FreeBSD/Linux Kernel Cross Reference
sys/kern/sched_4bsd.c
1 /*-
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.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 4. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD: releng/10.0/sys/kern/sched_4bsd.c 253604 2013-07-24 09:45:31Z avg $");
37
38 #include "opt_hwpmc_hooks.h"
39 #include "opt_sched.h"
40 #include "opt_kdtrace.h"
41
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/cpuset.h>
45 #include <sys/kernel.h>
46 #include <sys/ktr.h>
47 #include <sys/lock.h>
48 #include <sys/kthread.h>
49 #include <sys/mutex.h>
50 #include <sys/proc.h>
51 #include <sys/resourcevar.h>
52 #include <sys/sched.h>
53 #include <sys/sdt.h>
54 #include <sys/smp.h>
55 #include <sys/sysctl.h>
56 #include <sys/sx.h>
57 #include <sys/turnstile.h>
58 #include <sys/umtx.h>
59 #include <machine/pcb.h>
60 #include <machine/smp.h>
61
62 #ifdef HWPMC_HOOKS
63 #include <sys/pmckern.h>
64 #endif
65
66 #ifdef KDTRACE_HOOKS
67 #include <sys/dtrace_bsd.h>
68 int dtrace_vtime_active;
69 dtrace_vtime_switch_func_t dtrace_vtime_switch_func;
70 #endif
71
72 /*
73 * INVERSE_ESTCPU_WEIGHT is only suitable for statclock() frequencies in
74 * the range 100-256 Hz (approximately).
75 */
76 #define ESTCPULIM(e) \
77 min((e), INVERSE_ESTCPU_WEIGHT * (NICE_WEIGHT * (PRIO_MAX - PRIO_MIN) - \
78 RQ_PPQ) + INVERSE_ESTCPU_WEIGHT - 1)
79 #ifdef SMP
80 #define INVERSE_ESTCPU_WEIGHT (8 * smp_cpus)
81 #else
82 #define INVERSE_ESTCPU_WEIGHT 8 /* 1 / (priorities per estcpu level). */
83 #endif
84 #define NICE_WEIGHT 1 /* Priorities per nice level. */
85
86 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
87
88 /*
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
92 */
93 struct td_sched {
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. */
97 int ts_slice; /* Remaining part of time slice. */
98 int ts_flags;
99 struct runq *ts_runq; /* runq the thread is currently on */
100 #ifdef KTR
101 char ts_name[TS_NAME_LEN];
102 #endif
103 };
104
105 /* flags kept in td_flags */
106 #define TDF_DIDRUN TDF_SCHED0 /* thread actually ran. */
107 #define TDF_BOUND TDF_SCHED1 /* Bound to one CPU. */
108 #define TDF_SLICEEND TDF_SCHED2 /* Thread time slice is over. */
109
110 /* flags kept in ts_flags */
111 #define TSF_AFFINITY 0x0001 /* Has a non-"full" CPU set. */
112
113 #define SKE_RUNQ_PCPU(ts) \
114 ((ts)->ts_runq != 0 && (ts)->ts_runq != &runq)
115
116 #define THREAD_CAN_SCHED(td, cpu) \
117 CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
118
119 static struct td_sched td_sched0;
120 struct mtx sched_lock;
121
122 static int realstathz = 127; /* stathz is sometimes 0 and run off of hz. */
123 static int sched_tdcnt; /* Total runnable threads in the system. */
124 static int sched_slice = 12; /* Thread run time before rescheduling. */
125
126 static void setup_runqs(void);
127 static void schedcpu(void);
128 static void schedcpu_thread(void);
129 static void sched_priority(struct thread *td, u_char prio);
130 static void sched_setup(void *dummy);
131 static void maybe_resched(struct thread *td);
132 static void updatepri(struct thread *td);
133 static void resetpriority(struct thread *td);
134 static void resetpriority_thread(struct thread *td);
135 #ifdef SMP
136 static int sched_pickcpu(struct thread *td);
137 static int forward_wakeup(int cpunum);
138 static void kick_other_cpu(int pri, int cpuid);
139 #endif
140
141 static struct kproc_desc sched_kp = {
142 "schedcpu",
143 schedcpu_thread,
144 NULL
145 };
146 SYSINIT(schedcpu, SI_SUB_LAST, SI_ORDER_FIRST, kproc_start,
147 &sched_kp);
148 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
149
150 static void sched_initticks(void *dummy);
151 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
152 NULL);
153
154 /*
155 * Global run queue.
