2 * Copyright (c) 1982, 1986, 1990, 1991, 1993
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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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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>
54 #include <sys/sysctl.h>
56 #include <sys/turnstile.h>
58 #include <machine/pcb.h>
59 #include <machine/smp.h>
62 #include <sys/pmckern.h>
66 #include <sys/dtrace_bsd.h>
67 int dtrace_vtime_active;
68 dtrace_vtime_switch_func_t dtrace_vtime_switch_func;
72 * INVERSE_ESTCPU_WEIGHT is only suitable for statclock() frequencies in
73 * the range 100-256 Hz (approximately).
75 #define ESTCPULIM(e) \
76 min((e), INVERSE_ESTCPU_WEIGHT * (NICE_WEIGHT * (PRIO_MAX - PRIO_MIN) - \
77 RQ_PPQ) + INVERSE_ESTCPU_WEIGHT - 1)
79 #define INVERSE_ESTCPU_WEIGHT (8 * smp_cpus)
81 #define INVERSE_ESTCPU_WEIGHT 8 /* 1 / (priorities per estcpu level). */
83 #define NICE_WEIGHT 1 /* Priorities per nice level. */
85 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
88 * The schedulable entity that runs a context.
89 * This is an extension to the thread structure and is tailored to
90 * the requirements of this scheduler
93 fixpt_t ts_pctcpu; /* (j) %cpu during p_swtime. */
94 int ts_cpticks; /* (j) Ticks of cpu time. */
95 int ts_slptime; /* (j) Seconds !RUNNING. */
97 struct runq *ts_runq; /* runq the thread is currently on */
99 char ts_name[TS_NAME_LEN];
103 /* flags kept in td_flags */
104 #define TDF_DIDRUN TDF_SCHED0 /* thread actually ran. */
105 #define TDF_BOUND TDF_SCHED1 /* Bound to one CPU. */
107 /* flags kept in ts_flags */
108 #define TSF_AFFINITY 0x0001 /* Has a non-"full" CPU set. */
110 #define SKE_RUNQ_PCPU(ts) \
111 ((ts)->ts_runq != 0 && (ts)->ts_runq != &runq)
113 #define THREAD_CAN_SCHED(td, cpu) \
114 CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
116 static struct td_sched td_sched0;
117 struct mtx sched_lock;
119 static int sched_tdcnt; /* Total runnable threads in the system. */
120 static int sched_quantum; /* Roundrobin scheduling quantum in ticks. */
121 #define SCHED_QUANTUM (hz / 10) /* Default sched quantum */
123 static void setup_runqs(void);
124 static void schedcpu(void);
125 static void schedcpu_thread(void);
126 static void sched_priority(struct thread *td, u_char prio);
127 static void sched_setup(void *dummy);
128 static void maybe_resched(struct thread *td);
129 static void updatepri(struct thread *td);
130 static void resetpriority(struct thread *td);
131 static void resetpriority_thread(struct thread *td);
133 static int sched_pickcpu(struct thread *td);
134 static int forward_wakeup(int cpunum);
135 static void kick_other_cpu(int pri, int cpuid);
138 static struct kproc_desc sched_kp = {
143 SYSINIT(schedcpu, SI_SUB_RUN_SCHEDULER, SI_ORDER_FIRST, kproc_start,
145 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
150 static struct runq runq;
156 static struct runq runq_pcpu[MAXCPU];
157 long runq_length[MAXCPU];
160 struct pcpuidlestat {
164 static DPCPU_DEFINE(struct pcpuidlestat, idlestat);
172 for (i = 0; i < MAXCPU; ++i)
173 runq_init(&runq_pcpu[i]);
180 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
184 new_val = sched_quantum * tick;
185 error = sysctl_handle_int(oidp, &new_val, 0, req);
186 if (error != 0 || req->newptr == NULL)
190 sched_quantum = new_val / tick;
191 hogticks = 2 * sched_quantum;
195 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RD, 0, "Scheduler");
197 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "4BSD", 0,
200 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW,
201 0, sizeof sched_quantum, sysctl_kern_quantum, "I",
202 "Roundrobin scheduling quantum in microseconds");
205 /* Enable forwarding of wakeups to all other cpus */
206 SYSCTL_NODE(_kern_sched, OID_AUTO, ipiwakeup, CTLFLAG_RD, NULL, "Kernel SMP");
208 static int runq_fuzz = 1;
209 SYSCTL_INT(_kern_sched, OID_AUTO, runq_fuzz, CTLFLAG_RW, &runq_fuzz, 0, "");
211 static int forward_wakeup_enabled = 1;
212 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, enabled, CTLFLAG_RW,
213 &forward_wakeup_enabled, 0,
214 "Forwarding of wakeup to idle CPUs");
216 static int forward_wakeups_requested = 0;
217 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, requested, CTLFLAG_RD,
218 &forward_wakeups_requested, 0,
219 "Requests for Forwarding of wakeup to idle CPUs");
221 static int forward_wakeups_delivered = 0;
222 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, delivered, CTLFLAG_RD,
223 &forward_wakeups_delivered, 0,
224 "Completed Forwarding of wakeup to idle CPUs");
226 static int forward_wakeup_use_mask = 1;
227 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, usemask, CTLFLAG_RW,
228 &forward_wakeup_use_mask, 0,
229 "Use the mask of idle cpus");
231 static int forward_wakeup_use_loop = 0;
232 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, useloop, CTLFLAG_RW,
233 &forward_wakeup_use_loop, 0,
234 "Use a loop to find idle cpus");
236 static int forward_wakeup_use_single = 0;
237 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, onecpu, CTLFLAG_RW,
238 &forward_wakeup_use_single, 0,
239 "Only signal one idle cpu");
241 static int forward_wakeup_use_htt = 0;
242 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, htt2, CTLFLAG_RW,
243 &forward_wakeup_use_htt, 0,
248 static int sched_followon = 0;
249 SYSCTL_INT(_kern_sched, OID_AUTO, followon, CTLFLAG_RW,
251 "allow threads to share a quantum");
259 KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt);
267 KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt);
270 * Arrange to reschedule if necessary, taking the priorities and
271 * schedulers into account.
