2 * Copyright (c) 1982, 1986, 1990, 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.
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11 * modification, are permitted provided that the following conditions
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14 * notice, this list of conditions and the following disclaimer.
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35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD$");
38 #include "opt_hwpmc_hooks.h"
39 #include "opt_sched.h"
40 #include "opt_kdtrace.h"
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/cpuset.h>
45 #include <sys/kernel.h>
48 #include <sys/kthread.h>
49 #include <sys/mutex.h>
51 #include <sys/resourcevar.h>
52 #include <sys/sched.h>
55 #include <sys/sysctl.h>
57 #include <sys/turnstile.h>
59 #include <machine/pcb.h>
60 #include <machine/smp.h>
63 #include <sys/pmckern.h>
67 #include <sys/dtrace_bsd.h>
68 int dtrace_vtime_active;
69 dtrace_vtime_switch_func_t dtrace_vtime_switch_func;
73 * INVERSE_ESTCPU_WEIGHT is only suitable for statclock() frequencies in
74 * the range 100-256 Hz (approximately).
76 #define ESTCPULIM(e) \
77 min((e), INVERSE_ESTCPU_WEIGHT * (NICE_WEIGHT * (PRIO_MAX - PRIO_MIN) - \
78 RQ_PPQ) + INVERSE_ESTCPU_WEIGHT - 1)
80 #define INVERSE_ESTCPU_WEIGHT (8 * smp_cpus)
82 #define INVERSE_ESTCPU_WEIGHT 8 /* 1 / (priorities per estcpu level). */
84 #define NICE_WEIGHT 1 /* Priorities per nice level. */
86 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
89 * The schedulable entity that runs a context.
90 * This is an extension to the thread structure and is tailored to
91 * the requirements of this scheduler
94 fixpt_t ts_pctcpu; /* (j) %cpu during p_swtime. */
95 int ts_cpticks; /* (j) Ticks of cpu time. */
96 int ts_slptime; /* (j) Seconds !RUNNING. */
98 struct runq *ts_runq; /* runq the thread is currently on */
100 char ts_name[TS_NAME_LEN];
104 /* flags kept in td_flags */
105 #define TDF_DIDRUN TDF_SCHED0 /* thread actually ran. */
106 #define TDF_BOUND TDF_SCHED1 /* Bound to one CPU. */
108 /* flags kept in ts_flags */
109 #define TSF_AFFINITY 0x0001 /* Has a non-"full" CPU set. */
111 #define SKE_RUNQ_PCPU(ts) \
112 ((ts)->ts_runq != 0 && (ts)->ts_runq != &runq)
114 #define THREAD_CAN_SCHED(td, cpu) \
115 CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
117 static struct td_sched td_sched0;
118 struct mtx sched_lock;
120 static int sched_tdcnt; /* Total runnable threads in the system. */
121 static int sched_quantum; /* Roundrobin scheduling quantum in ticks. */
122 #define SCHED_QUANTUM (hz / 10) /* Default sched quantum */
124 static void setup_runqs(void);
125 static void schedcpu(void);
126 static void schedcpu_thread(void);
127 static void sched_priority(struct thread *td, u_char prio);
128 static void sched_setup(void *dummy);
129 static void maybe_resched(struct thread *td);
130 static void updatepri(struct thread *td);
131 static void resetpriority(struct thread *td);
132 static void resetpriority_thread(struct thread *td);
134 static int sched_pickcpu(struct thread *td);
135 static int forward_wakeup(int cpunum);
136 static void kick_other_cpu(int pri, int cpuid);
139 static struct kproc_desc sched_kp = {
144 SYSINIT(schedcpu, SI_SUB_RUN_SCHEDULER, SI_ORDER_FIRST, kproc_start,
146 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
151 static struct runq runq;
157 static struct runq runq_pcpu[MAXCPU];
158 long runq_length[MAXCPU];
160 static cpuset_t idle_cpus_mask;
163 struct pcpuidlestat {
167 static DPCPU_DEFINE(struct pcpuidlestat, idlestat);
175 for (i = 0; i < MAXCPU; ++i)
176 runq_init(&runq_pcpu[i]);
183 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
187 new_val = sched_quantum * tick;
188 error = sysctl_handle_int(oidp, &new_val, 0, req);
189 if (error != 0 || req->newptr == NULL)
193 sched_quantum = new_val / tick;
194 hogticks = 2 * sched_quantum;
198 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RD, 0, "Scheduler");
200 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "4BSD", 0,
203 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW,
204 0, sizeof sched_quantum, sysctl_kern_quantum, "I",
205 "Roundrobin scheduling quantum in microseconds");
208 /* Enable forwarding of wakeups to all other cpus */
209 SYSCTL_NODE(_kern_sched, OID_AUTO, ipiwakeup, CTLFLAG_RD, NULL, "Kernel SMP");
211 static int runq_fuzz = 1;
212 SYSCTL_INT(_kern_sched, OID_AUTO, runq_fuzz, CTLFLAG_RW, &runq_fuzz, 0, "");
214 static int forward_wakeup_enabled = 1;
215 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, enabled, CTLFLAG_RW,
216 &forward_wakeup_enabled, 0,
217 "Forwarding of wakeup to idle CPUs");
219 static int forward_wakeups_requested = 0;
220 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, requested, CTLFLAG_RD,
221 &forward_wakeups_requested, 0,
222 "Requests for Forwarding of wakeup to idle CPUs");
