xref: /freebsd/sys/kern/sched_ule.c (revision cfd6422a5217410fbd66f7a7a8a64d9d85e61229)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright (c) 2002-2007, Jeffrey Roberson <jeff@freebsd.org>
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice unmodified, this list of conditions, and the following
12  *    disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27  */
28 
29 /*
30  * This file implements the ULE scheduler.  ULE supports independent CPU
31  * run queues and fine grain locking.  It has superior interactive
32  * performance under load even on uni-processor systems.
33  *
34  * etymology:
35  *   ULE is the last three letters in schedule.  It owes its name to a
36  * generic user created for a scheduling system by Paul Mikesell at
37  * Isilon Systems and a general lack of creativity on the part of the author.
38  */
39 
40 #include <sys/cdefs.h>
41 __FBSDID("$FreeBSD$");
42 
43 #include "opt_hwpmc_hooks.h"
44 #include "opt_sched.h"
45 
46 #include <sys/param.h>
47 #include <sys/systm.h>
48 #include <sys/kdb.h>
49 #include <sys/kernel.h>
50 #include <sys/ktr.h>
51 #include <sys/limits.h>
52 #include <sys/lock.h>
53 #include <sys/mutex.h>
54 #include <sys/proc.h>
55 #include <sys/resource.h>
56 #include <sys/resourcevar.h>
57 #include <sys/sched.h>
58 #include <sys/sdt.h>
59 #include <sys/smp.h>
60 #include <sys/sx.h>
61 #include <sys/sysctl.h>
62 #include <sys/sysproto.h>
63 #include <sys/turnstile.h>
64 #include <sys/umtx.h>
65 #include <sys/vmmeter.h>
66 #include <sys/cpuset.h>
67 #include <sys/sbuf.h>
68 
69 #ifdef HWPMC_HOOKS
70 #include <sys/pmckern.h>
71 #endif
72 
73 #ifdef KDTRACE_HOOKS
74 #include <sys/dtrace_bsd.h>
75 int __read_mostly		dtrace_vtime_active;
76 dtrace_vtime_switch_func_t	dtrace_vtime_switch_func;
77 #endif
78 
79 #include <machine/cpu.h>
80 #include <machine/smp.h>
81 
82 #define	KTR_ULE	0
83 
84 #define	TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
85 #define	TDQ_NAME_LEN	(sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU)))
86 #define	TDQ_LOADNAME_LEN	(sizeof("CPU ") + sizeof(__XSTRING(MAXCPU)) - 1 + sizeof(" load"))
87 
88 /*
89  * Thread scheduler specific section.  All fields are protected
90  * by the thread lock.
91  */
92 struct td_sched {
93 	struct runq	*ts_runq;	/* Run-queue we're queued on. */
94 	short		ts_flags;	/* TSF_* flags. */
95 	int		ts_cpu;		/* CPU that we have affinity for. */
96 	int		ts_rltick;	/* Real last tick, for affinity. */
97 	int		ts_slice;	/* Ticks of slice remaining. */
98 	u_int		ts_slptime;	/* Number of ticks we vol. slept */
99 	u_int		ts_runtime;	/* Number of ticks we were running */
100 	int		ts_ltick;	/* Last tick that we were running on */
101 	int		ts_ftick;	/* First tick that we were running on */
102 	int		ts_ticks;	/* Tick count */
103 #ifdef KTR
104 	char		ts_name[TS_NAME_LEN];
105 #endif
106 };
107 /* flags kept in ts_flags */
108 #define	TSF_BOUND	0x0001		/* Thread can not migrate. */
109 #define	TSF_XFERABLE	0x0002		/* Thread was added as transferable. */
110 
111 #define	THREAD_CAN_MIGRATE(td)	((td)->td_pinned == 0)
112 #define	THREAD_CAN_SCHED(td, cpu)	\
113     CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
114 
115 _Static_assert(sizeof(struct thread) + sizeof(struct td_sched) <=
116     sizeof(struct thread0_storage),
117     "increase struct thread0_storage.t0st_sched size");
118 
119 /*
120  * Priority ranges used for interactive and non-interactive timeshare
121  * threads.  The timeshare priorities are split up into four ranges.
122  * The first range handles interactive threads.  The last three ranges
123  * (NHALF, x, and NHALF) handle non-interactive threads with the outer
124  * ranges supporting nice values.
125  */
126 #define	PRI_TIMESHARE_RANGE	(PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1)
127 #define	PRI_INTERACT_RANGE	((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2)
128 #define	PRI_BATCH_RANGE		(PRI_TIMESHARE_RANGE - PRI_INTERACT_RANGE)
129 
130 #define	PRI_MIN_INTERACT	PRI_MIN_TIMESHARE
131 #define	PRI_MAX_INTERACT	(PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE - 1)
132 #define	PRI_MIN_BATCH		(PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE)
133 #define	PRI_MAX_BATCH		PRI_MAX_TIMESHARE
134 
135 /*
136  * Cpu percentage computation macros and defines.
137  *
138  * SCHED_TICK_SECS:	Number of seconds to average the cpu usage across.
139  * SCHED_TICK_TARG:	Number of hz ticks to average the cpu usage across.
140  * SCHED_TICK_MAX:	Maximum number of ticks before scaling back.
141  * SCHED_TICK_SHIFT:	Shift factor to avoid rounding away results.
142  * SCHED_TICK_HZ:	Compute the number of hz ticks for a given ticks count.
143  * SCHED_TICK_TOTAL:	Gives the amount of time we've been recording ticks.
144  */
145 #define	SCHED_TICK_SECS		10
146 #define	SCHED_TICK_TARG		(hz * SCHED_TICK_SECS)
147 #define	SCHED_TICK_MAX		(SCHED_TICK_TARG + hz)
148 #define	SCHED_TICK_SHIFT	10
149 #define	SCHED_TICK_HZ(ts)	((ts)->ts_ticks >> SCHED_TICK_SHIFT)
150 #define	SCHED_TICK_TOTAL(ts)	(max((ts)->ts_ltick - (ts)->ts_ftick, hz))
151 
152 /*
153  * These macros determine priorities for non-interactive threads.  They are
154  * assigned a priority based on their recent cpu utilization as expressed
155  * by the ratio of ticks to the tick total.  NHALF priorities at the start
156  * and end of the MIN to MAX timeshare range are only reachable with negative
157  * or positive nice respectively.
158  *
159  * PRI_RANGE:	Priority range for utilization dependent priorities.
160  * PRI_NRESV:	Number of nice values.
161  * PRI_TICKS:	Compute a priority in PRI_RANGE from the ticks count and total.
162  * PRI_NICE:	Determines the part of the priority inherited from nice.
163  */
164 #define	SCHED_PRI_NRESV		(PRIO_MAX - PRIO_MIN)
165 #define	SCHED_PRI_NHALF		(SCHED_PRI_NRESV / 2)
166 #define	SCHED_PRI_MIN		(PRI_MIN_BATCH + SCHED_PRI_NHALF)
167 #define	SCHED_PRI_MAX		(PRI_MAX_BATCH - SCHED_PRI_NHALF)
168 #define	SCHED_PRI_RANGE		(SCHED_PRI_MAX - SCHED_PRI_MIN + 1)
169 #define	SCHED_PRI_TICKS(ts)						\
170     (SCHED_TICK_HZ((ts)) /						\
171     (roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE))
172 #define	SCHED_PRI_NICE(nice)	(nice)
173 
174 /*
175  * These determine the interactivity of a process.  Interactivity differs from
176  * cpu utilization in that it expresses the voluntary time slept vs time ran
177  * while cpu utilization includes all time not running.  This more accurately
178  * models the intent of the thread.
179  *
180  * SLP_RUN_MAX:	Maximum amount of sleep time + run time we'll accumulate
181  *		before throttling back.
182  * SLP_RUN_FORK:	Maximum slp+run time to inherit at fork time.
183  * INTERACT_MAX:	Maximum interactivity value.  Smaller is better.
184  * INTERACT_THRESH:	Threshold for placement on the current runq.
185  */
186 #define	SCHED_SLP_RUN_MAX	((hz * 5) << SCHED_TICK_SHIFT)
187 #define	SCHED_SLP_RUN_FORK	((hz / 2) << SCHED_TICK_SHIFT)
188 #define	SCHED_INTERACT_MAX	(100)
189 #define	SCHED_INTERACT_HALF	(SCHED_INTERACT_MAX / 2)
190 #define	SCHED_INTERACT_THRESH	(30)
191 
192 /*
193  * These parameters determine the slice behavior for batch work.
194  */
195 #define	SCHED_SLICE_DEFAULT_DIVISOR	10	/* ~94 ms, 12 stathz ticks. */
196 #define	SCHED_SLICE_MIN_DIVISOR		6	/* DEFAULT/MIN = ~16 ms. */
197 
198 /* Flags kept in td_flags. */
199 #define	TDF_SLICEEND	TDF_SCHED2	/* Thread time slice is over. */
200 
201 /*
202  * tickincr:		Converts a stathz tick into a hz domain scaled by
203  *			the shift factor.  Without the shift the error rate
204  *			due to rounding would be unacceptably high.
205  * realstathz:		stathz is sometimes 0 and run off of hz.
206  * sched_slice:		Runtime of each thread before rescheduling.
207  * preempt_thresh:	Priority threshold for preemption and remote IPIs.
208  */
209 static int __read_mostly sched_interact = SCHED_INTERACT_THRESH;
210 static int __read_mostly tickincr = 8 << SCHED_TICK_SHIFT;
211 static int __read_mostly realstathz = 127;	/* reset during boot. */
212 static int __read_mostly sched_slice = 10;	/* reset during boot. */
213 static int __read_mostly sched_slice_min = 1;	/* reset during boot. */
214 #ifdef PREEMPTION
215 #ifdef FULL_PREEMPTION
216 static int __read_mostly preempt_thresh = PRI_MAX_IDLE;
217 #else
218 static int __read_mostly preempt_thresh = PRI_MIN_KERN;
219 #endif
220 #else
221 static int __read_mostly preempt_thresh = 0;
222 #endif
223 static int __read_mostly static_boost = PRI_MIN_BATCH;
224 static int __read_mostly sched_idlespins = 10000;
225 static int __read_mostly sched_idlespinthresh = -1;
226 
227 /*
228  * tdq - per processor runqs and statistics.  All fields are protected by the
229  * tdq_lock.  The load and lowpri may be accessed without to avoid excess
230  * locking in sched_pickcpu();
231  */
232 struct tdq {
233 	/*
234 	 * Ordered to improve efficiency of cpu_search() and switch().
235 	 * tdq_lock is padded to avoid false sharing with tdq_load and
236 	 * tdq_cpu_idle.
237 	 */
238 	struct mtx_padalign tdq_lock;		/* run queue lock. */
239 	struct cpu_group *tdq_cg;		/* Pointer to cpu topology. */
240 	volatile int	tdq_load;		/* Aggregate load. */
241 	volatile int	tdq_cpu_idle;		/* cpu_idle() is active. */
242 	int		tdq_sysload;		/* For loadavg, !ITHD load. */
243 	volatile int	tdq_transferable;	/* Transferable thread count. */
244 	volatile short	tdq_switchcnt;		/* Switches this tick. */
245 	volatile short	tdq_oldswitchcnt;	/* Switches last tick. */
246 	u_char		tdq_lowpri;		/* Lowest priority thread. */
247 	u_char		tdq_owepreempt;		/* Remote preemption pending. */
248 	u_char		tdq_idx;		/* Current insert index. */
249 	u_char		tdq_ridx;		/* Current removal index. */
250 	int		tdq_id;			/* cpuid. */
251 	struct runq	tdq_realtime;		/* real-time run queue. */
252 	struct runq	tdq_timeshare;		/* timeshare run queue. */
253 	struct runq	tdq_idle;		/* Queue of IDLE threads. */
254 	char		tdq_name[TDQ_NAME_LEN];
255 #ifdef KTR
256 	char		tdq_loadname[TDQ_LOADNAME_LEN];
257 #endif
258 } __aligned(64);
259 
260 /* Idle thread states and config. */
261 #define	TDQ_RUNNING	1
262 #define	TDQ_IDLE	2
263 
264 #ifdef SMP
265 struct cpu_group __read_mostly *cpu_top;		/* CPU topology */
266 
267 #define	SCHED_AFFINITY_DEFAULT	(max(1, hz / 1000))
268 #define	SCHED_AFFINITY(ts, t)	((ts)->ts_rltick > ticks - ((t) * affinity))
269 
270 /*
271  * Run-time tunables.
272  */
273 static int rebalance = 1;
274 static int balance_interval = 128;	/* Default set in sched_initticks(). */
275 static int __read_mostly affinity;
276 static int __read_mostly steal_idle = 1;
277 static int __read_mostly steal_thresh = 2;
278 static int __read_mostly always_steal = 0;
279 static int __read_mostly trysteal_limit = 2;
280 
281 /*
282  * One thread queue per processor.