274 maybe_resched(struct thread *td)
277 THREAD_LOCK_ASSERT(td, MA_OWNED);
278 if (td->td_priority < curthread->td_priority)
279 curthread->td_flags |= TDF_NEEDRESCHED;
283 * This function is called when a thread is about to be put on run queue
284 * because it has been made runnable or its priority has been adjusted. It
285 * determines if the new thread should be immediately preempted to. If so,
286 * it switches to it and eventually returns true. If not, it returns false
287 * so that the caller may place the thread on an appropriate run queue.
290 maybe_preempt(struct thread *td)
297 * The new thread should not preempt the current thread if any of the
298 * following conditions are true:
300 * - The kernel is in the throes of crashing (panicstr).
301 * - The current thread has a higher (numerically lower) or
302 * equivalent priority. Note that this prevents curthread from
303 * trying to preempt to itself.
304 * - It is too early in the boot for context switches (cold is set).
305 * - The current thread has an inhibitor set or is in the process of
306 * exiting. In this case, the current thread is about to switch
307 * out anyways, so there's no point in preempting. If we did,
308 * the current thread would not be properly resumed as well, so
309 * just avoid that whole landmine.
310 * - If the new thread's priority is not a realtime priority and
311 * the current thread's priority is not an idle priority and
312 * FULL_PREEMPTION is disabled.
314 * If all of these conditions are false, but the current thread is in
315 * a nested critical section, then we have to defer the preemption
316 * until we exit the critical section. Otherwise, switch immediately
320 THREAD_LOCK_ASSERT(td, MA_OWNED);
321 KASSERT((td->td_inhibitors == 0),
322 ("maybe_preempt: trying to run inhibited thread"));
323 pri = td->td_priority;
324 cpri = ctd->td_priority;
325 if (panicstr != NULL || pri >= cpri || cold /* || dumping */ ||
326 TD_IS_INHIBITED(ctd))
328 #ifndef FULL_PREEMPTION
329 if (pri > PRI_MAX_ITHD && cpri < PRI_MIN_IDLE)
333 if (ctd->td_critnest > 1) {
334 CTR1(KTR_PROC, "maybe_preempt: in critical section %d",
336 ctd->td_owepreempt = 1;
340 * Thread is runnable but not yet put on system run queue.
342 MPASS(ctd->td_lock == td->td_lock);
343 MPASS(TD_ON_RUNQ(td));
345 CTR3(KTR_PROC, "preempting to thread %p (pid %d, %s)\n", td,
346 td->td_proc->p_pid, td->td_name);
347 mi_switch(SW_INVOL | SW_PREEMPT | SWT_PREEMPT, td);
349 * td's lock pointer may have changed. We have to return with it
363 * Constants for digital decay and forget:
364 * 90% of (td_estcpu) usage in 5 * loadav time
365 * 95% of (ts_pctcpu) usage in 60 seconds (load insensitive)
366 * Note that, as ps(1) mentions, this can let percentages
367 * total over 100% (I've seen 137.9% for 3 processes).
369 * Note that schedclock() updates td_estcpu and p_cpticks asynchronously.
371 * We wish to decay away 90% of td_estcpu in (5 * loadavg) seconds.
372 * That is, the system wants to compute a value of decay such
373 * that the following for loop:
374 * for (i = 0; i < (5 * loadavg); i++)
375 * td_estcpu *= decay;
378 * for all values of loadavg:
380 * Mathematically this loop can be expressed by saying:
381 * decay ** (5 * loadavg) ~= .1
383 * The system computes decay as:
384 * decay = (2 * loadavg) / (2 * loadavg + 1)
386 * We wish to prove that the system's computation of decay
387 * will always fulfill the equation:
388 * decay ** (5 * loadavg) ~= .1
390 * If we compute b as:
393 * decay = b / (b + 1)
395 * We now need to prove two things:
396 * 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1)
397 * 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg)
400 * For x close to zero, exp(x) =~ 1 + x, since
401 * exp(x) = 0! + x**1/1! + x**2/2! + ... .
402 * therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b.
403 * For x close to zero, ln(1+x) =~ x, since
404 * ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1
405 * therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1).
