202 	int		tdq_transferable;	/* Transferable thread count. */
203 	LIST_ENTRY(tdq)	tdq_siblings;		/* Next in tdq group. */
204 	struct tdq_group *tdq_group;		/* Our processor group. */
205 #else
206 	int		tdq_sysload;		/* For loadavg, !ITHD load. */
207 #endif
208 } __aligned(64);
209 
210 
211 #ifdef SMP
212 /*
213  * tdq groups are groups of processors which can cheaply share threads.  When
214  * one processor in the group goes idle it will check the runqs of the other
215  * processors in its group prior to halting and waiting for an interrupt.
216  * These groups are suitable for SMT (Symetric Multi-Threading) and not NUMA.
217  * In a numa environment we'd want an idle bitmap per group and a two tiered
218  * load balancer.
219  */
220 struct tdq_group {
221 	struct mtx	tdg_lock;	/* Protects all fields below. */
222 	int		tdg_cpus;	/* Count of CPUs in this tdq group. */
223 	cpumask_t 	tdg_cpumask;	/* Mask of cpus in this group. */
224 	cpumask_t 	tdg_idlemask;	/* Idle cpus in this group. */
225 	cpumask_t 	tdg_mask;	/* Bit mask for first cpu. */
226 	int		tdg_load;	/* Total load of this group. */
227 	int	tdg_transferable;	/* Transferable load of this group. */
228 	LIST_HEAD(, tdq) tdg_members;	/* Linked list of all members. */
229 	char		tdg_name[16];	/* lock name. */
230 } __aligned(64);
231 
232 #define	SCHED_AFFINITY_DEFAULT	(max(1, hz / 300))
233 #define	SCHED_AFFINITY(ts)	((ts)->ts_rltick > ticks - affinity)
234 
235 /*
236  * Run-time tunables.
237  */
238 static int rebalance = 1;
239 static int balance_interval = 128;	/* Default set in sched_initticks(). */
240 static int pick_pri = 1;
241 static int affinity;
242 static int tryself = 1;
243 static int steal_htt = 1;
244 static int steal_idle = 1;
245 static int steal_thresh = 2;
246 static int topology = 0;
247 
248 /*
249  * One thread queue per processor.
250  */
251 static volatile cpumask_t tdq_idle;
252 static int tdg_maxid;
253 static struct tdq	tdq_cpu[MAXCPU];
254 static struct tdq_group tdq_groups[MAXCPU];
255 static struct tdq	*balance_tdq;
256 static int balance_group_ticks;
257 static int balance_ticks;
258 
259 #define	TDQ_SELF()	(&tdq_cpu[PCPU_GET(cpuid)])
260 #define	TDQ_CPU(x)	(&tdq_cpu[(x)])
261 #define	TDQ_ID(x)	((int)((x) - tdq_cpu))
262 #define	TDQ_GROUP(x)	(&tdq_groups[(x)])
263 #define	TDG_ID(x)	((int)((x) - tdq_groups))
264 #else	/* !SMP */
265 static struct tdq	tdq_cpu;
266 static struct mtx	tdq_lock;
267 
268 #define	TDQ_ID(x)	(0)
269 #define	TDQ_SELF()	(&tdq_cpu)
270 #define	TDQ_CPU(x)	(&tdq_cpu)
271 #endif
272 
273 #define	TDQ_LOCK_ASSERT(t, type)	mtx_assert(TDQ_LOCKPTR((t)), (type))
274 #define	TDQ_LOCK(t)		mtx_lock_spin(TDQ_LOCKPTR((t)))
275 #define	TDQ_LOCK_FLAGS(t, f)	mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f))
276 #define	TDQ_UNLOCK(t)		mtx_unlock_spin(TDQ_LOCKPTR((t)))
277 #define	TDQ_LOCKPTR(t)		((t)->tdq_lock)
278 
279 static void sched_priority(struct thread *);
280 static void sched_thread_priority(struct thread *, u_char);
281 static int sched_interact_score(struct thread *);
282 static void sched_interact_update(struct thread *);
283 static void sched_interact_fork(struct thread *);
284 static void sched_pctcpu_update(struct td_sched *);
285 
286 /* Operations on per processor queues */
287 static struct td_sched * tdq_choose(struct tdq *);
288 static void tdq_setup(struct tdq *);
289 static void tdq_load_add(struct tdq *, struct td_sched *);
290 static void tdq_load_rem(struct tdq *, struct td_sched *);
291 static __inline void tdq_runq_add(struct tdq *, struct td_sched *, int);
292 static __inline void tdq_runq_rem(struct tdq *, struct td_sched *);
293 void tdq_print(int cpu);
294 static void runq_print(struct runq *rq);
295 static void tdq_add(struct tdq *, struct thread *, int);
296 #ifdef SMP
297 static void tdq_move(struct tdq *, struct tdq *);
298 static int tdq_idled(struct tdq *);
299 static void tdq_notify(struct td_sched *);
300 static struct td_sched *tdq_steal(struct tdq *);
301 static struct td_sched *runq_steal(struct runq *);
302 static int sched_pickcpu(struct td_sched *, int);
303 static void sched_balance(void);
304 static void sched_balance_groups(void);
305 static void sched_balance_group(struct tdq_group *);
306 static void sched_balance_pair(struct tdq *, struct tdq *);
307 static inline struct tdq *sched_setcpu(struct td_sched *, int, int);
308 static inline struct mtx *thread_block_switch(struct thread *);
309 static inline void thread_unblock_switch(struct thread *, struct mtx *);
310 static struct mtx *sched_switch_migrate(struct tdq *, struct thread *, int);
311 
312 #define	THREAD_CAN_MIGRATE(td)	 ((td)->td_pinned == 0)
313 #endif
314 
315 static void sched_setup(void *dummy);
316 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL)
317 
318 static void sched_initticks(void *dummy);
319 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks, NULL)
320 
321 /*
322  * Print the threads waiting on a run-queue.
323  */
324 static void
325 runq_print(struct runq *rq)
326 {
327 	struct rqhead *rqh;
328 	struct td_sched *ts;
329 	int pri;
330 	int j;
331 	int i;
332 
333 	for (i = 0; i < RQB_LEN; i++) {
334 		printf("\t\trunq bits %d 0x%zx\n",
335 		    i, rq->rq_status.rqb_bits[i]);
336 		for (j = 0; j < RQB_BPW; j++)
337 			if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
338 				pri = j + (i << RQB_L2BPW);
339 				rqh = &rq->rq_queues[pri];
340 				TAILQ_FOREACH(ts, rqh, ts_procq) {
341 					printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
342 					    ts->ts_thread, ts->ts_thread->td_name, ts->ts_thread->td_priority, ts->ts_rqindex, pri);
343 				}
344 			}
345 	}
346 }
347 
348 /*
349  * Print the status of a per-cpu thread queue.  Should be a ddb show cmd.
350  */
351 void
352 tdq_print(int cpu)
353 {
354 	struct tdq *tdq;
355 
356 	tdq = TDQ_CPU(cpu);
357 
358 	printf("tdq %d:\n", TDQ_ID(tdq));
359 	printf("\tlockptr         %p\n", TDQ_LOCKPTR(tdq));
360 	printf("\tload:           %d\n", tdq->tdq_load);
361 	printf("\ttimeshare idx:  %d\n", tdq->tdq_idx);
362 	printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
363 	printf("\trealtime runq:\n");
364 	runq_print(&tdq->tdq_realtime);
365 	printf("\ttimeshare runq:\n");
366 	runq_print(&tdq->tdq_timeshare);
367 	printf("\tidle runq:\n");
368 	runq_print(&tdq->tdq_idle);
369 #ifdef SMP
370 	printf("\tload transferable: %d\n", tdq->tdq_transferable);
371 	printf("\tlowest priority:   %d\n", tdq->tdq_lowpri);
372 	printf("\tgroup:             %d\n", TDG_ID(tdq->tdq_group));
373 	printf("\tLock name:         %s\n", tdq->tdq_group->tdg_name);
374 #endif
375 }
376 
377 #define	TS_RQ_PPQ	(((PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE) + 1) / RQ_NQS)
378 /*
379  * Add a thread to the actual run-queue.  Keeps transferable counts up to
380  * date with what is actually on the run-queue.  Selects the correct
381  * queue position for timeshare threads.
382  */
383 static __inline void
384 tdq_runq_add(struct tdq *tdq, struct td_sched *ts, int flags)
385 {
386 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
387 	THREAD_LOCK_ASSERT(ts->ts_thread, MA_OWNED);
388 #ifdef SMP
389 	if (THREAD_CAN_MIGRATE(ts->ts_thread)) {
390 		tdq->tdq_transferable++;
391 		tdq->tdq_group->tdg_transferable++;
392 		ts->ts_flags |= TSF_XFERABLE;
393 	}
394 #endif
395 	if (ts->ts_runq == &tdq->tdq_timeshare) {
396 		u_char pri;
397 
398 		pri = ts->ts_thread->td_priority;
399 		KASSERT(pri <= PRI_MAX_TIMESHARE && pri >= PRI_MIN_TIMESHARE,
400 			("Invalid priority %d on timeshare runq", pri));
401 		/*
402 		 * This queue contains only priorities between MIN and MAX
403 		 * realtime.  Use the whole queue to represent these values.
404 		 */
405 		if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
406 			pri = (pri - PRI_MIN_TIMESHARE) / TS_RQ_PPQ;
407 			pri = (pri + tdq->tdq_idx) % RQ_NQS;
408 			/*
409 			 * This effectively shortens the queue by one so we
410 			 * can have a one slot difference between idx and
411 			 * ridx while we wait for threads to drain.
412 			 */
413 			if (tdq->tdq_ridx != tdq->tdq_idx &&
414 			    pri == tdq->tdq_ridx)
415 				pri = (unsigned char)(pri - 1) % RQ_NQS;
416 		} else
417 			pri = tdq->tdq_ridx;
418 		runq_add_pri(ts->ts_runq, ts, pri, flags);
419 	} else
420 		runq_add(ts->ts_runq, ts, flags);
421 }
422 
423 /*
424  * Remove a thread from a run-queue.  This typically happens when a thread
425  * is selected to run.  Running threads are not on the queue and the
426  * transferable count does not reflect them.
427  */
428 static __inline void
429 tdq_runq_rem(struct tdq *tdq, struct td_sched *ts)
430 {
431 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
432 	KASSERT(ts->ts_runq != NULL,
433 	    ("tdq_runq_remove: thread %p null ts_runq", ts->ts_thread));
434 #ifdef SMP
435 	if (ts->ts_flags & TSF_XFERABLE) {
436 		tdq->tdq_transferable--;
437 		tdq->tdq_group->tdg_transferable--;
438 		ts->ts_flags &= ~TSF_XFERABLE;
439 	}
440 #endif
441 	if (ts->ts_runq == &tdq->tdq_timeshare) {
442 		if (tdq->tdq_idx != tdq->tdq_ridx)
443 			runq_remove_idx(ts->ts_runq, ts, &tdq->tdq_ridx);
444 		else
445 			runq_remove_idx(ts->ts_runq, ts, NULL);
446 		/*
447 		 * For timeshare threads we update the priority here so
448 		 * the priority reflects the time we've been sleeping.
449 		 */
450 		ts->ts_ltick = ticks;
451 		sched_pctcpu_update(ts);
452 		sched_priority(ts->ts_thread);
453 	} else
454 		runq_remove(ts->ts_runq, ts);
455 }
456 
457 /*
458  * Load is maintained for all threads RUNNING and ON_RUNQ.  Add the load
459  * for this thread to the referenced thread queue.