224 static int forward_wakeups_delivered = 0;
225 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, delivered, CTLFLAG_RD,
226 &forward_wakeups_delivered, 0,
227 "Completed Forwarding of wakeup to idle CPUs");
229 static int forward_wakeup_use_mask = 1;
230 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, usemask, CTLFLAG_RW,
231 &forward_wakeup_use_mask, 0,
232 "Use the mask of idle cpus");
234 static int forward_wakeup_use_loop = 0;
235 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, useloop, CTLFLAG_RW,
236 &forward_wakeup_use_loop, 0,
237 "Use a loop to find idle cpus");
241 static int sched_followon = 0;
242 SYSCTL_INT(_kern_sched, OID_AUTO, followon, CTLFLAG_RW,
244 "allow threads to share a quantum");
247 SDT_PROVIDER_DEFINE(sched);
249 SDT_PROBE_DEFINE3(sched, , , change_pri, change-pri, "struct thread *",
250 "struct proc *", "uint8_t");
251 SDT_PROBE_DEFINE3(sched, , , dequeue, dequeue, "struct thread *",
252 "struct proc *", "void *");
253 SDT_PROBE_DEFINE4(sched, , , enqueue, enqueue, "struct thread *",
254 "struct proc *", "void *", "int");
255 SDT_PROBE_DEFINE4(sched, , , lend_pri, lend-pri, "struct thread *",
256 "struct proc *", "uint8_t", "struct thread *");
257 SDT_PROBE_DEFINE2(sched, , , load_change, load-change, "int", "int");
258 SDT_PROBE_DEFINE2(sched, , , off_cpu, off-cpu, "struct thread *",
260 SDT_PROBE_DEFINE(sched, , , on_cpu, on-cpu);
261 SDT_PROBE_DEFINE(sched, , , remain_cpu, remain-cpu);
262 SDT_PROBE_DEFINE2(sched, , , surrender, surrender, "struct thread *",
270 KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt);
271 SDT_PROBE2(sched, , , load_change, NOCPU, sched_tdcnt);
279 KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt);
280 SDT_PROBE2(sched, , , load_change, NOCPU, sched_tdcnt);
283 * Arrange to reschedule if necessary, taking the priorities and
284 * schedulers into account.
287 maybe_resched(struct thread *td)
290 THREAD_LOCK_ASSERT(td, MA_OWNED);
291 if (td->td_priority < curthread->td_priority)
292 curthread->td_flags |= TDF_NEEDRESCHED;
296 * This function is called when a thread is about to be put on run queue
297 * because it has been made runnable or its priority has been adjusted. It
298 * determines if the new thread should be immediately preempted to. If so,
299 * it switches to it and eventually returns true. If not, it returns false
300 * so that the caller may place the thread on an appropriate run queue.
303 maybe_preempt(struct thread *td)
310 * The new thread should not preempt the current thread if any of the
311 * following conditions are true:
313 * - The kernel is in the throes of crashing (panicstr).
314 * - The current thread has a higher (numerically lower) or
315 * equivalent priority. Note that this prevents curthread from
316 * trying to preempt to itself.
317 * - It is too early in the boot for context switches (cold is set).
318 * - The current thread has an inhibitor set or is in the process of
319 * exiting. In this case, the current thread is about to switch
320 * out anyways, so there's no point in preempting. If we did,
321 * the current thread would not be properly resumed as well, so
322 * just avoid that whole landmine.
323 * - If the new thread's priority is not a realtime priority and
324 * the current thread's priority is not an idle priority and
325 * FULL_PREEMPTION is disabled.
327 * If all of these conditions are false, but the current thread is in
328 * a nested critical section, then we have to defer the preemption
329 * until we exit the critical section. Otherwise, switch immediately
333 THREAD_LOCK_ASSERT(td, MA_OWNED);
334 KASSERT((td->td_inhibitors == 0),
335 ("maybe_preempt: trying to run inhibited thread"));
336 pri = td->td_priority;
337 cpri = ctd->td_priority;
338 if (panicstr != NULL || pri >= cpri || cold /* || dumping */ ||
339 TD_IS_INHIBITED(ctd))
341 #ifndef FULL_PREEMPTION
342 if (pri > PRI_MAX_ITHD && cpri < PRI_MIN_IDLE)
346 if (ctd->td_critnest > 1) {
347 CTR1(KTR_PROC, "maybe_preempt: in critical section %d",
349 ctd->td_owepreempt = 1;
353 * Thread is runnable but not yet put on system run queue.
355 MPASS(ctd->td_lock == td->td_lock);
356 MPASS(TD_ON_RUNQ(td));
358 CTR3(KTR_PROC, "preempting to thread %p (pid %d, %s)\n", td,
359 td->td_proc->p_pid, td->td_name);
360 mi_switch(SW_INVOL | SW_PREEMPT | SWT_PREEMPT, td);
362 * td's lock pointer may have changed. We have to return with it
376 * Constants for digital decay and forget:
377 * 90% of (td_estcpu) usage in 5 * loadav time
378 * 95% of (ts_pctcpu) usage in 60 seconds (load insensitive)
379 * Note that, as ps(1) mentions, this can let percentages
380 * total over 100% (I've seen 137.9% for 3 processes).
382 * Note that schedclock() updates td_estcpu and p_cpticks asynchronously.
384 * We wish to decay away 90% of td_estcpu in (5 * loadavg) seconds.