409 * Solve (factor)**(power) =~ .1 given power (5*loadav):
410 * solving for factor,
411 * ln(factor) =~ (-2.30/5*loadav), or
412 * factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) =
413 * exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED
416 * Solve (factor)**(power) =~ .1 given factor == (b/(b+1)):
418 * power*ln(b/(b+1)) =~ -2.30, or
419 * power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED
421 * Actual power values for the implemented algorithm are as follows:
423 * power: 5.68 10.32 14.94 19.55
426 /* calculations for digital decay to forget 90% of usage in 5*loadav sec */
427 #define loadfactor(loadav) (2 * (loadav))
428 #define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE))
430 /* decay 95% of `ts_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */
431 static fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
432 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
435 * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the
436 * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below
437 * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT).
439 * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used:
440 * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits).
442 * If you don't want to bother with the faster/more-accurate formula, you
443 * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate
444 * (more general) method of calculating the %age of CPU used by a process.
446 #define CCPU_SHIFT 11
449 * Recompute process priorities, every hz ticks.
450 * MP-safe, called without the Giant mutex.
456 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
460 int awake, realstathz;
462 realstathz = stathz ? stathz : hz;
463 sx_slock(&allproc_lock);
464 FOREACH_PROC_IN_SYSTEM(p) {
466 FOREACH_THREAD_IN_PROC(p, td) {
471 * Increment sleep time (if sleeping). We
472 * ignore overflow, as above.
475 * The td_sched slptimes are not touched in wakeup
476 * because the thread may not HAVE everything in
477 * memory? XXX I think this is out of date.
479 if (TD_ON_RUNQ(td)) {
481 td->td_flags &= ~TDF_DIDRUN;
482 } else if (TD_IS_RUNNING(td)) {
484 /* Do not clear TDF_DIDRUN */
485 } else if (td->td_flags & TDF_DIDRUN) {
487 td->td_flags &= ~TDF_DIDRUN;
491 * ts_pctcpu is only for ps and ttyinfo().
493 ts->ts_pctcpu = (ts->ts_pctcpu * ccpu) >> FSHIFT;
495 * If the td_sched has been idle the entire second,
496 * stop recalculating its priority until
499 if (ts->ts_cpticks != 0) {
500 #if (FSHIFT >= CCPU_SHIFT)
501 ts->ts_pctcpu += (realstathz == 100)
502 ? ((fixpt_t) ts->ts_cpticks) <<
503 (FSHIFT - CCPU_SHIFT) :
504 100 * (((fixpt_t) ts->ts_cpticks)
505 << (FSHIFT - CCPU_SHIFT)) / realstathz;
507 ts->ts_pctcpu += ((FSCALE - ccpu) *
509 FSCALE / realstathz)) >> FSHIFT;
514 * If there are ANY running threads in this process,
515 * then don't count it as sleeping.
516 * XXX: this is broken.
519 if (ts->ts_slptime > 1) {
521 * In an ideal world, this should not
522 * happen, because whoever woke us
523 * up from the long sleep should have
524 * unwound the slptime and reset our
525 * priority before we run at the stale
526 * priority. Should KASSERT at some
527 * point when all the cases are fixed.
534 if (ts->ts_slptime > 1) {
538 td->td_estcpu = decay_cpu(loadfac, td->td_estcpu);
540 resetpriority_thread(td);
545 sx_sunlock(&allproc_lock);
549 * Main loop for a kthread that executes schedcpu once a second.
552 schedcpu_thread(void)
562 * Recalculate the priority of a process after it has slept for a while.
563 * For all load averages >= 1 and max td_estcpu of 255, sleeping for at
564 * least six times the loadfactor will decay td_estcpu to zero.
567 updatepri(struct thread *td)
574 loadfac = loadfactor(averunnable.ldavg[0]);
575 if (ts->ts_slptime > 5 * loadfac)
578 newcpu = td->td_estcpu;
579 ts->ts_slptime--; /* was incremented in schedcpu() */
580 while (newcpu && --ts->ts_slptime)
581 newcpu = decay_cpu(loadfac, newcpu);
582 td->td_estcpu = newcpu;
587 * Compute the priority of a process when running in user mode.
588 * Arrange to reschedule if the resulting priority is better
589 * than that of the current process.
592 resetpriority(struct thread *td)
594 register unsigned int newpriority;
596 if (td->td_pri_class == PRI_TIMESHARE) {
597 newpriority = PUSER + td->td_estcpu / INVERSE_ESTCPU_WEIGHT +
598 NICE_WEIGHT * (td->td_proc->p_nice - PRIO_MIN);
599 newpriority = min(max(newpriority, PRI_MIN_TIMESHARE),
601 sched_user_prio(td, newpriority);
606 * Update the thread's priority when the associated process's user
610 resetpriority_thread(struct thread *td)
613 /* Only change threads with a time sharing user priority. */
614 if (td->td_priority < PRI_MIN_TIMESHARE ||
615 td->td_priority > PRI_MAX_TIMESHARE)
618 /* XXX the whole needresched thing is broken, but not silly. */
621 sched_prio(td, td->td_user_pri);
626 sched_setup(void *dummy)
630 if (sched_quantum == 0)
631 sched_quantum = SCHED_QUANTUM;
632 hogticks = 2 * sched_quantum;
634 /* Account for thread0. */
638 /* External interfaces start here */
641 * Very early in the boot some setup of scheduler-specific
642 * parts of proc0 and of some scheduler resources needs to be done.