460  */
461 static void
462 tdq_load_add(struct tdq *tdq, struct td_sched *ts)
463 {
464 	int class;
465 
466 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
467 	THREAD_LOCK_ASSERT(ts->ts_thread, MA_OWNED);
468 	class = PRI_BASE(ts->ts_thread->td_pri_class);
469 	tdq->tdq_load++;
470 	CTR2(KTR_SCHED, "cpu %d load: %d", TDQ_ID(tdq), tdq->tdq_load);
471 	if (class != PRI_ITHD &&
472 	    (ts->ts_thread->td_proc->p_flag & P_NOLOAD) == 0)
473 #ifdef SMP
474 		tdq->tdq_group->tdg_load++;
475 #else
476 		tdq->tdq_sysload++;
477 #endif
478 }
479 
480 /*
481  * Remove the load from a thread that is transitioning to a sleep state or
482  * exiting.
483  */
484 static void
485 tdq_load_rem(struct tdq *tdq, struct td_sched *ts)
486 {
487 	int class;
488 
489 	THREAD_LOCK_ASSERT(ts->ts_thread, MA_OWNED);
490 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
491 	class = PRI_BASE(ts->ts_thread->td_pri_class);
492 	if (class != PRI_ITHD &&
493 	    (ts->ts_thread->td_proc->p_flag & P_NOLOAD) == 0)
494 #ifdef SMP
495 		tdq->tdq_group->tdg_load--;
496 #else
497 		tdq->tdq_sysload--;
498 #endif
499 	KASSERT(tdq->tdq_load != 0,
500 	    ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
501 	tdq->tdq_load--;
502 	CTR1(KTR_SCHED, "load: %d", tdq->tdq_load);
503 	ts->ts_runq = NULL;
504 }
505 
506 #ifdef SMP
507 /*
508  * sched_balance is a simple CPU load balancing algorithm.  It operates by
509  * finding the least loaded and most loaded cpu and equalizing their load
510  * by migrating some processes.
511  *
512  * Dealing only with two CPUs at a time has two advantages.  Firstly, most
513  * installations will only have 2 cpus.  Secondly, load balancing too much at
514  * once can have an unpleasant effect on the system.  The scheduler rarely has
515  * enough information to make perfect decisions.  So this algorithm chooses
516  * simplicity and more gradual effects on load in larger systems.
517  *
518  */
519 static void
520 sched_balance()
521 {
522 	struct tdq_group *high;
523 	struct tdq_group *low;
524 	struct tdq_group *tdg;
525 	struct tdq *tdq;
526 	int cnt;
527 	int i;
528 
529 	/*
530 	 * Select a random time between .5 * balance_interval and
531 	 * 1.5 * balance_interval.
532 	 */
533 	balance_ticks = max(balance_interval / 2, 1);
534 	balance_ticks += random() % balance_interval;
535 	if (smp_started == 0 || rebalance == 0)
536 		return;
537 	tdq = TDQ_SELF();
538 	TDQ_UNLOCK(tdq);
539 	low = high = NULL;
540 	i = random() % (tdg_maxid + 1);
541 	for (cnt = 0; cnt <= tdg_maxid; cnt++) {
542 		tdg = TDQ_GROUP(i);
543 		/*
544 		 * Find the CPU with the highest load that has some
545 		 * threads to transfer.
546 		 */
547 		if ((high == NULL || tdg->tdg_load > high->tdg_load)
548 		    && tdg->tdg_transferable)
549 			high = tdg;
550 		if (low == NULL || tdg->tdg_load < low->tdg_load)
551 			low = tdg;
552 		if (++i > tdg_maxid)
553 			i = 0;
554 	}
555 	if (low != NULL && high != NULL && high != low)
556 		sched_balance_pair(LIST_FIRST(&high->tdg_members),
557 		    LIST_FIRST(&low->tdg_members));
558 	TDQ_LOCK(tdq);
559 }
560 
561 /*
562  * Balance load between CPUs in a group.  Will only migrate within the group.
563  */
564 static void
565 sched_balance_groups()
566 {
567 	struct tdq *tdq;
568 	int i;
569 
570 	/*
571 	 * Select a random time between .5 * balance_interval and
572 	 * 1.5 * balance_interval.
573 	 */
574 	balance_group_ticks = max(balance_interval / 2, 1);
575 	balance_group_ticks += random() % balance_interval;
576 	if (smp_started == 0 || rebalance == 0)
577 		return;
578 	tdq = TDQ_SELF();
579 	TDQ_UNLOCK(tdq);
580 	for (i = 0; i <= tdg_maxid; i++)
581 		sched_balance_group(TDQ_GROUP(i));
582 	TDQ_LOCK(tdq);
583 }
584 
585 /*
586  * Finds the greatest imbalance between two tdqs in a group.
587  */
588 static void
589 sched_balance_group(struct tdq_group *tdg)
590 {
591 	struct tdq *tdq;
592 	struct tdq *high;
593 	struct tdq *low;
594 	int load;
595 
596 	if (tdg->tdg_transferable == 0)
597 		return;
598 	low = NULL;
599 	high = NULL;
600 	LIST_FOREACH(tdq, &tdg->tdg_members, tdq_siblings) {
601 		load = tdq->tdq_load;
602 		if (high == NULL || load > high->tdq_load)
603 			high = tdq;
604 		if (low == NULL || load < low->tdq_load)
605 			low = tdq;
606 	}
607 	if (high != NULL && low != NULL && high != low)
608 		sched_balance_pair(high, low);
609 }
610 
611 /*
612  * Lock two thread queues using their address to maintain lock order.
613  */
614 static void
615 tdq_lock_pair(struct tdq *one, struct tdq *two)
616 {
617 	if (one < two) {
618 		TDQ_LOCK(one);
619 		TDQ_LOCK_FLAGS(two, MTX_DUPOK);
620 	} else {
621 		TDQ_LOCK(two);
622 		TDQ_LOCK_FLAGS(one, MTX_DUPOK);
623 	}
624 }
625 
626 /*
627  * Unlock two thread queues.  Order is not important here.
628  */
629 static void
630 tdq_unlock_pair(struct tdq *one, struct tdq *two)
631 {
632 	TDQ_UNLOCK(one);
633 	TDQ_UNLOCK(two);
634 }
635 
636 /*
637  * Transfer load between two imbalanced thread queues.
638  */
639 static void
640 sched_balance_pair(struct tdq *high, struct tdq *low)
641 {
642 	int transferable;
643 	int high_load;
644 	int low_load;
645 	int move;
646 	int diff;
647 	int i;
648 
649 	tdq_lock_pair(high, low);
650 	/*
651 	 * If we're transfering within a group we have to use this specific
652 	 * tdq's transferable count, otherwise we can steal from other members
653 	 * of the group.
654 	 */
655 	if (high->tdq_group == low->tdq_group) {
656 		transferable = high->tdq_transferable;
657 		high_load = high->tdq_load;
658 		low_load = low->tdq_load;
659 	} else {
660 		transferable = high->tdq_group->tdg_transferable;
661 		high_load = high->tdq_group->tdg_load;
662 		low_load = low->tdq_group->tdg_load;
663 	}
664 	/*
665 	 * Determine what the imbalance is and then adjust that to how many
666 	 * threads we actually have to give up (transferable).
667 	 */
668 	if (transferable != 0) {
669 		diff = high_load - low_load;
670 		move = diff / 2;
671 		if (diff & 0x1)
672 			move++;
673 		move = min(move, transferable);
674 		for (i = 0; i < move; i++)
675 			tdq_move(high, low);
676 		/*
677 		 * IPI the target cpu to force it to reschedule with the new
678 		 * workload.
679 		 */
680 		ipi_selected(1 << TDQ_ID(low), IPI_PREEMPT);
681 	}
682 	tdq_unlock_pair(high, low);
683 	return;
684 }
685 
686 /*
687  * Move a thread from one thread queue to another.
688  */
689 static void
690 tdq_move(struct tdq *from, struct tdq *to)
691 {
692 	struct td_sched *ts;
693 	struct thread *td;
694 	struct tdq *tdq;
695 	int cpu;
696 
697 	TDQ_LOCK_ASSERT(from, MA_OWNED);
698 	TDQ_LOCK_ASSERT(to, MA_OWNED);
699 
700 	tdq = from;
701 	cpu = TDQ_ID(to);
702 	ts = tdq_steal(tdq);
703 	if (ts == NULL) {
704 		struct tdq_group *tdg;
705 
706 		tdg = tdq->tdq_group;
707 		LIST_FOREACH(tdq, &tdg->tdg_members, tdq_siblings) {
708 			if (tdq == from || tdq->tdq_transferable == 0)
709 				continue;
710 			ts = tdq_steal(tdq);
711 			break;
712 		}
713 		if (ts == NULL)
714 			return;
715 	}
716 	if (tdq == to)
717 		return;
718 	td = ts->ts_thread;
719 	/*
720 	 * Although the run queue is locked the thread may be blocked.  Lock
721 	 * it to clear this and acquire the run-queue lock.
722 	 */
723 	thread_lock(td);
724 	/* Drop recursive lock on from acquired via thread_lock(). */
725 	TDQ_UNLOCK(from);
726 	sched_rem(td);
727 	ts->ts_cpu = cpu;
728 	td->td_lock = TDQ_LOCKPTR(to);
729 	tdq_add(to, td, SRQ_YIELDING);
730 }
731 
732 /*
733  * This tdq has idled.  Try to steal a thread from another cpu and switch
734  * to it.
735  */
736 static int
737 tdq_idled(struct tdq *tdq)
738 {
739 	struct tdq_group *tdg;
740 	struct tdq *steal;
741 	int highload;
742 	int highcpu;
743 	int cpu;
744 
745 	if (smp_started == 0 || steal_idle == 0)
746 		return (1);
747 	/* We don't want to be preempted while we're iterating over tdqs */
748 	spinlock_enter();
749 	tdg = tdq->tdq_group;
750 	/*
751 	 * If we're in a cpu group, try and steal threads from another cpu in
752 	 * the group before idling.  In a HTT group all cpus share the same
753 	 * run-queue lock, however, we still need a recursive lock to
754 	 * call tdq_move().
755 	 */
756 	if (steal_htt && tdg->tdg_cpus > 1 && tdg->tdg_transferable) {
757 		TDQ_LOCK(tdq);
758 		LIST_FOREACH(steal, &tdg->tdg_members, tdq_siblings) {
759 			if (steal == tdq || steal->tdq_transferable == 0)
760 				continue;
761 			TDQ_LOCK(steal);
762 			goto steal;
763 		}
764 		TDQ_UNLOCK(tdq);
765 	}
766 	/*
767 	 * Find the least loaded CPU with a transferable thread and attempt
768 	 * to steal it.  We make a lockless pass and then verify that the
769 	 * thread is still available after locking.