283  */
284 static struct tdq __read_mostly *balance_tdq;
285 static int balance_ticks;
286 DPCPU_DEFINE_STATIC(struct tdq, tdq);
287 DPCPU_DEFINE_STATIC(uint32_t, randomval);
288 
289 #define	TDQ_SELF()	((struct tdq *)PCPU_GET(sched))
290 #define	TDQ_CPU(x)	(DPCPU_ID_PTR((x), tdq))
291 #define	TDQ_ID(x)	((x)->tdq_id)
292 #else	/* !SMP */
293 static struct tdq	tdq_cpu;
294 
295 #define	TDQ_ID(x)	(0)
296 #define	TDQ_SELF()	(&tdq_cpu)
297 #define	TDQ_CPU(x)	(&tdq_cpu)
298 #endif
299 
300 #define	TDQ_LOCK_ASSERT(t, type)	mtx_assert(TDQ_LOCKPTR((t)), (type))
301 #define	TDQ_LOCK(t)		mtx_lock_spin(TDQ_LOCKPTR((t)))
302 #define	TDQ_LOCK_FLAGS(t, f)	mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f))
303 #define	TDQ_UNLOCK(t)		mtx_unlock_spin(TDQ_LOCKPTR((t)))
304 #define	TDQ_LOCKPTR(t)		((struct mtx *)(&(t)->tdq_lock))
305 
306 static void sched_priority(struct thread *);
307 static void sched_thread_priority(struct thread *, u_char);
308 static int sched_interact_score(struct thread *);
309 static void sched_interact_update(struct thread *);
310 static void sched_interact_fork(struct thread *);
311 static void sched_pctcpu_update(struct td_sched *, int);
312 
313 /* Operations on per processor queues */
314 static struct thread *tdq_choose(struct tdq *);
315 static void tdq_setup(struct tdq *, int i);
316 static void tdq_load_add(struct tdq *, struct thread *);
317 static void tdq_load_rem(struct tdq *, struct thread *);
318 static __inline void tdq_runq_add(struct tdq *, struct thread *, int);
319 static __inline void tdq_runq_rem(struct tdq *, struct thread *);
320 static inline int sched_shouldpreempt(int, int, int);
321 void tdq_print(int cpu);
322 static void runq_print(struct runq *rq);
323 static void tdq_add(struct tdq *, struct thread *, int);
324 #ifdef SMP
325 static struct thread *tdq_move(struct tdq *, struct tdq *);
326 static int tdq_idled(struct tdq *);
327 static void tdq_notify(struct tdq *, struct thread *);
328 static struct thread *tdq_steal(struct tdq *, int);
329 static struct thread *runq_steal(struct runq *, int);
330 static int sched_pickcpu(struct thread *, int);
331 static void sched_balance(void);
332 static int sched_balance_pair(struct tdq *, struct tdq *);
333 static inline struct tdq *sched_setcpu(struct thread *, int, int);
334 static inline void thread_unblock_switch(struct thread *, struct mtx *);
335 static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS);
336 static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb,
337     struct cpu_group *cg, int indent);
338 #endif
339 
340 static void sched_setup(void *dummy);
341 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
342 
343 static void sched_initticks(void *dummy);
344 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
345     NULL);
346 
347 SDT_PROVIDER_DEFINE(sched);
348 
349 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *",
350     "struct proc *", "uint8_t");
351 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *",
352     "struct proc *", "void *");
353 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *",
354     "struct proc *", "void *", "int");
355 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *",
356     "struct proc *", "uint8_t", "struct thread *");
357 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int");
358 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *",
359     "struct proc *");
360 SDT_PROBE_DEFINE(sched, , , on__cpu);
361 SDT_PROBE_DEFINE(sched, , , remain__cpu);
362 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *",
363     "struct proc *");
364 
365 /*
366  * Print the threads waiting on a run-queue.
367  */
368 static void
369 runq_print(struct runq *rq)
370 {
371 	struct rqhead *rqh;
372 	struct thread *td;
373 	int pri;
374 	int j;
375 	int i;
376 
377 	for (i = 0; i < RQB_LEN; i++) {
378 		printf("\t\trunq bits %d 0x%zx\n",
379 		    i, rq->rq_status.rqb_bits[i]);
380 		for (j = 0; j < RQB_BPW; j++)
381 			if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
382 				pri = j + (i << RQB_L2BPW);
383 				rqh = &rq->rq_queues[pri];
384 				TAILQ_FOREACH(td, rqh, td_runq) {
385 					printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
386 					    td, td->td_name, td->td_priority,
387 					    td->td_rqindex, pri);
388 				}
389 			}
390 	}
391 }
392 
393 /*
394  * Print the status of a per-cpu thread queue.  Should be a ddb show cmd.
395  */
396 void
397 tdq_print(int cpu)
398 {
399 	struct tdq *tdq;
400 
401 	tdq = TDQ_CPU(cpu);
402 
403 	printf("tdq %d:\n", TDQ_ID(tdq));
404 	printf("\tlock            %p\n", TDQ_LOCKPTR(tdq));
405 	printf("\tLock name:      %s\n", tdq->tdq_name);
406 	printf("\tload:           %d\n", tdq->tdq_load);
407 	printf("\tswitch cnt:     %d\n", tdq->tdq_switchcnt);
408 	printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt);
409 	printf("\ttimeshare idx:  %d\n", tdq->tdq_idx);
410 	printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
411 	printf("\tload transferable: %d\n", tdq->tdq_transferable);
412 	printf("\tlowest priority:   %d\n", tdq->tdq_lowpri);
413 	printf("\trealtime runq:\n");
414 	runq_print(&tdq->tdq_realtime);
415 	printf("\ttimeshare runq:\n");
416 	runq_print(&tdq->tdq_timeshare);
417 	printf("\tidle runq:\n");
418 	runq_print(&tdq->tdq_idle);
419 }
420 
421 static inline int
422 sched_shouldpreempt(int pri, int cpri, int remote)
423 {
424 	/*
425 	 * If the new priority is not better than the current priority there is
426 	 * nothing to do.
427 	 */
428 	if (pri >= cpri)
429 		return (0);
430 	/*
431 	 * Always preempt idle.
432 	 */
433 	if (cpri >= PRI_MIN_IDLE)
434 		return (1);
435 	/*
436 	 * If preemption is disabled don't preempt others.
437 	 */
438 	if (preempt_thresh == 0)
439 		return (0);
440 	/*
441 	 * Preempt if we exceed the threshold.
442 	 */
443 	if (pri <= preempt_thresh)
444 		return (1);
445 	/*
446 	 * If we're interactive or better and there is non-interactive
447 	 * or worse running preempt only remote processors.
448 	 */
449 	if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT)
450 		return (1);
451 	return (0);
452 }
453 
454 /*
455  * Add a thread to the actual run-queue.  Keeps transferable counts up to
456  * date with what is actually on the run-queue.  Selects the correct
457  * queue position for timeshare threads.
458  */
459 static __inline void
460 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
461 {
462 	struct td_sched *ts;
463 	u_char pri;
464 
465 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
466 	THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
467 
468 	pri = td->td_priority;
469 	ts = td_get_sched(td);
470 	TD_SET_RUNQ(td);
471 	if (THREAD_CAN_MIGRATE(td)) {
472 		tdq->tdq_transferable++;
473 		ts->ts_flags |= TSF_XFERABLE;
474 	}
475 	if (pri < PRI_MIN_BATCH) {
476 		ts->ts_runq = &tdq->tdq_realtime;
477 	} else if (pri <= PRI_MAX_BATCH) {
478 		ts->ts_runq = &tdq->tdq_timeshare;
479 		KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH,
480 			("Invalid priority %d on timeshare runq", pri));
481 		/*
482 		 * This queue contains only priorities between MIN and MAX
483 		 * realtime.  Use the whole queue to represent these values.
484 		 */
485 		if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
486 			pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE;
487 			pri = (pri + tdq->tdq_idx) % RQ_NQS;
488 			/*
489 			 * This effectively shortens the queue by one so we
490 			 * can have a one slot difference between idx and
491 			 * ridx while we wait for threads to drain.
492 			 */
493 			if (tdq->tdq_ridx != tdq->tdq_idx &&
494 			    pri == tdq->tdq_ridx)
495 				pri = (unsigned char)(pri - 1) % RQ_NQS;
496 		} else
497 			pri = tdq->tdq_ridx;
498 		runq_add_pri(ts->ts_runq, td, pri, flags);
499 		return;
500 	} else
501 		ts->ts_runq = &tdq->tdq_idle;
502 	runq_add(ts->ts_runq, td, flags);
503 }
504 
505 /*
506  * Remove a thread from a run-queue.  This typically happens when a thread
507  * is selected to run.  Running threads are not on the queue and the
508  * transferable count does not reflect them.
509  */
510 static __inline void
511 tdq_runq_rem(struct tdq *tdq, struct thread *td)
512 {
513 	struct td_sched *ts;
514 
515 	ts = td_get_sched(td);
516 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
517 	THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
518 	KASSERT(ts->ts_runq != NULL,
519 	    ("tdq_runq_remove: thread %p null ts_runq", td));
520 	if (ts->ts_flags & TSF_XFERABLE) {
521 		tdq->tdq_transferable--;
522 		ts->ts_flags &= ~TSF_XFERABLE;
523 	}
524 	if (ts->ts_runq == &tdq->tdq_timeshare) {
525 		if (tdq->tdq_idx != tdq->tdq_ridx)
526 			runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx);
527 		else
528 			runq_remove_idx(ts->ts_runq, td, NULL);
529 	} else
530 		runq_remove(ts->ts_runq, td);
531 }
532 
533 /*
534  * Load is maintained for all threads RUNNING and ON_RUNQ.  Add the load
535  * for this thread to the referenced thread queue.
536  */
537 static void
538 tdq_load_add(struct tdq *tdq, struct thread *td)
539 {
540 
541 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
542 	THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
543 
544 	tdq->tdq_load++;
545 	if ((td->td_flags & TDF_NOLOAD) == 0)
546 		tdq->tdq_sysload++;
547 	KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
548 	SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
549 }
550 
551 /*
552  * Remove the load from a thread that is transitioning to a sleep state or
553  * exiting.
554  */
555 static void
556 tdq_load_rem(struct tdq *tdq, struct thread *td)
557 {
558 
559 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
560 	THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
561 	KASSERT(tdq->tdq_load != 0,
562 	    ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
563 
564 	tdq->tdq_load--;
565 	if ((td->td_flags & TDF_NOLOAD) == 0)
566 		tdq->tdq_sysload--;
567 	KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
568 	SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
569 }
570 
571 /*
572  * Bound timeshare latency by decreasing slice size as load increases.  We
573  * consider the maximum latency as the sum of the threads waiting to run
574  * aside from curthread and target no more than sched_slice latency but
575  * no less than sched_slice_min runtime.
576  */
577 static inline int
578 tdq_slice(struct tdq *tdq)
579 {
580 	int load;
581 
582 	/*
583 	 * It is safe to use sys_load here because this is called from
584 	 * contexts where timeshare threads are running and so there
585 	 * cannot be higher priority load in the system.
586 	 */
587 	load = tdq->tdq_sysload - 1;
588 	if (load >= SCHED_SLICE_MIN_DIVISOR)
589 		return (sched_slice_min);
590 	if (load <= 1)
591 		return (sched_slice);
592 	return (sched_slice / load);
593 }
594 
595 /*
596  * Set lowpri to its exact value by searching the run-queue and
597  * evaluating curthread.  curthread may be passed as an optimization.
598  */
599 static void
600 tdq_setlowpri(struct tdq *tdq, struct thread *ctd)
601 {
602 	struct thread *td;
603 
604 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
605 	if (ctd == NULL)
606 		ctd = pcpu_find(TDQ_ID(tdq))->pc_curthread;
607 	td = tdq_choose(tdq);
608 	if (td == NULL || td->td_priority > ctd->td_priority)
609 		tdq->tdq_lowpri = ctd->td_priority;
610 	else
611 		tdq->tdq_lowpri = td->td_priority;
612 }
613 
614 #ifdef SMP
615 /*
616  * We need some randomness. Implement a classic Linear Congruential
617  * Generator X_{n+1}=(aX_n+c) mod m. These values are optimized for
618  * m = 2^32, a = 69069 and c = 5. We only return the upper 16 bits
619  * of the random state (in the low bits of our answer) to keep
620  * the maximum randomness.
621  */
622 static uint32_t
623 sched_random(void)
624 {
625 	uint32_t *rndptr;
626 
627 	rndptr = DPCPU_PTR(randomval);
628 	*rndptr = *rndptr * 69069 + 5;
629 
630 	return (*rndptr >> 16);
631 }
632 
633 struct cpu_search {
634 	cpuset_t cs_mask;
635 	u_int	cs_prefer;
636 	int	cs_pri;		/* Min priority for low. */
637 	int	cs_limit;	/* Max load for low, min load for high. */
638 	int	cs_cpu;
639 	int	cs_load;
640 };
641 
642 #define	CPU_SEARCH_LOWEST	0x1
643 #define	CPU_SEARCH_HIGHEST	0x2
644 #define	CPU_SEARCH_BOTH		(CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST)
645 
646 static __always_inline int cpu_search(const struct cpu_group *cg,
647     struct cpu_search *low, struct cpu_search *high, const int match);
648 int __noinline cpu_search_lowest(const struct cpu_group *cg,
649     struct cpu_search *low);
650 int __noinline cpu_search_highest(const struct cpu_group *cg,
651     struct cpu_search *high);
652 int __noinline cpu_search_both(const struct cpu_group *cg,
653     struct cpu_search *low, struct cpu_search *high);
654 
655 /*
656  * Search the tree of cpu_groups for the lowest or highest loaded cpu
657  * according to the match argument.  This routine actually compares the
658  * load on all paths through the tree and finds the least loaded cpu on
659  * the least loaded path, which may differ from the least loaded cpu in
660  * the system.  This balances work among caches and buses.
661  *
662  * This inline is instantiated in three forms below using constants for the
663  * match argument.  It is reduced to the minimum set for each case.  It is
664  * also recursive to the depth of the tree.