650 * Set up the scheduler specific parts of proc0.
652 proc0.p_sched = NULL; /* XXX */
653 thread0.td_sched = &td_sched0;
654 thread0.td_lock = &sched_lock;
655 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE);
662 return runq_check(&runq) + runq_check(&runq_pcpu[PCPU_GET(cpuid)]);
664 return runq_check(&runq);
669 sched_rr_interval(void)
671 if (sched_quantum == 0)
672 sched_quantum = SCHED_QUANTUM;
673 return (sched_quantum);
677 * We adjust the priority of the current process. The priority of
678 * a process gets worse as it accumulates CPU time. The cpu usage
679 * estimator (td_estcpu) is increased here. resetpriority() will
680 * compute a different priority each time td_estcpu increases by
681 * INVERSE_ESTCPU_WEIGHT
682 * (until MAXPRI is reached). The cpu usage estimator ramps up
683 * quite quickly when the process is running (linearly), and decays
684 * away exponentially, at a rate which is proportionally slower when
685 * the system is busy. The basic principle is that the system will
686 * 90% forget that the process used a lot of CPU time in 5 * loadav
687 * seconds. This causes the system to favor processes which haven't
688 * run much recently, and to round-robin among other processes.
691 sched_clock(struct thread *td)
693 struct pcpuidlestat *stat;
696 THREAD_LOCK_ASSERT(td, MA_OWNED);
700 td->td_estcpu = ESTCPULIM(td->td_estcpu + 1);
701 if ((td->td_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) {
703 resetpriority_thread(td);
707 * Force a context switch if the current thread has used up a full
708 * quantum (default quantum is 100ms).
710 if (!TD_IS_IDLETHREAD(td) &&
711 ticks - PCPU_GET(switchticks) >= sched_quantum)
712 td->td_flags |= TDF_NEEDRESCHED;
714 stat = DPCPU_PTR(idlestat);
715 stat->oldidlecalls = stat->idlecalls;
720 * Charge child's scheduling CPU usage to parent.
723 sched_exit(struct proc *p, struct thread *td)
726 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "proc exit",
727 "prio:td", td->td_priority);
729 PROC_LOCK_ASSERT(p, MA_OWNED);
730 sched_exit_thread(FIRST_THREAD_IN_PROC(p), td);
734 sched_exit_thread(struct thread *td, struct thread *child)
737 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "exit",
738 "prio:td", child->td_priority);
740 td->td_estcpu = ESTCPULIM(td->td_estcpu + child->td_estcpu);
743 if ((child->td_flags & TDF_NOLOAD) == 0)
745 thread_unlock(child);
749 sched_fork(struct thread *td, struct thread *childtd)
751 sched_fork_thread(td, childtd);
755 sched_fork_thread(struct thread *td, struct thread *childtd)
759 childtd->td_estcpu = td->td_estcpu;
760 childtd->td_lock = &sched_lock;
761 childtd->td_cpuset = cpuset_ref(td->td_cpuset);
762 ts = childtd->td_sched;
763 bzero(ts, sizeof(*ts));
764 ts->ts_flags |= (td->td_sched->ts_flags & TSF_AFFINITY);
768 sched_nice(struct proc *p, int nice)
772 PROC_LOCK_ASSERT(p, MA_OWNED);
774 FOREACH_THREAD_IN_PROC(p, td) {
777 resetpriority_thread(td);
783 sched_class(struct thread *td, int class)
785 THREAD_LOCK_ASSERT(td, MA_OWNED);
786 td->td_pri_class = class;
790 * Adjust the priority of a thread.
793 sched_priority(struct thread *td, u_char prio)
797 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "priority change",
798 "prio:%d", td->td_priority, "new prio:%d", prio, KTR_ATTR_LINKED,
799 sched_tdname(curthread));
800 if (td != curthread && prio > td->td_priority) {
801 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
802 "lend prio", "prio:%d", td->td_priority, "new prio:%d",
803 prio, KTR_ATTR_LINKED, sched_tdname(td));
805 THREAD_LOCK_ASSERT(td, MA_OWNED);
806 if (td->td_priority == prio)
808 td->td_priority = prio;
809 if (TD_ON_RUNQ(td) && td->td_rqindex != (prio / RQ_PPQ)) {
811 sched_add(td, SRQ_BORING);
816 * Update a thread's priority when it is lent another thread's
820 sched_lend_prio(struct thread *td, u_char prio)
823 td->td_flags |= TDF_BORROWING;
824 sched_priority(td, prio);
828 * Restore a thread's priority when priority propagation is
829 * over. The prio argument is the minimum priority the thread
830 * needs to have to satisfy other possible priority lending
831 * requests. If the thread's regulary priority is less
832 * important than prio the thread will keep a priority boost
836 sched_unlend_prio(struct thread *td, u_char prio)
840 if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
841 td->td_base_pri <= PRI_MAX_TIMESHARE)
842 base_pri = td->td_user_pri;
844 base_pri = td->td_base_pri;
845 if (prio >= base_pri) {
846 td->td_flags &= ~TDF_BORROWING;
847 sched_prio(td, base_pri);
849 sched_lend_prio(td, prio);
853 sched_prio(struct thread *td, u_char prio)
857 /* First, update the base priority. */
858 td->td_base_pri = prio;
861 * If the thread is borrowing another thread's priority, don't ever
862 * lower the priority.