770 	 */
771 	for (;;) {
772 		highcpu = 0;
773 		highload = 0;
774 		for (cpu = 0; cpu <= mp_maxid; cpu++) {
775 			if (CPU_ABSENT(cpu))
776 				continue;
777 			steal = TDQ_CPU(cpu);
778 			if (steal->tdq_transferable == 0)
779 				continue;
780 			if (steal->tdq_load < highload)
781 				continue;
782 			highload = steal->tdq_load;
783 			highcpu = cpu;
784 		}
785 		if (highload < steal_thresh)
786 			break;
787 		steal = TDQ_CPU(highcpu);
788 		if (steal == tdq)
789 			break;
790 		tdq_lock_pair(tdq, steal);
791 		if (steal->tdq_load >= steal_thresh && steal->tdq_transferable)
792 			goto steal;
793 		tdq_unlock_pair(tdq, steal);
794 	}
795 	spinlock_exit();
796 	return (1);
797 steal:
798 	spinlock_exit();
799 	tdq_move(steal, tdq);
800 	TDQ_UNLOCK(steal);
801 	mi_switch(SW_VOL, NULL);
802 	thread_unlock(curthread);
803 
804 	return (0);
805 }
806 
807 /*
808  * Notify a remote cpu of new work.  Sends an IPI if criteria are met.
809  */
810 static void
811 tdq_notify(struct td_sched *ts)
812 {
813 	struct thread *ctd;
814 	struct pcpu *pcpu;
815 	int cpri;
816 	int pri;
817 	int cpu;
818 
819 	cpu = ts->ts_cpu;
820 	pri = ts->ts_thread->td_priority;
821 	pcpu = pcpu_find(cpu);
822 	ctd = pcpu->pc_curthread;
823 	cpri = ctd->td_priority;
824 
825 	/*
826 	 * If our priority is not better than the current priority there is
827 	 * nothing to do.
828 	 */
829 	if (pri > cpri)
830 		return;
831 	/*
832 	 * Always IPI idle.
833 	 */
834 	if (cpri > PRI_MIN_IDLE)
835 		goto sendipi;
836 	/*
837 	 * If we're realtime or better and there is timeshare or worse running
838 	 * send an IPI.
839 	 */
840 	if (pri < PRI_MAX_REALTIME && cpri > PRI_MAX_REALTIME)
841 		goto sendipi;
842 	/*
843 	 * Otherwise only IPI if we exceed the threshold.
844 	 */
845 	if (pri > preempt_thresh)
846 		return;
847 sendipi:
848 	ctd->td_flags |= TDF_NEEDRESCHED;
849 	ipi_selected(1 << cpu, IPI_PREEMPT);
850 }
851 
852 /*
853  * Steals load from a timeshare queue.  Honors the rotating queue head
854  * index.
855  */
856 static struct td_sched *
857 runq_steal_from(struct runq *rq, u_char start)
858 {
859 	struct td_sched *ts;
860 	struct rqbits *rqb;
861 	struct rqhead *rqh;
862 	int first;
863 	int bit;
864 	int pri;
865 	int i;
866 
867 	rqb = &rq->rq_status;
868 	bit = start & (RQB_BPW -1);
869 	pri = 0;
870 	first = 0;
871 again:
872 	for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
873 		if (rqb->rqb_bits[i] == 0)
874 			continue;
875 		if (bit != 0) {
876 			for (pri = bit; pri < RQB_BPW; pri++)
877 				if (rqb->rqb_bits[i] & (1ul << pri))
878 					break;
879 			if (pri >= RQB_BPW)
880 				continue;
881 		} else
882 			pri = RQB_FFS(rqb->rqb_bits[i]);
883 		pri += (i << RQB_L2BPW);
884 		rqh = &rq->rq_queues[pri];
885 		TAILQ_FOREACH(ts, rqh, ts_procq) {
886 			if (first && THREAD_CAN_MIGRATE(ts->ts_thread))
887 				return (ts);
888 			first = 1;
889 		}
890 	}
891 	if (start != 0) {
892 		start = 0;
893 		goto again;
894 	}
895 
896 	return (NULL);
897 }
898 
899 /*
900  * Steals load from a standard linear queue.
901  */
902 static struct td_sched *
903 runq_steal(struct runq *rq)
904 {
905 	struct rqhead *rqh;
906 	struct rqbits *rqb;
907 	struct td_sched *ts;
908 	int word;
909 	int bit;
910 
911 	rqb = &rq->rq_status;
912 	for (word = 0; word < RQB_LEN; word++) {
913 		if (rqb->rqb_bits[word] == 0)
914 			continue;
915 		for (bit = 0; bit < RQB_BPW; bit++) {
916 			if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
917 				continue;
918 			rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
919 			TAILQ_FOREACH(ts, rqh, ts_procq)
920 				if (THREAD_CAN_MIGRATE(ts->ts_thread))
921 					return (ts);
922 		}
923 	}
924 	return (NULL);
925 }
926 
927 /*
928  * Attempt to steal a thread in priority order from a thread queue.
929  */
930 static struct td_sched *
931 tdq_steal(struct tdq *tdq)
932 {
933 	struct td_sched *ts;
934 
935 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
936 	if ((ts = runq_steal(&tdq->tdq_realtime)) != NULL)
937 		return (ts);
938 	if ((ts = runq_steal_from(&tdq->tdq_timeshare, tdq->tdq_ridx)) != NULL)
939 		return (ts);
940 	return (runq_steal(&tdq->tdq_idle));
941 }
942 
943 /*
944  * Sets the thread lock and ts_cpu to match the requested cpu.  Unlocks the
945  * current lock and returns with the assigned queue locked.
946  */
947 static inline struct tdq *
948 sched_setcpu(struct td_sched *ts, int cpu, int flags)
949 {
950 	struct thread *td;
951 	struct tdq *tdq;
952 
953 	THREAD_LOCK_ASSERT(ts->ts_thread, MA_OWNED);
954 
955 	tdq = TDQ_CPU(cpu);
956 	td = ts->ts_thread;
957 	ts->ts_cpu = cpu;
958 
959 	/* If the lock matches just return the queue. */
960 	if (td->td_lock == TDQ_LOCKPTR(tdq))
961 		return (tdq);
962 #ifdef notyet
963 	/*
964 	 * If the thread isn't running its lockptr is a
965 	 * turnstile or a sleepqueue.  We can just lock_set without
966 	 * blocking.
967 	 */
968 	if (TD_CAN_RUN(td)) {
969 		TDQ_LOCK(tdq);
970 		thread_lock_set(td, TDQ_LOCKPTR(tdq));
971 		return (tdq);
972 	}
973 #endif
974 	/*
975 	 * The hard case, migration, we need to block the thread first to
976 	 * prevent order reversals with other cpus locks.
977 	 */
978 	thread_lock_block(td);
979 	TDQ_LOCK(tdq);
980 	thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
981 	return (tdq);
982 }
983 
984 /*
985  * Find the thread queue running the lowest priority thread.
986  */
987 static int
988 tdq_lowestpri(void)
989 {
990 	struct tdq *tdq;
991 	int lowpri;
992 	int lowcpu;
993 	int lowload;
994 	int load;
995 	int cpu;
996 	int pri;
997 
998 	lowload = 0;
999 	lowpri = lowcpu = 0;
1000 	for (cpu = 0; cpu <= mp_maxid; cpu++) {
1001 		if (CPU_ABSENT(cpu))
1002 			continue;
1003 		tdq = TDQ_CPU(cpu);
1004 		pri = tdq->tdq_lowpri;
1005 		load = TDQ_CPU(cpu)->tdq_load;
1006 		CTR4(KTR_ULE,
1007 		    "cpu %d pri %d lowcpu %d lowpri %d",
1008 		    cpu, pri, lowcpu, lowpri);
1009 		if (pri < lowpri)
1010 			continue;
1011 		if (lowpri && lowpri == pri && load > lowload)
1012 			continue;
1013 		lowpri = pri;
1014 		lowcpu = cpu;
1015 		lowload = load;
1016 	}
1017 
1018 	return (lowcpu);
1019 }
1020 
1021 /*
1022  * Find the thread queue with the least load.
1023  */
1024 static int
1025 tdq_lowestload(void)
1026 {
1027 	struct tdq *tdq;
1028 	int lowload;
1029 	int lowpri;
1030 	int lowcpu;
1031 	int load;
1032 	int cpu;
1033 	int pri;
1034 
1035 	lowcpu = 0;
1036 	lowload = TDQ_CPU(0)->tdq_load;
1037 	lowpri = TDQ_CPU(0)->tdq_lowpri;
1038 	for (cpu = 1; cpu <= mp_maxid; cpu++) {
1039 		if (CPU_ABSENT(cpu))
1040 			continue;
1041 		tdq = TDQ_CPU(cpu);
1042 		load = tdq->tdq_load;
1043 		pri = tdq->tdq_lowpri;
1044 		CTR4(KTR_ULE, "cpu %d load %d lowcpu %d lowload %d",
1045 		    cpu, load, lowcpu, lowload);
1046 		if (load > lowload)
1047 			continue;
1048 		if (load == lowload && pri < lowpri)
1049 			continue;
1050 		lowcpu = cpu;
1051 		lowload = load;
1052 		lowpri = pri;
1053 	}
1054 
1055 	return (lowcpu);
1056 }
1057 
1058 /*
1059  * Pick the destination cpu for sched_add().  Respects affinity and makes
1060  * a determination based on load or priority of available processors.
1061  */
1062 static int
1063 sched_pickcpu(struct td_sched *ts, int flags)
1064 {
1065 	struct tdq *tdq;
1066 	int self;
1067 	int pri;
1068 	int cpu;
1069 
1070 	cpu = self = PCPU_GET(cpuid);
1071 	if (smp_started == 0)
1072 		return (self);
1073 	/*
1074 	 * Don't migrate a running thread from sched_switch().
1075 	 */
1076 	if (flags & SRQ_OURSELF) {
1077 		CTR1(KTR_ULE, "YIELDING %d",
1078 		    curthread->td_priority);
1079 		return (self);
1080 	}
1081 	pri = ts->ts_thread->td_priority;
1082 	cpu = ts->ts_cpu;
1083 	/*
1084 	 * Regardless of affinity, if the last cpu is idle send it there.
1085 	 */
1086 	tdq = TDQ_CPU(cpu);
1087 	if (tdq->tdq_lowpri > PRI_MIN_IDLE) {
1088 		CTR5(KTR_ULE,
1089 		    "ts_cpu %d idle, ltick %d ticks %d pri %d curthread %d",
1090 		    ts->ts_cpu, ts->ts_rltick, ticks, pri,
1091 		    tdq->tdq_lowpri);
1092 		return (ts->ts_cpu);
1093 	}
1094 	/*
1095 	 * If we have affinity, try to place it on the cpu we last ran on.
1096 	 */
1097 	if (SCHED_AFFINITY(ts) && tdq->tdq_lowpri > pri) {
1098 		CTR5(KTR_ULE,
1099 		    "affinity for %d, ltick %d ticks %d pri %d curthread %d",
1100 		    ts->ts_cpu, ts->ts_rltick, ticks, pri,
1101 		    tdq->tdq_lowpri);
1102 		return (ts->ts_cpu);
1103 	}
1104 	/*
1105 	 * Look for an idle group.
1106 	 */
1107 	CTR1(KTR_ULE, "tdq_idle %X", tdq_idle);
1108 	cpu = ffs(tdq_idle);
1109 	if (cpu)
1110 		return (--cpu);
1111 	/*
1112 	 * If there are no idle cores see if we can run the thread locally.
1113 	 * This may improve locality among sleepers and wakers when there
1114 	 * is shared data.
1115 	 */
1116 	if (tryself && pri < curthread->td_priority) {
1117 		CTR1(KTR_ULE, "tryself %d",
1118 		    curthread->td_priority);
1119 		return (self);
1120 	}
1121 	/*
1122  	 * Now search for the cpu running the lowest priority thread with
1123 	 * the least load.