665  */
666 static __always_inline int
667 cpu_search(const struct cpu_group *cg, struct cpu_search *low,
668     struct cpu_search *high, const int match)
669 {
670 	struct cpu_search lgroup;
671 	struct cpu_search hgroup;
672 	cpuset_t cpumask;
673 	struct cpu_group *child;
674 	struct tdq *tdq;
675 	int cpu, i, hload, lload, load, total, rnd;
676 
677 	total = 0;
678 	cpumask = cg->cg_mask;
679 	if (match & CPU_SEARCH_LOWEST) {
680 		lload = INT_MAX;
681 		lgroup = *low;
682 	}
683 	if (match & CPU_SEARCH_HIGHEST) {
684 		hload = INT_MIN;
685 		hgroup = *high;
686 	}
687 
688 	/* Iterate through the child CPU groups and then remaining CPUs. */
689 	for (i = cg->cg_children, cpu = mp_maxid; ; ) {
690 		if (i == 0) {
691 #ifdef HAVE_INLINE_FFSL
692 			cpu = CPU_FFS(&cpumask) - 1;
693 #else
694 			while (cpu >= 0 && !CPU_ISSET(cpu, &cpumask))
695 				cpu--;
696 #endif
697 			if (cpu < 0)
698 				break;
699 			child = NULL;
700 		} else
701 			child = &cg->cg_child[i - 1];
702 
703 		if (match & CPU_SEARCH_LOWEST)
704 			lgroup.cs_cpu = -1;
705 		if (match & CPU_SEARCH_HIGHEST)
706 			hgroup.cs_cpu = -1;
707 		if (child) {			/* Handle child CPU group. */
708 			CPU_ANDNOT(&cpumask, &child->cg_mask);
709 			switch (match) {
710 			case CPU_SEARCH_LOWEST:
711 				load = cpu_search_lowest(child, &lgroup);
712 				break;
713 			case CPU_SEARCH_HIGHEST:
714 				load = cpu_search_highest(child, &hgroup);
715 				break;
716 			case CPU_SEARCH_BOTH:
717 				load = cpu_search_both(child, &lgroup, &hgroup);
718 				break;
719 			}
720 		} else {			/* Handle child CPU. */
721 			CPU_CLR(cpu, &cpumask);
722 			tdq = TDQ_CPU(cpu);
723 			load = tdq->tdq_load * 256;
724 			rnd = sched_random() % 32;
725 			if (match & CPU_SEARCH_LOWEST) {
726 				if (cpu == low->cs_prefer)
727 					load -= 64;
728 				/* If that CPU is allowed and get data. */
729 				if (tdq->tdq_lowpri > lgroup.cs_pri &&
730 				    tdq->tdq_load <= lgroup.cs_limit &&
731 				    CPU_ISSET(cpu, &lgroup.cs_mask)) {
732 					lgroup.cs_cpu = cpu;
733 					lgroup.cs_load = load - rnd;
734 				}
735 			}
736 			if (match & CPU_SEARCH_HIGHEST)
737 				if (tdq->tdq_load >= hgroup.cs_limit &&
738 				    tdq->tdq_transferable &&
739 				    CPU_ISSET(cpu, &hgroup.cs_mask)) {
740 					hgroup.cs_cpu = cpu;
741 					hgroup.cs_load = load - rnd;
742 				}
743 		}
744 		total += load;
745 
746 		/* We have info about child item. Compare it. */
747 		if (match & CPU_SEARCH_LOWEST) {
748 			if (lgroup.cs_cpu >= 0 &&
749 			    (load < lload ||
750 			     (load == lload && lgroup.cs_load < low->cs_load))) {
751 				lload = load;
752 				low->cs_cpu = lgroup.cs_cpu;
753 				low->cs_load = lgroup.cs_load;
754 			}
755 		}
756 		if (match & CPU_SEARCH_HIGHEST)
757 			if (hgroup.cs_cpu >= 0 &&
758 			    (load > hload ||
759 			     (load == hload && hgroup.cs_load > high->cs_load))) {
760 				hload = load;
761 				high->cs_cpu = hgroup.cs_cpu;
762 				high->cs_load = hgroup.cs_load;
763 			}
764 		if (child) {
765 			i--;
766 			if (i == 0 && CPU_EMPTY(&cpumask))
767 				break;
768 		}
769 #ifndef HAVE_INLINE_FFSL
770 		else
771 			cpu--;
772 #endif
773 	}
774 	return (total);
775 }
776 
777 /*
778  * cpu_search instantiations must pass constants to maintain the inline
779  * optimization.
780  */
781 int
782 cpu_search_lowest(const struct cpu_group *cg, struct cpu_search *low)
783 {
784 	return cpu_search(cg, low, NULL, CPU_SEARCH_LOWEST);
785 }
786 
787 int
788 cpu_search_highest(const struct cpu_group *cg, struct cpu_search *high)
789 {
790 	return cpu_search(cg, NULL, high, CPU_SEARCH_HIGHEST);
791 }
792 
793 int
794 cpu_search_both(const struct cpu_group *cg, struct cpu_search *low,
795     struct cpu_search *high)
796 {
797 	return cpu_search(cg, low, high, CPU_SEARCH_BOTH);
798 }
799 
800 /*
801  * Find the cpu with the least load via the least loaded path that has a
802  * lowpri greater than pri  pri.  A pri of -1 indicates any priority is
803  * acceptable.
804  */
805 static inline int
806 sched_lowest(const struct cpu_group *cg, cpuset_t mask, int pri, int maxload,
807     int prefer)
808 {
809 	struct cpu_search low;
810 
811 	low.cs_cpu = -1;
812 	low.cs_prefer = prefer;
813 	low.cs_mask = mask;
814 	low.cs_pri = pri;
815 	low.cs_limit = maxload;
816 	cpu_search_lowest(cg, &low);
817 	return low.cs_cpu;
818 }
819 
820 /*
821  * Find the cpu with the highest load via the highest loaded path.
822  */
823 static inline int
824 sched_highest(const struct cpu_group *cg, cpuset_t mask, int minload)
825 {
826 	struct cpu_search high;
827 
828 	high.cs_cpu = -1;
829 	high.cs_mask = mask;
830 	high.cs_limit = minload;
831 	cpu_search_highest(cg, &high);
832 	return high.cs_cpu;
833 }
834 
835 static void
836 sched_balance_group(struct cpu_group *cg)
837 {
838 	struct tdq *tdq;
839 	cpuset_t hmask, lmask;
840 	int high, low, anylow;
841 
842 	CPU_FILL(&hmask);
843 	for (;;) {
844 		high = sched_highest(cg, hmask, 2);
845 		/* Stop if there is no more CPU with transferrable threads. */
846 		if (high == -1)
847 			break;
848 		CPU_CLR(high, &hmask);
849 		CPU_COPY(&hmask, &lmask);
850 		/* Stop if there is no more CPU left for low. */
851 		if (CPU_EMPTY(&lmask))
852 			break;
853 		anylow = 1;
854 		tdq = TDQ_CPU(high);
855 nextlow:
856 		low = sched_lowest(cg, lmask, -1, tdq->tdq_load - 1, high);
857 		/* Stop if we looked well and found no less loaded CPU. */
858 		if (anylow && low == -1)
859 			break;
860 		/* Go to next high if we found no less loaded CPU. */
861 		if (low == -1)
862 			continue;
863 		/* Transfer thread from high to low. */
864 		if (sched_balance_pair(tdq, TDQ_CPU(low))) {
865 			/* CPU that got thread can no longer be a donor. */
866 			CPU_CLR(low, &hmask);
867 		} else {
868 			/*
869 			 * If failed, then there is no threads on high
870 			 * that can run on this low. Drop low from low
871 			 * mask and look for different one.
872 			 */
873 			CPU_CLR(low, &lmask);
874 			anylow = 0;
875 			goto nextlow;
876 		}
877 	}
878 }
879 
880 static void
881 sched_balance(void)
882 {
883 	struct tdq *tdq;
884 
885 	balance_ticks = max(balance_interval / 2, 1) +
886 	    (sched_random() % balance_interval);
887 	tdq = TDQ_SELF();
888 	TDQ_UNLOCK(tdq);
889 	sched_balance_group(cpu_top);
890 	TDQ_LOCK(tdq);
891 }
892 
893 /*
894  * Lock two thread queues using their address to maintain lock order.
895  */
896 static void
897 tdq_lock_pair(struct tdq *one, struct tdq *two)
898 {
899 	if (one < two) {
900 		TDQ_LOCK(one);
901 		TDQ_LOCK_FLAGS(two, MTX_DUPOK);
902 	} else {
903 		TDQ_LOCK(two);
904 		TDQ_LOCK_FLAGS(one, MTX_DUPOK);
905 	}
906 }
907 
908 /*
909  * Unlock two thread queues.  Order is not important here.
910  */
911 static void
912 tdq_unlock_pair(struct tdq *one, struct tdq *two)
913 {
914 	TDQ_UNLOCK(one);
915 	TDQ_UNLOCK(two);
916 }
917 
918 /*
919  * Transfer load between two imbalanced thread queues.
920  */
921 static int
922 sched_balance_pair(struct tdq *high, struct tdq *low)
923 {
924 	struct thread *td;
925 	int cpu;
926 
927 	tdq_lock_pair(high, low);
928 	td = NULL;
929 	/*
930 	 * Transfer a thread from high to low.
931 	 */
932 	if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load &&
933 	    (td = tdq_move(high, low)) != NULL) {
934 		/*
935 		 * In case the target isn't the current cpu notify it of the
936 		 * new load, possibly sending an IPI to force it to reschedule.
937 		 */
938 		cpu = TDQ_ID(low);
939 		if (cpu != PCPU_GET(cpuid))
940 			tdq_notify(low, td);
941 	}
942 	tdq_unlock_pair(high, low);
943 	return (td != NULL);
944 }
945 
946 /*
947  * Move a thread from one thread queue to another.
948  */
949 static struct thread *
950 tdq_move(struct tdq *from, struct tdq *to)
951 {
952 	struct thread *td;
953 	struct tdq *tdq;
954 	int cpu;
955 
956 	TDQ_LOCK_ASSERT(from, MA_OWNED);
957 	TDQ_LOCK_ASSERT(to, MA_OWNED);
958 
959 	tdq = from;
960 	cpu = TDQ_ID(to);
961 	td = tdq_steal(tdq, cpu);
962 	if (td == NULL)
963 		return (NULL);
964 
965 	/*
966 	 * Although the run queue is locked the thread may be
967 	 * blocked.  We can not set the lock until it is unblocked.
968 	 */
969 	thread_lock_block_wait(td);
970 	sched_rem(td);
971 	THREAD_LOCKPTR_ASSERT(td, TDQ_LOCKPTR(from));
972 	td->td_lock = TDQ_LOCKPTR(to);
973 	td_get_sched(td)->ts_cpu = cpu;
974 	tdq_add(to, td, SRQ_YIELDING);
975 
976 	return (td);
977 }
978 
979 /*
980  * This tdq has idled.  Try to steal a thread from another cpu and switch
981  * to it.
982  */
983 static int
984 tdq_idled(struct tdq *tdq)
985 {
986 	struct cpu_group *cg;
987 	struct tdq *steal;
988 	cpuset_t mask;
989 	int cpu, switchcnt;
990 
991 	if (smp_started == 0 || steal_idle == 0 || tdq->tdq_cg == NULL)
992 		return (1);
993 	CPU_FILL(&mask);
994 	CPU_CLR(PCPU_GET(cpuid), &mask);
995     restart:
996 	switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
997 	for (cg = tdq->tdq_cg; ; ) {
998 		cpu = sched_highest(cg, mask, steal_thresh);
999 		/*
1000 		 * We were assigned a thread but not preempted.  Returning
1001 		 * 0 here will cause our caller to switch to it.
1002 		 */
1003 		if (tdq->tdq_load)
1004 			return (0);
1005 		if (cpu == -1) {
1006 			cg = cg->cg_parent;
1007 			if (cg == NULL)
1008 				return (1);
1009 			continue;
1010 		}
1011 		steal = TDQ_CPU(cpu);
1012 		/*
1013 		 * The data returned by sched_highest() is stale and
1014 		 * the chosen CPU no longer has an eligible thread.
1015 		 *
1016 		 * Testing this ahead of tdq_lock_pair() only catches
1017 		 * this situation about 20% of the time on an 8 core
1018 		 * 16 thread Ryzen 7, but it still helps performance.
1019 		 */
1020 		if (steal->tdq_load < steal_thresh ||
1021 		    steal->tdq_transferable == 0)
1022 			goto restart;
1023 		tdq_lock_pair(tdq, steal);
1024 		/*
1025 		 * We were assigned a thread while waiting for the locks.
1026 		 * Switch to it now instead of stealing a thread.
1027 		 */
1028 		if (tdq->tdq_load)
1029 			break;
1030 		/*
1031 		 * The data returned by sched_highest() is stale and
1032 		 * the chosen CPU no longer has an eligible thread, or
1033 		 * we were preempted and the CPU loading info may be out
1034 		 * of date.  The latter is rare.  In either case restart
1035 		 * the search.
1036 		 */
1037 		if (steal->tdq_load < steal_thresh ||
1038 		    steal->tdq_transferable == 0 ||
1039 		    switchcnt != tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt) {
1040 			tdq_unlock_pair(tdq, steal);
1041 			goto restart;
1042 		}
1043 		/*
1044 		 * Steal the thread and switch to it.
1045 		 */
1046 		if (tdq_move(steal, tdq) != NULL)
1047 			break;
1048 		/*
1049 		 * We failed to acquire a thread even though it looked
1050 		 * like one was available.  This could be due to affinity
1051 		 * restrictions or for other reasons.  Loop again after
1052 		 * removing this CPU from the set.  The restart logic
1053 		 * above does not restore this CPU to the set due to the
1054 		 * likelyhood of failing here again.
1055 		 */
1056 		CPU_CLR(cpu, &mask);
1057 		tdq_unlock_pair(tdq, steal);
1058 	}
1059 	TDQ_UNLOCK(steal);
1060 	mi_switch(SW_VOL | SWT_IDLE);
1061 	return (0);
1062 }
1063 
1064 /*
1065  * Notify a remote cpu of new work.  Sends an IPI if criteria are met.
1066  */
1067 static void
1068 tdq_notify(struct tdq *tdq, struct thread *td)
1069 {
1070 	struct thread *ctd;
1071 	int pri;
1072 	int cpu;
1073 
1074 	if (tdq->tdq_owepreempt)
1075 		return;
1076 	cpu = td_get_sched(td)->ts_cpu;
1077 	pri = td->td_priority;
1078 	ctd = pcpu_find(cpu)->pc_curthread;
1079 	if (!sched_shouldpreempt(pri, ctd->td_priority, 1))
1080 		return;
1081 
1082 	/*
1083 	 * Make sure that our caller's earlier update to tdq_load is
1084 	 * globally visible before we read tdq_cpu_idle.  Idle thread
1085 	 * accesses both of them without locks, and the order is important.
1086 	 */
1087 	atomic_thread_fence_seq_cst();
1088 
1089 	if (TD_IS_IDLETHREAD(ctd)) {
1090 		/*
1091 		 * If the MD code has an idle wakeup routine try that before
1092 		 * falling back to IPI.
1093 		 */
1094 		if (!tdq->tdq_cpu_idle || cpu_idle_wakeup(cpu))
1095 			return;
1096 	}
1097 
1098 	/*
1099 	 * The run queues have been updated, so any switch on the remote CPU
1100 	 * will satisfy the preemption request.
1101 	 */
1102 	tdq->tdq_owepreempt = 1;
1103 	ipi_cpu(cpu, IPI_PREEMPT);
1104 }
1105 
1106 /*
1107  * Steals load from a timeshare queue.  Honors the rotating queue head
1108  * index.