864 if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
867 /* Change the real priority. */
868 oldprio = td->td_priority;
869 sched_priority(td, prio);
872 * If the thread is on a turnstile, then let the turnstile update
875 if (TD_ON_LOCK(td) && oldprio != prio)
876 turnstile_adjust(td, oldprio);
880 sched_user_prio(struct thread *td, u_char prio)
884 THREAD_LOCK_ASSERT(td, MA_OWNED);
885 td->td_base_user_pri = prio;
886 if (td->td_flags & TDF_UBORROWING && td->td_user_pri <= prio)
888 oldprio = td->td_user_pri;
889 td->td_user_pri = prio;
893 sched_lend_user_prio(struct thread *td, u_char prio)
897 THREAD_LOCK_ASSERT(td, MA_OWNED);
898 td->td_flags |= TDF_UBORROWING;
899 oldprio = td->td_user_pri;
900 td->td_user_pri = prio;
904 sched_unlend_user_prio(struct thread *td, u_char prio)
908 THREAD_LOCK_ASSERT(td, MA_OWNED);
909 base_pri = td->td_base_user_pri;
910 if (prio >= base_pri) {
911 td->td_flags &= ~TDF_UBORROWING;
912 sched_user_prio(td, base_pri);
914 sched_lend_user_prio(td, prio);
919 sched_sleep(struct thread *td, int pri)
922 THREAD_LOCK_ASSERT(td, MA_OWNED);
923 td->td_slptick = ticks;
924 td->td_sched->ts_slptime = 0;
927 if (TD_IS_SUSPENDED(td) || pri >= PSOCK)
928 td->td_flags |= TDF_CANSWAP;
932 sched_switch(struct thread *td, struct thread *newtd, int flags)
942 THREAD_LOCK_ASSERT(td, MA_OWNED);
945 * Switch to the sched lock to fix things up and pick
947 * Block the td_lock in order to avoid breaking the critical path.
949 if (td->td_lock != &sched_lock) {
950 mtx_lock_spin(&sched_lock);
951 tmtx = thread_lock_block(td);
954 if ((td->td_flags & TDF_NOLOAD) == 0)
958 MPASS(newtd->td_lock == &sched_lock);
959 newtd->td_flags |= (td->td_flags & TDF_NEEDRESCHED);
962 td->td_lastcpu = td->td_oncpu;
963 td->td_flags &= ~TDF_NEEDRESCHED;
964 td->td_owepreempt = 0;
965 td->td_oncpu = NOCPU;
968 * At the last moment, if this thread is still marked RUNNING,
969 * then put it back on the run queue as it has not been suspended
970 * or stopped or any thing else similar. We never put the idle
971 * threads on the run queue, however.
973 if (td->td_flags & TDF_IDLETD) {
976 idle_cpus_mask &= ~PCPU_GET(cpumask);
979 if (TD_IS_RUNNING(td)) {
980 /* Put us back on the run queue. */
981 sched_add(td, (flags & SW_PREEMPT) ?
982 SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
983 SRQ_OURSELF|SRQ_YIELDING);
988 * The thread we are about to run needs to be counted
989 * as if it had been added to the run queue and selected.
995 KASSERT((newtd->td_inhibitors == 0),
996 ("trying to run inhibited thread"));
997 newtd->td_flags |= TDF_DIDRUN;
998 TD_SET_RUNNING(newtd);
999 if ((newtd->td_flags & TDF_NOLOAD) == 0)
1002 newtd = choosethread();
1003 MPASS(newtd->td_lock == &sched_lock);
1008 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
1009 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
1012 lock_profile_release_lock(&sched_lock.lock_object);
1013 #ifdef KDTRACE_HOOKS
1015 * If DTrace has set the active vtime enum to anything
1016 * other than INACTIVE (0), then it should have set the
1019 if (dtrace_vtime_active)
1020 (*dtrace_vtime_switch_func)(newtd);
1023 cpu_switch(td, newtd, tmtx != NULL ? tmtx : td->td_lock);
1024 lock_profile_obtain_lock_success(&sched_lock.lock_object,
1025 0, 0, __FILE__, __LINE__);
1027 * Where am I? What year is it?
1028 * We are in the same thread that went to sleep above,
1029 * but any amount of time may have passed. All our context
1030 * will still be available as will local variables.
1031 * PCPU values however may have changed as we may have
1032 * changed CPU so don't trust cached values of them.