385 * That is, the system wants to compute a value of decay such
386 * that the following for loop:
387 * for (i = 0; i < (5 * loadavg); i++)
388 * td_estcpu *= decay;
391 * for all values of loadavg:
393 * Mathematically this loop can be expressed by saying:
394 * decay ** (5 * loadavg) ~= .1
396 * The system computes decay as:
397 * decay = (2 * loadavg) / (2 * loadavg + 1)
399 * We wish to prove that the system's computation of decay
400 * will always fulfill the equation:
401 * decay ** (5 * loadavg) ~= .1
403 * If we compute b as:
406 * decay = b / (b + 1)
408 * We now need to prove two things:
409 * 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1)
410 * 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg)
413 * For x close to zero, exp(x) =~ 1 + x, since
414 * exp(x) = 0! + x**1/1! + x**2/2! + ... .
415 * therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b.
416 * For x close to zero, ln(1+x) =~ x, since
417 * ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1
418 * therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1).
422 * Solve (factor)**(power) =~ .1 given power (5*loadav):
423 * solving for factor,
424 * ln(factor) =~ (-2.30/5*loadav), or
425 * factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) =
426 * exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED
429 * Solve (factor)**(power) =~ .1 given factor == (b/(b+1)):
431 * power*ln(b/(b+1)) =~ -2.30, or
432 * power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED
434 * Actual power values for the implemented algorithm are as follows:
436 * power: 5.68 10.32 14.94 19.55
439 /* calculations for digital decay to forget 90% of usage in 5*loadav sec */
440 #define loadfactor(loadav) (2 * (loadav))
441 #define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE))
443 /* decay 95% of `ts_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */
444 static fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
445 SYSCTL_UINT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
448 * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the
449 * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below
450 * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT).
452 * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used:
453 * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits).
455 * If you don't want to bother with the faster/more-accurate formula, you
456 * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate
457 * (more general) method of calculating the %age of CPU used by a process.
459 #define CCPU_SHIFT 11
462 * Recompute process priorities, every hz ticks.
463 * MP-safe, called without the Giant mutex.
469 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
473 int awake, realstathz;
475 realstathz = stathz ? stathz : hz;
476 sx_slock(&allproc_lock);
477 FOREACH_PROC_IN_SYSTEM(p) {
479 if (p->p_state == PRS_NEW) {
483 FOREACH_THREAD_IN_PROC(p, td) {
488 * Increment sleep time (if sleeping). We
489 * ignore overflow, as above.
492 * The td_sched slptimes are not touched in wakeup
493 * because the thread may not HAVE everything in
494 * memory? XXX I think this is out of date.
496 if (TD_ON_RUNQ(td)) {
498 td->td_flags &= ~TDF_DIDRUN;
499 } else if (TD_IS_RUNNING(td)) {
501 /* Do not clear TDF_DIDRUN */
502 } else if (td->td_flags & TDF_DIDRUN) {
504 td->td_flags &= ~TDF_DIDRUN;
508 * ts_pctcpu is only for ps and ttyinfo().
510 ts->ts_pctcpu = (ts->ts_pctcpu * ccpu) >> FSHIFT;
512 * If the td_sched has been idle the entire second,
513 * stop recalculating its priority until
516 if (ts->ts_cpticks != 0) {
517 #if (FSHIFT >= CCPU_SHIFT)
518 ts->ts_pctcpu += (realstathz == 100)
519 ? ((fixpt_t) ts->ts_cpticks) <<
520 (FSHIFT - CCPU_SHIFT) :
521 100 * (((fixpt_t) ts->ts_cpticks)
522 << (FSHIFT - CCPU_SHIFT)) / realstathz;
524 ts->ts_pctcpu += ((FSCALE - ccpu) *
526 FSCALE / realstathz)) >> FSHIFT;
531 * If there are ANY running threads in this process,
532 * then don't count it as sleeping.
533 * XXX: this is broken.
536 if (ts->ts_slptime > 1) {
538 * In an ideal world, this should not
539 * happen, because whoever woke us
540 * up from the long sleep should have
541 * unwound the slptime and reset our
542 * priority before we run at the stale
543 * priority. Should KASSERT at some
544 * point when all the cases are fixed.
551 if (ts->ts_slptime > 1) {
555 td->td_estcpu = decay_cpu(loadfac, td->td_estcpu);
557 resetpriority_thread(td);
562 sx_sunlock(&allproc_lock);
566 * Main loop for a kthread that executes schedcpu once a second.
569 schedcpu_thread(void)
579 * Recalculate the priority of a process after it has slept for a while.
580 * For all load averages >= 1 and max td_estcpu of 255, sleeping for at
581 * least six times the loadfactor will decay td_estcpu to zero.
584 updatepri(struct thread *td)
591 loadfac = loadfactor(averunnable.ldavg[0]);
592 if (ts->ts_slptime > 5 * loadfac)
595 newcpu = td->td_estcpu;
596 ts->ts_slptime--; /* was incremented in schedcpu() */
597 while (newcpu && --ts->ts_slptime)
598 newcpu = decay_cpu(loadfac, newcpu);
599 td->td_estcpu = newcpu;
604 * Compute the priority of a process when running in user mode.
605 * Arrange to reschedule if the resulting priority is better
606 * than that of the current process.