1109  */
1110 static struct thread *
1111 runq_steal_from(struct runq *rq, int cpu, u_char start)
1112 {
1113 	struct rqbits *rqb;
1114 	struct rqhead *rqh;
1115 	struct thread *td, *first;
1116 	int bit;
1117 	int i;
1118 
1119 	rqb = &rq->rq_status;
1120 	bit = start & (RQB_BPW -1);
1121 	first = NULL;
1122 again:
1123 	for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
1124 		if (rqb->rqb_bits[i] == 0)
1125 			continue;
1126 		if (bit == 0)
1127 			bit = RQB_FFS(rqb->rqb_bits[i]);
1128 		for (; bit < RQB_BPW; bit++) {
1129 			if ((rqb->rqb_bits[i] & (1ul << bit)) == 0)
1130 				continue;
1131 			rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)];
1132 			TAILQ_FOREACH(td, rqh, td_runq) {
1133 				if (first && THREAD_CAN_MIGRATE(td) &&
1134 				    THREAD_CAN_SCHED(td, cpu))
1135 					return (td);
1136 				first = td;
1137 			}
1138 		}
1139 	}
1140 	if (start != 0) {
1141 		start = 0;
1142 		goto again;
1143 	}
1144 
1145 	if (first && THREAD_CAN_MIGRATE(first) &&
1146 	    THREAD_CAN_SCHED(first, cpu))
1147 		return (first);
1148 	return (NULL);
1149 }
1150 
1151 /*
1152  * Steals load from a standard linear queue.
1153  */
1154 static struct thread *
1155 runq_steal(struct runq *rq, int cpu)
1156 {
1157 	struct rqhead *rqh;
1158 	struct rqbits *rqb;
1159 	struct thread *td;
1160 	int word;
1161 	int bit;
1162 
1163 	rqb = &rq->rq_status;
1164 	for (word = 0; word < RQB_LEN; word++) {
1165 		if (rqb->rqb_bits[word] == 0)
1166 			continue;
1167 		for (bit = 0; bit < RQB_BPW; bit++) {
1168 			if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
1169 				continue;
1170 			rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
1171 			TAILQ_FOREACH(td, rqh, td_runq)
1172 				if (THREAD_CAN_MIGRATE(td) &&
1173 				    THREAD_CAN_SCHED(td, cpu))
1174 					return (td);
1175 		}
1176 	}
1177 	return (NULL);
1178 }
1179 
1180 /*
1181  * Attempt to steal a thread in priority order from a thread queue.
1182  */
1183 static struct thread *
1184 tdq_steal(struct tdq *tdq, int cpu)
1185 {
1186 	struct thread *td;
1187 
1188 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
1189 	if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL)
1190 		return (td);
1191 	if ((td = runq_steal_from(&tdq->tdq_timeshare,
1192 	    cpu, tdq->tdq_ridx)) != NULL)
1193 		return (td);
1194 	return (runq_steal(&tdq->tdq_idle, cpu));
1195 }
1196 
1197 /*
1198  * Sets the thread lock and ts_cpu to match the requested cpu.  Unlocks the
1199  * current lock and returns with the assigned queue locked.
1200  */
1201 static inline struct tdq *
1202 sched_setcpu(struct thread *td, int cpu, int flags)
1203 {
1204 
1205 	struct tdq *tdq;
1206 	struct mtx *mtx;
1207 
1208 	THREAD_LOCK_ASSERT(td, MA_OWNED);
1209 	tdq = TDQ_CPU(cpu);
1210 	td_get_sched(td)->ts_cpu = cpu;
1211 	/*
1212 	 * If the lock matches just return the queue.
1213 	 */
1214 	if (td->td_lock == TDQ_LOCKPTR(tdq)) {
1215 		KASSERT((flags & SRQ_HOLD) == 0,
1216 		    ("sched_setcpu: Invalid lock for SRQ_HOLD"));
1217 		return (tdq);
1218 	}
1219 
1220 	/*
1221 	 * The hard case, migration, we need to block the thread first to
1222 	 * prevent order reversals with other cpus locks.
1223 	 */
1224 	spinlock_enter();
1225 	mtx = thread_lock_block(td);
1226 	if ((flags & SRQ_HOLD) == 0)
1227 		mtx_unlock_spin(mtx);
1228 	TDQ_LOCK(tdq);
1229 	thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
1230 	spinlock_exit();
1231 	return (tdq);
1232 }
1233 
1234 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding");
1235 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity");
1236 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity");
1237 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load");
1238 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu");
1239 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration");
1240 
1241 static int
1242 sched_pickcpu(struct thread *td, int flags)
1243 {
1244 	struct cpu_group *cg, *ccg;
1245 	struct td_sched *ts;
1246 	struct tdq *tdq;
1247 	cpuset_t mask;
1248 	int cpu, pri, self, intr;
1249 
1250 	self = PCPU_GET(cpuid);
1251 	ts = td_get_sched(td);
1252 	KASSERT(!CPU_ABSENT(ts->ts_cpu), ("sched_pickcpu: Start scheduler on "
1253 	    "absent CPU %d for thread %s.", ts->ts_cpu, td->td_name));
1254 	if (smp_started == 0)
1255 		return (self);
1256 	/*
1257 	 * Don't migrate a running thread from sched_switch().
1258 	 */
1259 	if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td))
1260 		return (ts->ts_cpu);
1261 	/*
1262 	 * Prefer to run interrupt threads on the processors that generate
1263 	 * the interrupt.
1264 	 */
1265 	if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
1266 	    curthread->td_intr_nesting_level) {
1267 		tdq = TDQ_SELF();
1268 		if (tdq->tdq_lowpri >= PRI_MIN_IDLE) {
1269 			SCHED_STAT_INC(pickcpu_idle_affinity);
1270 			return (self);
1271 		}
1272 		ts->ts_cpu = self;
1273 		intr = 1;
1274 		cg = tdq->tdq_cg;
1275 		goto llc;
1276 	} else {
1277 		intr = 0;
1278 		tdq = TDQ_CPU(ts->ts_cpu);
1279 		cg = tdq->tdq_cg;
1280 	}
1281 	/*
1282 	 * If the thread can run on the last cpu and the affinity has not
1283 	 * expired and it is idle, run it there.
1284 	 */
1285 	if (THREAD_CAN_SCHED(td, ts->ts_cpu) &&
1286 	    tdq->tdq_lowpri >= PRI_MIN_IDLE &&
1287 	    SCHED_AFFINITY(ts, CG_SHARE_L2)) {
1288 		if (cg->cg_flags & CG_FLAG_THREAD) {
1289 			/* Check all SMT threads for being idle. */
1290 			for (cpu = CPU_FFS(&cg->cg_mask) - 1; ; cpu++) {
1291 				if (CPU_ISSET(cpu, &cg->cg_mask) &&
1292 				    TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE)
1293 					break;
1294 				if (cpu >= mp_maxid) {
1295 					SCHED_STAT_INC(pickcpu_idle_affinity);
1296 					return (ts->ts_cpu);
1297 				}
1298 			}
1299 		} else {
1300 			SCHED_STAT_INC(pickcpu_idle_affinity);
1301 			return (ts->ts_cpu);
1302 		}
1303 	}
1304 llc:
1305 	/*
1306 	 * Search for the last level cache CPU group in the tree.
1307 	 * Skip SMT, identical groups and caches with expired affinity.
1308 	 * Interrupt threads affinity is explicit and never expires.
1309 	 */
1310 	for (ccg = NULL; cg != NULL; cg = cg->cg_parent) {
1311 		if (cg->cg_flags & CG_FLAG_THREAD)
1312 			continue;
1313 		if (cg->cg_children == 1 || cg->cg_count == 1)
1314 			continue;
1315 		if (cg->cg_level == CG_SHARE_NONE ||
1316 		    (!intr && !SCHED_AFFINITY(ts, cg->cg_level)))
1317 			continue;
1318 		ccg = cg;
1319 	}
1320 	/* Found LLC shared by all CPUs, so do a global search. */
1321 	if (ccg == cpu_top)
1322 		ccg = NULL;
1323 	cpu = -1;
1324 	mask = td->td_cpuset->cs_mask;
1325 	pri = td->td_priority;
1326 	/*
1327 	 * Try hard to keep interrupts within found LLC.  Search the LLC for
1328 	 * the least loaded CPU we can run now.  For NUMA systems it should
1329 	 * be within target domain, and it also reduces scheduling overhead.
1330 	 */
1331 	if (ccg != NULL && intr) {
1332 		cpu = sched_lowest(ccg, mask, pri, INT_MAX, ts->ts_cpu);
1333 		if (cpu >= 0)
1334 			SCHED_STAT_INC(pickcpu_intrbind);
1335 	} else
1336 	/* Search the LLC for the least loaded idle CPU we can run now. */
1337 	if (ccg != NULL) {
1338 		cpu = sched_lowest(ccg, mask, max(pri, PRI_MAX_TIMESHARE),
1339 		    INT_MAX, ts->ts_cpu);
1340 		if (cpu >= 0)
1341 			SCHED_STAT_INC(pickcpu_affinity);
1342 	}
1343 	/* Search globally for the least loaded CPU we can run now. */
1344 	if (cpu < 0) {
1345 		cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu);
1346 		if (cpu >= 0)
1347 			SCHED_STAT_INC(pickcpu_lowest);
1348 	}
1349 	/* Search globally for the least loaded CPU. */
1350 	if (cpu < 0) {
1351 		cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu);
1352 		if (cpu >= 0)
1353 			SCHED_STAT_INC(pickcpu_lowest);
1354 	}
1355 	KASSERT(cpu >= 0, ("sched_pickcpu: Failed to find a cpu."));
1356 	KASSERT(!CPU_ABSENT(cpu), ("sched_pickcpu: Picked absent CPU %d.", cpu));
1357 	/*
1358 	 * Compare the lowest loaded cpu to current cpu.
1359 	 */
1360 	tdq = TDQ_CPU(cpu);
1361 	if (THREAD_CAN_SCHED(td, self) && TDQ_SELF()->tdq_lowpri > pri &&
1362 	    tdq->tdq_lowpri < PRI_MIN_IDLE &&
1363 	    TDQ_SELF()->tdq_load <= tdq->tdq_load + 1) {
1364 		SCHED_STAT_INC(pickcpu_local);
1365 		cpu = self;
1366 	}
1367 	if (cpu != ts->ts_cpu)
1368 		SCHED_STAT_INC(pickcpu_migration);
1369 	return (cpu);
1370 }
1371 #endif
1372 
1373 /*
1374  * Pick the highest priority task we have and return it.
1375  */
1376 static struct thread *
1377 tdq_choose(struct tdq *tdq)
1378 {
1379 	struct thread *td;
1380 
1381 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
1382 	td = runq_choose(&tdq->tdq_realtime);
1383 	if (td != NULL)
1384 		return (td);
1385 	td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
1386 	if (td != NULL) {
1387 		KASSERT(td->td_priority >= PRI_MIN_BATCH,
1388 		    ("tdq_choose: Invalid priority on timeshare queue %d",
1389 		    td->td_priority));
1390 		return (td);
1391 	}
1392 	td = runq_choose(&tdq->tdq_idle);
1393 	if (td != NULL) {
1394 		KASSERT(td->td_priority >= PRI_MIN_IDLE,
1395 		    ("tdq_choose: Invalid priority on idle queue %d",
1396 		    td->td_priority));
1397 		return (td);
1398 	}
1399 
1400 	return (NULL);
1401 }
1402 
1403 /*
1404  * Initialize a thread queue.
1405  */
1406 static void
1407 tdq_setup(struct tdq *tdq, int id)
1408 {
1409 
1410 	if (bootverbose)
1411 		printf("ULE: setup cpu %d\n", id);
1412 	runq_init(&tdq->tdq_realtime);
1413 	runq_init(&tdq->tdq_timeshare);
1414 	runq_init(&tdq->tdq_idle);
1415 	tdq->tdq_id = id;
1416 	snprintf(tdq->tdq_name, sizeof(tdq->tdq_name),
1417 	    "sched lock %d", (int)TDQ_ID(tdq));
1418 	mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock", MTX_SPIN);
1419 #ifdef KTR
1420 	snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname),
1421 	    "CPU %d load", (int)TDQ_ID(tdq));
1422 #endif
1423 }
1424 
1425 #ifdef SMP
1426 static void
1427 sched_setup_smp(void)
1428 {
1429 	struct tdq *tdq;
1430 	int i;
1431 
1432 	cpu_top = smp_topo();
1433 	CPU_FOREACH(i) {
1434 		tdq = DPCPU_ID_PTR(i, tdq);
1435 		tdq_setup(tdq, i);
1436 		tdq->tdq_cg = smp_topo_find(cpu_top, i);
1437 		if (tdq->tdq_cg == NULL)
1438 			panic("Can't find cpu group for %d\n", i);
1439 	}
1440 	PCPU_SET(sched, DPCPU_PTR(tdq));
1441 	balance_tdq = TDQ_SELF();
1442 }
1443 #endif
1444 
1445 /*
1446  * Setup the thread queues and initialize the topology based on MD
1447  * information.
1448  */
1449 static void
1450 sched_setup(void *dummy)
1451 {
1452 	struct tdq *tdq;
1453 
1454 #ifdef SMP
1455 	sched_setup_smp();
1456 #else
1457 	tdq_setup(TDQ_SELF(), 0);
1458 #endif
1459 	tdq = TDQ_SELF();
1460 
1461 	/* Add thread0's load since it's running. */
1462 	TDQ_LOCK(tdq);
1463 	thread0.td_lock = TDQ_LOCKPTR(tdq);
1464 	tdq_load_add(tdq, &thread0);
1465 	tdq->tdq_lowpri = thread0.td_priority;
1466 	TDQ_UNLOCK(tdq);
1467 }
1468 
1469 /*
1470  * This routine determines time constants after stathz and hz are setup.
1471  */
1472 /* ARGSUSED */
1473 static void
1474 sched_initticks(void *dummy)
1475 {
1476 	int incr;
1477 
1478 	realstathz = stathz ? stathz : hz;
1479 	sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR;
1480 	sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
1481 	hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
1482 	    realstathz);
1483 
1484 	/*
1485 	 * tickincr is shifted out by 10 to avoid rounding errors due to
1486 	 * hz not being evenly divisible by stathz on all platforms.
1487 	 */
1488 	incr = (hz << SCHED_TICK_SHIFT) / realstathz;
1489 	/*
1490 	 * This does not work for values of stathz that are more than
1491 	 * 1 << SCHED_TICK_SHIFT * hz.  In practice this does not happen.
1492 	 */
1493 	if (incr == 0)
1494 		incr = 1;
1495 	tickincr = incr;
1496 #ifdef SMP
1497 	/*
1498 	 * Set the default balance interval now that we know
1499 	 * what realstathz is.
