FreeBSD/Linux Kernel Cross Reference
sys/kern/sched_4bsd.c
1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1982, 1986, 1990, 1991, 1993
5 * The Regents of the University of California. All rights reserved.
6 * (c) UNIX System Laboratories, Inc.
7 * All or some portions of this file are derived from material licensed
8 * to the University of California by American Telephone and Telegraph
9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
10 * the permission of UNIX System Laboratories, Inc.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37 #include <sys/cdefs.h>
38 __FBSDID("$FreeBSD$");
39
40 #include "opt_hwpmc_hooks.h"
41 #include "opt_sched.h"
42
43 #include <sys/param.h>
44 #include <sys/systm.h>
45 #include <sys/cpuset.h>
46 #include <sys/kernel.h>
47 #include <sys/ktr.h>
48 #include <sys/lock.h>
49 #include <sys/kthread.h>
50 #include <sys/mutex.h>
51 #include <sys/proc.h>
52 #include <sys/resourcevar.h>
53 #include <sys/sched.h>
54 #include <sys/sdt.h>
55 #include <sys/smp.h>
56 #include <sys/sysctl.h>
57 #include <sys/sx.h>
58 #include <sys/turnstile.h>
59 #include <sys/umtxvar.h>
60 #include <machine/pcb.h>
61 #include <machine/smp.h>
62
63 #ifdef HWPMC_HOOKS
64 #include <sys/pmckern.h>
65 #endif
66
67 #ifdef KDTRACE_HOOKS
68 #include <sys/dtrace_bsd.h>
69 int __read_mostly dtrace_vtime_active;
70 dtrace_vtime_switch_func_t dtrace_vtime_switch_func;
71 #endif
72
73 /*
74 * INVERSE_ESTCPU_WEIGHT is only suitable for statclock() frequencies in
75 * the range 100-256 Hz (approximately).
76 */
77 #define ESTCPULIM(e) \
78 min((e), INVERSE_ESTCPU_WEIGHT * (NICE_WEIGHT * (PRIO_MAX - PRIO_MIN) - \
79 RQ_PPQ) + INVERSE_ESTCPU_WEIGHT - 1)
80 #ifdef SMP
81 #define INVERSE_ESTCPU_WEIGHT (8 * smp_cpus)
82 #else
83 #define INVERSE_ESTCPU_WEIGHT 8 /* 1 / (priorities per estcpu level). */
84 #endif
85 #define NICE_WEIGHT 1 /* Priorities per nice level. */
86
87 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
88
89 /*
90 * The schedulable entity that runs a context.
91 * This is an extension to the thread structure and is tailored to
92 * the requirements of this scheduler.
93 * All fields are protected by the scheduler lock.
94 */
95 struct td_sched {
96 fixpt_t ts_pctcpu; /* %cpu during p_swtime. */
97 u_int ts_estcpu; /* Estimated cpu utilization. */
98 int ts_cpticks; /* Ticks of cpu time. */
99 int ts_slptime; /* Seconds !RUNNING. */
100 int ts_slice; /* Remaining part of time slice. */
101 int ts_flags;
102 struct runq *ts_runq; /* runq the thread is currently on */
103 #ifdef KTR
104 char ts_name[TS_NAME_LEN];
105 #endif
106 };
107
108 /* flags kept in td_flags */
109 #define TDF_DIDRUN TDF_SCHED0 /* thread actually ran. */
110 #define TDF_BOUND TDF_SCHED1 /* Bound to one CPU. */
111 #define TDF_SLICEEND TDF_SCHED2 /* Thread time slice is over. */
112
113 /* flags kept in ts_flags */
114 #define TSF_AFFINITY 0x0001 /* Has a non-"full" CPU set. */
115
116 #define SKE_RUNQ_PCPU(ts) \
117 ((ts)->ts_runq != 0 && (ts)->ts_runq != &runq)
118
119 #define THREAD_CAN_SCHED(td, cpu) \
120 CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
121
122 _Static_assert(sizeof(struct thread) + sizeof(struct td_sched) <=
123 sizeof(struct thread0_storage),
124 "increase struct thread0_storage.t0st_sched size");
125
126 static struct mtx sched_lock;
127
128 static int realstathz = 127; /* stathz is sometimes 0 and run off of hz. */
129 static int sched_tdcnt; /* Total runnable threads in the system. */
130 static int sched_slice = 12; /* Thread run time before rescheduling. */
131
132 static void setup_runqs(void);
133 static void schedcpu(void);
134 static void schedcpu_thread(void);
135 static void sched_priority(struct thread *td, u_char prio);
136 static void sched_setup(void *dummy);
137 static void maybe_resched(struct thread *td);
138 static void updatepri(struct thread *td);
139 static void resetpriority(struct thread *td);
140 static void resetpriority_thread(struct thread *td);
141 #ifdef SMP
142 static int sched_pickcpu(struct thread *td);
143 static int forward_wakeup(int cpunum);
144 static void kick_other_cpu(int pri, int cpuid);
145 #endif
146
147 static struct kproc_desc sched_kp = {
148 "schedcpu",
149 schedcpu_thread,
150 NULL
151 };
152 SYSINIT(schedcpu, SI_SUB_LAST, SI_ORDER_FIRST, kproc_start,
153 &sched_kp);
154 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
155
156 static void sched_initticks(void *dummy);
157 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
158 NULL);
159
160 /*
161 * Global run queue.
162 */
163 static struct runq runq;
164
165 #ifdef SMP
166 /*
167 * Per-CPU run queues
168 */
169 static struct runq runq_pcpu[MAXCPU];
170 long runq_length[MAXCPU];
171
172 static cpuset_t idle_cpus_mask;
173 #endif
174
175 struct pcpuidlestat {
176 u_int idlecalls;
177 u_int oldidlecalls;
178 };
179 DPCPU_DEFINE_STATIC(struct pcpuidlestat, idlestat);
180
181 static void
182 setup_runqs(void)
183 {
184 #ifdef SMP
185 int i;
186
187 for (i = 0; i < MAXCPU; ++i)
188 runq_init(&runq_pcpu[i]);
189 #endif
190
191 runq_init(&runq);
192 }
193
194 static int
195 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
196 {
197 int error, new_val, period;
198
199 period = 1000000 / realstathz;
200 new_val = period * sched_slice;
201 error = sysctl_handle_int(oidp, &new_val, 0, req);
202 if (error != 0 || req->newptr == NULL)
203 return (error);
204 if (new_val <= 0)
205 return (EINVAL);
206 sched_slice = imax(1, (new_val + period / 2) / period);
207 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
208 realstathz);
209 return (0);
210 }
211
212 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
213 "Scheduler");
214
215 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "4BSD", 0,
216 "Scheduler name");
217 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum,
218 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
219 sysctl_kern_quantum, "I",
220 "Quantum for timeshare threads in microseconds");
221 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
222 "Quantum for timeshare threads in stathz ticks");
223 #ifdef SMP
224 /* Enable forwarding of wakeups to all other cpus */
225 static SYSCTL_NODE(_kern_sched, OID_AUTO, ipiwakeup,
226 CTLFLAG_RD | CTLFLAG_MPSAFE, NULL,
227 "Kernel SMP");
228
229 static int runq_fuzz = 1;
230 SYSCTL_INT(_kern_sched, OID_AUTO, runq_fuzz, CTLFLAG_RW, &runq_fuzz, 0, "");
231
232 static int forward_wakeup_enabled = 1;
233 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, enabled, CTLFLAG_RW,
234 &forward_wakeup_enabled, 0,
235 "Forwarding of wakeup to idle CPUs");
236
237 static int forward_wakeups_requested = 0;
238 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, requested, CTLFLAG_RD,
239 &forward_wakeups_requested, 0,
240 "Requests for Forwarding of wakeup to idle CPUs");
241
242 static int forward_wakeups_delivered = 0;
243 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, delivered, CTLFLAG_RD,
244 &forward_wakeups_delivered, 0,
245 "Completed Forwarding of wakeup to idle CPUs");
246
247 static int forward_wakeup_use_mask = 1;
248 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, usemask, CTLFLAG_RW,
249 &forward_wakeup_use_mask, 0,
250 "Use the mask of idle cpus");
251
252 static int forward_wakeup_use_loop = 0;
253 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, useloop, CTLFLAG_RW,
254 &forward_wakeup_use_loop, 0,
255 "Use a loop to find idle cpus");
256
257 #endif
258 #if 0
259 static int sched_followon = 0;
260 SYSCTL_INT(_kern_sched, OID_AUTO, followon, CTLFLAG_RW,
261 &sched_followon, 0,
262 "allow threads to share a quantum");
263 #endif
264
265 SDT_PROVIDER_DEFINE(sched);
266
267 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *",
268 "struct proc *", "uint8_t");
269 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *",
270 "struct proc *", "void *");
271 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *",
272 "struct proc *", "void *", "int");
273 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *",
274 "struct proc *", "uint8_t", "struct thread *");
275 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int");
276 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *",
277 "struct proc *");
278 SDT_PROBE_DEFINE(sched, , , on__cpu);
279 SDT_PROBE_DEFINE(sched, , , remain__cpu);
280 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *",
281 "struct proc *");
282
283 static __inline void
284 sched_load_add(void)
285 {
286
287 sched_tdcnt++;
288 KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt);
289 SDT_PROBE2(sched, , , load__change, NOCPU, sched_tdcnt);
290 }
291
292 static __inline void
293 sched_load_rem(void)
294 {
295
296 sched_tdcnt--;
297 KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt);
298 SDT_PROBE2(sched, , , load__change, NOCPU, sched_tdcnt);
299 }
300 /*
301 * Arrange to reschedule if necessary, taking the priorities and
302 * schedulers into account.