609 resetpriority(struct thread *td)
611 register unsigned int newpriority;
613 if (td->td_pri_class == PRI_TIMESHARE) {
614 newpriority = PUSER + td->td_estcpu / INVERSE_ESTCPU_WEIGHT +
615 NICE_WEIGHT * (td->td_proc->p_nice - PRIO_MIN);
616 newpriority = min(max(newpriority, PRI_MIN_TIMESHARE),
618 sched_user_prio(td, newpriority);
623 * Update the thread's priority when the associated process's user
627 resetpriority_thread(struct thread *td)
630 /* Only change threads with a time sharing user priority. */
631 if (td->td_priority < PRI_MIN_TIMESHARE ||
632 td->td_priority > PRI_MAX_TIMESHARE)
635 /* XXX the whole needresched thing is broken, but not silly. */
638 sched_prio(td, td->td_user_pri);
643 sched_setup(void *dummy)
647 if (sched_quantum == 0)
648 sched_quantum = SCHED_QUANTUM;
649 hogticks = 2 * sched_quantum;
651 /* Account for thread0. */
655 /* External interfaces start here */
658 * Very early in the boot some setup of scheduler-specific
659 * parts of proc0 and of some scheduler resources needs to be done.
667 * Set up the scheduler specific parts of proc0.
669 proc0.p_sched = NULL; /* XXX */
670 thread0.td_sched = &td_sched0;
671 thread0.td_lock = &sched_lock;
672 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE);
679 return runq_check(&runq) + runq_check(&runq_pcpu[PCPU_GET(cpuid)]);
681 return runq_check(&runq);
686 sched_rr_interval(void)
688 if (sched_quantum == 0)
689 sched_quantum = SCHED_QUANTUM;
690 return (sched_quantum);
694 * We adjust the priority of the current process. The priority of
695 * a process gets worse as it accumulates CPU time. The cpu usage
696 * estimator (td_estcpu) is increased here. resetpriority() will
697 * compute a different priority each time td_estcpu increases by
698 * INVERSE_ESTCPU_WEIGHT
699 * (until MAXPRI is reached). The cpu usage estimator ramps up
700 * quite quickly when the process is running (linearly), and decays
701 * away exponentially, at a rate which is proportionally slower when
702 * the system is busy. The basic principle is that the system will
703 * 90% forget that the process used a lot of CPU time in 5 * loadav
704 * seconds. This causes the system to favor processes which haven't
705 * run much recently, and to round-robin among other processes.
708 sched_clock(struct thread *td)
710 struct pcpuidlestat *stat;
713 THREAD_LOCK_ASSERT(td, MA_OWNED);
717 td->td_estcpu = ESTCPULIM(td->td_estcpu + 1);
718 if ((td->td_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) {
720 resetpriority_thread(td);
724 * Force a context switch if the current thread has used up a full
725 * quantum (default quantum is 100ms).
727 if (!TD_IS_IDLETHREAD(td) &&
728 ticks - PCPU_GET(switchticks) >= sched_quantum)
729 td->td_flags |= TDF_NEEDRESCHED;
731 stat = DPCPU_PTR(idlestat);
732 stat->oldidlecalls = stat->idlecalls;
737 * Charge child's scheduling CPU usage to parent.
740 sched_exit(struct proc *p, struct thread *td)
743 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "proc exit",
744 "prio:%d", td->td_priority);
746 PROC_LOCK_ASSERT(p, MA_OWNED);
747 sched_exit_thread(FIRST_THREAD_IN_PROC(p), td);
751 sched_exit_thread(struct thread *td, struct thread *child)
754 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "exit",
755 "prio:%d", child->td_priority);
757 td->td_estcpu = ESTCPULIM(td->td_estcpu + child->td_estcpu);
760 if ((child->td_flags & TDF_NOLOAD) == 0)
762 thread_unlock(child);
766 sched_fork(struct thread *td, struct thread *childtd)
768 sched_fork_thread(td, childtd);
772 sched_fork_thread(struct thread *td, struct thread *childtd)
776 childtd->td_estcpu = td->td_estcpu;
777 childtd->td_lock = &sched_lock;
778 childtd->td_cpuset = cpuset_ref(td->td_cpuset);
779 childtd->td_priority = childtd->td_base_pri;
780 ts = childtd->td_sched;
781 bzero(ts, sizeof(*ts));
782 ts->ts_flags |= (td->td_sched->ts_flags & TSF_AFFINITY);
786 sched_nice(struct proc *p, int nice)
790 PROC_LOCK_ASSERT(p, MA_OWNED);
792 FOREACH_THREAD_IN_PROC(p, td) {
795 resetpriority_thread(td);
801 sched_class(struct thread *td, int class)
803 THREAD_LOCK_ASSERT(td, MA_OWNED);
804 td->td_pri_class = class;
808 * Adjust the priority of a thread.
811 sched_priority(struct thread *td, u_char prio)
815 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "priority change",
816 "prio:%d", td->td_priority, "new prio:%d", prio, KTR_ATTR_LINKED,
817 sched_tdname(curthread));
818 SDT_PROBE3(sched, , , change_pri, td, td->td_proc, prio);
819 if (td != curthread && prio > td->td_priority) {
820 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
821 "lend prio", "prio:%d", td->td_priority, "new prio:%d",
822 prio, KTR_ATTR_LINKED, sched_tdname(td));
823 SDT_PROBE4(sched, , , lend_pri, td, td->td_proc, prio,
826 THREAD_LOCK_ASSERT(td, MA_OWNED);
827 if (td->td_priority == prio)
829 td->td_priority = prio;
830 if (TD_ON_RUNQ(td) && td->td_rqindex != (prio / RQ_PPQ)) {
832 sched_add(td, SRQ_BORING);
837 * Update a thread's priority when it is lent another thread's
841 sched_lend_prio(struct thread *td, u_char prio)
844 td->td_flags |= TDF_BORROWING;
845 sched_priority(td, prio);
849 * Restore a thread's priority when priority propagation is
850 * over. The prio argument is the minimum priority the thread
851 * needs to have to satisfy other possible priority lending
852 * requests. If the thread's regulary priority is less
853 * important than prio the thread will keep a priority boost
857 sched_unlend_prio(struct thread *td, u_char prio)
861 if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
862 td->td_base_pri <= PRI_MAX_TIMESHARE)
863 base_pri = td->td_user_pri;
865 base_pri = td->td_base_pri;
866 if (prio >= base_pri) {
867 td->td_flags &= ~TDF_BORROWING;
868 sched_prio(td, base_pri);
870 sched_lend_prio(td, prio);
874 sched_prio(struct thread *td, u_char prio)
878 /* First, update the base priority. */
879 td->td_base_pri = prio;
882 * If the thread is borrowing another thread's priority, don't ever
883 * lower the priority.