1500 	 */
1501 	balance_interval = realstathz;
1502 	balance_ticks = balance_interval;
1503 	affinity = SCHED_AFFINITY_DEFAULT;
1504 #endif
1505 	if (sched_idlespinthresh < 0)
1506 		sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz;
1507 }
1508 
1509 /*
1510  * This is the core of the interactivity algorithm.  Determines a score based
1511  * on past behavior.  It is the ratio of sleep time to run time scaled to
1512  * a [0, 100] integer.  This is the voluntary sleep time of a process, which
1513  * differs from the cpu usage because it does not account for time spent
1514  * waiting on a run-queue.  Would be prettier if we had floating point.
1515  *
1516  * When a thread's sleep time is greater than its run time the
1517  * calculation is:
1518  *
1519  *                           scaling factor
1520  * interactivity score =  ---------------------
1521  *                        sleep time / run time
1522  *
1523  *
1524  * When a thread's run time is greater than its sleep time the
1525  * calculation is:
1526  *
1527  *                           scaling factor
1528  * interactivity score =  ---------------------    + scaling factor
1529  *                        run time / sleep time
1530  */
1531 static int
1532 sched_interact_score(struct thread *td)
1533 {
1534 	struct td_sched *ts;
1535 	int div;
1536 
1537 	ts = td_get_sched(td);
1538 	/*
1539 	 * The score is only needed if this is likely to be an interactive
1540 	 * task.  Don't go through the expense of computing it if there's
1541 	 * no chance.
1542 	 */
1543 	if (sched_interact <= SCHED_INTERACT_HALF &&
1544 		ts->ts_runtime >= ts->ts_slptime)
1545 			return (SCHED_INTERACT_HALF);
1546 
1547 	if (ts->ts_runtime > ts->ts_slptime) {
1548 		div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
1549 		return (SCHED_INTERACT_HALF +
1550 		    (SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
1551 	}
1552 	if (ts->ts_slptime > ts->ts_runtime) {
1553 		div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
1554 		return (ts->ts_runtime / div);
1555 	}
1556 	/* runtime == slptime */
1557 	if (ts->ts_runtime)
1558 		return (SCHED_INTERACT_HALF);
1559 
1560 	/*
1561 	 * This can happen if slptime and runtime are 0.
1562 	 */
1563 	return (0);
1564 
1565 }
1566 
1567 /*
1568  * Scale the scheduling priority according to the "interactivity" of this
1569  * process.
1570  */
1571 static void
1572 sched_priority(struct thread *td)
1573 {
1574 	int score;
1575 	int pri;
1576 
1577 	if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
1578 		return;
1579 	/*
1580 	 * If the score is interactive we place the thread in the realtime
1581 	 * queue with a priority that is less than kernel and interrupt
1582 	 * priorities.  These threads are not subject to nice restrictions.
1583 	 *
1584 	 * Scores greater than this are placed on the normal timeshare queue
1585 	 * where the priority is partially decided by the most recent cpu
1586 	 * utilization and the rest is decided by nice value.
1587 	 *
1588 	 * The nice value of the process has a linear effect on the calculated
1589 	 * score.  Negative nice values make it easier for a thread to be
1590 	 * considered interactive.
1591 	 */
1592 	score = imax(0, sched_interact_score(td) + td->td_proc->p_nice);
1593 	if (score < sched_interact) {
1594 		pri = PRI_MIN_INTERACT;
1595 		pri += ((PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) /
1596 		    sched_interact) * score;
1597 		KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT,
1598 		    ("sched_priority: invalid interactive priority %d score %d",
1599 		    pri, score));
1600 	} else {
1601 		pri = SCHED_PRI_MIN;
1602 		if (td_get_sched(td)->ts_ticks)
1603 			pri += min(SCHED_PRI_TICKS(td_get_sched(td)),
1604 			    SCHED_PRI_RANGE - 1);
1605 		pri += SCHED_PRI_NICE(td->td_proc->p_nice);
1606 		KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH,
1607 		    ("sched_priority: invalid priority %d: nice %d, "
1608 		    "ticks %d ftick %d ltick %d tick pri %d",
1609 		    pri, td->td_proc->p_nice, td_get_sched(td)->ts_ticks,
1610 		    td_get_sched(td)->ts_ftick, td_get_sched(td)->ts_ltick,
1611 		    SCHED_PRI_TICKS(td_get_sched(td))));
1612 	}
1613 	sched_user_prio(td, pri);
1614 
1615 	return;
1616 }
1617 
1618 /*
1619  * This routine enforces a maximum limit on the amount of scheduling history
1620  * kept.  It is called after either the slptime or runtime is adjusted.  This
1621  * function is ugly due to integer math.
1622  */
1623 static void
1624 sched_interact_update(struct thread *td)
1625 {
1626 	struct td_sched *ts;
1627 	u_int sum;
1628 
1629 	ts = td_get_sched(td);
1630 	sum = ts->ts_runtime + ts->ts_slptime;
1631 	if (sum < SCHED_SLP_RUN_MAX)
1632 		return;
1633 	/*
1634 	 * This only happens from two places:
1635 	 * 1) We have added an unusual amount of run time from fork_exit.
1636 	 * 2) We have added an unusual amount of sleep time from sched_sleep().
1637 	 */
1638 	if (sum > SCHED_SLP_RUN_MAX * 2) {
1639 		if (ts->ts_runtime > ts->ts_slptime) {
1640 			ts->ts_runtime = SCHED_SLP_RUN_MAX;
1641 			ts->ts_slptime = 1;
1642 		} else {
1643 			ts->ts_slptime = SCHED_SLP_RUN_MAX;
1644 			ts->ts_runtime = 1;
1645 		}
1646 		return;
1647 	}
1648 	/*
1649 	 * If we have exceeded by more than 1/5th then the algorithm below
1650 	 * will not bring us back into range.  Dividing by two here forces
1651 	 * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
1652 	 */
1653 	if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
1654 		ts->ts_runtime /= 2;
1655 		ts->ts_slptime /= 2;
1656 		return;
1657 	}
1658 	ts->ts_runtime = (ts->ts_runtime / 5) * 4;
1659 	ts->ts_slptime = (ts->ts_slptime / 5) * 4;
1660 }
1661 
1662 /*
1663  * Scale back the interactivity history when a child thread is created.  The
1664  * history is inherited from the parent but the thread may behave totally
1665  * differently.  For example, a shell spawning a compiler process.  We want
1666  * to learn that the compiler is behaving badly very quickly.
1667  */
1668 static void
1669 sched_interact_fork(struct thread *td)
1670 {
1671 	struct td_sched *ts;
1672 	int ratio;
1673 	int sum;
1674 
1675 	ts = td_get_sched(td);
1676 	sum = ts->ts_runtime + ts->ts_slptime;
1677 	if (sum > SCHED_SLP_RUN_FORK) {
1678 		ratio = sum / SCHED_SLP_RUN_FORK;
1679 		ts->ts_runtime /= ratio;
1680 		ts->ts_slptime /= ratio;
1681 	}
1682 }
1683 
1684 /*
1685  * Called from proc0_init() to setup the scheduler fields.
1686  */
1687 void
1688 schedinit(void)
1689 {
1690 	struct td_sched *ts0;
1691 
1692 	/*
1693 	 * Set up the scheduler specific parts of thread0.
1694 	 */
1695 	ts0 = td_get_sched(&thread0);
1696 	ts0->ts_ltick = ticks;
1697 	ts0->ts_ftick = ticks;
1698 	ts0->ts_slice = 0;
1699 	ts0->ts_cpu = curcpu;	/* set valid CPU number */
1700 }
1701 
1702 /*
1703  * This is only somewhat accurate since given many processes of the same
1704  * priority they will switch when their slices run out, which will be
1705  * at most sched_slice stathz ticks.
1706  */
1707 int
1708 sched_rr_interval(void)
1709 {
1710 
1711 	/* Convert sched_slice from stathz to hz. */
1712 	return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
1713 }
1714 
1715 /*
1716  * Update the percent cpu tracking information when it is requested or
1717  * the total history exceeds the maximum.  We keep a sliding history of
1718  * tick counts that slowly decays.  This is less precise than the 4BSD
1719  * mechanism since it happens with less regular and frequent events.
1720  */
1721 static void
1722 sched_pctcpu_update(struct td_sched *ts, int run)
1723 {
1724 	int t = ticks;
1725 
1726 	/*
1727 	 * The signed difference may be negative if the thread hasn't run for
1728 	 * over half of the ticks rollover period.
1729 	 */
1730 	if ((u_int)(t - ts->ts_ltick) >= SCHED_TICK_TARG) {
1731 		ts->ts_ticks = 0;
1732 		ts->ts_ftick = t - SCHED_TICK_TARG;
1733 	} else if (t - ts->ts_ftick >= SCHED_TICK_MAX) {
1734 		ts->ts_ticks = (ts->ts_ticks / (ts->ts_ltick - ts->ts_ftick)) *
1735 		    (ts->ts_ltick - (t - SCHED_TICK_TARG));
1736 		ts->ts_ftick = t - SCHED_TICK_TARG;
1737 	}
1738 	if (run)
1739 		ts->ts_ticks += (t - ts->ts_ltick) << SCHED_TICK_SHIFT;
1740 	ts->ts_ltick = t;
1741 }
1742 
1743 /*
1744  * Adjust the priority of a thread.  Move it to the appropriate run-queue
1745  * if necessary.  This is the back-end for several priority related
1746  * functions.
1747  */
1748 static void
1749 sched_thread_priority(struct thread *td, u_char prio)
1750 {
1751 	struct td_sched *ts;
1752 	struct tdq *tdq;
1753 	int oldpri;
1754 
1755 	KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio",
1756 	    "prio:%d", td->td_priority, "new prio:%d", prio,
1757 	    KTR_ATTR_LINKED, sched_tdname(curthread));
1758 	SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio);
1759 	if (td != curthread && prio < td->td_priority) {
1760 		KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
1761 		    "lend prio", "prio:%d", td->td_priority, "new prio:%d",
1762 		    prio, KTR_ATTR_LINKED, sched_tdname(td));
1763 		SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio,
1764 		    curthread);
1765 	}
1766 	ts = td_get_sched(td);
1767 	THREAD_LOCK_ASSERT(td, MA_OWNED);
1768 	if (td->td_priority == prio)
1769 		return;
1770 	/*
1771 	 * If the priority has been elevated due to priority
1772 	 * propagation, we may have to move ourselves to a new
1773 	 * queue.  This could be optimized to not re-add in some
1774 	 * cases.
1775 	 */
1776 	if (TD_ON_RUNQ(td) && prio < td->td_priority) {
1777 		sched_rem(td);
1778 		td->td_priority = prio;
1779 		sched_add(td, SRQ_BORROWING | SRQ_HOLDTD);
1780 		return;
1781 	}
1782 	/*
1783 	 * If the thread is currently running we may have to adjust the lowpri
1784 	 * information so other cpus are aware of our current priority.
1785 	 */
1786 	if (TD_IS_RUNNING(td)) {
1787 		tdq = TDQ_CPU(ts->ts_cpu);
1788 		oldpri = td->td_priority;
1789 		td->td_priority = prio;
1790 		if (prio < tdq->tdq_lowpri)
1791 			tdq->tdq_lowpri = prio;
1792 		else if (tdq->tdq_lowpri == oldpri)
1793 			tdq_setlowpri(tdq, td);
1794 		return;
1795 	}
1796 	td->td_priority = prio;
1797 }
1798 
1799 /*
1800  * Update a thread's priority when it is lent another thread's
1801  * priority.
1802  */
1803 void
1804 sched_lend_prio(struct thread *td, u_char prio)
1805 {
1806 
1807 	td->td_flags |= TDF_BORROWING;
1808 	sched_thread_priority(td, prio);
1809 }
1810 
1811 /*
1812  * Restore a thread's priority when priority propagation is
1813  * over.  The prio argument is the minimum priority the thread
1814  * needs to have to satisfy other possible priority lending
1815  * requests.  If the thread's regular priority is less
1816  * important than prio, the thread will keep a priority boost
1817  * of prio.
1818  */
1819 void
1820 sched_unlend_prio(struct thread *td, u_char prio)
1821 {
1822 	u_char base_pri;
1823 
1824 	if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
1825 	    td->td_base_pri <= PRI_MAX_TIMESHARE)
1826 		base_pri = td->td_user_pri;
1827 	else
1828 		base_pri = td->td_base_pri;
1829 	if (prio >= base_pri) {
1830 		td->td_flags &= ~TDF_BORROWING;
1831 		sched_thread_priority(td, base_pri);
1832 	} else
1833 		sched_lend_prio(td, prio);
1834 }
1835 
1836 /*
1837  * Standard entry for setting the priority to an absolute value.
1838  */
1839 void
1840 sched_prio(struct thread *td, u_char prio)
1841 {
1842 	u_char oldprio;
1843 
1844 	/* First, update the base priority. */
1845 	td->td_base_pri = prio;
1846 
1847 	/*
1848 	 * If the thread is borrowing another thread's priority, don't
1849 	 * ever lower the priority.
1850 	 */
1851 	if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
1852 		return;
1853 
1854 	/* Change the real priority. */
1855 	oldprio = td->td_priority;
1856 	sched_thread_priority(td, prio);
1857 
1858 	/*
1859 	 * If the thread is on a turnstile, then let the turnstile update
1860 	 * its state.
1861 	 */
1862 	if (TD_ON_LOCK(td) && oldprio != prio)
1863 		turnstile_adjust(td, oldprio);
1864 }
1865 
1866 /*
1867  * Set the base user priority, does not effect current running priority.
1868  */
1869 void
1870 sched_user_prio(struct thread *td, u_char prio)
1871 {
1872 
1873 	td->td_base_user_pri = prio;
1874 	if (td->td_lend_user_pri <= prio)
1875 		return;
1876 	td->td_user_pri = prio;
1877 }
1878 
1879 void
1880 sched_lend_user_prio(struct thread *td, u_char prio)
1881 {
1882 
1883 	THREAD_LOCK_ASSERT(td, MA_OWNED);
1884 	td->td_lend_user_pri = prio;
1885 	td->td_user_pri = min(prio, td->td_base_user_pri);
1886 	if (td->td_priority > td->td_user_pri)
1887 		sched_prio(td, td->td_user_pri);
1888 	else if (td->td_priority != td->td_user_pri)
1889 		td->td_flags |= TDF_NEEDRESCHED;
1890 }
1891 
1892 /*
1893  * Like the above but first check if there is anything to do.