303 */
304 static void
305 maybe_resched(struct thread *td)
306 {
307
308 THREAD_LOCK_ASSERT(td, MA_OWNED);
309 if (td->td_priority < curthread->td_priority)
310 ast_sched_locked(curthread, TDA_SCHED);
311 }
312
313 /*
314 * This function is called when a thread is about to be put on run queue
315 * because it has been made runnable or its priority has been adjusted. It
316 * determines if the new thread should preempt the current thread. If so,
317 * it sets td_owepreempt to request a preemption.
318 */
319 int
320 maybe_preempt(struct thread *td)
321 {
322 #ifdef PREEMPTION
323 struct thread *ctd;
324 int cpri, pri;
325
326 /*
327 * The new thread should not preempt the current thread if any of the
328 * following conditions are true:
329 *
330 * - The kernel is in the throes of crashing (panicstr).
331 * - The current thread has a higher (numerically lower) or
332 * equivalent priority. Note that this prevents curthread from
333 * trying to preempt to itself.
334 * - The current thread has an inhibitor set or is in the process of
335 * exiting. In this case, the current thread is about to switch
336 * out anyways, so there's no point in preempting. If we did,
337 * the current thread would not be properly resumed as well, so
338 * just avoid that whole landmine.
339 * - If the new thread's priority is not a realtime priority and
340 * the current thread's priority is not an idle priority and
341 * FULL_PREEMPTION is disabled.
342 *
343 * If all of these conditions are false, but the current thread is in
344 * a nested critical section, then we have to defer the preemption
345 * until we exit the critical section. Otherwise, switch immediately
346 * to the new thread.
347 */
348 ctd = curthread;
349 THREAD_LOCK_ASSERT(td, MA_OWNED);
350 KASSERT((td->td_inhibitors == 0),
351 ("maybe_preempt: trying to run inhibited thread"));
352 pri = td->td_priority;
353 cpri = ctd->td_priority;
354 if (KERNEL_PANICKED() || pri >= cpri /* || dumping */ ||
355 TD_IS_INHIBITED(ctd))
356 return (0);
357 #ifndef FULL_PREEMPTION
358 if (pri > PRI_MAX_ITHD && cpri < PRI_MIN_IDLE)
359 return (0);
360 #endif
361
362 CTR0(KTR_PROC, "maybe_preempt: scheduling preemption");
363 ctd->td_owepreempt = 1;
364 return (1);
365 #else
366 return (0);
367 #endif
368 }
369
370 /*
371 * Constants for digital decay and forget:
372 * 90% of (ts_estcpu) usage in 5 * loadav time
373 * 95% of (ts_pctcpu) usage in 60 seconds (load insensitive)
374 * Note that, as ps(1) mentions, this can let percentages
375 * total over 100% (I've seen 137.9% for 3 processes).
376 *
377 * Note that schedclock() updates ts_estcpu and p_cpticks asynchronously.
378 *
379 * We wish to decay away 90% of ts_estcpu in (5 * loadavg) seconds.
380 * That is, the system wants to compute a value of decay such
381 * that the following for loop:
382 * for (i = 0; i < (5 * loadavg); i++)
383 * ts_estcpu *= decay;
384 * will compute
385 * ts_estcpu *= 0.1;
386 * for all values of loadavg:
387 *
388 * Mathematically this loop can be expressed by saying:
389 * decay ** (5 * loadavg) ~= .1
390 *
391 * The system computes decay as:
392 * decay = (2 * loadavg) / (2 * loadavg + 1)
393 *
394 * We wish to prove that the system's computation of decay
395 * will always fulfill the equation:
396 * decay ** (5 * loadavg) ~= .1
397 *
398 * If we compute b as:
399 * b = 2 * loadavg
400 * then
401 * decay = b / (b + 1)
402 *
403 * We now need to prove two things:
404 * 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1)
405 * 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg)
406 *
407 * Facts:
408 * For x close to zero, exp(x) =~ 1 + x, since
409 * exp(x) = 0! + x**1/1! + x**2/2! + ... .
410 * therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b.
411 * For x close to zero, ln(1+x) =~ x, since
412 * ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1
413 * therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1).
414 * ln(.1) =~ -2.30
415 *
416 * Proof of (1):
417 * Solve (factor)**(power) =~ .1 given power (5*loadav):
418 * solving for factor,
419 * ln(factor) =~ (-2.30/5*loadav), or
420 * factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) =
421 * exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED
422 *
423 * Proof of (2):
424 * Solve (factor)**(power) =~ .1 given factor == (b/(b+1)):
425 * solving for power,
426 * power*ln(b/(b+1)) =~ -2.30, or
427 * power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED
428 *
429 * Actual power values for the implemented algorithm are as follows:
430 * loadav: 1 2 3 4
431 * power: 5.68 10.32 14.94 19.55
432 */
433
434 /* calculations for digital decay to forget 90% of usage in 5*loadav sec */
435 #define loadfactor(loadav) (2 * (loadav))
436 #define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE))
437
438 /* decay 95% of `ts_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */
439 static fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
440 SYSCTL_UINT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0,
441 "Decay factor used for updating %CPU");
442
443 /*
444 * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the
445 * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below
446 * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT).
447 *
448 * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used:
449 * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits).
450 *
451 * If you don't want to bother with the faster/more-accurate formula, you
452 * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate
453 * (more general) method of calculating the %age of CPU used by a process.
454 */
455 #define CCPU_SHIFT 11
456
457 /*
458 * Recompute process priorities, every hz ticks.
459 * MP-safe, called without the Giant mutex.