885 if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
888 /* Change the real priority. */
889 oldprio = td->td_priority;
890 sched_priority(td, prio);
893 * If the thread is on a turnstile, then let the turnstile update
896 if (TD_ON_LOCK(td) && oldprio != prio)
897 turnstile_adjust(td, oldprio);
901 sched_user_prio(struct thread *td, u_char prio)
904 THREAD_LOCK_ASSERT(td, MA_OWNED);
905 td->td_base_user_pri = prio;
906 if (td->td_lend_user_pri <= prio)
908 td->td_user_pri = prio;
912 sched_lend_user_prio(struct thread *td, u_char prio)
915 THREAD_LOCK_ASSERT(td, MA_OWNED);
916 td->td_lend_user_pri = prio;
917 td->td_user_pri = min(prio, td->td_base_user_pri);
918 if (td->td_priority > td->td_user_pri)
919 sched_prio(td, td->td_user_pri);
920 else if (td->td_priority != td->td_user_pri)
921 td->td_flags |= TDF_NEEDRESCHED;
925 sched_sleep(struct thread *td, int pri)
928 THREAD_LOCK_ASSERT(td, MA_OWNED);
929 td->td_slptick = ticks;
930 td->td_sched->ts_slptime = 0;
931 if (pri != 0 && PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
933 if (TD_IS_SUSPENDED(td) || pri >= PSOCK)
934 td->td_flags |= TDF_CANSWAP;
938 sched_switch(struct thread *td, struct thread *newtd, int flags)
948 THREAD_LOCK_ASSERT(td, MA_OWNED);
951 * Switch to the sched lock to fix things up and pick
953 * Block the td_lock in order to avoid breaking the critical path.
955 if (td->td_lock != &sched_lock) {
956 mtx_lock_spin(&sched_lock);
957 tmtx = thread_lock_block(td);
960 if ((td->td_flags & TDF_NOLOAD) == 0)
963 td->td_lastcpu = td->td_oncpu;
964 if (!(flags & SW_PREEMPT))
965 td->td_flags &= ~TDF_NEEDRESCHED;
966 td->td_owepreempt = 0;
967 td->td_oncpu = NOCPU;
970 * At the last moment, if this thread is still marked RUNNING,
971 * then put it back on the run queue as it has not been suspended
972 * or stopped or any thing else similar. We never put the idle
973 * threads on the run queue, however.
975 if (td->td_flags & TDF_IDLETD) {
978 CPU_CLR(PCPU_GET(cpuid), &idle_cpus_mask);
981 if (TD_IS_RUNNING(td)) {
982 /* Put us back on the run queue. */
983 sched_add(td, (flags & SW_PREEMPT) ?
984 SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
985 SRQ_OURSELF|SRQ_YIELDING);
990 * The thread we are about to run needs to be counted
991 * as if it had been added to the run queue and selected.
997 KASSERT((newtd->td_inhibitors == 0),
998 ("trying to run inhibited thread"));
999 newtd->td_flags |= TDF_DIDRUN;
1000 TD_SET_RUNNING(newtd);
1001 if ((newtd->td_flags & TDF_NOLOAD) == 0)
1004 newtd = choosethread();
1005 MPASS(newtd->td_lock == &sched_lock);
1010 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
1011 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
1014 SDT_PROBE2(sched, , , off_cpu, td, td->td_proc);
1017 lock_profile_release_lock(&sched_lock.lock_object);
1018 #ifdef KDTRACE_HOOKS
1020 * If DTrace has set the active vtime enum to anything
1021 * other than INACTIVE (0), then it should have set the
1024 if (dtrace_vtime_active)
1025 (*dtrace_vtime_switch_func)(newtd);
1028 cpu_switch(td, newtd, tmtx != NULL ? tmtx : td->td_lock);
1029 lock_profile_obtain_lock_success(&sched_lock.lock_object,
1030 0, 0, __FILE__, __LINE__);
1032 * Where am I? What year is it?
1033 * We are in the same thread that went to sleep above,
1034 * but any amount of time may have passed. All our context
1035 * will still be available as will local variables.
1036 * PCPU values however may have changed as we may have
1037 * changed CPU so don't trust cached values of them.