1894  */
1895 void
1896 sched_lend_user_prio_cond(struct thread *td, u_char prio)
1897 {
1898 
1899 	if (td->td_lend_user_pri != prio)
1900 		goto lend;
1901 	if (td->td_user_pri != min(prio, td->td_base_user_pri))
1902 		goto lend;
1903 	if (td->td_priority != td->td_user_pri)
1904 		goto lend;
1905 	return;
1906 
1907 lend:
1908 	thread_lock(td);
1909 	sched_lend_user_prio(td, prio);
1910 	thread_unlock(td);
1911 }
1912 
1913 #ifdef SMP
1914 /*
1915  * This tdq is about to idle.  Try to steal a thread from another CPU before
1916  * choosing the idle thread.
1917  */
1918 static void
1919 tdq_trysteal(struct tdq *tdq)
1920 {
1921 	struct cpu_group *cg;
1922 	struct tdq *steal;
1923 	cpuset_t mask;
1924 	int cpu, i;
1925 
1926 	if (smp_started == 0 || trysteal_limit == 0 || tdq->tdq_cg == NULL)
1927 		return;
1928 	CPU_FILL(&mask);
1929 	CPU_CLR(PCPU_GET(cpuid), &mask);
1930 	/* We don't want to be preempted while we're iterating. */
1931 	spinlock_enter();
1932 	TDQ_UNLOCK(tdq);
1933 	for (i = 1, cg = tdq->tdq_cg; ; ) {
1934 		cpu = sched_highest(cg, mask, steal_thresh);
1935 		/*
1936 		 * If a thread was added while interrupts were disabled don't
1937 		 * steal one here.
1938 		 */
1939 		if (tdq->tdq_load > 0) {
1940 			TDQ_LOCK(tdq);
1941 			break;
1942 		}
1943 		if (cpu == -1) {
1944 			i++;
1945 			cg = cg->cg_parent;
1946 			if (cg == NULL || i > trysteal_limit) {
1947 				TDQ_LOCK(tdq);
1948 				break;
1949 			}
1950 			continue;
1951 		}
1952 		steal = TDQ_CPU(cpu);
1953 		/*
1954 		 * The data returned by sched_highest() is stale and
1955                  * the chosen CPU no longer has an eligible thread.
1956 		 */
1957 		if (steal->tdq_load < steal_thresh ||
1958 		    steal->tdq_transferable == 0)
1959 			continue;
1960 		tdq_lock_pair(tdq, steal);
1961 		/*
1962 		 * If we get to this point, unconditonally exit the loop
1963 		 * to bound the time spent in the critcal section.
1964 		 *
1965 		 * If a thread was added while interrupts were disabled don't
1966 		 * steal one here.
1967 		 */
1968 		if (tdq->tdq_load > 0) {
1969 			TDQ_UNLOCK(steal);
1970 			break;
1971 		}
1972 		/*
1973 		 * The data returned by sched_highest() is stale and
1974                  * the chosen CPU no longer has an eligible thread.
1975 		 */
1976 		if (steal->tdq_load < steal_thresh ||
1977 		    steal->tdq_transferable == 0) {
1978 			TDQ_UNLOCK(steal);
1979 			break;
1980 		}
1981 		/*
1982 		 * If we fail to acquire one due to affinity restrictions,
1983 		 * bail out and let the idle thread to a more complete search
1984 		 * outside of a critical section.
1985 		 */
1986 		if (tdq_move(steal, tdq) == NULL) {
1987 			TDQ_UNLOCK(steal);
1988 			break;
1989 		}
1990 		TDQ_UNLOCK(steal);
1991 		break;
1992 	}
1993 	spinlock_exit();
1994 }
1995 #endif
1996 
1997 /*
1998  * Handle migration from sched_switch().  This happens only for
1999  * cpu binding.
2000  */
2001 static struct mtx *
2002 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
2003 {
2004 	struct tdq *tdn;
2005 
2006 	KASSERT(THREAD_CAN_MIGRATE(td) ||
2007 	    (td_get_sched(td)->ts_flags & TSF_BOUND) != 0,
2008 	    ("Thread %p shouldn't migrate", td));
2009 	KASSERT(!CPU_ABSENT(td_get_sched(td)->ts_cpu), ("sched_switch_migrate: "
2010 	    "thread %s queued on absent CPU %d.", td->td_name,
2011 	    td_get_sched(td)->ts_cpu));
2012 	tdn = TDQ_CPU(td_get_sched(td)->ts_cpu);
2013 #ifdef SMP
2014 	tdq_load_rem(tdq, td);
2015 	/*
2016 	 * Do the lock dance required to avoid LOR.  We have an
2017 	 * extra spinlock nesting from sched_switch() which will
2018 	 * prevent preemption while we're holding neither run-queue lock.
2019 	 */
2020 	TDQ_UNLOCK(tdq);
2021 	TDQ_LOCK(tdn);
2022 	tdq_add(tdn, td, flags);
2023 	tdq_notify(tdn, td);
2024 	TDQ_UNLOCK(tdn);
2025 	TDQ_LOCK(tdq);
2026 #endif
2027 	return (TDQ_LOCKPTR(tdn));
2028 }
2029 
2030 /*
2031  * thread_lock_unblock() that does not assume td_lock is blocked.
2032  */
2033 static inline void
2034 thread_unblock_switch(struct thread *td, struct mtx *mtx)
2035 {
2036 	atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock,
2037 	    (uintptr_t)mtx);
2038 }
2039 
2040 /*
2041  * Switch threads.  This function has to handle threads coming in while
2042  * blocked for some reason, running, or idle.  It also must deal with
2043  * migrating a thread from one queue to another as running threads may
2044  * be assigned elsewhere via binding.
2045  */
2046 void
2047 sched_switch(struct thread *td, int flags)
2048 {
2049 	struct thread *newtd;
2050 	struct tdq *tdq;
2051 	struct td_sched *ts;
2052 	struct mtx *mtx;
2053 	int srqflag;
2054 	int cpuid, preempted;
2055 
2056 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2057 
2058 	cpuid = PCPU_GET(cpuid);
2059 	tdq = TDQ_SELF();
2060 	ts = td_get_sched(td);
2061 	sched_pctcpu_update(ts, 1);
2062 	ts->ts_rltick = ticks;
2063 	td->td_lastcpu = td->td_oncpu;
2064 	preempted = (td->td_flags & TDF_SLICEEND) == 0 &&
2065 	    (flags & SW_PREEMPT) != 0;
2066 	td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND);
2067 	td->td_owepreempt = 0;
2068 	tdq->tdq_owepreempt = 0;
2069 	if (!TD_IS_IDLETHREAD(td))
2070 		tdq->tdq_switchcnt++;
2071 
2072 	/*
2073 	 * Always block the thread lock so we can drop the tdq lock early.
2074 	 */
2075 	mtx = thread_lock_block(td);
2076 	spinlock_enter();
2077 	if (TD_IS_IDLETHREAD(td)) {
2078 		MPASS(mtx == TDQ_LOCKPTR(tdq));
2079 		TD_SET_CAN_RUN(td);
2080 	} else if (TD_IS_RUNNING(td)) {
2081 		MPASS(mtx == TDQ_LOCKPTR(tdq));
2082 		srqflag = preempted ?
2083 		    SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
2084 		    SRQ_OURSELF|SRQ_YIELDING;
2085 #ifdef SMP
2086 		if (THREAD_CAN_MIGRATE(td) && !THREAD_CAN_SCHED(td, ts->ts_cpu))
2087 			ts->ts_cpu = sched_pickcpu(td, 0);
2088 #endif
2089 		if (ts->ts_cpu == cpuid)
2090 			tdq_runq_add(tdq, td, srqflag);
2091 		else
2092 			mtx = sched_switch_migrate(tdq, td, srqflag);
2093 	} else {
2094 		/* This thread must be going to sleep. */
2095 		if (mtx != TDQ_LOCKPTR(tdq)) {
2096 			mtx_unlock_spin(mtx);
2097 			TDQ_LOCK(tdq);
2098 		}
2099 		tdq_load_rem(tdq, td);
2100 #ifdef SMP
2101 		if (tdq->tdq_load == 0)
2102 			tdq_trysteal(tdq);
2103 #endif
2104 	}
2105 
2106 #if (KTR_COMPILE & KTR_SCHED) != 0
2107 	if (TD_IS_IDLETHREAD(td))
2108 		KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle",
2109 		    "prio:%d", td->td_priority);
2110 	else
2111 		KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td),
2112 		    "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg,
2113 		    "lockname:\"%s\"", td->td_lockname);
2114 #endif
2115 
2116 	/*
2117 	 * We enter here with the thread blocked and assigned to the
2118 	 * appropriate cpu run-queue or sleep-queue and with the current
2119 	 * thread-queue locked.
2120 	 */
2121 	TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
2122 	newtd = choosethread();
2123 	sched_pctcpu_update(td_get_sched(newtd), 0);
2124 	TDQ_UNLOCK(tdq);
2125 
2126 	/*
2127 	 * Call the MD code to switch contexts if necessary.
2128 	 */
2129 	if (td != newtd) {
2130 #ifdef	HWPMC_HOOKS
2131 		if (PMC_PROC_IS_USING_PMCS(td->td_proc))
2132 			PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
2133 #endif
2134 		SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc);
2135 
2136 #ifdef KDTRACE_HOOKS
2137 		/*
2138 		 * If DTrace has set the active vtime enum to anything
2139 		 * other than INACTIVE (0), then it should have set the
2140 		 * function to call.
2141 		 */
2142 		if (dtrace_vtime_active)
2143 			(*dtrace_vtime_switch_func)(newtd);
2144 #endif
2145 		td->td_oncpu = NOCPU;
2146 		cpu_switch(td, newtd, mtx);
2147 		cpuid = td->td_oncpu = PCPU_GET(cpuid);
2148 
2149 		SDT_PROBE0(sched, , , on__cpu);
2150 #ifdef	HWPMC_HOOKS
2151 		if (PMC_PROC_IS_USING_PMCS(td->td_proc))
2152 			PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
2153 #endif
2154 	} else {
2155 		thread_unblock_switch(td, mtx);
2156 		SDT_PROBE0(sched, , , remain__cpu);
2157 	}
2158 	KASSERT(curthread->td_md.md_spinlock_count == 1,
2159 	    ("invalid count %d", curthread->td_md.md_spinlock_count));
2160 
2161 	KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
2162 	    "prio:%d", td->td_priority);
2163 }
2164 
2165 /*
2166  * Adjust thread priorities as a result of a nice request.
2167  */
2168 void
2169 sched_nice(struct proc *p, int nice)
2170 {
2171 	struct thread *td;
2172 
2173 	PROC_LOCK_ASSERT(p, MA_OWNED);
2174 
2175 	p->p_nice = nice;
2176 	FOREACH_THREAD_IN_PROC(p, td) {
2177 		thread_lock(td);
2178 		sched_priority(td);
2179 		sched_prio(td, td->td_base_user_pri);
2180 		thread_unlock(td);
2181 	}
2182 }
2183 
2184 /*
2185  * Record the sleep time for the interactivity scorer.
2186  */
2187 void
2188 sched_sleep(struct thread *td, int prio)
2189 {
2190 
2191 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2192 
2193 	td->td_slptick = ticks;
2194 	if (TD_IS_SUSPENDED(td) || prio >= PSOCK)
2195 		td->td_flags |= TDF_CANSWAP;
2196 	if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
2197 		return;
2198 	if (static_boost == 1 && prio)
2199 		sched_prio(td, prio);
2200 	else if (static_boost && td->td_priority > static_boost)
2201 		sched_prio(td, static_boost);
2202 }
2203 
2204 /*
2205  * Schedule a thread to resume execution and record how long it voluntarily
2206  * slept.  We also update the pctcpu, interactivity, and priority.
2207  *
2208  * Requires the thread lock on entry, drops on exit.
2209  */
2210 void
2211 sched_wakeup(struct thread *td, int srqflags)
2212 {
2213 	struct td_sched *ts;
2214 	int slptick;
2215 
2216 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2217 	ts = td_get_sched(td);
2218 	td->td_flags &= ~TDF_CANSWAP;
2219 
2220 	/*
2221 	 * If we slept for more than a tick update our interactivity and
2222 	 * priority.
2223 	 */
2224 	slptick = td->td_slptick;
2225 	td->td_slptick = 0;
2226 	if (slptick && slptick != ticks) {
2227 		ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT;
2228 		sched_interact_update(td);
2229 		sched_pctcpu_update(ts, 0);
2230 	}
2231 	/*
2232 	 * Reset the slice value since we slept and advanced the round-robin.
2233 	 */
2234 	ts->ts_slice = 0;
2235 	sched_add(td, SRQ_BORING | srqflags);
2236 }
2237 
2238 /*
2239  * Penalize the parent for creating a new child and initialize the child's
2240  * priority.
2241  */
2242 void
2243 sched_fork(struct thread *td, struct thread *child)
2244 {
2245 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2246 	sched_pctcpu_update(td_get_sched(td), 1);
2247 	sched_fork_thread(td, child);
2248 	/*
2249 	 * Penalize the parent and child for forking.
2250 	 */
2251 	sched_interact_fork(child);
2252 	sched_priority(child);
2253 	td_get_sched(td)->ts_runtime += tickincr;
2254 	sched_interact_update(td);
2255 	sched_priority(td);
2256 }
2257 
2258 /*
2259  * Fork a new thread, may be within the same process.
2260  */
2261 void
2262 sched_fork_thread(struct thread *td, struct thread *child)
2263 {
2264 	struct td_sched *ts;
2265 	struct td_sched *ts2;
2266 	struct tdq *tdq;
2267 
2268 	tdq = TDQ_SELF();
2269 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2270 	/*
2271 	 * Initialize child.
2272 	 */
2273 	ts = td_get_sched(td);
2274 	ts2 = td_get_sched(child);
2275 	child->td_oncpu = NOCPU;
2276 	child->td_lastcpu = NOCPU;
2277 	child->td_lock = TDQ_LOCKPTR(tdq);
2278 	child->td_cpuset = cpuset_ref(td->td_cpuset);
2279 	child->td_domain.dr_policy = td->td_cpuset->cs_domain;
2280 	ts2->ts_cpu = ts->ts_cpu;
2281 	ts2->ts_flags = 0;
2282 	/*
2283 	 * Grab our parents cpu estimation information.
2284 	 */
2285 	ts2->ts_ticks = ts->ts_ticks;
2286 	ts2->ts_ltick = ts->ts_ltick;
2287 	ts2->ts_ftick = ts->ts_ftick;
2288 	/*
2289 	 * Do not inherit any borrowed priority from the parent.