460 */
461 /* ARGSUSED */
462 static void
463 schedcpu(void)
464 {
465 fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
466 struct thread *td;
467 struct proc *p;
468 struct td_sched *ts;
469 int awake;
470
471 sx_slock(&allproc_lock);
472 FOREACH_PROC_IN_SYSTEM(p) {
473 PROC_LOCK(p);
474 if (p->p_state == PRS_NEW) {
475 PROC_UNLOCK(p);
476 continue;
477 }
478 FOREACH_THREAD_IN_PROC(p, td) {
479 awake = 0;
480 ts = td_get_sched(td);
481 thread_lock(td);
482 /*
483 * Increment sleep time (if sleeping). We
484 * ignore overflow, as above.
485 */
486 /*
487 * The td_sched slptimes are not touched in wakeup
488 * because the thread may not HAVE everything in
489 * memory? XXX I think this is out of date.
490 */
491 if (TD_ON_RUNQ(td)) {
492 awake = 1;
493 td->td_flags &= ~TDF_DIDRUN;
494 } else if (TD_IS_RUNNING(td)) {
495 awake = 1;
496 /* Do not clear TDF_DIDRUN */
497 } else if (td->td_flags & TDF_DIDRUN) {
498 awake = 1;
499 td->td_flags &= ~TDF_DIDRUN;
500 }
501
502 /*
503 * ts_pctcpu is only for ps and ttyinfo().
504 */
505 ts->ts_pctcpu = (ts->ts_pctcpu * ccpu) >> FSHIFT;
506 /*
507 * If the td_sched has been idle the entire second,
508 * stop recalculating its priority until
509 * it wakes up.
510 */
511 if (ts->ts_cpticks != 0) {
512 #if (FSHIFT >= CCPU_SHIFT)
513 ts->ts_pctcpu += (realstathz == 100)
514 ? ((fixpt_t) ts->ts_cpticks) <<
515 (FSHIFT - CCPU_SHIFT) :
516 100 * (((fixpt_t) ts->ts_cpticks)
517 << (FSHIFT - CCPU_SHIFT)) / realstathz;
518 #else
519 ts->ts_pctcpu += ((FSCALE - ccpu) *
520 (ts->ts_cpticks *
521 FSCALE / realstathz)) >> FSHIFT;
522 #endif
523 ts->ts_cpticks = 0;
524 }
525 /*
526 * If there are ANY running threads in this process,
527 * then don't count it as sleeping.
528 * XXX: this is broken.
529 */
530 if (awake) {
531 if (ts->ts_slptime > 1) {
532 /*
533 * In an ideal world, this should not
534 * happen, because whoever woke us
535 * up from the long sleep should have
536 * unwound the slptime and reset our
537 * priority before we run at the stale
538 * priority. Should KASSERT at some
539 * point when all the cases are fixed.
540 */
541 updatepri(td);
542 }
543 ts->ts_slptime = 0;
544 } else
545 ts->ts_slptime++;
546 if (ts->ts_slptime > 1) {
547 thread_unlock(td);
548 continue;
549 }
550 ts->ts_estcpu = decay_cpu(loadfac, ts->ts_estcpu);
551 resetpriority(td);
552 resetpriority_thread(td);
553 thread_unlock(td);
554 }
555 PROC_UNLOCK(p);
556 }
557 sx_sunlock(&allproc_lock);
558 }
559
560 /*
561 * Main loop for a kthread that executes schedcpu once a second.
562 */
563 static void
564 schedcpu_thread(void)
565 {
566
567 for (;;) {
568 schedcpu();
569 pause("-", hz);
570 }
571 }
572
573 /*
574 * Recalculate the priority of a process after it has slept for a while.
575 * For all load averages >= 1 and max ts_estcpu of 255, sleeping for at
576 * least six times the loadfactor will decay ts_estcpu to zero.
577 */
578 static void
579 updatepri(struct thread *td)
580 {
581 struct td_sched *ts;
582 fixpt_t loadfac;
583 unsigned int newcpu;
584
585 ts = td_get_sched(td);
586 loadfac = loadfactor(averunnable.ldavg[0]);
587 if (ts->ts_slptime > 5 * loadfac)
588 ts->ts_estcpu = 0;
589 else {
590 newcpu = ts->ts_estcpu;
591 ts->ts_slptime--; /* was incremented in schedcpu() */
592 while (newcpu && --ts->ts_slptime)
593 newcpu = decay_cpu(loadfac, newcpu);
594 ts->ts_estcpu = newcpu;
595 }
596 }
597
598 /*
599 * Compute the priority of a process when running in user mode.
600 * Arrange to reschedule if the resulting priority is better
601 * than that of the current process.
602 */
603 static void
604 resetpriority(struct thread *td)
605 {
606 u_int newpriority;
607
608 if (td->td_pri_class != PRI_TIMESHARE)
609 return;
610 newpriority = PUSER +
611 td_get_sched(td)->ts_estcpu / INVERSE_ESTCPU_WEIGHT +
612 NICE_WEIGHT * (td->td_proc->p_nice - PRIO_MIN);
613 newpriority = min(max(newpriority, PRI_MIN_TIMESHARE),
614 PRI_MAX_TIMESHARE);
615 sched_user_prio(td, newpriority);
616 }
617
618 /*
619 * Update the thread's priority when the associated process's user
620 * priority changes.
621 */
622 static void
623 resetpriority_thread(struct thread *td)
624 {
625
626 /* Only change threads with a time sharing user priority. */
627 if (td->td_priority < PRI_MIN_TIMESHARE ||
628 td->td_priority > PRI_MAX_TIMESHARE)
629 return;
630
631 /* XXX the whole needresched thing is broken, but not silly. */
632 maybe_resched(td);
633
634 sched_prio(td, td->td_user_pri);
635 }
636
637 /* ARGSUSED */
638 static void
639 sched_setup(void *dummy)
640 {
641
642 setup_runqs();
643
644 /* Account for thread0. */
645 sched_load_add();
646 }
647
648 /*
649 * This routine determines time constants after stathz and hz are setup.
650 */
651 static void
652 sched_initticks(void *dummy)
653 {
654
655 realstathz = stathz ? stathz : hz;
656 sched_slice = realstathz / 10; /* ~100ms */
657 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
658 realstathz);
659 }
660
661 /* External interfaces start here */
662
663 /*
664 * Very early in the boot some setup of scheduler-specific
665 * parts of proc0 and of some scheduler resources needs to be done.
666 * Called from:
667 * proc0_init()
668 */
669 void
670 schedinit(void)
671 {
672
673 /*
674 * Set up the scheduler specific parts of thread0.
675 */
676 thread0.td_lock = &sched_lock;
677 td_get_sched(&thread0)->ts_slice = sched_slice;
678 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN);
679 }
680
681 void
682 schedinit_ap(void)
683 {
684
685 /* Nothing needed. */
686 }
687
688 int
689 sched_runnable(void)
690 {
691 #ifdef SMP
692 return runq_check(&runq) + runq_check(&runq_pcpu[PCPU_GET(cpuid)]);
693 #else
694 return runq_check(&runq);
695 #endif
696 }
697
698 int
699 sched_rr_interval(void)
700 {
701
702 /* Convert sched_slice from stathz to hz. */
703 return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
704 }
705
706 SCHED_STAT_DEFINE(ithread_demotions, "Interrupt thread priority demotions");
707 SCHED_STAT_DEFINE(ithread_preemptions,
708 "Interrupt thread preemptions due to time-sharing");
709
710 /*
711 * We adjust the priority of the current process. The priority of a
712 * process gets worse as it accumulates CPU time. The cpu usage
713 * estimator (ts_estcpu) is increased here. resetpriority() will
714 * compute a different priority each time ts_estcpu increases by
715 * INVERSE_ESTCPU_WEIGHT (until PRI_MAX_TIMESHARE is reached). The
716 * cpu usage estimator ramps up quite quickly when the process is
717 * running (linearly), and decays away exponentially, at a rate which
718 * is proportionally slower when the system is busy. The basic
719 * principle is that the system will 90% forget that the process used
720 * a lot of CPU time in 5 * loadav seconds. This causes the system to
721 * favor processes which haven't run much recently, and to round-robin
722 * among other processes.