1038 * New threads will go to fork_exit() instead of here
1039 * so if you change things here you may need to change
1042 * If the thread above was exiting it will never wake
1043 * up again here, so either it has saved everything it
1044 * needed to, or the thread_wait() or wait() will
1048 SDT_PROBE0(sched, , , on_cpu);
1050 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
1051 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
1054 SDT_PROBE0(sched, , , remain_cpu);
1057 if (td->td_flags & TDF_IDLETD)
1058 CPU_SET(PCPU_GET(cpuid), &idle_cpus_mask);
1060 sched_lock.mtx_lock = (uintptr_t)td;
1061 td->td_oncpu = PCPU_GET(cpuid);
1062 MPASS(td->td_lock == &sched_lock);
1066 sched_wakeup(struct thread *td)
1068 struct td_sched *ts;
1070 THREAD_LOCK_ASSERT(td, MA_OWNED);
1072 td->td_flags &= ~TDF_CANSWAP;
1073 if (ts->ts_slptime > 1) {
1079 sched_add(td, SRQ_BORING);
1084 forward_wakeup(int cpunum)
1087 cpuset_t dontuse, map, map2;
1091 mtx_assert(&sched_lock, MA_OWNED);
1093 CTR0(KTR_RUNQ, "forward_wakeup()");
1095 if ((!forward_wakeup_enabled) ||
1096 (forward_wakeup_use_mask == 0 && forward_wakeup_use_loop == 0))
1098 if (!smp_started || cold || panicstr)
1101 forward_wakeups_requested++;
1104 * Check the idle mask we received against what we calculated
1105 * before in the old version.
1107 me = PCPU_GET(cpuid);
1109 /* Don't bother if we should be doing it ourself. */
1110 if (CPU_ISSET(me, &idle_cpus_mask) &&
1111 (cpunum == NOCPU || me == cpunum))
1114 CPU_SETOF(me, &dontuse);
1115 CPU_OR(&dontuse, &stopped_cpus);
1116 CPU_OR(&dontuse, &hlt_cpus_mask);
1118 if (forward_wakeup_use_loop) {
1119 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
1121 if (!CPU_ISSET(id, &dontuse) &&
1122 pc->pc_curthread == pc->pc_idlethread) {
1128 if (forward_wakeup_use_mask) {
1129 map = idle_cpus_mask;
1130 CPU_NAND(&map, &dontuse);
1132 /* If they are both on, compare and use loop if different. */
1133 if (forward_wakeup_use_loop) {
1134 if (CPU_CMP(&map, &map2)) {
1135 printf("map != map2, loop method preferred\n");
1143 /* If we only allow a specific CPU, then mask off all the others. */
1144 if (cpunum != NOCPU) {
1145 KASSERT((cpunum <= mp_maxcpus),("forward_wakeup: bad cpunum."));
1146 iscpuset = CPU_ISSET(cpunum, &map);
1150 CPU_SETOF(cpunum, &map);
1152 if (!CPU_EMPTY(&map)) {
1153 forward_wakeups_delivered++;
1154 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
1156 if (!CPU_ISSET(id, &map))
1158 if (cpu_idle_wakeup(pc->pc_cpuid))
1161 if (!CPU_EMPTY(&map))
1162 ipi_selected(map, IPI_AST);
1165 if (cpunum == NOCPU)
1166 printf("forward_wakeup: Idle processor not found\n");
1171 kick_other_cpu(int pri, int cpuid)
1176 pcpu = pcpu_find(cpuid);
1177 if (CPU_ISSET(cpuid, &idle_cpus_mask)) {
1178 forward_wakeups_delivered++;
1179 if (!cpu_idle_wakeup(cpuid))
1180 ipi_cpu(cpuid, IPI_AST);
1184 cpri = pcpu->pc_curthread->td_priority;
1188 #if defined(IPI_PREEMPTION) && defined(PREEMPTION)
1189 #if !defined(FULL_PREEMPTION)
1190 if (pri <= PRI_MAX_ITHD)
1191 #endif /* ! FULL_PREEMPTION */
1193 ipi_cpu(cpuid, IPI_PREEMPT);
1196 #endif /* defined(IPI_PREEMPTION) && defined(PREEMPTION) */
1198 pcpu->pc_curthread->td_flags |= TDF_NEEDRESCHED;
1199 ipi_cpu(cpuid, IPI_AST);
1206 sched_pickcpu(struct thread *td)
1210 mtx_assert(&sched_lock, MA_OWNED);
1212 if (THREAD_CAN_SCHED(td, td->td_lastcpu))
1213 best = td->td_lastcpu;
1217 if (!THREAD_CAN_SCHED(td, cpu))
1222 else if (runq_length[cpu] < runq_length[best])
1225 KASSERT(best != NOCPU, ("no valid CPUs"));
1232 sched_add(struct thread *td, int flags)
1236 struct td_sched *ts;
1242 THREAD_LOCK_ASSERT(td, MA_OWNED);
1243 KASSERT((td->td_inhibitors == 0),
1244 ("sched_add: trying to run inhibited thread"));
1245 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
1246 ("sched_add: bad thread state"));
1247 KASSERT(td->td_flags & TDF_INMEM,
1248 ("sched_add: thread swapped out"));
1250 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
1251 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
1252 sched_tdname(curthread));
1253 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
1254 KTR_ATTR_LINKED, sched_tdname(td));
1255 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL,
1256 flags & SRQ_PREEMPTED);
1260 * Now that the thread is moving to the run-queue, set the lock
1261 * to the scheduler's lock.
1263 if (td->td_lock != &sched_lock) {
1264 mtx_lock_spin(&sched_lock);
1265 thread_lock_set(td, &sched_lock);
1270 * If SMP is started and the thread is pinned or otherwise limited to
1271 * a specific set of CPUs, queue the thread to a per-CPU run queue.
1272 * Otherwise, queue the thread to the global run queue.
1274 * If SMP has not yet been started we must use the global run queue
1275 * as per-CPU state may not be initialized yet and we may crash if we
1276 * try to access the per-CPU run queues.