2290 	 */
2291 	child->td_priority = child->td_base_pri;
2292 	/*
2293 	 * And update interactivity score.
2294 	 */
2295 	ts2->ts_slptime = ts->ts_slptime;
2296 	ts2->ts_runtime = ts->ts_runtime;
2297 	/* Attempt to quickly learn interactivity. */
2298 	ts2->ts_slice = tdq_slice(tdq) - sched_slice_min;
2299 #ifdef KTR
2300 	bzero(ts2->ts_name, sizeof(ts2->ts_name));
2301 #endif
2302 }
2303 
2304 /*
2305  * Adjust the priority class of a thread.
2306  */
2307 void
2308 sched_class(struct thread *td, int class)
2309 {
2310 
2311 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2312 	if (td->td_pri_class == class)
2313 		return;
2314 	td->td_pri_class = class;
2315 }
2316 
2317 /*
2318  * Return some of the child's priority and interactivity to the parent.
2319  */
2320 void
2321 sched_exit(struct proc *p, struct thread *child)
2322 {
2323 	struct thread *td;
2324 
2325 	KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit",
2326 	    "prio:%d", child->td_priority);
2327 	PROC_LOCK_ASSERT(p, MA_OWNED);
2328 	td = FIRST_THREAD_IN_PROC(p);
2329 	sched_exit_thread(td, child);
2330 }
2331 
2332 /*
2333  * Penalize another thread for the time spent on this one.  This helps to
2334  * worsen the priority and interactivity of processes which schedule batch
2335  * jobs such as make.  This has little effect on the make process itself but
2336  * causes new processes spawned by it to receive worse scores immediately.
2337  */
2338 void
2339 sched_exit_thread(struct thread *td, struct thread *child)
2340 {
2341 
2342 	KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit",
2343 	    "prio:%d", child->td_priority);
2344 	/*
2345 	 * Give the child's runtime to the parent without returning the
2346 	 * sleep time as a penalty to the parent.  This causes shells that
2347 	 * launch expensive things to mark their children as expensive.
2348 	 */
2349 	thread_lock(td);
2350 	td_get_sched(td)->ts_runtime += td_get_sched(child)->ts_runtime;
2351 	sched_interact_update(td);
2352 	sched_priority(td);
2353 	thread_unlock(td);
2354 }
2355 
2356 void
2357 sched_preempt(struct thread *td)
2358 {
2359 	struct tdq *tdq;
2360 	int flags;
2361 
2362 	SDT_PROBE2(sched, , , surrender, td, td->td_proc);
2363 
2364 	thread_lock(td);
2365 	tdq = TDQ_SELF();
2366 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2367 	if (td->td_priority > tdq->tdq_lowpri) {
2368 		if (td->td_critnest == 1) {
2369 			flags = SW_INVOL | SW_PREEMPT;
2370 			flags |= TD_IS_IDLETHREAD(td) ? SWT_REMOTEWAKEIDLE :
2371 			    SWT_REMOTEPREEMPT;
2372 			mi_switch(flags);
2373 			/* Switch dropped thread lock. */
2374 			return;
2375 		}
2376 		td->td_owepreempt = 1;
2377 	} else {
2378 		tdq->tdq_owepreempt = 0;
2379 	}
2380 	thread_unlock(td);
2381 }
2382 
2383 /*
2384  * Fix priorities on return to user-space.  Priorities may be elevated due
2385  * to static priorities in msleep() or similar.
2386  */
2387 void
2388 sched_userret_slowpath(struct thread *td)
2389 {
2390 
2391 	thread_lock(td);
2392 	td->td_priority = td->td_user_pri;
2393 	td->td_base_pri = td->td_user_pri;
2394 	tdq_setlowpri(TDQ_SELF(), td);
2395 	thread_unlock(td);
2396 }
2397 
2398 /*
2399  * Handle a stathz tick.  This is really only relevant for timeshare
2400  * threads.
2401  */
2402 void
2403 sched_clock(struct thread *td, int cnt)
2404 {
2405 	struct tdq *tdq;
2406 	struct td_sched *ts;
2407 
2408 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2409 	tdq = TDQ_SELF();
2410 #ifdef SMP
2411 	/*
2412 	 * We run the long term load balancer infrequently on the first cpu.
2413 	 */
2414 	if (balance_tdq == tdq && smp_started != 0 && rebalance != 0 &&
2415 	    balance_ticks != 0) {
2416 		balance_ticks -= cnt;
2417 		if (balance_ticks <= 0)
2418 			sched_balance();
2419 	}
2420 #endif
2421 	/*
2422 	 * Save the old switch count so we have a record of the last ticks
2423 	 * activity.   Initialize the new switch count based on our load.
2424 	 * If there is some activity seed it to reflect that.
2425 	 */
2426 	tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt;
2427 	tdq->tdq_switchcnt = tdq->tdq_load;
2428 	/*
2429 	 * Advance the insert index once for each tick to ensure that all
2430 	 * threads get a chance to run.
2431 	 */
2432 	if (tdq->tdq_idx == tdq->tdq_ridx) {
2433 		tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
2434 		if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
2435 			tdq->tdq_ridx = tdq->tdq_idx;
2436 	}
2437 	ts = td_get_sched(td);
2438 	sched_pctcpu_update(ts, 1);
2439 	if ((td->td_pri_class & PRI_FIFO_BIT) || TD_IS_IDLETHREAD(td))
2440 		return;
2441 
2442 	if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) {
2443 		/*
2444 		 * We used a tick; charge it to the thread so
2445 		 * that we can compute our interactivity.
2446 		 */
2447 		td_get_sched(td)->ts_runtime += tickincr * cnt;
2448 		sched_interact_update(td);
2449 		sched_priority(td);
2450 	}
2451 
2452 	/*
2453 	 * Force a context switch if the current thread has used up a full
2454 	 * time slice (default is 100ms).
2455 	 */
2456 	ts->ts_slice += cnt;
2457 	if (ts->ts_slice >= tdq_slice(tdq)) {
2458 		ts->ts_slice = 0;
2459 		td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND;
2460 	}
2461 }
2462 
2463 u_int
2464 sched_estcpu(struct thread *td __unused)
2465 {
2466 
2467 	return (0);
2468 }
2469 
2470 /*
2471  * Return whether the current CPU has runnable tasks.  Used for in-kernel
2472  * cooperative idle threads.
2473  */
2474 int
2475 sched_runnable(void)
2476 {
2477 	struct tdq *tdq;
2478 	int load;
2479 
2480 	load = 1;
2481 
2482 	tdq = TDQ_SELF();
2483 	if ((curthread->td_flags & TDF_IDLETD) != 0) {
2484 		if (tdq->tdq_load > 0)
2485 			goto out;
2486 	} else
2487 		if (tdq->tdq_load - 1 > 0)
2488 			goto out;
2489 	load = 0;
2490 out:
2491 	return (load);
2492 }
2493 
2494 /*
2495  * Choose the highest priority thread to run.  The thread is removed from
2496  * the run-queue while running however the load remains.  For SMP we set
2497  * the tdq in the global idle bitmask if it idles here.
2498  */
2499 struct thread *
2500 sched_choose(void)
2501 {
2502 	struct thread *td;
2503 	struct tdq *tdq;
2504 
2505 	tdq = TDQ_SELF();
2506 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2507 	td = tdq_choose(tdq);
2508 	if (td) {
2509 		tdq_runq_rem(tdq, td);
2510 		tdq->tdq_lowpri = td->td_priority;
2511 		return (td);
2512 	}
2513 	tdq->tdq_lowpri = PRI_MAX_IDLE;
2514 	return (PCPU_GET(idlethread));
2515 }
2516 
2517 /*
2518  * Set owepreempt if necessary.  Preemption never happens directly in ULE,
2519  * we always request it once we exit a critical section.
2520  */
2521 static inline void
2522 sched_setpreempt(struct thread *td)
2523 {
2524 	struct thread *ctd;
2525 	int cpri;
2526 	int pri;
2527 
2528 	THREAD_LOCK_ASSERT(curthread, MA_OWNED);
2529 
2530 	ctd = curthread;
2531 	pri = td->td_priority;
2532 	cpri = ctd->td_priority;
2533 	if (pri < cpri)
2534 		ctd->td_flags |= TDF_NEEDRESCHED;
2535 	if (KERNEL_PANICKED() || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
2536 		return;
2537 	if (!sched_shouldpreempt(pri, cpri, 0))
2538 		return;
2539 	ctd->td_owepreempt = 1;
2540 }
2541 
2542 /*
2543  * Add a thread to a thread queue.  Select the appropriate runq and add the
2544  * thread to it.  This is the internal function called when the tdq is
2545  * predetermined.
2546  */
2547 void
2548 tdq_add(struct tdq *tdq, struct thread *td, int flags)
2549 {
2550 
2551 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2552 	THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
2553 	KASSERT((td->td_inhibitors == 0),
2554 	    ("sched_add: trying to run inhibited thread"));
2555 	KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
2556 	    ("sched_add: bad thread state"));
2557 	KASSERT(td->td_flags & TDF_INMEM,
2558 	    ("sched_add: thread swapped out"));
2559 
2560 	if (td->td_priority < tdq->tdq_lowpri)
2561 		tdq->tdq_lowpri = td->td_priority;
2562 	tdq_runq_add(tdq, td, flags);
2563 	tdq_load_add(tdq, td);
2564 }
2565 
2566 /*
2567  * Select the target thread queue and add a thread to it.  Request
2568  * preemption or IPI a remote processor if required.
2569  *
2570  * Requires the thread lock on entry, drops on exit.
2571  */
2572 void
2573 sched_add(struct thread *td, int flags)
2574 {
2575 	struct tdq *tdq;
2576 #ifdef SMP
2577 	int cpu;
2578 #endif
2579 
2580 	KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
2581 	    "prio:%d", td->td_priority, KTR_ATTR_LINKED,
2582 	    sched_tdname(curthread));
2583 	KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
2584 	    KTR_ATTR_LINKED, sched_tdname(td));
2585 	SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL,
2586 	    flags & SRQ_PREEMPTED);
2587 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2588 	/*
2589 	 * Recalculate the priority before we select the target cpu or
2590 	 * run-queue.
2591 	 */
2592 	if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
2593 		sched_priority(td);
2594 #ifdef SMP
2595 	/*
2596 	 * Pick the destination cpu and if it isn't ours transfer to the
2597 	 * target cpu.
2598 	 */
2599 	cpu = sched_pickcpu(td, flags);
2600 	tdq = sched_setcpu(td, cpu, flags);
2601 	tdq_add(tdq, td, flags);
2602 	if (cpu != PCPU_GET(cpuid))
2603 		tdq_notify(tdq, td);
2604 	else if (!(flags & SRQ_YIELDING))
2605 		sched_setpreempt(td);
2606 #else
2607 	tdq = TDQ_SELF();
2608 	/*
2609 	 * Now that the thread is moving to the run-queue, set the lock
2610 	 * to the scheduler's lock.
2611 	 */
2612 	if (td->td_lock != TDQ_LOCKPTR(tdq)) {
2613 		TDQ_LOCK(tdq);
2614 		if ((flags & SRQ_HOLD) != 0)
2615 			td->td_lock = TDQ_LOCKPTR(tdq);
2616 		else
2617 			thread_lock_set(td, TDQ_LOCKPTR(tdq));
2618 	}
2619 	tdq_add(tdq, td, flags);
2620 	if (!(flags & SRQ_YIELDING))
2621 		sched_setpreempt(td);
2622 #endif
2623 	if (!(flags & SRQ_HOLDTD))
2624 		thread_unlock(td);
2625 }
2626 
2627 /*
2628  * Remove a thread from a run-queue without running it.  This is used
2629  * when we're stealing a thread from a remote queue.  Otherwise all threads
2630  * exit by calling sched_exit_thread() and sched_throw() themselves.
2631  */
2632 void
2633 sched_rem(struct thread *td)
2634 {
2635 	struct tdq *tdq;
2636 
2637 	KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
2638 	    "prio:%d", td->td_priority);
2639 	SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
2640 	tdq = TDQ_CPU(td_get_sched(td)->ts_cpu);
2641 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2642 	MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
2643 	KASSERT(TD_ON_RUNQ(td),
2644 	    ("sched_rem: thread not on run queue"));
2645 	tdq_runq_rem(tdq, td);
2646 	tdq_load_rem(tdq, td);
2647 	TD_SET_CAN_RUN(td);
2648 	if (td->td_priority == tdq->tdq_lowpri)
2649 		tdq_setlowpri(tdq, NULL);
2650 }
2651 
2652 /*
2653  * Fetch cpu utilization information.  Updates on demand.
2654  */
2655 fixpt_t
2656 sched_pctcpu(struct thread *td)
2657 {
2658 	fixpt_t pctcpu;
2659 	struct td_sched *ts;
2660 
2661 	pctcpu = 0;
2662 	ts = td_get_sched(td);
2663 
2664 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2665 	sched_pctcpu_update(ts, TD_IS_RUNNING(td));
2666 	if (ts->ts_ticks) {
2667 		int rtick;
2668 
2669 		/* How many rtick per second ? */
2670 		rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
2671 		pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
2672 	}
2673 
2674 	return (pctcpu);
2675 }
2676 
2677 /*
2678  * Enforce affinity settings for a thread.  Called after adjustments to
2679  * cpumask.
2680  */
2681 void
2682 sched_affinity(struct thread *td)
2683 {
2684 #ifdef SMP
2685 	struct td_sched *ts;
2686 
2687 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2688 	ts = td_get_sched(td);
2689 	if (THREAD_CAN_SCHED(td, ts->ts_cpu))
2690 		return;
2691 	if (TD_ON_RUNQ(td)) {
2692 		sched_rem(td);
2693 		sched_add(td, SRQ_BORING | SRQ_HOLDTD);
2694 		return;
2695 	}
2696 	if (!TD_IS_RUNNING(td))
2697 		return;
2698 	/*
2699 	 * Force a switch before returning to userspace.  If the
2700 	 * target thread is not running locally send an ipi to force
2701 	 * the issue.
2702 	 */
2703 	td->td_flags |= TDF_NEEDRESCHED;
2704 	if (td != curthread)
2705 		ipi_cpu(ts->ts_cpu, IPI_PREEMPT);
2706 #endif
2707 }
2708 
2709 /*
2710  * Bind a thread to a target cpu.