723 */
724 static void
725 sched_clock_tick(struct thread *td)
726 {
727 struct pcpuidlestat *stat;
728 struct td_sched *ts;
729
730 THREAD_LOCK_ASSERT(td, MA_OWNED);
731 ts = td_get_sched(td);
732
733 ts->ts_cpticks++;
734 ts->ts_estcpu = ESTCPULIM(ts->ts_estcpu + 1);
735 if ((ts->ts_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) {
736 resetpriority(td);
737 resetpriority_thread(td);
738 }
739
740 /*
741 * Force a context switch if the current thread has used up a full
742 * time slice (default is 100ms).
743 */
744 if (!TD_IS_IDLETHREAD(td) && --ts->ts_slice <= 0) {
745 ts->ts_slice = sched_slice;
746
747 /*
748 * If an ithread uses a full quantum, demote its
749 * priority and preempt it.
750 */
751 if (PRI_BASE(td->td_pri_class) == PRI_ITHD) {
752 SCHED_STAT_INC(ithread_preemptions);
753 td->td_owepreempt = 1;
754 if (td->td_base_pri + RQ_PPQ < PRI_MAX_ITHD) {
755 SCHED_STAT_INC(ithread_demotions);
756 sched_prio(td, td->td_base_pri + RQ_PPQ);
757 }
758 } else {
759 td->td_flags |= TDF_SLICEEND;
760 ast_sched_locked(td, TDA_SCHED);
761 }
762 }
763
764 stat = DPCPU_PTR(idlestat);
765 stat->oldidlecalls = stat->idlecalls;
766 stat->idlecalls = 0;
767 }
768
769 void
770 sched_clock(struct thread *td, int cnt)
771 {
772
773 for ( ; cnt > 0; cnt--)
774 sched_clock_tick(td);
775 }
776
777 /*
778 * Charge child's scheduling CPU usage to parent.
779 */
780 void
781 sched_exit(struct proc *p, struct thread *td)
782 {
783
784 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "proc exit",
785 "prio:%d", td->td_priority);
786
787 PROC_LOCK_ASSERT(p, MA_OWNED);
788 sched_exit_thread(FIRST_THREAD_IN_PROC(p), td);
789 }
790
791 void
792 sched_exit_thread(struct thread *td, struct thread *child)
793 {
794
795 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "exit",
796 "prio:%d", child->td_priority);
797 thread_lock(td);
798 td_get_sched(td)->ts_estcpu = ESTCPULIM(td_get_sched(td)->ts_estcpu +
799 td_get_sched(child)->ts_estcpu);
800 thread_unlock(td);
801 thread_lock(child);
802 if ((child->td_flags & TDF_NOLOAD) == 0)
803 sched_load_rem();
804 thread_unlock(child);
805 }
806
807 void
808 sched_fork(struct thread *td, struct thread *childtd)
809 {
810 sched_fork_thread(td, childtd);
811 }
812
813 void
814 sched_fork_thread(struct thread *td, struct thread *childtd)
815 {
816 struct td_sched *ts, *tsc;
817
818 childtd->td_oncpu = NOCPU;
819 childtd->td_lastcpu = NOCPU;
820 childtd->td_lock = &sched_lock;
821 childtd->td_cpuset = cpuset_ref(td->td_cpuset);
822 childtd->td_domain.dr_policy = td->td_cpuset->cs_domain;
823 childtd->td_priority = childtd->td_base_pri;
824 ts = td_get_sched(childtd);
825 bzero(ts, sizeof(*ts));
826 tsc = td_get_sched(td);
827 ts->ts_estcpu = tsc->ts_estcpu;
828 ts->ts_flags |= (tsc->ts_flags & TSF_AFFINITY);
829 ts->ts_slice = 1;
830 }
831
832 void
833 sched_nice(struct proc *p, int nice)
834 {
835 struct thread *td;
836
837 PROC_LOCK_ASSERT(p, MA_OWNED);
838 p->p_nice = nice;
839 FOREACH_THREAD_IN_PROC(p, td) {
840 thread_lock(td);
841 resetpriority(td);
842 resetpriority_thread(td);
843 thread_unlock(td);
844 }
845 }
846
847 void
848 sched_class(struct thread *td, int class)
849 {
850 THREAD_LOCK_ASSERT(td, MA_OWNED);
851 td->td_pri_class = class;
852 }
853
854 /*
855 * Adjust the priority of a thread.
856 */
857 static void
858 sched_priority(struct thread *td, u_char prio)
859 {
860
861 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "priority change",
862 "prio:%d", td->td_priority, "new prio:%d", prio, KTR_ATTR_LINKED,
863 sched_tdname(curthread));
864 SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio);
865 if (td != curthread && prio > td->td_priority) {
866 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
867 "lend prio", "prio:%d", td->td_priority, "new prio:%d",
868 prio, KTR_ATTR_LINKED, sched_tdname(td));
869 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio,
870 curthread);
871 }
872 THREAD_LOCK_ASSERT(td, MA_OWNED);
873 if (td->td_priority == prio)
874 return;
875 td->td_priority = prio;
876 if (TD_ON_RUNQ(td) && td->td_rqindex != (prio / RQ_PPQ)) {
877 sched_rem(td);
878 sched_add(td, SRQ_BORING | SRQ_HOLDTD);
879 }
880 }
881
882 /*
883 * Update a thread's priority when it is lent another thread's
884 * priority.
885 */
886 void
887 sched_lend_prio(struct thread *td, u_char prio)
888 {
889
890 td->td_flags |= TDF_BORROWING;
891 sched_priority(td, prio);
892 }
893
894 /*
895 * Restore a thread's priority when priority propagation is
896 * over. The prio argument is the minimum priority the thread
897 * needs to have to satisfy other possible priority lending
898 * requests. If the thread's regulary priority is less
899 * important than prio the thread will keep a priority boost
900 * of prio.
901 */
902 void
903 sched_unlend_prio(struct thread *td, u_char prio)
904 {
905 u_char base_pri;
906
907 if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
908 td->td_base_pri <= PRI_MAX_TIMESHARE)
909 base_pri = td->td_user_pri;
910 else
911 base_pri = td->td_base_pri;
912 if (prio >= base_pri) {
913 td->td_flags &= ~TDF_BORROWING;
914 sched_prio(td, base_pri);
915 } else
916 sched_lend_prio(td, prio);
917 }
918
919 void
920 sched_prio(struct thread *td, u_char prio)
921 {
922 u_char oldprio;
923
924 /* First, update the base priority. */
925 td->td_base_pri = prio;
926
927 /*
928 * If the thread is borrowing another thread's priority, don't ever
929 * lower the priority.
930 */
931 if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
932 return;
933
934 /* Change the real priority. */
935 oldprio = td->td_priority;
936 sched_priority(td, prio);
937
938 /*
939 * If the thread is on a turnstile, then let the turnstile update
940 * its state.