156 */
157 static struct runq runq;
158
159 #ifdef SMP
160 /*
161 * Per-CPU run queues
162 */
163 static struct runq runq_pcpu[MAXCPU];
164 long runq_length[MAXCPU];
165
166 static cpuset_t idle_cpus_mask;
167 #endif
168
169 struct pcpuidlestat {
170 u_int idlecalls;
171 u_int oldidlecalls;
172 };
173 static DPCPU_DEFINE(struct pcpuidlestat, idlestat);
174
175 static void
176 setup_runqs(void)
177 {
178 #ifdef SMP
179 int i;
180
181 for (i = 0; i < MAXCPU; ++i)
182 runq_init(&runq_pcpu[i]);
183 #endif
184
185 runq_init(&runq);
186 }
187
188 static int
189 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
190 {
191 int error, new_val, period;
192
193 period = 1000000 / realstathz;
194 new_val = period * sched_slice;
195 error = sysctl_handle_int(oidp, &new_val, 0, req);
196 if (error != 0 || req->newptr == NULL)
197 return (error);
198 if (new_val <= 0)
199 return (EINVAL);
200 sched_slice = imax(1, (new_val + period / 2) / period);
201 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
202 realstathz);
203 return (0);
204 }
205
206 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RD, 0, "Scheduler");
207
208 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "4BSD", 0,
209 "Scheduler name");
210 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW,
211 NULL, 0, sysctl_kern_quantum, "I",
212 "Quantum for timeshare threads in microseconds");
213 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
214 "Quantum for timeshare threads in stathz ticks");
215 #ifdef SMP
216 /* Enable forwarding of wakeups to all other cpus */
217 static SYSCTL_NODE(_kern_sched, OID_AUTO, ipiwakeup, CTLFLAG_RD, NULL,
218 "Kernel SMP");
219
220 static int runq_fuzz = 1;
221 SYSCTL_INT(_kern_sched, OID_AUTO, runq_fuzz, CTLFLAG_RW, &runq_fuzz, 0, "");
222
223 static int forward_wakeup_enabled = 1;
224 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, enabled, CTLFLAG_RW,
225 &forward_wakeup_enabled, 0,
226 "Forwarding of wakeup to idle CPUs");
227
228 static int forward_wakeups_requested = 0;
229 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, requested, CTLFLAG_RD,
230 &forward_wakeups_requested, 0,
231 "Requests for Forwarding of wakeup to idle CPUs");
232
233 static int forward_wakeups_delivered = 0;
234 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, delivered, CTLFLAG_RD,
235 &forward_wakeups_delivered, 0,
236 "Completed Forwarding of wakeup to idle CPUs");
237
238 static int forward_wakeup_use_mask = 1;
239 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, usemask, CTLFLAG_RW,
240 &forward_wakeup_use_mask, 0,
241 "Use the mask of idle cpus");
242
243 static int forward_wakeup_use_loop = 0;
244 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, useloop, CTLFLAG_RW,
245 &forward_wakeup_use_loop, 0,
246 "Use a loop to find idle cpus");
247
248 #endif
249 #if 0
250 static int sched_followon = 0;
251 SYSCTL_INT(_kern_sched, OID_AUTO, followon, CTLFLAG_RW,
252 &sched_followon, 0,
253 "allow threads to share a quantum");
254 #endif
255
256 SDT_PROVIDER_DEFINE(sched);
257
258 SDT_PROBE_DEFINE3(sched, , , change_pri, change-pri, "struct thread *",
259 "struct proc *", "uint8_t");
260 SDT_PROBE_DEFINE3(sched, , , dequeue, dequeue, "struct thread *",
261 "struct proc *", "void *");
262 SDT_PROBE_DEFINE4(sched, , , enqueue, enqueue, "struct thread *",
263 "struct proc *", "void *", "int");
264 SDT_PROBE_DEFINE4(sched, , , lend_pri, lend-pri, "struct thread *",
265 "struct proc *", "uint8_t", "struct thread *");
266 SDT_PROBE_DEFINE2(sched, , , load_change, load-change, "int", "int");
267 SDT_PROBE_DEFINE2(sched, , , off_cpu, off-cpu, "struct thread *",
268 "struct proc *");
269 SDT_PROBE_DEFINE(sched, , , on_cpu, on-cpu);
270 SDT_PROBE_DEFINE(sched, , , remain_cpu, remain-cpu);
271 SDT_PROBE_DEFINE2(sched, , , surrender, surrender, "struct thread *",
272 "struct proc *");
273
274 static __inline void
275 sched_load_add(void)
276 {
277
278 sched_tdcnt++;
279 KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt);
280 SDT_PROBE2(sched, , , load_change, NOCPU, sched_tdcnt);
281 }
282
283 static __inline void
284 sched_load_rem(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 * Arrange to reschedule if necessary, taking the priorities and
293 * schedulers into account.
294 */
295 static void
296 maybe_resched(struct thread *td)
297 {
298
299 THREAD_LOCK_ASSERT(td, MA_OWNED);
300 if (td->td_priority < curthread->td_priority)
301 curthread->td_flags |= TDF_NEEDRESCHED;
302 }
303
304 /*
305 * This function is called when a thread is about to be put on run queue
306 * because it has been made runnable or its priority has been adjusted. It
307 * determines if the new thread should be immediately preempted to. If so,
308 * it switches to it and eventually returns true. If not, it returns false
309 * so that the caller may place the thread on an appropriate run queue.