1124 	 */
1125 	if (pick_pri)
1126 		cpu = tdq_lowestpri();
1127 	else
1128 		cpu = tdq_lowestload();
1129 	return (cpu);
1130 }
1131 
1132 #endif	/* SMP */
1133 
1134 /*
1135  * Pick the highest priority task we have and return it.
1136  */
1137 static struct td_sched *
1138 tdq_choose(struct tdq *tdq)
1139 {
1140 	struct td_sched *ts;
1141 
1142 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
1143 	ts = runq_choose(&tdq->tdq_realtime);
1144 	if (ts != NULL)
1145 		return (ts);
1146 	ts = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
1147 	if (ts != NULL) {
1148 		KASSERT(ts->ts_thread->td_priority >= PRI_MIN_TIMESHARE,
1149 		    ("tdq_choose: Invalid priority on timeshare queue %d",
1150 		    ts->ts_thread->td_priority));
1151 		return (ts);
1152 	}
1153 
1154 	ts = runq_choose(&tdq->tdq_idle);
1155 	if (ts != NULL) {
1156 		KASSERT(ts->ts_thread->td_priority >= PRI_MIN_IDLE,
1157 		    ("tdq_choose: Invalid priority on idle queue %d",
1158 		    ts->ts_thread->td_priority));
1159 		return (ts);
1160 	}
1161 
1162 	return (NULL);
1163 }
1164 
1165 /*
1166  * Initialize a thread queue.
1167  */
1168 static void
1169 tdq_setup(struct tdq *tdq)
1170 {
1171 
1172 	if (bootverbose)
1173 		printf("ULE: setup cpu %d\n", TDQ_ID(tdq));
1174 	runq_init(&tdq->tdq_realtime);
1175 	runq_init(&tdq->tdq_timeshare);
1176 	runq_init(&tdq->tdq_idle);
1177 	tdq->tdq_load = 0;
1178 }
1179 
1180 #ifdef SMP
1181 static void
1182 tdg_setup(struct tdq_group *tdg)
1183 {
1184 	if (bootverbose)
1185 		printf("ULE: setup cpu group %d\n", TDG_ID(tdg));
1186 	snprintf(tdg->tdg_name, sizeof(tdg->tdg_name),
1187 	    "sched lock %d", (int)TDG_ID(tdg));
1188 	mtx_init(&tdg->tdg_lock, tdg->tdg_name, "sched lock",
1189 	    MTX_SPIN | MTX_RECURSE);
1190 	LIST_INIT(&tdg->tdg_members);
1191 	tdg->tdg_load = 0;
1192 	tdg->tdg_transferable = 0;
1193 	tdg->tdg_cpus = 0;
1194 	tdg->tdg_mask = 0;
1195 	tdg->tdg_cpumask = 0;
1196 	tdg->tdg_idlemask = 0;
1197 }
1198 
1199 static void
1200 tdg_add(struct tdq_group *tdg, struct tdq *tdq)
1201 {
1202 	if (tdg->tdg_mask == 0)
1203 		tdg->tdg_mask |= 1 << TDQ_ID(tdq);
1204 	tdg->tdg_cpumask |= 1 << TDQ_ID(tdq);
1205 	tdg->tdg_cpus++;
1206 	tdq->tdq_group = tdg;
1207 	tdq->tdq_lock = &tdg->tdg_lock;
1208 	LIST_INSERT_HEAD(&tdg->tdg_members, tdq, tdq_siblings);
1209 	if (bootverbose)
1210 		printf("ULE: adding cpu %d to group %d: cpus %d mask 0x%X\n",
1211 		    TDQ_ID(tdq), TDG_ID(tdg), tdg->tdg_cpus, tdg->tdg_cpumask);
1212 }
1213 
1214 static void
1215 sched_setup_topology(void)
1216 {
1217 	struct tdq_group *tdg;
1218 	struct cpu_group *cg;
1219 	int balance_groups;
1220 	struct tdq *tdq;
1221 	int i;
1222 	int j;
1223 
1224 	topology = 1;
1225 	balance_groups = 0;
1226 	for (i = 0; i < smp_topology->ct_count; i++) {
1227 		cg = &smp_topology->ct_group[i];
1228 		tdg = &tdq_groups[i];
1229 		/*
1230 		 * Initialize the group.
1231 		 */
1232 		tdg_setup(tdg);
1233 		/*
1234 		 * Find all of the group members and add them.
1235 		 */
1236 		for (j = 0; j < MAXCPU; j++) {
1237 			if ((cg->cg_mask & (1 << j)) != 0) {
1238 				tdq = TDQ_CPU(j);
1239 				tdq_setup(tdq);
1240 				tdg_add(tdg, tdq);
1241 			}
1242 		}
1243 		if (tdg->tdg_cpus > 1)
1244 			balance_groups = 1;
1245 	}
1246 	tdg_maxid = smp_topology->ct_count - 1;
1247 	if (balance_groups)
1248 		sched_balance_groups();
1249 }
1250 
1251 static void
1252 sched_setup_smp(void)
1253 {
1254 	struct tdq_group *tdg;
1255 	struct tdq *tdq;
1256 	int cpus;
1257 	int i;
1258 
1259 	for (cpus = 0, i = 0; i < MAXCPU; i++) {
1260 		if (CPU_ABSENT(i))
1261 			continue;
1262 		tdq = &tdq_cpu[i];
1263 		tdg = &tdq_groups[i];
1264 		/*
1265 		 * Setup a tdq group with one member.
1266 		 */
1267 		tdg_setup(tdg);
1268 		tdq_setup(tdq);
1269 		tdg_add(tdg, tdq);
1270 		cpus++;
1271 	}
1272 	tdg_maxid = cpus - 1;
1273 }
1274 
1275 /*
1276  * Fake a topology with one group containing all CPUs.
1277  */
1278 static void
1279 sched_fake_topo(void)
1280 {
1281 #ifdef SCHED_FAKE_TOPOLOGY
1282 	static struct cpu_top top;
1283 	static struct cpu_group group;
1284 
1285 	top.ct_count = 1;
1286 	top.ct_group = &group;
1287 	group.cg_mask = all_cpus;
1288 	group.cg_count = mp_ncpus;
1289 	group.cg_children = 0;
1290 	smp_topology = &top;
1291 #endif
1292 }
1293 #endif
1294 
1295 /*
1296  * Setup the thread queues and initialize the topology based on MD
1297  * information.
1298  */
1299 static void
1300 sched_setup(void *dummy)
1301 {
1302 	struct tdq *tdq;
1303 
1304 	tdq = TDQ_SELF();
1305 #ifdef SMP
1306 	sched_fake_topo();
1307 	/*
1308 	 * Setup tdqs based on a topology configuration or vanilla SMP based
1309 	 * on mp_maxid.
1310 	 */
1311 	if (smp_topology == NULL)
1312 		sched_setup_smp();
1313 	else
1314 		sched_setup_topology();
1315 	balance_tdq = tdq;
1316 	sched_balance();
1317 #else
1318 	tdq_setup(tdq);
1319 	mtx_init(&tdq_lock, "sched lock", "sched lock", MTX_SPIN | MTX_RECURSE);
1320 	tdq->tdq_lock = &tdq_lock;
1321 #endif
1322 	/*
1323 	 * To avoid divide-by-zero, we set realstathz a dummy value
1324 	 * in case which sched_clock() called before sched_initticks().
1325 	 */
1326 	realstathz = hz;
1327 	sched_slice = (realstathz/10);	/* ~100ms */
1328 	tickincr = 1 << SCHED_TICK_SHIFT;
1329 
1330 	/* Add thread0's load since it's running. */
1331 	TDQ_LOCK(tdq);
1332 	thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF());
1333 	tdq_load_add(tdq, &td_sched0);
1334 	TDQ_UNLOCK(tdq);
1335 }
1336 
1337 /*
1338  * This routine determines the tickincr after stathz and hz are setup.
1339  */
1340 /* ARGSUSED */
1341 static void
1342 sched_initticks(void *dummy)
1343 {
1344 	int incr;
1345 
1346 	realstathz = stathz ? stathz : hz;
1347 	sched_slice = (realstathz/10);	/* ~100ms */
1348 
1349 	/*
1350 	 * tickincr is shifted out by 10 to avoid rounding errors due to
1351 	 * hz not being evenly divisible by stathz on all platforms.
1352 	 */
1353 	incr = (hz << SCHED_TICK_SHIFT) / realstathz;
1354 	/*
1355 	 * This does not work for values of stathz that are more than
1356 	 * 1 << SCHED_TICK_SHIFT * hz.  In practice this does not happen.
1357 	 */
1358 	if (incr == 0)
1359 		incr = 1;
1360 	tickincr = incr;
1361 #ifdef SMP
1362 	/*
1363 	 * Set the default balance interval now that we know
1364 	 * what realstathz is.
1365 	 */
1366 	balance_interval = realstathz;
1367 	/*
1368 	 * Set steal thresh to log2(mp_ncpu) but no greater than 4.  This
1369 	 * prevents excess thrashing on large machines and excess idle on
1370 	 * smaller machines.
1371 	 */
1372 	steal_thresh = min(ffs(mp_ncpus) - 1, 4);
1373 	affinity = SCHED_AFFINITY_DEFAULT;
1374 #endif
1375 }
1376 
1377 
1378 /*
1379  * This is the core of the interactivity algorithm.  Determines a score based
1380  * on past behavior.  It is the ratio of sleep time to run time scaled to
1381  * a [0, 100] integer.  This is the voluntary sleep time of a process, which
1382  * differs from the cpu usage because it does not account for time spent
1383  * waiting on a run-queue.  Would be prettier if we had floating point.
1384  */
1385 static int
1386 sched_interact_score(struct thread *td)
1387 {
1388 	struct td_sched *ts;
1389 	int div;
1390 
1391 	ts = td->td_sched;
1392 	/*
1393 	 * The score is only needed if this is likely to be an interactive
1394 	 * task.  Don't go through the expense of computing it if there's
1395 	 * no chance.
1396 	 */
1397 	if (sched_interact <= SCHED_INTERACT_HALF &&
1398 		ts->ts_runtime >= ts->ts_slptime)
1399 			return (SCHED_INTERACT_HALF);
1400 
1401 	if (ts->ts_runtime > ts->ts_slptime) {
1402 		div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
1403 		return (SCHED_INTERACT_HALF +
1404 		    (SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
1405 	}
1406 	if (ts->ts_slptime > ts->ts_runtime) {
1407 		div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
1408 		return (ts->ts_runtime / div);
1409 	}
1410 	/* runtime == slptime */
1411 	if (ts->ts_runtime)
1412 		return (SCHED_INTERACT_HALF);
1413 
1414 	/*
1415 	 * This can happen if slptime and runtime are 0.
1416 	 */
1417 	return (0);
1418 
1419 }
1420 
1421 /*
1422  * Scale the scheduling priority according to the "interactivity" of this
1423  * process.
1424  */
1425 static void
1426 sched_priority(struct thread *td)
1427 {
1428 	int score;
1429 	int pri;
1430 
1431 	if (td->td_pri_class != PRI_TIMESHARE)
1432 		return;
1433 	/*
1434 	 * If the score is interactive we place the thread in the realtime
1435 	 * queue with a priority that is less than kernel and interrupt
1436 	 * priorities.  These threads are not subject to nice restrictions.