941 */
942 if (TD_ON_LOCK(td) && oldprio != prio)
943 turnstile_adjust(td, oldprio);
944 }
945
946 void
947 sched_ithread_prio(struct thread *td, u_char prio)
948 {
949 THREAD_LOCK_ASSERT(td, MA_OWNED);
950 MPASS(td->td_pri_class == PRI_ITHD);
951 td->td_base_ithread_pri = prio;
952 sched_prio(td, prio);
953 }
954
955 void
956 sched_user_prio(struct thread *td, u_char prio)
957 {
958
959 THREAD_LOCK_ASSERT(td, MA_OWNED);
960 td->td_base_user_pri = prio;
961 if (td->td_lend_user_pri <= prio)
962 return;
963 td->td_user_pri = prio;
964 }
965
966 void
967 sched_lend_user_prio(struct thread *td, u_char prio)
968 {
969
970 THREAD_LOCK_ASSERT(td, MA_OWNED);
971 td->td_lend_user_pri = prio;
972 td->td_user_pri = min(prio, td->td_base_user_pri);
973 if (td->td_priority > td->td_user_pri)
974 sched_prio(td, td->td_user_pri);
975 else if (td->td_priority != td->td_user_pri)
976 ast_sched_locked(td, TDA_SCHED);
977 }
978
979 /*
980 * Like the above but first check if there is anything to do.
981 */
982 void
983 sched_lend_user_prio_cond(struct thread *td, u_char prio)
984 {
985
986 if (td->td_lend_user_pri != prio)
987 goto lend;
988 if (td->td_user_pri != min(prio, td->td_base_user_pri))
989 goto lend;
990 if (td->td_priority != td->td_user_pri)
991 goto lend;
992 return;
993
994 lend:
995 thread_lock(td);
996 sched_lend_user_prio(td, prio);
997 thread_unlock(td);
998 }
999
1000 void
1001 sched_sleep(struct thread *td, int pri)
1002 {
1003
1004 THREAD_LOCK_ASSERT(td, MA_OWNED);
1005 td->td_slptick = ticks;
1006 td_get_sched(td)->ts_slptime = 0;
1007 if (pri != 0 && PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
1008 sched_prio(td, pri);
1009 if (TD_IS_SUSPENDED(td) || pri >= PSOCK)
1010 td->td_flags |= TDF_CANSWAP;
1011 }
1012
1013 void
1014 sched_switch(struct thread *td, int flags)
1015 {
1016 struct thread *newtd;
1017 struct mtx *tmtx;
1018 int preempted;
1019
1020 tmtx = &sched_lock;
1021
1022 THREAD_LOCK_ASSERT(td, MA_OWNED);
1023
1024 td->td_lastcpu = td->td_oncpu;
1025 preempted = (td->td_flags & TDF_SLICEEND) == 0 &&
1026 (flags & SW_PREEMPT) != 0;
1027 td->td_flags &= ~TDF_SLICEEND;
1028 ast_unsched_locked(td, TDA_SCHED);
1029 td->td_owepreempt = 0;
1030 td->td_oncpu = NOCPU;
1031
1032 /*
1033 * At the last moment, if this thread is still marked RUNNING,
1034 * then put it back on the run queue as it has not been suspended
1035 * or stopped or any thing else similar. We never put the idle
1036 * threads on the run queue, however.
1037 */
1038 if (td->td_flags & TDF_IDLETD) {
1039 TD_SET_CAN_RUN(td);
1040 #ifdef SMP
1041 CPU_CLR(PCPU_GET(cpuid), &idle_cpus_mask);
1042 #endif
1043 } else {
1044 if (TD_IS_RUNNING(td)) {
1045 /* Put us back on the run queue. */
1046 sched_add(td, preempted ?
1047 SRQ_HOLDTD|SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
1048 SRQ_HOLDTD|SRQ_OURSELF|SRQ_YIELDING);
1049 }
1050 }
1051
1052 /*
1053 * Switch to the sched lock to fix things up and pick
1054 * a new thread. Block the td_lock in order to avoid
1055 * breaking the critical path.
1056 */
1057 if (td->td_lock != &sched_lock) {
1058 mtx_lock_spin(&sched_lock);
1059 tmtx = thread_lock_block(td);
1060 mtx_unlock_spin(tmtx);
1061 }
1062
1063 if ((td->td_flags & TDF_NOLOAD) == 0)
1064 sched_load_rem();
1065
1066 newtd = choosethread();
1067 MPASS(newtd->td_lock == &sched_lock);
1068
1069 #if (KTR_COMPILE & KTR_SCHED) != 0
1070 if (TD_IS_IDLETHREAD(td))
1071 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle",
1072 "prio:%d", td->td_priority);
1073 else
1074 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td),
1075 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg,
1076 "lockname:\"%s\"", td->td_lockname);
1077 #endif
1078
1079 if (td != newtd) {
1080 #ifdef HWPMC_HOOKS
1081 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
1082 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
1083 #endif
1084
1085 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc);
1086
1087 /* I feel sleepy */
1088 lock_profile_release_lock(&sched_lock.lock_object, true);
1089 #ifdef KDTRACE_HOOKS
1090 /*
1091 * If DTrace has set the active vtime enum to anything
1092 * other than INACTIVE (0), then it should have set the
1093 * function to call.
1094 */
1095 if (dtrace_vtime_active)
1096 (*dtrace_vtime_switch_func)(newtd);
1097 #endif
1098
1099 cpu_switch(td, newtd, tmtx);
1100 lock_profile_obtain_lock_success(&sched_lock.lock_object, true,
1101 0, 0, __FILE__, __LINE__);
1102 /*
1103 * Where am I? What year is it?
1104 * We are in the same thread that went to sleep above,
1105 * but any amount of time may have passed. All our context
1106 * will still be available as will local variables.
1107 * PCPU values however may have changed as we may have
1108 * changed CPU so don't trust cached values of them.
1109 * New threads will go to fork_exit() instead of here
1110 * so if you change things here you may need to change
1111 * things there too.
1112 *
1113 * If the thread above was exiting it will never wake
1114 * up again here, so either it has saved everything it
1115 * needed to, or the thread_wait() or wait() will
1116 * need to reap it.
1117 */
1118
1119 SDT_PROBE0(sched, , , on__cpu);
1120 #ifdef HWPMC_HOOKS
1121 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
1122 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
1123 #endif
1124 } else {
1125 td->td_lock = &sched_lock;
1126 SDT_PROBE0(sched, , , remain__cpu);
1127 }
1128
1129 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
1130 "prio:%d", td->td_priority);
1131
1132 #ifdef SMP
1133 if (td->td_flags & TDF_IDLETD)
1134 CPU_SET(PCPU_GET(cpuid), &idle_cpus_mask);
1135 #endif
1136 sched_lock.mtx_lock = (uintptr_t)td;
1137 td->td_oncpu = PCPU_GET(cpuid);
1138 spinlock_enter();
1139 mtx_unlock_spin(&sched_lock);
1140 }
1141
1142 void
1143 sched_wakeup(struct thread *td, int srqflags)
1144 {
1145 struct td_sched *ts;
1146
1147 THREAD_LOCK_ASSERT(td, MA_OWNED);
1148 ts = td_get_sched(td);
1149 td->td_flags &= ~TDF_CANSWAP;
1150 if (ts->ts_slptime > 1) {
1151 updatepri(td);
1152 resetpriority(td);
1153 }
1154 td->td_slptick = 0;
1155 ts->ts_slptime = 0;
1156 ts->ts_slice = sched_slice;
1157
1158 /*
1159 * When resuming an idle ithread, restore its base ithread
1160 * priority.
1161 */
1162 if (PRI_BASE(td->td_pri_class) == PRI_ITHD &&
1163 td->td_base_pri != td->td_base_ithread_pri)
1164 sched_prio(td, td->td_base_ithread_pri);
1165
1166 sched_add(td, srqflags);
1167 }
1168
1169 #ifdef SMP
1170 static int
1171 forward_wakeup(int cpunum)
1172 {
1173 struct pcpu *pc;
1174 cpuset_t dontuse, map, map2;
1175 u_int id, me;
1176 int iscpuset;
1177
1178 mtx_assert(&sched_lock, MA_OWNED);
1179
1180 CTR0(KTR_RUNQ, "forward_wakeup()");
1181
1182 if ((!forward_wakeup_enabled) ||
1183 (forward_wakeup_use_mask == 0 && forward_wakeup_use_loop == 0))
1184 return (0);
1185 if (!smp_started || KERNEL_PANICKED())
1186 return (0);
1187
1188 forward_wakeups_requested++;
1189
1190 /*
1191 * Check the idle mask we received against what we calculated
1192 * before in the old version.