1278 if (smp_started && (td->td_pinned != 0 || td->td_flags & TDF_BOUND ||
1279 ts->ts_flags & TSF_AFFINITY)) {
1280 if (td->td_pinned != 0)
1281 cpu = td->td_lastcpu;
1282 else if (td->td_flags & TDF_BOUND) {
1283 /* Find CPU from bound runq. */
1284 KASSERT(SKE_RUNQ_PCPU(ts),
1285 ("sched_add: bound td_sched not on cpu runq"));
1286 cpu = ts->ts_runq - &runq_pcpu[0];
1288 /* Find a valid CPU for our cpuset */
1289 cpu = sched_pickcpu(td);
1290 ts->ts_runq = &runq_pcpu[cpu];
1293 "sched_add: Put td_sched:%p(td:%p) on cpu%d runq", ts, td,
1297 "sched_add: adding td_sched:%p (td:%p) to gbl runq", ts,
1300 ts->ts_runq = &runq;
1303 cpuid = PCPU_GET(cpuid);
1304 if (single_cpu && cpu != cpuid) {
1305 kick_other_cpu(td->td_priority, cpu);
1308 tidlemsk = idle_cpus_mask;
1309 CPU_NAND(&tidlemsk, &hlt_cpus_mask);
1310 CPU_CLR(cpuid, &tidlemsk);
1312 if (!CPU_ISSET(cpuid, &idle_cpus_mask) &&
1313 ((flags & SRQ_INTR) == 0) &&
1314 !CPU_EMPTY(&tidlemsk))
1315 forwarded = forward_wakeup(cpu);
1319 if ((flags & SRQ_YIELDING) == 0 && maybe_preempt(td))
1326 if ((td->td_flags & TDF_NOLOAD) == 0)
1328 runq_add(ts->ts_runq, td, flags);
1334 struct td_sched *ts;
1337 THREAD_LOCK_ASSERT(td, MA_OWNED);
1338 KASSERT((td->td_inhibitors == 0),
1339 ("sched_add: trying to run inhibited thread"));
1340 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
1341 ("sched_add: bad thread state"));
1342 KASSERT(td->td_flags & TDF_INMEM,
1343 ("sched_add: thread swapped out"));
1344 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
1345 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
1346 sched_tdname(curthread));
1347 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
1348 KTR_ATTR_LINKED, sched_tdname(td));
1349 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL,
1350 flags & SRQ_PREEMPTED);
1353 * Now that the thread is moving to the run-queue, set the lock
1354 * to the scheduler's lock.
1356 if (td->td_lock != &sched_lock) {
1357 mtx_lock_spin(&sched_lock);
1358 thread_lock_set(td, &sched_lock);
1361 CTR2(KTR_RUNQ, "sched_add: adding td_sched:%p (td:%p) to runq", ts, td);
1362 ts->ts_runq = &runq;
1365 * If we are yielding (on the way out anyhow) or the thread
1366 * being saved is US, then don't try be smart about preemption
1367 * or kicking off another CPU as it won't help and may hinder.
1368 * In the YIEDLING case, we are about to run whoever is being
1369 * put in the queue anyhow, and in the OURSELF case, we are
1370 * puting ourself on the run queue which also only happens
1371 * when we are about to yield.
1373 if ((flags & SRQ_YIELDING) == 0) {
1374 if (maybe_preempt(td))
1377 if ((td->td_flags & TDF_NOLOAD) == 0)
1379 runq_add(ts->ts_runq, td, flags);
1385 sched_rem(struct thread *td)
1387 struct td_sched *ts;
1390 KASSERT(td->td_flags & TDF_INMEM,
1391 ("sched_rem: thread swapped out"));
1392 KASSERT(TD_ON_RUNQ(td),
1393 ("sched_rem: thread not on run queue"));
1394 mtx_assert(&sched_lock, MA_OWNED);
1395 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
1396 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
1397 sched_tdname(curthread));
1398 SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
1400 if ((td->td_flags & TDF_NOLOAD) == 0)
1403 if (ts->ts_runq != &runq)
1404 runq_length[ts->ts_runq - runq_pcpu]--;
1406 runq_remove(ts->ts_runq, td);
1411 * Select threads to run. Note that running threads still consume a
1420 mtx_assert(&sched_lock, MA_OWNED);
1422 struct thread *tdcpu;
1425 td = runq_choose_fuzz(&runq, runq_fuzz);
1426 tdcpu = runq_choose(&runq_pcpu[PCPU_GET(cpuid)]);
1430 tdcpu->td_priority < td->td_priority)) {
1431 CTR2(KTR_RUNQ, "choosing td %p from pcpu runq %d", tdcpu,
1434 rq = &runq_pcpu[PCPU_GET(cpuid)];
1436 CTR1(KTR_RUNQ, "choosing td_sched %p from main runq", td);
1441 td = runq_choose(&runq);
1447 runq_length[PCPU_GET(cpuid)]--;
1449 runq_remove(rq, td);
1450 td->td_flags |= TDF_DIDRUN;
1452 KASSERT(td->td_flags & TDF_INMEM,
1453 ("sched_choose: thread swapped out"));
1456 return (PCPU_GET(idlethread));
1460 sched_preempt(struct thread *td)
1463 SDT_PROBE2(sched, , , surrender, td, td->td_proc);
1465 if (td->td_critnest > 1)
1466 td->td_owepreempt = 1;
1468 mi_switch(SW_INVOL | SW_PREEMPT | SWT_PREEMPT, NULL);
1473 sched_userret(struct thread *td)
1476 * XXX we cheat slightly on the locking here to avoid locking in
1477 * the usual case. Setting td_priority here is essentially an
1478 * incomplete workaround for not setting it properly elsewhere.