1437 	 *
1438 	 * Scores greater than this are placed on the normal timeshare queue
1439 	 * where the priority is partially decided by the most recent cpu
1440 	 * utilization and the rest is decided by nice value.
1441 	 *
1442 	 * The nice value of the process has a linear effect on the calculated
1443 	 * score.  Negative nice values make it easier for a thread to be
1444 	 * considered interactive.
1445 	 */
1446 	score = imax(0, sched_interact_score(td) - td->td_proc->p_nice);
1447 	if (score < sched_interact) {
1448 		pri = PRI_MIN_REALTIME;
1449 		pri += ((PRI_MAX_REALTIME - PRI_MIN_REALTIME) / sched_interact)
1450 		    * score;
1451 		KASSERT(pri >= PRI_MIN_REALTIME && pri <= PRI_MAX_REALTIME,
1452 		    ("sched_priority: invalid interactive priority %d score %d",
1453 		    pri, score));
1454 	} else {
1455 		pri = SCHED_PRI_MIN;
1456 		if (td->td_sched->ts_ticks)
1457 			pri += SCHED_PRI_TICKS(td->td_sched);
1458 		pri += SCHED_PRI_NICE(td->td_proc->p_nice);
1459 		KASSERT(pri >= PRI_MIN_TIMESHARE && pri <= PRI_MAX_TIMESHARE,
1460 		    ("sched_priority: invalid priority %d: nice %d, "
1461 		    "ticks %d ftick %d ltick %d tick pri %d",
1462 		    pri, td->td_proc->p_nice, td->td_sched->ts_ticks,
1463 		    td->td_sched->ts_ftick, td->td_sched->ts_ltick,
1464 		    SCHED_PRI_TICKS(td->td_sched)));
1465 	}
1466 	sched_user_prio(td, pri);
1467 
1468 	return;
1469 }
1470 
1471 /*
1472  * This routine enforces a maximum limit on the amount of scheduling history
1473  * kept.  It is called after either the slptime or runtime is adjusted.  This
1474  * function is ugly due to integer math.
1475  */
1476 static void
1477 sched_interact_update(struct thread *td)
1478 {
1479 	struct td_sched *ts;
1480 	u_int sum;
1481 
1482 	ts = td->td_sched;
1483 	sum = ts->ts_runtime + ts->ts_slptime;
1484 	if (sum < SCHED_SLP_RUN_MAX)
1485 		return;
1486 	/*
1487 	 * This only happens from two places:
1488 	 * 1) We have added an unusual amount of run time from fork_exit.
1489 	 * 2) We have added an unusual amount of sleep time from sched_sleep().
1490 	 */
1491 	if (sum > SCHED_SLP_RUN_MAX * 2) {
1492 		if (ts->ts_runtime > ts->ts_slptime) {
1493 			ts->ts_runtime = SCHED_SLP_RUN_MAX;
1494 			ts->ts_slptime = 1;
1495 		} else {
1496 			ts->ts_slptime = SCHED_SLP_RUN_MAX;
1497 			ts->ts_runtime = 1;
1498 		}
1499 		return;
1500 	}
1501 	/*
1502 	 * If we have exceeded by more than 1/5th then the algorithm below
1503 	 * will not bring us back into range.  Dividing by two here forces
1504 	 * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
1505 	 */
1506 	if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
1507 		ts->ts_runtime /= 2;
1508 		ts->ts_slptime /= 2;
1509 		return;
1510 	}
1511 	ts->ts_runtime = (ts->ts_runtime / 5) * 4;
1512 	ts->ts_slptime = (ts->ts_slptime / 5) * 4;
1513 }
1514 
1515 /*
1516  * Scale back the interactivity history when a child thread is created.  The
1517  * history is inherited from the parent but the thread may behave totally
1518  * differently.  For example, a shell spawning a compiler process.  We want
1519  * to learn that the compiler is behaving badly very quickly.
1520  */
1521 static void
1522 sched_interact_fork(struct thread *td)
1523 {
1524 	int ratio;
1525 	int sum;
1526 
1527 	sum = td->td_sched->ts_runtime + td->td_sched->ts_slptime;
1528 	if (sum > SCHED_SLP_RUN_FORK) {
1529 		ratio = sum / SCHED_SLP_RUN_FORK;
1530 		td->td_sched->ts_runtime /= ratio;
1531 		td->td_sched->ts_slptime /= ratio;
1532 	}
1533 }
1534 
1535 /*
1536  * Called from proc0_init() to setup the scheduler fields.
1537  */
1538 void
1539 schedinit(void)
1540 {
1541 
1542 	/*
1543 	 * Set up the scheduler specific parts of proc0.
1544 	 */
1545 	proc0.p_sched = NULL; /* XXX */
1546 	thread0.td_sched = &td_sched0;
1547 	td_sched0.ts_ltick = ticks;
1548 	td_sched0.ts_ftick = ticks;
1549 	td_sched0.ts_thread = &thread0;
1550 }
1551 
1552 /*
1553  * This is only somewhat accurate since given many processes of the same
1554  * priority they will switch when their slices run out, which will be
1555  * at most sched_slice stathz ticks.
1556  */
1557 int
1558 sched_rr_interval(void)
1559 {
1560 
1561 	/* Convert sched_slice to hz */
1562 	return (hz/(realstathz/sched_slice));
1563 }
1564 
1565 /*
1566  * Update the percent cpu tracking information when it is requested or
1567  * the total history exceeds the maximum.  We keep a sliding history of
1568  * tick counts that slowly decays.  This is less precise than the 4BSD
1569  * mechanism since it happens with less regular and frequent events.
1570  */
1571 static void
1572 sched_pctcpu_update(struct td_sched *ts)
1573 {
1574 
1575 	if (ts->ts_ticks == 0)
1576 		return;
1577 	if (ticks - (hz / 10) < ts->ts_ltick &&
1578 	    SCHED_TICK_TOTAL(ts) < SCHED_TICK_MAX)
1579 		return;
1580 	/*
1581 	 * Adjust counters and watermark for pctcpu calc.
1582 	 */
1583 	if (ts->ts_ltick > ticks - SCHED_TICK_TARG)
1584 		ts->ts_ticks = (ts->ts_ticks / (ticks - ts->ts_ftick)) *
1585 			    SCHED_TICK_TARG;
1586 	else
1587 		ts->ts_ticks = 0;
1588 	ts->ts_ltick = ticks;
1589 	ts->ts_ftick = ts->ts_ltick - SCHED_TICK_TARG;
1590 }
1591 
1592 /*
1593  * Adjust the priority of a thread.  Move it to the appropriate run-queue
1594  * if necessary.  This is the back-end for several priority related
1595  * functions.
1596  */
1597 static void
1598 sched_thread_priority(struct thread *td, u_char prio)
1599 {
1600 	struct td_sched *ts;
1601 
1602 	CTR6(KTR_SCHED, "sched_prio: %p(%s) prio %d newprio %d by %p(%s)",
1603 	    td, td->td_name, td->td_priority, prio, curthread,
1604 	    curthread->td_name);
1605 	ts = td->td_sched;
1606 	THREAD_LOCK_ASSERT(td, MA_OWNED);
1607 	if (td->td_priority == prio)
1608 		return;
1609 
1610 	if (TD_ON_RUNQ(td) && prio < td->td_priority) {
1611 		/*
1612 		 * If the priority has been elevated due to priority
1613 		 * propagation, we may have to move ourselves to a new
1614 		 * queue.  This could be optimized to not re-add in some
1615 		 * cases.
1616 		 */
1617 		sched_rem(td);
1618 		td->td_priority = prio;
1619 		sched_add(td, SRQ_BORROWING);
1620 	} else {
1621 #ifdef SMP
1622 		struct tdq *tdq;
1623 
1624 		tdq = TDQ_CPU(ts->ts_cpu);
1625 		if (prio < tdq->tdq_lowpri)
1626 			tdq->tdq_lowpri = prio;
1627 #endif
1628 		td->td_priority = prio;
1629 	}
1630 }
1631 
1632 /*
1633  * Update a thread's priority when it is lent another thread's
1634  * priority.
1635  */
1636 void
1637 sched_lend_prio(struct thread *td, u_char prio)
1638 {
1639 
1640 	td->td_flags |= TDF_BORROWING;
1641 	sched_thread_priority(td, prio);
1642 }
1643 
1644 /*
1645  * Restore a thread's priority when priority propagation is
1646  * over.  The prio argument is the minimum priority the thread
1647  * needs to have to satisfy other possible priority lending
1648  * requests.  If the thread's regular priority is less
1649  * important than prio, the thread will keep a priority boost
1650  * of prio.
1651  */
1652 void
1653 sched_unlend_prio(struct thread *td, u_char prio)
1654 {
1655 	u_char base_pri;
1656 
1657 	if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
1658 	    td->td_base_pri <= PRI_MAX_TIMESHARE)
1659 		base_pri = td->td_user_pri;
1660 	else
1661 		base_pri = td->td_base_pri;
1662 	if (prio >= base_pri) {
1663 		td->td_flags &= ~TDF_BORROWING;
1664 		sched_thread_priority(td, base_pri);
1665 	} else
1666 		sched_lend_prio(td, prio);
1667 }
1668 
1669 /*
1670  * Standard entry for setting the priority to an absolute value.
1671  */
1672 void
1673 sched_prio(struct thread *td, u_char prio)
1674 {
1675 	u_char oldprio;
1676 
1677 	/* First, update the base priority. */
1678 	td->td_base_pri = prio;
1679 
1680 	/*
1681 	 * If the thread is borrowing another thread's priority, don't
1682 	 * ever lower the priority.
1683 	 */
1684 	if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
1685 		return;
1686 
1687 	/* Change the real priority. */
1688 	oldprio = td->td_priority;
1689 	sched_thread_priority(td, prio);
1690 
1691 	/*
1692 	 * If the thread is on a turnstile, then let the turnstile update
1693 	 * its state.
1694 	 */
1695 	if (TD_ON_LOCK(td) && oldprio != prio)
1696 		turnstile_adjust(td, oldprio);
1697 }
1698 
1699 /*
1700  * Set the base user priority, does not effect current running priority.
1701  */
1702 void
1703 sched_user_prio(struct thread *td, u_char prio)
1704 {
1705 	u_char oldprio;
1706 
1707 	td->td_base_user_pri = prio;
1708 	if (td->td_flags & TDF_UBORROWING && td->td_user_pri <= prio)
1709                 return;
1710 	oldprio = td->td_user_pri;
1711 	td->td_user_pri = prio;
1712 }
1713 
1714 void
1715 sched_lend_user_prio(struct thread *td, u_char prio)
1716 {
1717 	u_char oldprio;
1718 
1719 	THREAD_LOCK_ASSERT(td, MA_OWNED);
1720 	td->td_flags |= TDF_UBORROWING;
1721 	oldprio = td->td_user_pri;
1722 	td->td_user_pri = prio;
1723 }
1724 
1725 void
1726 sched_unlend_user_prio(struct thread *td, u_char prio)
1727 {
1728 	u_char base_pri;
1729 
1730 	THREAD_LOCK_ASSERT(td, MA_OWNED);
1731 	base_pri = td->td_base_user_pri;
1732 	if (prio >= base_pri) {
1733 		td->td_flags &= ~TDF_UBORROWING;
1734 		sched_user_prio(td, base_pri);
1735 	} else {
1736 		sched_lend_user_prio(td, prio);
1737 	}
1738 }
1739 
1740 /*
1741  * Add the thread passed as 'newtd' to the run queue before selecting
1742  * the next thread to run.  This is only used for KSE.