1193 */
1194 me = PCPU_GET(cpuid);
1195
1196 /* Don't bother if we should be doing it ourself. */
1197 if (CPU_ISSET(me, &idle_cpus_mask) &&
1198 (cpunum == NOCPU || me == cpunum))
1199 return (0);
1200
1201 CPU_SETOF(me, &dontuse);
1202 CPU_OR(&dontuse, &dontuse, &stopped_cpus);
1203 CPU_OR(&dontuse, &dontuse, &hlt_cpus_mask);
1204 CPU_ZERO(&map2);
1205 if (forward_wakeup_use_loop) {
1206 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
1207 id = pc->pc_cpuid;
1208 if (!CPU_ISSET(id, &dontuse) &&
1209 pc->pc_curthread == pc->pc_idlethread) {
1210 CPU_SET(id, &map2);
1211 }
1212 }
1213 }
1214
1215 if (forward_wakeup_use_mask) {
1216 map = idle_cpus_mask;
1217 CPU_ANDNOT(&map, &map, &dontuse);
1218
1219 /* If they are both on, compare and use loop if different. */
1220 if (forward_wakeup_use_loop) {
1221 if (CPU_CMP(&map, &map2)) {
1222 printf("map != map2, loop method preferred\n");
1223 map = map2;
1224 }
1225 }
1226 } else {
1227 map = map2;
1228 }
1229
1230 /* If we only allow a specific CPU, then mask off all the others. */
1231 if (cpunum != NOCPU) {
1232 KASSERT((cpunum <= mp_maxcpus),("forward_wakeup: bad cpunum."));
1233 iscpuset = CPU_ISSET(cpunum, &map);
1234 if (iscpuset == 0)
1235 CPU_ZERO(&map);
1236 else
1237 CPU_SETOF(cpunum, &map);
1238 }
1239 if (!CPU_EMPTY(&map)) {
1240 forward_wakeups_delivered++;
1241 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
1242 id = pc->pc_cpuid;
1243 if (!CPU_ISSET(id, &map))
1244 continue;
1245 if (cpu_idle_wakeup(pc->pc_cpuid))
1246 CPU_CLR(id, &map);
1247 }
1248 if (!CPU_EMPTY(&map))
1249 ipi_selected(map, IPI_AST);
1250 return (1);
1251 }
1252 if (cpunum == NOCPU)
1253 printf("forward_wakeup: Idle processor not found\n");
1254 return (0);
1255 }
1256
1257 static void
1258 kick_other_cpu(int pri, int cpuid)
1259 {
1260 struct pcpu *pcpu;
1261 int cpri;
1262
1263 pcpu = pcpu_find(cpuid);
1264 if (CPU_ISSET(cpuid, &idle_cpus_mask)) {
1265 forward_wakeups_delivered++;
1266 if (!cpu_idle_wakeup(cpuid))
1267 ipi_cpu(cpuid, IPI_AST);
1268 return;
1269 }
1270
1271 cpri = pcpu->pc_curthread->td_priority;
1272 if (pri >= cpri)
1273 return;
1274
1275 #if defined(IPI_PREEMPTION) && defined(PREEMPTION)
1276 #if !defined(FULL_PREEMPTION)
1277 if (pri <= PRI_MAX_ITHD)
1278 #endif /* ! FULL_PREEMPTION */
1279 {
1280 ipi_cpu(cpuid, IPI_PREEMPT);
1281 return;
1282 }
1283 #endif /* defined(IPI_PREEMPTION) && defined(PREEMPTION) */
1284
1285 if (pcpu->pc_curthread->td_lock == &sched_lock) {
1286 ast_sched_locked(pcpu->pc_curthread, TDA_SCHED);
1287 ipi_cpu(cpuid, IPI_AST);
1288 }
1289 }
1290 #endif /* SMP */
1291
1292 #ifdef SMP
1293 static int
1294 sched_pickcpu(struct thread *td)
1295 {
1296 int best, cpu;
1297
1298 mtx_assert(&sched_lock, MA_OWNED);
1299
1300 if (td->td_lastcpu != NOCPU && THREAD_CAN_SCHED(td, td->td_lastcpu))
1301 best = td->td_lastcpu;
1302 else
1303 best = NOCPU;
1304 CPU_FOREACH(cpu) {
1305 if (!THREAD_CAN_SCHED(td, cpu))
1306 continue;
1307
1308 if (best == NOCPU)
1309 best = cpu;
1310 else if (runq_length[cpu] < runq_length[best])
1311 best = cpu;
1312 }
1313 KASSERT(best != NOCPU, ("no valid CPUs"));
1314
1315 return (best);
1316 }
1317 #endif
1318
1319 void
1320 sched_add(struct thread *td, int flags)
1321 #ifdef SMP
1322 {
1323 cpuset_t tidlemsk;
1324 struct td_sched *ts;
1325 u_int cpu, cpuid;
1326 int forwarded = 0;
1327 int single_cpu = 0;
1328
1329 ts = td_get_sched(td);
1330 THREAD_LOCK_ASSERT(td, MA_OWNED);
1331 KASSERT((td->td_inhibitors == 0),
1332 ("sched_add: trying to run inhibited thread"));
1333 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
1334 ("sched_add: bad thread state"));
1335 KASSERT(td->td_flags & TDF_INMEM,
1336 ("sched_add: thread swapped out"));
1337
1338 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
1339 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
1340 sched_tdname(curthread));
1341 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
1342 KTR_ATTR_LINKED, sched_tdname(td));
1343 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL,
1344 flags & SRQ_PREEMPTED);
1345
1346 /*
1347 * Now that the thread is moving to the run-queue, set the lock
1348 * to the scheduler's lock.
1349 */
1350 if (td->td_lock != &sched_lock) {
1351 mtx_lock_spin(&sched_lock);
1352 if ((flags & SRQ_HOLD) != 0)
1353 td->td_lock = &sched_lock;
1354 else
1355 thread_lock_set(td, &sched_lock);
1356 }
1357 TD_SET_RUNQ(td);
1358
1359 /*
1360 * If SMP is started and the thread is pinned or otherwise limited to
1361 * a specific set of CPUs, queue the thread to a per-CPU run queue.
1362 * Otherwise, queue the thread to the global run queue.
1363 *
1364 * If SMP has not yet been started we must use the global run queue
1365 * as per-CPU state may not be initialized yet and we may crash if we
1366 * try to access the per-CPU run queues.