2711  */
2712 void
2713 sched_bind(struct thread *td, int cpu)
2714 {
2715 	struct td_sched *ts;
2716 
2717 	THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
2718 	KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
2719 	ts = td_get_sched(td);
2720 	if (ts->ts_flags & TSF_BOUND)
2721 		sched_unbind(td);
2722 	KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td));
2723 	ts->ts_flags |= TSF_BOUND;
2724 	sched_pin();
2725 	if (PCPU_GET(cpuid) == cpu)
2726 		return;
2727 	ts->ts_cpu = cpu;
2728 	/* When we return from mi_switch we'll be on the correct cpu. */
2729 	mi_switch(SW_VOL);
2730 	thread_lock(td);
2731 }
2732 
2733 /*
2734  * Release a bound thread.
2735  */
2736 void
2737 sched_unbind(struct thread *td)
2738 {
2739 	struct td_sched *ts;
2740 
2741 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2742 	KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
2743 	ts = td_get_sched(td);
2744 	if ((ts->ts_flags & TSF_BOUND) == 0)
2745 		return;
2746 	ts->ts_flags &= ~TSF_BOUND;
2747 	sched_unpin();
2748 }
2749 
2750 int
2751 sched_is_bound(struct thread *td)
2752 {
2753 	THREAD_LOCK_ASSERT(td, MA_OWNED);
2754 	return (td_get_sched(td)->ts_flags & TSF_BOUND);
2755 }
2756 
2757 /*
2758  * Basic yield call.
2759  */
2760 void
2761 sched_relinquish(struct thread *td)
2762 {
2763 	thread_lock(td);
2764 	mi_switch(SW_VOL | SWT_RELINQUISH);
2765 }
2766 
2767 /*
2768  * Return the total system load.
2769  */
2770 int
2771 sched_load(void)
2772 {
2773 #ifdef SMP
2774 	int total;
2775 	int i;
2776 
2777 	total = 0;
2778 	CPU_FOREACH(i)
2779 		total += TDQ_CPU(i)->tdq_sysload;
2780 	return (total);
2781 #else
2782 	return (TDQ_SELF()->tdq_sysload);
2783 #endif
2784 }
2785 
2786 int
2787 sched_sizeof_proc(void)
2788 {
2789 	return (sizeof(struct proc));
2790 }
2791 
2792 int
2793 sched_sizeof_thread(void)
2794 {
2795 	return (sizeof(struct thread) + sizeof(struct td_sched));
2796 }
2797 
2798 #ifdef SMP
2799 #define	TDQ_IDLESPIN(tdq)						\
2800     ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0)
2801 #else
2802 #define	TDQ_IDLESPIN(tdq)	1
2803 #endif
2804 
2805 /*
2806  * The actual idle process.
2807  */
2808 void
2809 sched_idletd(void *dummy)
2810 {
2811 	struct thread *td;
2812 	struct tdq *tdq;
2813 	int oldswitchcnt, switchcnt;
2814 	int i;
2815 
2816 	mtx_assert(&Giant, MA_NOTOWNED);
2817 	td = curthread;
2818 	tdq = TDQ_SELF();
2819 	THREAD_NO_SLEEPING();
2820 	oldswitchcnt = -1;
2821 	for (;;) {
2822 		if (tdq->tdq_load) {
2823 			thread_lock(td);
2824 			mi_switch(SW_VOL | SWT_IDLE);
2825 		}
2826 		switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
2827 #ifdef SMP
2828 		if (always_steal || switchcnt != oldswitchcnt) {
2829 			oldswitchcnt = switchcnt;
2830 			if (tdq_idled(tdq) == 0)
2831 				continue;
2832 		}
2833 		switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
2834 #else
2835 		oldswitchcnt = switchcnt;
2836 #endif
2837 		/*
2838 		 * If we're switching very frequently, spin while checking
2839 		 * for load rather than entering a low power state that
2840 		 * may require an IPI.  However, don't do any busy
2841 		 * loops while on SMT machines as this simply steals
2842 		 * cycles from cores doing useful work.
2843 		 */
2844 		if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) {
2845 			for (i = 0; i < sched_idlespins; i++) {
2846 				if (tdq->tdq_load)
2847 					break;
2848 				cpu_spinwait();
2849 			}
2850 		}
2851 
2852 		/* If there was context switch during spin, restart it. */
2853 		switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
2854 		if (tdq->tdq_load != 0 || switchcnt != oldswitchcnt)
2855 			continue;
2856 
2857 		/* Run main MD idle handler. */
2858 		tdq->tdq_cpu_idle = 1;
2859 		/*
2860 		 * Make sure that tdq_cpu_idle update is globally visible
2861 		 * before cpu_idle() read tdq_load.  The order is important
2862 		 * to avoid race with tdq_notify.
2863 		 */
2864 		atomic_thread_fence_seq_cst();
2865 		/*
2866 		 * Checking for again after the fence picks up assigned
2867 		 * threads often enough to make it worthwhile to do so in
2868 		 * order to avoid calling cpu_idle().
2869 		 */
2870 		if (tdq->tdq_load != 0) {
2871 			tdq->tdq_cpu_idle = 0;
2872 			continue;
2873 		}
2874 		cpu_idle(switchcnt * 4 > sched_idlespinthresh);
2875 		tdq->tdq_cpu_idle = 0;
2876 
2877 		/*
2878 		 * Account thread-less hardware interrupts and
2879 		 * other wakeup reasons equal to context switches.
2880 		 */
2881 		switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
2882 		if (switchcnt != oldswitchcnt)
2883 			continue;
2884 		tdq->tdq_switchcnt++;
2885 		oldswitchcnt++;
2886 	}
2887 }
2888 
2889 /*
2890  * A CPU is entering for the first time or a thread is exiting.
2891  */
2892 void
2893 sched_throw(struct thread *td)
2894 {
2895 	struct thread *newtd;
2896 	struct tdq *tdq;
2897 
2898 	if (__predict_false(td == NULL)) {
2899 #ifdef SMP
2900 		PCPU_SET(sched, DPCPU_PTR(tdq));
2901 #endif
2902 		/* Correct spinlock nesting and acquire the correct lock. */
2903 		tdq = TDQ_SELF();
2904 		TDQ_LOCK(tdq);
2905 		spinlock_exit();
2906 		PCPU_SET(switchtime, cpu_ticks());
2907 		PCPU_SET(switchticks, ticks);
2908 		PCPU_GET(idlethread)->td_lock = TDQ_LOCKPTR(tdq);
2909 	} else {
2910 		tdq = TDQ_SELF();
2911 		THREAD_LOCK_ASSERT(td, MA_OWNED);
2912 		THREAD_LOCKPTR_ASSERT(td, TDQ_LOCKPTR(tdq));
2913 		tdq_load_rem(tdq, td);
2914 		td->td_lastcpu = td->td_oncpu;
2915 		td->td_oncpu = NOCPU;
2916 		thread_lock_block(td);
2917 	}
2918 	newtd = choosethread();
2919 	spinlock_enter();
2920 	TDQ_UNLOCK(tdq);
2921 	KASSERT(curthread->td_md.md_spinlock_count == 1,
2922 	    ("invalid count %d", curthread->td_md.md_spinlock_count));
2923 	/* doesn't return */
2924 	if (__predict_false(td == NULL))
2925 		cpu_throw(td, newtd);		/* doesn't return */
2926 	else
2927 		cpu_switch(td, newtd, TDQ_LOCKPTR(tdq));
2928 }
2929 
2930 /*
2931  * This is called from fork_exit().  Just acquire the correct locks and
2932  * let fork do the rest of the work.
2933  */
2934 void
2935 sched_fork_exit(struct thread *td)
2936 {
2937 	struct tdq *tdq;
2938 	int cpuid;
2939 
2940 	/*
2941 	 * Finish setting up thread glue so that it begins execution in a
2942 	 * non-nested critical section with the scheduler lock held.
2943 	 */
2944 	KASSERT(curthread->td_md.md_spinlock_count == 1,
2945 	    ("invalid count %d", curthread->td_md.md_spinlock_count));
2946 	cpuid = PCPU_GET(cpuid);
2947 	tdq = TDQ_SELF();
2948 	TDQ_LOCK(tdq);
2949 	spinlock_exit();
2950 	MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
2951 	td->td_oncpu = cpuid;
2952 	KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
2953 	    "prio:%d", td->td_priority);
2954 	SDT_PROBE0(sched, , , on__cpu);
2955 }
2956 
2957 /*
2958  * Create on first use to catch odd startup conditons.
2959  */
2960 char *
2961 sched_tdname(struct thread *td)
2962 {
2963 #ifdef KTR
2964 	struct td_sched *ts;
2965 
2966 	ts = td_get_sched(td);
2967 	if (ts->ts_name[0] == '\0')
2968 		snprintf(ts->ts_name, sizeof(ts->ts_name),
2969 		    "%s tid %d", td->td_name, td->td_tid);
2970 	return (ts->ts_name);
2971 #else
2972 	return (td->td_name);
2973 #endif
2974 }
2975 
2976 #ifdef KTR
2977 void
2978 sched_clear_tdname(struct thread *td)
2979 {
2980 	struct td_sched *ts;
2981 
2982 	ts = td_get_sched(td);
2983 	ts->ts_name[0] = '\0';
2984 }
2985 #endif
2986 
2987 #ifdef SMP
2988 
2989 /*
2990  * Build the CPU topology dump string. Is recursively called to collect
2991  * the topology tree.
2992  */
2993 static int
2994 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg,
2995     int indent)
2996 {
2997 	char cpusetbuf[CPUSETBUFSIZ];
2998 	int i, first;
2999 
3000 	sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent,
3001 	    "", 1 + indent / 2, cg->cg_level);
3002 	sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "",
3003 	    cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask));
3004 	first = TRUE;
3005 	for (i = 0; i < MAXCPU; i++) {
3006 		if (CPU_ISSET(i, &cg->cg_mask)) {
3007 			if (!first)
3008 				sbuf_printf(sb, ", ");
3009 			else
3010 				first = FALSE;
3011 			sbuf_printf(sb, "%d", i);
3012 		}
3013 	}
3014 	sbuf_printf(sb, "</cpu>\n");
3015 
3016 	if (cg->cg_flags != 0) {
3017 		sbuf_printf(sb, "%*s <flags>", indent, "");
3018 		if ((cg->cg_flags & CG_FLAG_HTT) != 0)
3019 			sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>");
3020 		if ((cg->cg_flags & CG_FLAG_THREAD) != 0)
3021 			sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>");
3022 		if ((cg->cg_flags & CG_FLAG_SMT) != 0)
3023 			sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>");
3024 		sbuf_printf(sb, "</flags>\n");
3025 	}
3026 
3027 	if (cg->cg_children > 0) {
3028 		sbuf_printf(sb, "%*s <children>\n", indent, "");
3029 		for (i = 0; i < cg->cg_children; i++)
3030 			sysctl_kern_sched_topology_spec_internal(sb,
3031 			    &cg->cg_child[i], indent+2);
3032 		sbuf_printf(sb, "%*s </children>\n", indent, "");
3033 	}
3034 	sbuf_printf(sb, "%*s</group>\n", indent, "");
3035 	return (0);
3036 }
3037 
3038 /*
3039  * Sysctl handler for retrieving topology dump. It's a wrapper for
3040  * the recursive sysctl_kern_smp_topology_spec_internal().
3041  */
3042 static int
3043 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS)
3044 {
3045 	struct sbuf *topo;
3046 	int err;
3047 
3048 	KASSERT(cpu_top != NULL, ("cpu_top isn't initialized"));
3049 
3050 	topo = sbuf_new_for_sysctl(NULL, NULL, 512, req);
3051 	if (topo == NULL)
3052 		return (ENOMEM);
3053 
3054 	sbuf_printf(topo, "<groups>\n");
3055 	err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1);
3056 	sbuf_printf(topo, "</groups>\n");
3057 
3058 	if (err == 0) {
3059 		err = sbuf_finish(topo);
3060 	}
3061 	sbuf_delete(topo);
3062 	return (err);
3063 }
3064 
3065 #endif
3066 
3067 static int
3068 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
3069 {
3070 	int error, new_val, period;
3071 
3072 	period = 1000000 / realstathz;
3073 	new_val = period * sched_slice;
3074 	error = sysctl_handle_int(oidp, &new_val, 0, req);
3075 	if (error != 0 || req->newptr == NULL)
3076 		return (error);
3077 	if (new_val <= 0)
3078 		return (EINVAL);
3079 	sched_slice = imax(1, (new_val + period / 2) / period);
3080 	sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
3081 	hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
3082 	    realstathz);
3083 	return (0);
3084 }
3085 
3086 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
3087     "Scheduler");
3088 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
3089     "Scheduler name");
3090 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum,
3091     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
3092     sysctl_kern_quantum, "I",
3093     "Quantum for timeshare threads in microseconds");
3094 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
3095     "Quantum for timeshare threads in stathz ticks");
3096 SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
3097     "Interactivity score threshold");
3098 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW,
3099     &preempt_thresh, 0,
3100     "Maximal (lowest) priority for preemption");
3101 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost, 0,
3102     "Assign static kernel priorities to sleeping threads");
3103 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins, 0,
3104     "Number of times idle thread will spin waiting for new work");
3105 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW,
3106     &sched_idlespinthresh, 0,
3107     "Threshold before we will permit idle thread spinning");
3108 #ifdef SMP
3109 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
3110     "Number of hz ticks to keep thread affinity for");
3111 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0,
3112     "Enables the long-term load balancer");
3113 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
3114     &balance_interval, 0,
3115     "Average period in stathz ticks to run the long-term balancer");
3116 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
3117     "Attempts to steal work from other cores before idling");
3118 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
3119     "Minimum load on remote CPU before we'll steal");
3120 SYSCTL_INT(_kern_sched, OID_AUTO, trysteal_limit, CTLFLAG_RW, &trysteal_limit,
3121     0, "Topological distance limit for stealing threads in sched_switch()");
3122 SYSCTL_INT(_kern_sched, OID_AUTO, always_steal, CTLFLAG_RW, &always_steal, 0,
3123     "Always run the stealer from the idle thread");
3124 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
3125     CTLFLAG_MPSAFE | CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A",
3126     "XML dump of detected CPU topology");
3127 #endif
3128 
3129 /* ps compat.  All cpu percentages from ULE are weighted. */
3130 static int ccpu = 0;
3131 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0,
3132     "Decay factor used for updating %CPU in 4BSD scheduler");
3133