1743  */
1744 static void
1745 sched_switchin(struct tdq *tdq, struct thread *td)
1746 {
1747 #ifdef SMP
1748 	spinlock_enter();
1749 	TDQ_UNLOCK(tdq);
1750 	thread_lock(td);
1751 	spinlock_exit();
1752 	sched_setcpu(td->td_sched, TDQ_ID(tdq), SRQ_YIELDING);
1753 #else
1754 	td->td_lock = TDQ_LOCKPTR(tdq);
1755 #endif
1756 	tdq_add(tdq, td, SRQ_YIELDING);
1757 	MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
1758 }
1759 
1760 /*
1761  * Block a thread for switching.  Similar to thread_block() but does not
1762  * bump the spin count.
1763  */
1764 static inline struct mtx *
1765 thread_block_switch(struct thread *td)
1766 {
1767 	struct mtx *lock;
1768 
1769 	THREAD_LOCK_ASSERT(td, MA_OWNED);
1770 	lock = td->td_lock;
1771 	td->td_lock = &blocked_lock;
1772 	mtx_unlock_spin(lock);
1773 
1774 	return (lock);
1775 }
1776 
1777 /*
1778  * Handle migration from sched_switch().  This happens only for
1779  * cpu binding.
1780  */
1781 static struct mtx *
1782 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
1783 {
1784 	struct tdq *tdn;
1785 
1786 	tdn = TDQ_CPU(td->td_sched->ts_cpu);
1787 #ifdef SMP
1788 	/*
1789 	 * Do the lock dance required to avoid LOR.  We grab an extra
1790 	 * spinlock nesting to prevent preemption while we're
1791 	 * not holding either run-queue lock.
1792 	 */
1793 	spinlock_enter();
1794 	thread_block_switch(td);	/* This releases the lock on tdq. */
1795 	TDQ_LOCK(tdn);
1796 	tdq_add(tdn, td, flags);
1797 	tdq_notify(td->td_sched);
1798 	/*
1799 	 * After we unlock tdn the new cpu still can't switch into this
1800 	 * thread until we've unblocked it in cpu_switch().  The lock
1801 	 * pointers may match in the case of HTT cores.  Don't unlock here
1802 	 * or we can deadlock when the other CPU runs the IPI handler.
1803 	 */
1804 	if (TDQ_LOCKPTR(tdn) != TDQ_LOCKPTR(tdq)) {
1805 		TDQ_UNLOCK(tdn);
1806 		TDQ_LOCK(tdq);
1807 	}
1808 	spinlock_exit();
1809 #endif
1810 	return (TDQ_LOCKPTR(tdn));
1811 }
1812 
1813 /*
1814  * Release a thread that was blocked with thread_block_switch().
1815  */
1816 static inline void
1817 thread_unblock_switch(struct thread *td, struct mtx *mtx)
1818 {
1819 	atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock,
1820 	    (uintptr_t)mtx);
1821 }
1822 
1823 /*
1824  * Switch threads.  This function has to handle threads coming in while
1825  * blocked for some reason, running, or idle.  It also must deal with
1826  * migrating a thread from one queue to another as running threads may
1827  * be assigned elsewhere via binding.
1828  */
1829 void
1830 sched_switch(struct thread *td, struct thread *newtd, int flags)
1831 {
1832 	struct tdq *tdq;
1833 	struct td_sched *ts;
1834 	struct mtx *mtx;
1835 	int srqflag;
1836 	int cpuid;
1837 
1838 	THREAD_LOCK_ASSERT(td, MA_OWNED);
1839 
1840 	cpuid = PCPU_GET(cpuid);
1841 	tdq = TDQ_CPU(cpuid);
1842 	ts = td->td_sched;
1843 	mtx = td->td_lock;
1844 #ifdef SMP
1845 	ts->ts_rltick = ticks;
1846 	if (newtd && newtd->td_priority < tdq->tdq_lowpri)
1847 		tdq->tdq_lowpri = newtd->td_priority;
1848 #endif
1849 	td->td_lastcpu = td->td_oncpu;
1850 	td->td_oncpu = NOCPU;
1851 	td->td_flags &= ~TDF_NEEDRESCHED;
1852 	td->td_owepreempt = 0;
1853 	/*
1854 	 * The lock pointer in an idle thread should never change.  Reset it
1855 	 * to CAN_RUN as well.
1856 	 */
1857 	if (TD_IS_IDLETHREAD(td)) {
1858 		MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
1859 		TD_SET_CAN_RUN(td);
1860 	} else if (TD_IS_RUNNING(td)) {
1861 		MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
1862 		tdq_load_rem(tdq, ts);
1863 		srqflag = (flags & SW_PREEMPT) ?
1864 		    SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
1865 		    SRQ_OURSELF|SRQ_YIELDING;
1866 		if (ts->ts_cpu == cpuid)
1867 			tdq_add(tdq, td, srqflag);
1868 		else
1869 			mtx = sched_switch_migrate(tdq, td, srqflag);
1870 	} else {
1871 		/* This thread must be going to sleep. */
1872 		TDQ_LOCK(tdq);
1873 		mtx = thread_block_switch(td);
1874 		tdq_load_rem(tdq, ts);
1875 	}
1876 	/*
1877 	 * We enter here with the thread blocked and assigned to the
1878 	 * appropriate cpu run-queue or sleep-queue and with the current
1879 	 * thread-queue locked.
1880 	 */
1881 	TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
1882 	/*
1883 	 * If KSE assigned a new thread just add it here and let choosethread
1884 	 * select the best one.
1885 	 */
1886 	if (newtd != NULL)
1887 		sched_switchin(tdq, newtd);
1888 	newtd = choosethread();
1889 	/*
1890 	 * Call the MD code to switch contexts if necessary.
1891 	 */
1892 	if (td != newtd) {
1893 #ifdef	HWPMC_HOOKS
1894 		if (PMC_PROC_IS_USING_PMCS(td->td_proc))
1895 			PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
1896 #endif
1897 		lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
1898 		TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
1899 		cpu_switch(td, newtd, mtx);
1900 		/*
1901 		 * We may return from cpu_switch on a different cpu.  However,
1902 		 * we always return with td_lock pointing to the current cpu's
1903 		 * run queue lock.
1904 		 */
1905 		cpuid = PCPU_GET(cpuid);
1906 		tdq = TDQ_CPU(cpuid);
1907 		lock_profile_obtain_lock_success(
1908 		    &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
1909 #ifdef	HWPMC_HOOKS
1910 		if (PMC_PROC_IS_USING_PMCS(td->td_proc))
1911 			PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
1912 #endif
1913 	} else
1914 		thread_unblock_switch(td, mtx);
1915 	/*
1916 	 * Assert that all went well and return.
1917 	 */
1918 #ifdef SMP
1919 	/* We should always get here with the lowest priority td possible */
1920 	tdq->tdq_lowpri = td->td_priority;
1921 #endif
1922 	TDQ_LOCK_ASSERT(tdq, MA_OWNED|MA_NOTRECURSED);
1923 	MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
1924 	td->td_oncpu = cpuid;
1925 }
1926 
1927 /*
1928  * Adjust thread priorities as a result of a nice request.
1929  */
1930 void
1931 sched_nice(struct proc *p, int nice)
1932 {
1933 	struct thread *td;
1934 
1935 	PROC_LOCK_ASSERT(p, MA_OWNED);
1936 	PROC_SLOCK_ASSERT(p, MA_OWNED);
1937 
1938 	p->p_nice = nice;
1939 	FOREACH_THREAD_IN_PROC(p, td) {
1940 		thread_lock(td);
1941 		sched_priority(td);
1942 		sched_prio(td, td->td_base_user_pri);
1943 		thread_unlock(td);
1944 	}
1945 }
1946 
1947 /*
1948  * Record the sleep time for the interactivity scorer.
1949  */
1950 void
1951 sched_sleep(struct thread *td)
1952 {
1953 
1954 	THREAD_LOCK_ASSERT(td, MA_OWNED);
1955 
1956 	td->td_slptick = ticks;
1957 }
1958 
1959 /*
1960  * Schedule a thread to resume execution and record how long it voluntarily
1961  * slept.  We also update the pctcpu, interactivity, and priority.
1962  */
1963 void
1964 sched_wakeup(struct thread *td)
1965 {
1966 	struct td_sched *ts;
1967 	int slptick;
1968 
1969 	THREAD_LOCK_ASSERT(td, MA_OWNED);
1970 	ts = td->td_sched;
1971 	/*
1972 	 * If we slept for more than a tick update our interactivity and
1973 	 * priority.
1974 	 */
1975 	slptick = td->td_slptick;
1976 	td->td_slptick = 0;
1977 	if (slptick && slptick != ticks) {
1978 		u_int hzticks;
1979 
1980 		hzticks = (ticks - slptick) << SCHED_TICK_SHIFT;
1981 		ts->ts_slptime += hzticks;
1982 		sched_interact_update(td);
1983 		sched_pctcpu_update(ts);
1984 		sched_priority(td);
1985 	}
1986 	/* Reset the slice value after we sleep. */
1987 	ts->ts_slice = sched_slice;
1988 	sched_add(td, SRQ_BORING);
1989 }
1990 
1991 /*
1992  * Penalize the parent for creating a new child and initialize the child's
1993  * priority.
1994  */
1995 void
1996 sched_fork(struct thread *td, struct thread *child)
1997 {
1998 	THREAD_LOCK_ASSERT(td, MA_OWNED);
1999 	sched_fork_thread(td, child);
2000 	/*
2001 	 * Penalize the parent and child for forking.
2002 	 */
2003 	sched_interact_fork(child);
2004 	sched_priority(child);
2005 	td->td_sched->ts_runtime += tickincr;
2006 	sched_interact_update(td);
2007 	sched_priority(td);
2008 }
2009 
2010 /*
2011  * Fork a new thread, may be within the same process.
2012  */
2013 void
2014 sched_fork_thread(struct thread *td, struct thread *child)
2015 {
2016 	struct td_sched *ts;
2017 	struct td_sched *ts2;
2018 
2019 	/*
2020 	 * Initialize child.
2021 	 */
2022 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2023 	sched_newthread(child);
2024 	child->td_lock = TDQ_LOCKPTR(TDQ_SELF());
2025 	ts = td->td_sched;
2026 	ts2 = child->td_sched;
2027 	ts2->ts_cpu = ts->ts_cpu;
2028 	ts2->ts_runq = NULL;
2029 	/*
2030 	 * Grab our parents cpu estimation information and priority.
2031 	 */
2032 	ts2->ts_ticks = ts->ts_ticks;
2033 	ts2->ts_ltick = ts->ts_ltick;
2034 	ts2->ts_ftick = ts->ts_ftick;
2035 	child->td_user_pri = td->td_user_pri;
2036 	child->td_base_user_pri = td->td_base_user_pri;
2037 	/*
2038 	 * And update interactivity score.
2039 	 */
2040 	ts2->ts_slptime = ts->ts_slptime;
2041 	ts2->ts_runtime = ts->ts_runtime;
2042 	ts2->ts_slice = 1;	/* Attempt to quickly learn interactivity. */
2043 }
2044 
2045 /*
2046  * Adjust the priority class of a thread.