1367 */
1368 if (smp_started && (td->td_pinned != 0 || td->td_flags & TDF_BOUND ||
1369 ts->ts_flags & TSF_AFFINITY)) {
1370 if (td->td_pinned != 0)
1371 cpu = td->td_lastcpu;
1372 else if (td->td_flags & TDF_BOUND) {
1373 /* Find CPU from bound runq. */
1374 KASSERT(SKE_RUNQ_PCPU(ts),
1375 ("sched_add: bound td_sched not on cpu runq"));
1376 cpu = ts->ts_runq - &runq_pcpu[0];
1377 } else
1378 /* Find a valid CPU for our cpuset */
1379 cpu = sched_pickcpu(td);
1380 ts->ts_runq = &runq_pcpu[cpu];
1381 single_cpu = 1;
1382 CTR3(KTR_RUNQ,
1383 "sched_add: Put td_sched:%p(td:%p) on cpu%d runq", ts, td,
1384 cpu);
1385 } else {
1386 CTR2(KTR_RUNQ,
1387 "sched_add: adding td_sched:%p (td:%p) to gbl runq", ts,
1388 td);
1389 cpu = NOCPU;
1390 ts->ts_runq = &runq;
1391 }
1392
1393 if ((td->td_flags & TDF_NOLOAD) == 0)
1394 sched_load_add();
1395 runq_add(ts->ts_runq, td, flags);
1396 if (cpu != NOCPU)
1397 runq_length[cpu]++;
1398
1399 cpuid = PCPU_GET(cpuid);
1400 if (single_cpu && cpu != cpuid) {
1401 kick_other_cpu(td->td_priority, cpu);
1402 } else {
1403 if (!single_cpu) {
1404 tidlemsk = idle_cpus_mask;
1405 CPU_ANDNOT(&tidlemsk, &tidlemsk, &hlt_cpus_mask);
1406 CPU_CLR(cpuid, &tidlemsk);
1407
1408 if (!CPU_ISSET(cpuid, &idle_cpus_mask) &&
1409 ((flags & SRQ_INTR) == 0) &&
1410 !CPU_EMPTY(&tidlemsk))
1411 forwarded = forward_wakeup(cpu);
1412 }
1413
1414 if (!forwarded) {
1415 if (!maybe_preempt(td))
1416 maybe_resched(td);
1417 }
1418 }
1419 if ((flags & SRQ_HOLDTD) == 0)
1420 thread_unlock(td);
1421 }
1422 #else /* SMP */
1423 {
1424 struct td_sched *ts;
1425
1426 ts = td_get_sched(td);
1427 THREAD_LOCK_ASSERT(td, MA_OWNED);
1428 KASSERT((td->td_inhibitors == 0),
1429 ("sched_add: trying to run inhibited thread"));
1430 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
1431 ("sched_add: bad thread state"));
1432 KASSERT(td->td_flags & TDF_INMEM,
1433 ("sched_add: thread swapped out"));
1434 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
1435 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
1436 sched_tdname(curthread));
1437 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
1438 KTR_ATTR_LINKED, sched_tdname(td));
1439 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL,
1440 flags & SRQ_PREEMPTED);
1441
1442 /*
1443 * Now that the thread is moving to the run-queue, set the lock
1444 * to the scheduler's lock.
1445 */
1446 if (td->td_lock != &sched_lock) {
1447 mtx_lock_spin(&sched_lock);
1448 if ((flags & SRQ_HOLD) != 0)
1449 td->td_lock = &sched_lock;
1450 else
1451 thread_lock_set(td, &sched_lock);
1452 }
1453 TD_SET_RUNQ(td);
1454 CTR2(KTR_RUNQ, "sched_add: adding td_sched:%p (td:%p) to runq", ts, td);
1455 ts->ts_runq = &runq;
1456
1457 if ((td->td_flags & TDF_NOLOAD) == 0)
1458 sched_load_add();
1459 runq_add(ts->ts_runq, td, flags);
1460 if (!maybe_preempt(td))
1461 maybe_resched(td);
1462 if ((flags & SRQ_HOLDTD) == 0)
1463 thread_unlock(td);
1464 }
1465 #endif /* SMP */
1466
1467 void
1468 sched_rem(struct thread *td)
1469 {
1470 struct td_sched *ts;
1471
1472 ts = td_get_sched(td);
1473 KASSERT(td->td_flags & TDF_INMEM,
1474 ("sched_rem: thread swapped out"));
1475 KASSERT(TD_ON_RUNQ(td),
1476 ("sched_rem: thread not on run queue"));
1477 mtx_assert(&sched_lock, MA_OWNED);
1478 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
1479 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
1480 sched_tdname(curthread));
1481 SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
1482
1483 if ((td->td_flags & TDF_NOLOAD) == 0)
1484 sched_load_rem();
1485 #ifdef SMP
1486 if (ts->ts_runq != &runq)
1487 runq_length[ts->ts_runq - runq_pcpu]--;
1488 #endif
1489 runq_remove(ts->ts_runq, td);
1490 TD_SET_CAN_RUN(td);
1491 }
1492
1493 /*
1494 * Select threads to run. Note that running threads still consume a
1495 * slot.
1496 */
1497 struct thread *
1498 sched_choose(void)
1499 {
1500 struct thread *td;
1501 struct runq *rq;
1502
1503 mtx_assert(&sched_lock, MA_OWNED);
1504 #ifdef SMP
1505 struct thread *tdcpu;
1506
1507 rq = &runq;
1508 td = runq_choose_fuzz(&runq, runq_fuzz);
1509 tdcpu = runq_choose(&runq_pcpu[PCPU_GET(cpuid)]);
1510
1511 if (td == NULL ||
1512 (tdcpu != NULL &&
1513 tdcpu->td_priority < td->td_priority)) {
1514 CTR2(KTR_RUNQ, "choosing td %p from pcpu runq %d", tdcpu,
1515 PCPU_GET(cpuid));
1516 td = tdcpu;
1517 rq = &runq_pcpu[PCPU_GET(cpuid)];
1518 } else {
1519 CTR1(KTR_RUNQ, "choosing td_sched %p from main runq", td);
1520 }
1521
1522 #else
1523 rq = &runq;
1524 td = runq_choose(&runq);
1525 #endif
1526
1527 if (td) {
1528 #ifdef SMP
1529 if (td == tdcpu)
1530 runq_length[PCPU_GET(cpuid)]--;
1531 #endif
1532 runq_remove(rq, td);
1533 td->td_flags |= TDF_DIDRUN;
1534
1535 KASSERT(td->td_flags & TDF_INMEM,
1536 ("sched_choose: thread swapped out"));
1537 return (td);
1538 }
1539 return (PCPU_GET(idlethread));
1540 }
1541
1542 void
1543 sched_preempt(struct thread *td)
1544 {
1545
1546 SDT_PROBE2(sched, , , surrender, td, td->td_proc);
1547 if (td->td_critnest > 1) {
1548 td->td_owepreempt = 1;
1549 } else {
1550 thread_lock(td);
1551 mi_switch(SW_INVOL | SW_PREEMPT | SWT_PREEMPT);
1552 }
1553 }
1554
1555 void
1556 sched_userret_slowpath(struct thread *td)
1557 {
1558
1559 thread_lock(td);
1560 td->td_priority = td->td_user_pri;
1561 td->td_base_pri = td->td_user_pri;
1562 thread_unlock(td);
1563 }
1564
1565 void
1566 sched_bind(struct thread *td, int cpu)
1567 {
1568 #ifdef SMP
1569 struct td_sched *ts = td_get_sched(td);
1570 #endif
1571
1572 THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
1573 KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
1574
1575 td->td_flags |= TDF_BOUND;
1576 #ifdef SMP
1577 ts->ts_runq = &runq_pcpu[cpu];
1578 if (PCPU_GET(cpuid) == cpu)
1579 return;
1580
1581 mi_switch(SW_VOL);
1582 thread_lock(td);
1583 #endif
1584 }
1585
1586 void
1587 sched_unbind(struct thread* td)
1588 {
1589 THREAD_LOCK_ASSERT(td, MA_OWNED);
1590 KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
1591 td->td_flags &= ~TDF_BOUND;
1592 }
1593
1594 int
1595 sched_is_bound(struct thread *td)
1596 {
1597 THREAD_LOCK_ASSERT(td, MA_OWNED);
1598 return (td->td_flags & TDF_BOUND);
1599 }
1600
1601 void
1602 sched_relinquish(struct thread *td)
1603 {
1604 thread_lock(td);
1605 mi_switch(SW_VOL | SWT_RELINQUISH);
1606 }
1607
1608 int
1609 sched_load(void)
1610 {
1611 return (sched_tdcnt);
1612 }
1613
1614 int
1615 sched_sizeof_proc(void)
1616 {
1617 return (sizeof(struct proc));
1618 }
1619
1620 int
1621 sched_sizeof_thread(void)
1622 {
1623 return (sizeof(struct thread) + sizeof(struct td_sched));
1624 }
1625
1626 fixpt_t
1627 sched_pctcpu(struct thread *td)
1628 {
1629 struct td_sched *ts;
1630
1631 THREAD_LOCK_ASSERT(td, MA_OWNED);
1632 ts = td_get_sched(td);
1633 return (ts->ts_pctcpu);
1634 }
1635
1636 #ifdef RACCT
1637 /*
1638 * Calculates the contribution to the thread cpu usage for the latest
1639 * (unfinished) second.