1033 * New threads will go to fork_exit() instead of here
1034 * so if you change things here you may need to change
1037 * If the thread above was exiting it will never wake
1038 * up again here, so either it has saved everything it
1039 * needed to, or the thread_wait() or wait() will
1043 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
1044 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
1049 if (td->td_flags & TDF_IDLETD)
1050 idle_cpus_mask |= PCPU_GET(cpumask);
1052 sched_lock.mtx_lock = (uintptr_t)td;
1053 td->td_oncpu = PCPU_GET(cpuid);
1054 MPASS(td->td_lock == &sched_lock);
1058 sched_wakeup(struct thread *td)
1060 struct td_sched *ts;
1062 THREAD_LOCK_ASSERT(td, MA_OWNED);
1064 td->td_flags &= ~TDF_CANSWAP;
1065 if (ts->ts_slptime > 1) {
1071 sched_add(td, SRQ_BORING);
1076 forward_wakeup(int cpunum)
1079 cpumask_t dontuse, id, map, map2, map3, me;
1081 mtx_assert(&sched_lock, MA_OWNED);
1083 CTR0(KTR_RUNQ, "forward_wakeup()");
1085 if ((!forward_wakeup_enabled) ||
1086 (forward_wakeup_use_mask == 0 && forward_wakeup_use_loop == 0))
1088 if (!smp_started || cold || panicstr)
1091 forward_wakeups_requested++;
1094 * Check the idle mask we received against what we calculated
1095 * before in the old version.
1097 me = PCPU_GET(cpumask);
1099 /* Don't bother if we should be doing it ourself. */
1100 if ((me & idle_cpus_mask) && (cpunum == NOCPU || me == (1 << cpunum)))
1103 dontuse = me | stopped_cpus | hlt_cpus_mask;
1105 if (forward_wakeup_use_loop) {
1106 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) {
1107 id = pc->pc_cpumask;
1108 if ((id & dontuse) == 0 &&
1109 pc->pc_curthread == pc->pc_idlethread) {
1115 if (forward_wakeup_use_mask) {
1117 map = idle_cpus_mask & ~dontuse;
1119 /* If they are both on, compare and use loop if different. */
1120 if (forward_wakeup_use_loop) {
1122 printf("map (%02X) != map3 (%02X)\n", map,
1131 /* If we only allow a specific CPU, then mask off all the others. */
1132 if (cpunum != NOCPU) {
1133 KASSERT((cpunum <= mp_maxcpus),("forward_wakeup: bad cpunum."));
1134 map &= (1 << cpunum);
1136 /* Try choose an idle die. */
1137 if (forward_wakeup_use_htt) {
1138 map2 = (map & (map >> 1)) & 0x5555;
1144 /* Set only one bit. */
1145 if (forward_wakeup_use_single) {
1146 map = map & ((~map) + 1);
1150 forward_wakeups_delivered++;
1151 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) {
1152 id = pc->pc_cpumask;
1153 if ((map & id) == 0)
1155 if (cpu_idle_wakeup(pc->pc_cpuid))
1159 ipi_selected(map, IPI_AST);
1162 if (cpunum == NOCPU)
1163 printf("forward_wakeup: Idle processor not found\n");
1168 kick_other_cpu(int pri, int cpuid)
1173 pcpu = pcpu_find(cpuid);
1174 if (idle_cpus_mask & pcpu->pc_cpumask) {
1175 forward_wakeups_delivered++;
1176 if (!cpu_idle_wakeup(cpuid))
1177 ipi_cpu(cpuid, IPI_AST);
1181 cpri = pcpu->pc_curthread->td_priority;
1185 #if defined(IPI_PREEMPTION) && defined(PREEMPTION)
1186 #if !defined(FULL_PREEMPTION)
1187 if (pri <= PRI_MAX_ITHD)
1188 #endif /* ! FULL_PREEMPTION */
1190 ipi_cpu(cpuid, IPI_PREEMPT);
1193 #endif /* defined(IPI_PREEMPTION) && defined(PREEMPTION) */
1195 pcpu->pc_curthread->td_flags |= TDF_NEEDRESCHED;
1196 ipi_cpu(cpuid, IPI_AST);
1203 sched_pickcpu(struct thread *td)
1207 mtx_assert(&sched_lock, MA_OWNED);
1209 if (THREAD_CAN_SCHED(td, td->td_lastcpu))
1210 best = td->td_lastcpu;
1214 if (!THREAD_CAN_SCHED(td, cpu))
1219 else if (runq_length[cpu] < runq_length[best])
1222 KASSERT(best != NOCPU, ("no valid CPUs"));
1229 sched_add(struct thread *td, int flags)
1232 struct td_sched *ts;
1238 THREAD_LOCK_ASSERT(td, MA_OWNED);
1239 KASSERT((td->td_inhibitors == 0),
1240 ("sched_add: trying to run inhibited thread"));
1241 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
1242 ("sched_add: bad thread state"));
1243 KASSERT(td->td_flags & TDF_INMEM,
1244 ("sched_add: thread swapped out"));
1246 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
1247 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
1248 sched_tdname(curthread));
1249 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
1250 KTR_ATTR_LINKED, sched_tdname(td));
1254 * Now that the thread is moving to the run-queue, set the lock
1255 * to the scheduler's lock.