2047  */
2048 void
2049 sched_class(struct thread *td, int class)
2050 {
2051 
2052 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2053 	if (td->td_pri_class == class)
2054 		return;
2055 
2056 #ifdef SMP
2057 	/*
2058 	 * On SMP if we're on the RUNQ we must adjust the transferable
2059 	 * count because could be changing to or from an interrupt
2060 	 * class.
2061 	 */
2062 	if (TD_ON_RUNQ(td)) {
2063 		struct tdq *tdq;
2064 
2065 		tdq = TDQ_CPU(td->td_sched->ts_cpu);
2066 		if (THREAD_CAN_MIGRATE(td)) {
2067 			tdq->tdq_transferable--;
2068 			tdq->tdq_group->tdg_transferable--;
2069 		}
2070 		td->td_pri_class = class;
2071 		if (THREAD_CAN_MIGRATE(td)) {
2072 			tdq->tdq_transferable++;
2073 			tdq->tdq_group->tdg_transferable++;
2074 		}
2075 	}
2076 #endif
2077 	td->td_pri_class = class;
2078 }
2079 
2080 /*
2081  * Return some of the child's priority and interactivity to the parent.
2082  */
2083 void
2084 sched_exit(struct proc *p, struct thread *child)
2085 {
2086 	struct thread *td;
2087 
2088 	CTR3(KTR_SCHED, "sched_exit: %p(%s) prio %d",
2089 	    child, child->td_name, child->td_priority);
2090 
2091 	PROC_SLOCK_ASSERT(p, MA_OWNED);
2092 	td = FIRST_THREAD_IN_PROC(p);
2093 	sched_exit_thread(td, child);
2094 }
2095 
2096 /*
2097  * Penalize another thread for the time spent on this one.  This helps to
2098  * worsen the priority and interactivity of processes which schedule batch
2099  * jobs such as make.  This has little effect on the make process itself but
2100  * causes new processes spawned by it to receive worse scores immediately.
2101  */
2102 void
2103 sched_exit_thread(struct thread *td, struct thread *child)
2104 {
2105 
2106 	CTR3(KTR_SCHED, "sched_exit_thread: %p(%s) prio %d",
2107 	    child, child->td_name, child->td_priority);
2108 
2109 #ifdef KSE
2110 	/*
2111 	 * KSE forks and exits so often that this penalty causes short-lived
2112 	 * threads to always be non-interactive.  This causes mozilla to
2113 	 * crawl under load.
2114 	 */
2115 	if ((td->td_pflags & TDP_SA) && td->td_proc == child->td_proc)
2116 		return;
2117 #endif
2118 	/*
2119 	 * Give the child's runtime to the parent without returning the
2120 	 * sleep time as a penalty to the parent.  This causes shells that
2121 	 * launch expensive things to mark their children as expensive.
2122 	 */
2123 	thread_lock(td);
2124 	td->td_sched->ts_runtime += child->td_sched->ts_runtime;
2125 	sched_interact_update(td);
2126 	sched_priority(td);
2127 	thread_unlock(td);
2128 }
2129 
2130 /*
2131  * Fix priorities on return to user-space.  Priorities may be elevated due
2132  * to static priorities in msleep() or similar.
2133  */
2134 void
2135 sched_userret(struct thread *td)
2136 {
2137 	/*
2138 	 * XXX we cheat slightly on the locking here to avoid locking in
2139 	 * the usual case.  Setting td_priority here is essentially an
2140 	 * incomplete workaround for not setting it properly elsewhere.
2141 	 * Now that some interrupt handlers are threads, not setting it
2142 	 * properly elsewhere can clobber it in the window between setting
2143 	 * it here and returning to user mode, so don't waste time setting
2144 	 * it perfectly here.
2145 	 */
2146 	KASSERT((td->td_flags & TDF_BORROWING) == 0,
2147 	    ("thread with borrowed priority returning to userland"));
2148 	if (td->td_priority != td->td_user_pri) {
2149 		thread_lock(td);
2150 		td->td_priority = td->td_user_pri;
2151 		td->td_base_pri = td->td_user_pri;
2152 		thread_unlock(td);
2153         }
2154 }
2155 
2156 /*
2157  * Handle a stathz tick.  This is really only relevant for timeshare
2158  * threads.
2159  */
2160 void
2161 sched_clock(struct thread *td)
2162 {
2163 	struct tdq *tdq;
2164 	struct td_sched *ts;
2165 
2166 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2167 	tdq = TDQ_SELF();
2168 #ifdef SMP
2169 	/*
2170 	 * We run the long term load balancer infrequently on the first cpu.
2171 	 */
2172 	if (balance_tdq == tdq) {
2173 		if (balance_ticks && --balance_ticks == 0)
2174 			sched_balance();
2175 		if (balance_group_ticks && --balance_group_ticks == 0)
2176 			sched_balance_groups();
2177 	}
2178 #endif
2179 	/*
2180 	 * Advance the insert index once for each tick to ensure that all
2181 	 * threads get a chance to run.
2182 	 */
2183 	if (tdq->tdq_idx == tdq->tdq_ridx) {
2184 		tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
2185 		if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
2186 			tdq->tdq_ridx = tdq->tdq_idx;
2187 	}
2188 	ts = td->td_sched;
2189 	/*
2190 	 * We only do slicing code for TIMESHARE threads.
2191 	 */
2192 	if (td->td_pri_class != PRI_TIMESHARE)
2193 		return;
2194 	/*
2195 	 * We used a tick; charge it to the thread so that we can compute our
2196 	 * interactivity.
2197 	 */
2198 	td->td_sched->ts_runtime += tickincr;
2199 	sched_interact_update(td);
2200 	/*
2201 	 * We used up one time slice.
2202 	 */
2203 	if (--ts->ts_slice > 0)
2204 		return;
2205 	/*
2206 	 * We're out of time, recompute priorities and requeue.
2207 	 */
2208 	sched_priority(td);
2209 	td->td_flags |= TDF_NEEDRESCHED;
2210 }
2211 
2212 /*
2213  * Called once per hz tick.  Used for cpu utilization information.  This
2214  * is easier than trying to scale based on stathz.
2215  */
2216 void
2217 sched_tick(void)
2218 {
2219 	struct td_sched *ts;
2220 
2221 	ts = curthread->td_sched;
2222 	/* Adjust ticks for pctcpu */
2223 	ts->ts_ticks += 1 << SCHED_TICK_SHIFT;
2224 	ts->ts_ltick = ticks;
2225 	/*
2226 	 * Update if we've exceeded our desired tick threshhold by over one
2227 	 * second.
2228 	 */
2229 	if (ts->ts_ftick + SCHED_TICK_MAX < ts->ts_ltick)
2230 		sched_pctcpu_update(ts);
2231 }
2232 
2233 /*
2234  * Return whether the current CPU has runnable tasks.  Used for in-kernel
2235  * cooperative idle threads.
2236  */
2237 int
2238 sched_runnable(void)
2239 {
2240 	struct tdq *tdq;
2241 	int load;
2242 
2243 	load = 1;
2244 
2245 	tdq = TDQ_SELF();
2246 	if ((curthread->td_flags & TDF_IDLETD) != 0) {
2247 		if (tdq->tdq_load > 0)
2248 			goto out;
2249 	} else
2250 		if (tdq->tdq_load - 1 > 0)
2251 			goto out;
2252 	load = 0;
2253 out:
2254 	return (load);
2255 }
2256 
2257 /*
2258  * Choose the highest priority thread to run.  The thread is removed from
2259  * the run-queue while running however the load remains.  For SMP we set
2260  * the tdq in the global idle bitmask if it idles here.
2261  */
2262 struct thread *
2263 sched_choose(void)
2264 {
2265 #ifdef SMP
2266 	struct tdq_group *tdg;
2267 #endif
2268 	struct td_sched *ts;
2269 	struct tdq *tdq;
2270 
2271 	tdq = TDQ_SELF();
2272 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2273 	ts = tdq_choose(tdq);
2274 	if (ts) {
2275 		tdq_runq_rem(tdq, ts);
2276 		return (ts->ts_thread);
2277 	}
2278 #ifdef SMP
2279 	/*
2280 	 * We only set the idled bit when all of the cpus in the group are
2281 	 * idle.  Otherwise we could get into a situation where a thread bounces
2282 	 * back and forth between two idle cores on seperate physical CPUs.
2283 	 */
2284 	tdg = tdq->tdq_group;
2285 	tdg->tdg_idlemask |= PCPU_GET(cpumask);
2286 	if (tdg->tdg_idlemask == tdg->tdg_cpumask)
2287 		atomic_set_int(&tdq_idle, tdg->tdg_mask);
2288 	tdq->tdq_lowpri = PRI_MAX_IDLE;
2289 #endif
2290 	return (PCPU_GET(idlethread));
2291 }
2292 
2293 /*
2294  * Set owepreempt if necessary.  Preemption never happens directly in ULE,
2295  * we always request it once we exit a critical section.
2296  */
2297 static inline void
2298 sched_setpreempt(struct thread *td)
2299 {
2300 	struct thread *ctd;
2301 	int cpri;
2302 	int pri;
2303 
2304 	ctd = curthread;
2305 	pri = td->td_priority;
2306 	cpri = ctd->td_priority;
2307 	if (td->td_priority < ctd->td_priority)
2308 		curthread->td_flags |= TDF_NEEDRESCHED;
2309 	if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
2310 		return;
2311 	/*
2312 	 * Always preempt IDLE threads.  Otherwise only if the preempting
2313 	 * thread is an ithread.
2314 	 */
2315 	if (pri > preempt_thresh && cpri < PRI_MIN_IDLE)
2316 		return;
2317 	ctd->td_owepreempt = 1;
2318 	return;
2319 }
2320 
2321 /*
2322  * Add a thread to a thread queue.  Initializes priority, slice, runq, and
2323  * add it to the appropriate queue.  This is the internal function called
2324  * when the tdq is predetermined.
2325  */
2326 void
2327 tdq_add(struct tdq *tdq, struct thread *td, int flags)
2328 {
2329 	struct td_sched *ts;
2330 	int class;
2331 #ifdef SMP
2332 	int cpumask;
2333 #endif
2334 
2335 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2336 	KASSERT((td->td_inhibitors == 0),
2337 	    ("sched_add: trying to run inhibited thread"));
2338 	KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
2339 	    ("sched_add: bad thread state"));
2340 	KASSERT(td->td_flags & TDF_INMEM,
2341 	    ("sched_add: thread swapped out"));
2342 
2343 	ts = td->td_sched;
2344 	class = PRI_BASE(td->td_pri_class);
2345         TD_SET_RUNQ(td);
2346 	if (ts->ts_slice == 0)
2347 		ts->ts_slice = sched_slice;
2348 	/*
2349 	 * Pick the run queue based on priority.
2350 	 */
2351 	if (td->td_priority <= PRI_MAX_REALTIME)
2352 		ts->ts_runq = &tdq->tdq_realtime;
2353 	else if (td->td_priority <= PRI_MAX_TIMESHARE)
2354 		ts->ts_runq = &tdq->tdq_timeshare;
2355 	else
2356 		ts->ts_runq = &tdq->tdq_idle;
2357 #ifdef SMP
2358 	cpumask = 1 << ts->ts_cpu;
2359 	/*
2360 	 * If we had been idle, clear our bit in the group and potentially
2361 	 * the global bitmap.