1640 */
1641 fixpt_t
1642 sched_pctcpu_delta(struct thread *td)
1643 {
1644 struct td_sched *ts;
1645 fixpt_t delta;
1646 int realstathz;
1647
1648 THREAD_LOCK_ASSERT(td, MA_OWNED);
1649 ts = td_get_sched(td);
1650 delta = 0;
1651 realstathz = stathz ? stathz : hz;
1652 if (ts->ts_cpticks != 0) {
1653 #if (FSHIFT >= CCPU_SHIFT)
1654 delta = (realstathz == 100)
1655 ? ((fixpt_t) ts->ts_cpticks) <<
1656 (FSHIFT - CCPU_SHIFT) :
1657 100 * (((fixpt_t) ts->ts_cpticks)
1658 << (FSHIFT - CCPU_SHIFT)) / realstathz;
1659 #else
1660 delta = ((FSCALE - ccpu) *
1661 (ts->ts_cpticks *
1662 FSCALE / realstathz)) >> FSHIFT;
1663 #endif
1664 }
1665
1666 return (delta);
1667 }
1668 #endif
1669
1670 u_int
1671 sched_estcpu(struct thread *td)
1672 {
1673
1674 return (td_get_sched(td)->ts_estcpu);
1675 }
1676
1677 /*
1678 * The actual idle process.
1679 */
1680 void
1681 sched_idletd(void *dummy)
1682 {
1683 struct pcpuidlestat *stat;
1684
1685 THREAD_NO_SLEEPING();
1686 stat = DPCPU_PTR(idlestat);
1687 for (;;) {
1688 mtx_assert(&Giant, MA_NOTOWNED);
1689
1690 while (sched_runnable() == 0) {
1691 cpu_idle(stat->idlecalls + stat->oldidlecalls > 64);
1692 stat->idlecalls++;
1693 }
1694
1695 mtx_lock_spin(&sched_lock);
1696 mi_switch(SW_VOL | SWT_IDLE);
1697 }
1698 }
1699
1700 static void
1701 sched_throw_tail(struct thread *td)
1702 {
1703
1704 mtx_assert(&sched_lock, MA_OWNED);
1705 KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
1706 cpu_throw(td, choosethread()); /* doesn't return */
1707 }
1708
1709 /*
1710 * A CPU is entering for the first time.
1711 */
1712 void
1713 sched_ap_entry(void)
1714 {
1715
1716 /*
1717 * Correct spinlock nesting. The idle thread context that we are
1718 * borrowing was created so that it would start out with a single
1719 * spin lock (sched_lock) held in fork_trampoline(). Since we've
1720 * explicitly acquired locks in this function, the nesting count
1721 * is now 2 rather than 1. Since we are nested, calling
1722 * spinlock_exit() will simply adjust the counts without allowing
1723 * spin lock using code to interrupt us.
1724 */
1725 mtx_lock_spin(&sched_lock);
1726 spinlock_exit();
1727 PCPU_SET(switchtime, cpu_ticks());
1728 PCPU_SET(switchticks, ticks);
1729
1730 sched_throw_tail(NULL);
1731 }
1732
1733 /*
1734 * A thread is exiting.
1735 */
1736 void
1737 sched_throw(struct thread *td)
1738 {
1739
1740 MPASS(td != NULL);
1741 MPASS(td->td_lock == &sched_lock);
1742
1743 lock_profile_release_lock(&sched_lock.lock_object, true);
1744 td->td_lastcpu = td->td_oncpu;
1745 td->td_oncpu = NOCPU;
1746
1747 sched_throw_tail(td);
1748 }
1749
1750 void
1751 sched_fork_exit(struct thread *td)
1752 {
1753
1754 /*
1755 * Finish setting up thread glue so that it begins execution in a
1756 * non-nested critical section with sched_lock held but not recursed.
1757 */
1758 td->td_oncpu = PCPU_GET(cpuid);
1759 sched_lock.mtx_lock = (uintptr_t)td;
1760 lock_profile_obtain_lock_success(&sched_lock.lock_object, true,
1761 0, 0, __FILE__, __LINE__);
1762 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
1763
1764 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
1765 "prio:%d", td->td_priority);
1766 SDT_PROBE0(sched, , , on__cpu);
1767 }
1768
1769 char *
1770 sched_tdname(struct thread *td)
1771 {
1772 #ifdef KTR
1773 struct td_sched *ts;
1774
1775 ts = td_get_sched(td);
1776 if (ts->ts_name[0] == '\0')
1777 snprintf(ts->ts_name, sizeof(ts->ts_name),
1778 "%s tid %d", td->td_name, td->td_tid);
1779 return (ts->ts_name);
1780 #else
1781 return (td->td_name);
1782 #endif
1783 }
1784
1785 #ifdef KTR
1786 void
1787 sched_clear_tdname(struct thread *td)
1788 {
1789 struct td_sched *ts;
1790
1791 ts = td_get_sched(td);
1792 ts->ts_name[0] = '\0';
1793 }
1794 #endif
1795
1796 void
1797 sched_affinity(struct thread *td)
1798 {
1799 #ifdef SMP
1800 struct td_sched *ts;
1801 int cpu;
1802
1803 THREAD_LOCK_ASSERT(td, MA_OWNED);
1804
1805 /*
1806 * Set the TSF_AFFINITY flag if there is at least one CPU this
1807 * thread can't run on.
1808 */
1809 ts = td_get_sched(td);
1810 ts->ts_flags &= ~TSF_AFFINITY;
1811 CPU_FOREACH(cpu) {
1812 if (!THREAD_CAN_SCHED(td, cpu)) {
1813 ts->ts_flags |= TSF_AFFINITY;
1814 break;
1815 }
1816 }
1817
1818 /*
1819 * If this thread can run on all CPUs, nothing else to do.
1820 */
1821 if (!(ts->ts_flags & TSF_AFFINITY))
1822 return;
1823
1824 /* Pinned threads and bound threads should be left alone. */
1825 if (td->td_pinned != 0 || td->td_flags & TDF_BOUND)
1826 return;
1827
1828 switch (TD_GET_STATE(td)) {
1829 case TDS_RUNQ:
1830 /*
1831 * If we are on a per-CPU runqueue that is in the set,
1832 * then nothing needs to be done.
1833 */
1834 if (ts->ts_runq != &runq &&
1835 THREAD_CAN_SCHED(td, ts->ts_runq - runq_pcpu))
1836 return;
1837
1838 /* Put this thread on a valid per-CPU runqueue. */
1839 sched_rem(td);
1840 sched_add(td, SRQ_HOLDTD | SRQ_BORING);
1841 break;
1842 case TDS_RUNNING:
1843 /*
1844 * See if our current CPU is in the set. If not, force a
1845 * context switch.
1846 */
1847 if (THREAD_CAN_SCHED(td, td->td_oncpu))
1848 return;
1849
1850 ast_sched_locked(td, TDA_SCHED);
1851 if (td != curthread)
1852 ipi_cpu(cpu, IPI_AST);
1853 break;
1854 default:
1855 break;
1856 }
1857 #endif
1858 }
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