1479 * Now that some interrupt handlers are threads, not setting it
1480 * properly elsewhere can clobber it in the window between setting
1481 * it here and returning to user mode, so don't waste time setting
1482 * it perfectly here.
1484 KASSERT((td->td_flags & TDF_BORROWING) == 0,
1485 ("thread with borrowed priority returning to userland"));
1486 if (td->td_priority != td->td_user_pri) {
1488 td->td_priority = td->td_user_pri;
1489 td->td_base_pri = td->td_user_pri;
1495 sched_bind(struct thread *td, int cpu)
1497 struct td_sched *ts;
1499 THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
1500 KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
1504 td->td_flags |= TDF_BOUND;
1506 ts->ts_runq = &runq_pcpu[cpu];
1507 if (PCPU_GET(cpuid) == cpu)
1510 mi_switch(SW_VOL, NULL);
1515 sched_unbind(struct thread* td)
1517 THREAD_LOCK_ASSERT(td, MA_OWNED);
1518 KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
1519 td->td_flags &= ~TDF_BOUND;
1523 sched_is_bound(struct thread *td)
1525 THREAD_LOCK_ASSERT(td, MA_OWNED);
1526 return (td->td_flags & TDF_BOUND);
1530 sched_relinquish(struct thread *td)
1533 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
1540 return (sched_tdcnt);
1544 sched_sizeof_proc(void)
1546 return (sizeof(struct proc));
1550 sched_sizeof_thread(void)
1552 return (sizeof(struct thread) + sizeof(struct td_sched));
1556 sched_pctcpu(struct thread *td)
1558 struct td_sched *ts;
1560 THREAD_LOCK_ASSERT(td, MA_OWNED);
1562 return (ts->ts_pctcpu);
1571 * The actual idle process.
1574 sched_idletd(void *dummy)
1576 struct pcpuidlestat *stat;
1578 stat = DPCPU_PTR(idlestat);
1580 mtx_assert(&Giant, MA_NOTOWNED);
1582 while (sched_runnable() == 0) {
1583 cpu_idle(stat->idlecalls + stat->oldidlecalls > 64);
1587 mtx_lock_spin(&sched_lock);
1588 mi_switch(SW_VOL | SWT_IDLE, NULL);
1589 mtx_unlock_spin(&sched_lock);
1594 * A CPU is entering for the first time or a thread is exiting.
1597 sched_throw(struct thread *td)
1600 * Correct spinlock nesting. The idle thread context that we are
1601 * borrowing was created so that it would start out with a single
1602 * spin lock (sched_lock) held in fork_trampoline(). Since we've
1603 * explicitly acquired locks in this function, the nesting count
1604 * is now 2 rather than 1. Since we are nested, calling
1605 * spinlock_exit() will simply adjust the counts without allowing
1606 * spin lock using code to interrupt us.
1609 mtx_lock_spin(&sched_lock);
1611 PCPU_SET(switchtime, cpu_ticks());
1612 PCPU_SET(switchticks, ticks);
1614 lock_profile_release_lock(&sched_lock.lock_object);
1615 MPASS(td->td_lock == &sched_lock);
1617 mtx_assert(&sched_lock, MA_OWNED);
1618 KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
1619 cpu_throw(td, choosethread()); /* doesn't return */
1623 sched_fork_exit(struct thread *td)
1627 * Finish setting up thread glue so that it begins execution in a
1628 * non-nested critical section with sched_lock held but not recursed.
1630 td->td_oncpu = PCPU_GET(cpuid);
1631 sched_lock.mtx_lock = (uintptr_t)td;
1632 lock_profile_obtain_lock_success(&sched_lock.lock_object,
1633 0, 0, __FILE__, __LINE__);
1634 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
1638 sched_tdname(struct thread *td)
1641 struct td_sched *ts;
1644 if (ts->ts_name[0] == '\0')
1645 snprintf(ts->ts_name, sizeof(ts->ts_name),
1646 "%s tid %d", td->td_name, td->td_tid);
1647 return (ts->ts_name);
1649 return (td->td_name);
1655 sched_clear_tdname(struct thread *td)
1657 struct td_sched *ts;
1660 ts->ts_name[0] = '\0';
1665 sched_affinity(struct thread *td)
1668 struct td_sched *ts;
1671 THREAD_LOCK_ASSERT(td, MA_OWNED);
1674 * Set the TSF_AFFINITY flag if there is at least one CPU this
1675 * thread can't run on.
1678 ts->ts_flags &= ~TSF_AFFINITY;
1680 if (!THREAD_CAN_SCHED(td, cpu)) {
1681 ts->ts_flags |= TSF_AFFINITY;
1687 * If this thread can run on all CPUs, nothing else to do.
1689 if (!(ts->ts_flags & TSF_AFFINITY))
1692 /* Pinned threads and bound threads should be left alone. */
1693 if (td->td_pinned != 0 || td->td_flags & TDF_BOUND)
1696 switch (td->td_state) {
1699 * If we are on a per-CPU runqueue that is in the set,
1700 * then nothing needs to be done.
1702 if (ts->ts_runq != &runq &&
1703 THREAD_CAN_SCHED(td, ts->ts_runq - runq_pcpu))
1706 /* Put this thread on a valid per-CPU runqueue. */
1708 sched_add(td, SRQ_BORING);
1712 * See if our current CPU is in the set. If not, force a
1715 if (THREAD_CAN_SCHED(td, td->td_oncpu))
1718 td->td_flags |= TDF_NEEDRESCHED;
1719 if (td != curthread)
1720 ipi_cpu(cpu, IPI_AST);