2362 	 */
2363 	if ((class != PRI_IDLE && class != PRI_ITHD) &&
2364 	    (tdq->tdq_group->tdg_idlemask & cpumask) != 0) {
2365 		/*
2366 		 * Check to see if our group is unidling, and if so, remove it
2367 		 * from the global idle mask.
2368 		 */
2369 		if (tdq->tdq_group->tdg_idlemask ==
2370 		    tdq->tdq_group->tdg_cpumask)
2371 			atomic_clear_int(&tdq_idle, tdq->tdq_group->tdg_mask);
2372 		/*
2373 		 * Now remove ourselves from the group specific idle mask.
2374 		 */
2375 		tdq->tdq_group->tdg_idlemask &= ~cpumask;
2376 	}
2377 	if (td->td_priority < tdq->tdq_lowpri)
2378 		tdq->tdq_lowpri = td->td_priority;
2379 #endif
2380 	tdq_runq_add(tdq, ts, flags);
2381 	tdq_load_add(tdq, ts);
2382 }
2383 
2384 /*
2385  * Select the target thread queue and add a thread to it.  Request
2386  * preemption or IPI a remote processor if required.
2387  */
2388 void
2389 sched_add(struct thread *td, int flags)
2390 {
2391 	struct td_sched *ts;
2392 	struct tdq *tdq;
2393 #ifdef SMP
2394 	int cpuid;
2395 	int cpu;
2396 #endif
2397 	CTR5(KTR_SCHED, "sched_add: %p(%s) prio %d by %p(%s)",
2398 	    td, td->td_name, td->td_priority, curthread,
2399 	    curthread->td_name);
2400 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2401 	ts = td->td_sched;
2402 	/*
2403 	 * Recalculate the priority before we select the target cpu or
2404 	 * run-queue.
2405 	 */
2406 	if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
2407 		sched_priority(td);
2408 #ifdef SMP
2409 	cpuid = PCPU_GET(cpuid);
2410 	/*
2411 	 * Pick the destination cpu and if it isn't ours transfer to the
2412 	 * target cpu.
2413 	 */
2414 	if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_MIGRATE(td))
2415 		cpu = cpuid;
2416 	else if (!THREAD_CAN_MIGRATE(td))
2417 		cpu = ts->ts_cpu;
2418 	else
2419 		cpu = sched_pickcpu(ts, flags);
2420 	tdq = sched_setcpu(ts, cpu, flags);
2421 	tdq_add(tdq, td, flags);
2422 	if (cpu != cpuid) {
2423 		tdq_notify(ts);
2424 		return;
2425 	}
2426 #else
2427 	tdq = TDQ_SELF();
2428 	TDQ_LOCK(tdq);
2429 	/*
2430 	 * Now that the thread is moving to the run-queue, set the lock
2431 	 * to the scheduler's lock.
2432 	 */
2433 	thread_lock_set(td, TDQ_LOCKPTR(tdq));
2434 	tdq_add(tdq, td, flags);
2435 #endif
2436 	if (!(flags & SRQ_YIELDING))
2437 		sched_setpreempt(td);
2438 }
2439 
2440 /*
2441  * Remove a thread from a run-queue without running it.  This is used
2442  * when we're stealing a thread from a remote queue.  Otherwise all threads
2443  * exit by calling sched_exit_thread() and sched_throw() themselves.
2444  */
2445 void
2446 sched_rem(struct thread *td)
2447 {
2448 	struct tdq *tdq;
2449 	struct td_sched *ts;
2450 
2451 	CTR5(KTR_SCHED, "sched_rem: %p(%s) prio %d by %p(%s)",
2452 	    td, td->td_name, td->td_priority, curthread,
2453 	    curthread->td_name);
2454 	ts = td->td_sched;
2455 	tdq = TDQ_CPU(ts->ts_cpu);
2456 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2457 	MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
2458 	KASSERT(TD_ON_RUNQ(td),
2459 	    ("sched_rem: thread not on run queue"));
2460 	tdq_runq_rem(tdq, ts);
2461 	tdq_load_rem(tdq, ts);
2462 	TD_SET_CAN_RUN(td);
2463 }
2464 
2465 /*
2466  * Fetch cpu utilization information.  Updates on demand.
2467  */
2468 fixpt_t
2469 sched_pctcpu(struct thread *td)
2470 {
2471 	fixpt_t pctcpu;
2472 	struct td_sched *ts;
2473 
2474 	pctcpu = 0;
2475 	ts = td->td_sched;
2476 	if (ts == NULL)
2477 		return (0);
2478 
2479 	thread_lock(td);
2480 	if (ts->ts_ticks) {
2481 		int rtick;
2482 
2483 		sched_pctcpu_update(ts);
2484 		/* How many rtick per second ? */
2485 		rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
2486 		pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
2487 	}
2488 	thread_unlock(td);
2489 
2490 	return (pctcpu);
2491 }
2492 
2493 /*
2494  * Bind a thread to a target cpu.
2495  */
2496 void
2497 sched_bind(struct thread *td, int cpu)
2498 {
2499 	struct td_sched *ts;
2500 
2501 	THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
2502 	ts = td->td_sched;
2503 	if (ts->ts_flags & TSF_BOUND)
2504 		sched_unbind(td);
2505 	ts->ts_flags |= TSF_BOUND;
2506 #ifdef SMP
2507 	sched_pin();
2508 	if (PCPU_GET(cpuid) == cpu)
2509 		return;
2510 	ts->ts_cpu = cpu;
2511 	/* When we return from mi_switch we'll be on the correct cpu. */
2512 	mi_switch(SW_VOL, NULL);
2513 #endif
2514 }
2515 
2516 /*
2517  * Release a bound thread.
2518  */
2519 void
2520 sched_unbind(struct thread *td)
2521 {
2522 	struct td_sched *ts;
2523 
2524 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2525 	ts = td->td_sched;
2526 	if ((ts->ts_flags & TSF_BOUND) == 0)
2527 		return;
2528 	ts->ts_flags &= ~TSF_BOUND;
2529 #ifdef SMP
2530 	sched_unpin();
2531 #endif
2532 }
2533 
2534 int
2535 sched_is_bound(struct thread *td)
2536 {
2537 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2538 	return (td->td_sched->ts_flags & TSF_BOUND);
2539 }
2540 
2541 /*
2542  * Basic yield call.
2543  */
2544 void
2545 sched_relinquish(struct thread *td)
2546 {
2547 	thread_lock(td);
2548 	SCHED_STAT_INC(switch_relinquish);
2549 	mi_switch(SW_VOL, NULL);
2550 	thread_unlock(td);
2551 }
2552 
2553 /*
2554  * Return the total system load.
2555  */
2556 int
2557 sched_load(void)
2558 {
2559 #ifdef SMP
2560 	int total;
2561 	int i;
2562 
2563 	total = 0;
2564 	for (i = 0; i <= tdg_maxid; i++)
2565 		total += TDQ_GROUP(i)->tdg_load;
2566 	return (total);
2567 #else
2568 	return (TDQ_SELF()->tdq_sysload);
2569 #endif
2570 }
2571 
2572 int
2573 sched_sizeof_proc(void)
2574 {
2575 	return (sizeof(struct proc));
2576 }
2577 
2578 int
2579 sched_sizeof_thread(void)
2580 {
2581 	return (sizeof(struct thread) + sizeof(struct td_sched));
2582 }
2583 
2584 /*
2585  * The actual idle process.
2586  */
2587 void
2588 sched_idletd(void *dummy)
2589 {
2590 	struct thread *td;
2591 	struct tdq *tdq;
2592 
2593 	td = curthread;
2594 	tdq = TDQ_SELF();
2595 	mtx_assert(&Giant, MA_NOTOWNED);
2596 	/* ULE relies on preemption for idle interruption. */
2597 	for (;;) {
2598 #ifdef SMP
2599 		if (tdq_idled(tdq))
2600 			cpu_idle();
2601 #else
2602 		cpu_idle();
2603 #endif
2604 	}
2605 }
2606 
2607 /*
2608  * A CPU is entering for the first time or a thread is exiting.
2609  */
2610 void
2611 sched_throw(struct thread *td)
2612 {
2613 	struct thread *newtd;
2614 	struct tdq *tdq;
2615 
2616 	tdq = TDQ_SELF();
2617 	if (td == NULL) {
2618 		/* Correct spinlock nesting and acquire the correct lock. */
2619 		TDQ_LOCK(tdq);
2620 		spinlock_exit();
2621 	} else {
2622 		MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
2623 		tdq_load_rem(tdq, td->td_sched);
2624 		lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
2625 	}
2626 	KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
2627 	newtd = choosethread();
2628 	TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
2629 	PCPU_SET(switchtime, cpu_ticks());
2630 	PCPU_SET(switchticks, ticks);
2631 	cpu_throw(td, newtd);		/* doesn't return */
2632 }
2633 
2634 /*
2635  * This is called from fork_exit().  Just acquire the correct locks and
2636  * let fork do the rest of the work.
2637  */
2638 void
2639 sched_fork_exit(struct thread *td)
2640 {
2641 	struct td_sched *ts;
2642 	struct tdq *tdq;
2643 	int cpuid;
2644 
2645 	/*
2646 	 * Finish setting up thread glue so that it begins execution in a
2647 	 * non-nested critical section with the scheduler lock held.
2648 	 */
2649 	cpuid = PCPU_GET(cpuid);
2650 	tdq = TDQ_CPU(cpuid);
2651 	ts = td->td_sched;
2652 	if (TD_IS_IDLETHREAD(td))
2653 		td->td_lock = TDQ_LOCKPTR(tdq);
2654 	MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
2655 	td->td_oncpu = cpuid;
2656 	TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
2657 	lock_profile_obtain_lock_success(
2658 	    &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
2659 }
2660 
2661 static SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0,
2662     "Scheduler");
2663 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
2664     "Scheduler name");
2665 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
2666     "Slice size for timeshare threads");
2667 SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
2668      "Interactivity score threshold");
2669 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW, &preempt_thresh,
2670      0,"Min priority for preemption, lower priorities have greater precedence");
2671 #ifdef SMP
2672 SYSCTL_INT(_kern_sched, OID_AUTO, pick_pri, CTLFLAG_RW, &pick_pri, 0,
2673     "Pick the target cpu based on priority rather than load.");
2674 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
2675     "Number of hz ticks to keep thread affinity for");
2676 SYSCTL_INT(_kern_sched, OID_AUTO, tryself, CTLFLAG_RW, &tryself, 0, "");
2677 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0,
2678     "Enables the long-term load balancer");
2679 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
2680     &balance_interval, 0,
2681     "Average frequency in stathz ticks to run the long-term balancer");
2682 SYSCTL_INT(_kern_sched, OID_AUTO, steal_htt, CTLFLAG_RW, &steal_htt, 0,
2683     "Steals work from another hyper-threaded core on idle");
2684 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
2685     "Attempts to steal work from other cores before idling");
2686 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
2687     "Minimum load on remote cpu before we'll steal");
2688 SYSCTL_INT(_kern_sched, OID_AUTO, topology, CTLFLAG_RD, &topology, 0,
2689     "True when a topology has been specified by the MD code.");
2690 #endif
2691 
2692 /* ps compat.  All cpu percentages from ULE are weighted. */
2693 static int ccpu = 0;
2694 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
2695 
2696 
2697 #define KERN_SWITCH_INCLUDE 1
2698 #include "kern/kern_switch.c"
2699