1257 if (td->td_lock != &sched_lock) {
1258 mtx_lock_spin(&sched_lock);
1259 thread_lock_set(td, &sched_lock);
1263 if (td->td_pinned != 0) {
1264 cpu = td->td_lastcpu;
1265 ts->ts_runq = &runq_pcpu[cpu];
1268 "sched_add: Put td_sched:%p(td:%p) on cpu%d runq", ts, td,
1270 } else if (td->td_flags & TDF_BOUND) {
1271 /* Find CPU from bound runq. */
1272 KASSERT(SKE_RUNQ_PCPU(ts),
1273 ("sched_add: bound td_sched not on cpu runq"));
1274 cpu = ts->ts_runq - &runq_pcpu[0];
1277 "sched_add: Put td_sched:%p(td:%p) on cpu%d runq", ts, td,
1279 } else if (ts->ts_flags & TSF_AFFINITY) {
1280 /* Find a valid CPU for our cpuset */
1281 cpu = sched_pickcpu(td);
1282 ts->ts_runq = &runq_pcpu[cpu];
1285 "sched_add: Put td_sched:%p(td:%p) on cpu%d runq", ts, td,
1289 "sched_add: adding td_sched:%p (td:%p) to gbl runq", ts,
1292 ts->ts_runq = &runq;
1295 if (single_cpu && (cpu != PCPU_GET(cpuid))) {
1296 kick_other_cpu(td->td_priority, cpu);
1299 cpumask_t me = PCPU_GET(cpumask);
1300 cpumask_t idle = idle_cpus_mask & me;
1302 if (!idle && ((flags & SRQ_INTR) == 0) &&
1303 (idle_cpus_mask & ~(hlt_cpus_mask | me)))
1304 forwarded = forward_wakeup(cpu);
1308 if ((flags & SRQ_YIELDING) == 0 && maybe_preempt(td))
1315 if ((td->td_flags & TDF_NOLOAD) == 0)
1317 runq_add(ts->ts_runq, td, flags);
1323 struct td_sched *ts;
1326 THREAD_LOCK_ASSERT(td, MA_OWNED);
1327 KASSERT((td->td_inhibitors == 0),
1328 ("sched_add: trying to run inhibited thread"));
1329 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
1330 ("sched_add: bad thread state"));
1331 KASSERT(td->td_flags & TDF_INMEM,
1332 ("sched_add: thread swapped out"));
1333 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
1334 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
1335 sched_tdname(curthread));
1336 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
1337 KTR_ATTR_LINKED, sched_tdname(td));
1340 * Now that the thread is moving to the run-queue, set the lock
1341 * to the scheduler's lock.
1343 if (td->td_lock != &sched_lock) {
1344 mtx_lock_spin(&sched_lock);
1345 thread_lock_set(td, &sched_lock);
1348 CTR2(KTR_RUNQ, "sched_add: adding td_sched:%p (td:%p) to runq", ts, td);
1349 ts->ts_runq = &runq;
1352 * If we are yielding (on the way out anyhow) or the thread
1353 * being saved is US, then don't try be smart about preemption
1354 * or kicking off another CPU as it won't help and may hinder.
1355 * In the YIEDLING case, we are about to run whoever is being
1356 * put in the queue anyhow, and in the OURSELF case, we are
1357 * puting ourself on the run queue which also only happens
1358 * when we are about to yield.
1360 if ((flags & SRQ_YIELDING) == 0) {
1361 if (maybe_preempt(td))
1364 if ((td->td_flags & TDF_NOLOAD) == 0)
1366 runq_add(ts->ts_runq, td, flags);
1372 sched_rem(struct thread *td)
1374 struct td_sched *ts;
1377 KASSERT(td->td_flags & TDF_INMEM,
1378 ("sched_rem: thread swapped out"));
1379 KASSERT(TD_ON_RUNQ(td),
1380 ("sched_rem: thread not on run queue"));
1381 mtx_assert(&sched_lock, MA_OWNED);
1382 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
1383 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
1384 sched_tdname(curthread));
1386 if ((td->td_flags & TDF_NOLOAD) == 0)
1389 if (ts->ts_runq != &runq)
1390 runq_length[ts->ts_runq - runq_pcpu]--;
1392 runq_remove(ts->ts_runq, td);
1397 * Select threads to run. Note that running threads still consume a
1406 mtx_assert(&sched_lock, MA_OWNED);
1408 struct thread *tdcpu;
1411 td = runq_choose_fuzz(&runq, runq_fuzz);
1412 tdcpu = runq_choose(&runq_pcpu[PCPU_GET(cpuid)]);
1416 tdcpu->td_priority < td->td_priority)) {
1417 CTR2(KTR_RUNQ, "choosing td %p from pcpu runq %d", tdcpu,
1420 rq = &runq_pcpu[PCPU_GET(cpuid)];
1422 CTR1(KTR_RUNQ, "choosing td_sched %p from main runq", td);
1427 td = runq_choose(&runq);
1433 runq_length[PCPU_GET(cpuid)]--;
1435 runq_remove(rq, td);
1436 td->td_flags |= TDF_DIDRUN;
1438 KASSERT(td->td_flags & TDF_INMEM,
1439 ("sched_choose: thread swapped out"));
1442 return (PCPU_GET(idlethread));
1446 sched_preempt(struct thread *td)
1449 if (td->td_critnest > 1)
1450 td->td_owepreempt = 1;
1452 mi_switch(SW_INVOL | SW_PREEMPT | SWT_PREEMPT, NULL);
1457 sched_userret(struct thread *td)
1460 * XXX we cheat slightly on the locking here to avoid locking in
1461 * the usual case. Setting td_priority here is essentially an
1462 * incomplete workaround for not setting it properly elsewhere.
1463 * Now that some interrupt handlers are threads, not setting it
1464 * properly elsewhere can clobber it in the window between setting
1465 * it here and returning to user mode, so don't waste time setting
1466 * it perfectly here.
1468 KASSERT((td->td_flags & TDF_BORROWING) == 0,
1469 ("thread with borrowed priority returning to userland"));
1470 if (td->td_priority != td->td_user_pri) {
1472 td->td_priority = td->td_user_pri;
1473 td->td_base_pri = td->td_user_pri;
1479 sched_bind(struct thread *td, int cpu)
1481 struct td_sched *ts;
1483 THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
1484 KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
1488 td->td_flags |= TDF_BOUND;
1490 ts->ts_runq = &runq_pcpu[cpu];
1491 if (PCPU_GET(cpuid) == cpu)
1494 mi_switch(SW_VOL, NULL);
1499 sched_unbind(struct thread* td)
1501 THREAD_LOCK_ASSERT(td, MA_OWNED);
1502 KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
1503 td->td_flags &= ~TDF_BOUND;
1507 sched_is_bound(struct thread *td)
1509 THREAD_LOCK_ASSERT(td, MA_OWNED);
1510 return (td->td_flags & TDF_BOUND);
1514 sched_relinquish(struct thread *td)
1517 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
1524 return (sched_tdcnt);
1528 sched_sizeof_proc(void)
1530 return (sizeof(struct proc));
1534 sched_sizeof_thread(void)
1536 return (sizeof(struct thread) + sizeof(struct td_sched));
1540 sched_pctcpu(struct thread *td)
1542 struct td_sched *ts;
1544 THREAD_LOCK_ASSERT(td, MA_OWNED);
1546 return (ts->ts_pctcpu);
1555 * The actual idle process.
1558 sched_idletd(void *dummy)
1560 struct pcpuidlestat *stat;
1562 stat = DPCPU_PTR(idlestat);
1564 mtx_assert(&Giant, MA_NOTOWNED);
1566 while (sched_runnable() == 0) {
1567 cpu_idle(stat->idlecalls + stat->oldidlecalls > 64);
1571 mtx_lock_spin(&sched_lock);
1572 mi_switch(SW_VOL | SWT_IDLE, NULL);
1573 mtx_unlock_spin(&sched_lock);
1578 * A CPU is entering for the first time or a thread is exiting.
1581 sched_throw(struct thread *td)
1584 * Correct spinlock nesting. The idle thread context that we are
1585 * borrowing was created so that it would start out with a single
1586 * spin lock (sched_lock) held in fork_trampoline(). Since we've
1587 * explicitly acquired locks in this function, the nesting count
1588 * is now 2 rather than 1. Since we are nested, calling
1589 * spinlock_exit() will simply adjust the counts without allowing
1590 * spin lock using code to interrupt us.
1593 mtx_lock_spin(&sched_lock);
1596 lock_profile_release_lock(&sched_lock.lock_object);
1597 MPASS(td->td_lock == &sched_lock);
1599 mtx_assert(&sched_lock, MA_OWNED);
1600 KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
1601 PCPU_SET(switchtime, cpu_ticks());
1602 PCPU_SET(switchticks, ticks);
1603 cpu_throw(td, choosethread()); /* doesn't return */
1607 sched_fork_exit(struct thread *td)
1611 * Finish setting up thread glue so that it begins execution in a
1612 * non-nested critical section with sched_lock held but not recursed.
1614 td->td_oncpu = PCPU_GET(cpuid);
1615 sched_lock.mtx_lock = (uintptr_t)td;
1616 lock_profile_obtain_lock_success(&sched_lock.lock_object,
1617 0, 0, __FILE__, __LINE__);
1618 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
1622 sched_tdname(struct thread *td)
1625 struct td_sched *ts;
1628 if (ts->ts_name[0] == '\0')
1629 snprintf(ts->ts_name, sizeof(ts->ts_name),
1630 "%s tid %d", td->td_name, td->td_tid);
1631 return (ts->ts_name);
1633 return (td->td_name);
1638 sched_affinity(struct thread *td)
1641 struct td_sched *ts;
1644 THREAD_LOCK_ASSERT(td, MA_OWNED);
1647 * Set the TSF_AFFINITY flag if there is at least one CPU this
1648 * thread can't run on.
1651 ts->ts_flags &= ~TSF_AFFINITY;
1653 if (!THREAD_CAN_SCHED(td, cpu)) {
1654 ts->ts_flags |= TSF_AFFINITY;
1660 * If this thread can run on all CPUs, nothing else to do.
1662 if (!(ts->ts_flags & TSF_AFFINITY))
1665 /* Pinned threads and bound threads should be left alone. */
1666 if (td->td_pinned != 0 || td->td_flags & TDF_BOUND)
1669 switch (td->td_state) {
1672 * If we are on a per-CPU runqueue that is in the set,
1673 * then nothing needs to be done.
1675 if (ts->ts_runq != &runq &&
1676 THREAD_CAN_SCHED(td, ts->ts_runq - runq_pcpu))
1679 /* Put this thread on a valid per-CPU runqueue. */
1681 sched_add(td, SRQ_BORING);
1685 * See if our current CPU is in the set. If not, force a
1688 if (THREAD_CAN_SCHED(td, td->td_oncpu))
1691 td->td_flags |= TDF_NEEDRESCHED;
1692 if (td != curthread)
1693 ipi_cpu(cpu, IPI_AST);