310 */
311 int
312 maybe_preempt(struct thread *td)
313 {
314 #ifdef PREEMPTION
315 struct thread *ctd;
316 int cpri, pri;
317
318 /*
319 * The new thread should not preempt the current thread if any of the
320 * following conditions are true:
321 *
322 * - The kernel is in the throes of crashing (panicstr).
323 * - The current thread has a higher (numerically lower) or
324 * equivalent priority. Note that this prevents curthread from
325 * trying to preempt to itself.
326 * - It is too early in the boot for context switches (cold is set).
327 * - The current thread has an inhibitor set or is in the process of
328 * exiting. In this case, the current thread is about to switch
329 * out anyways, so there's no point in preempting. If we did,
330 * the current thread would not be properly resumed as well, so
331 * just avoid that whole landmine.
332 * - If the new thread's priority is not a realtime priority and
333 * the current thread's priority is not an idle priority and
334 * FULL_PREEMPTION is disabled.
335 *
336 * If all of these conditions are false, but the current thread is in
337 * a nested critical section, then we have to defer the preemption
338 * until we exit the critical section. Otherwise, switch immediately
339 * to the new thread.
340 */
341 ctd = curthread;
342 THREAD_LOCK_ASSERT(td, MA_OWNED);
343 KASSERT((td->td_inhibitors == 0),
344 ("maybe_preempt: trying to run inhibited thread"));
345 pri = td->td_priority;
346 cpri = ctd->td_priority;
347 if (panicstr != NULL || pri >= cpri || cold /* || dumping */ ||
348 TD_IS_INHIBITED(ctd))
349 return (0);
350 #ifndef FULL_PREEMPTION
351 if (pri > PRI_MAX_ITHD && cpri < PRI_MIN_IDLE)
352 return (0);
353 #endif
354
355 if (ctd->td_critnest > 1) {
356 CTR1(KTR_PROC, "maybe_preempt: in critical section %d",
357 ctd->td_critnest);
358 ctd->td_owepreempt = 1;
359 return (0);
360 }
361 /*
362 * Thread is runnable but not yet put on system run queue.
363 */
364 MPASS(ctd->td_lock == td->td_lock);
365 MPASS(TD_ON_RUNQ(td));
366 TD_SET_RUNNING(td);
367 CTR3(KTR_PROC, "preempting to thread %p (pid %d, %s)\n", td,
368 td->td_proc->p_pid, td->td_name);
369 mi_switch(SW_INVOL | SW_PREEMPT | SWT_PREEMPT, td);
370 /*
371 * td's lock pointer may have changed. We have to return with it
372 * locked.
373 */
374 spinlock_enter();
375 thread_unlock(ctd);
376 thread_lock(td);
377 spinlock_exit();
378 return (1);
379 #else
380 return (0);
381 #endif
382 }
383
384 /*
385 * Constants for digital decay and forget:
386 * 90% of (td_estcpu) usage in 5 * loadav time
387 * 95% of (ts_pctcpu) usage in 60 seconds (load insensitive)
388 * Note that, as ps(1) mentions, this can let percentages
389 * total over 100% (I've seen 137.9% for 3 processes).
390 *
391 * Note that schedclock() updates td_estcpu and p_cpticks asynchronously.
392 *
393 * We wish to decay away 90% of td_estcpu in (5 * loadavg) seconds.
394 * That is, the system wants to compute a value of decay such
395 * that the following for loop:
396 * for (i = 0; i < (5 * loadavg); i++)
397 * td_estcpu *= decay;
398 * will compute
399 * td_estcpu *= 0.1;
400 * for all values of loadavg:
401 *
402 * Mathematically this loop can be expressed by saying:
403 * decay ** (5 * loadavg) ~= .1
404 *
405 * The system computes decay as:
406 * decay = (2 * loadavg) / (2 * loadavg + 1)
407 *
408 * We wish to prove that the system's computation of decay
409 * will always fulfill the equation:
410 * decay ** (5 * loadavg) ~= .1
411 *
412 * If we compute b as:
413 * b = 2 * loadavg
414 * then
415 * decay = b / (b + 1)
416 *
417 * We now need to prove two things:
418 * 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1)
419 * 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg)
420 *
421 * Facts:
422 * For x close to zero, exp(x) =~ 1 + x, since
423 * exp(x) = 0! + x**1/1! + x**2/2! + ... .
424 * therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b.
425 * For x close to zero, ln(1+x) =~ x, since
426 * ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1
427 * therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1).
428 * ln(.1) =~ -2.30
429 *
430 * Proof of (1):
431 * Solve (factor)**(power) =~ .1 given power (5*loadav):
432 * solving for factor,
433 * ln(factor) =~ (-2.30/5*loadav), or
434 * factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) =
435 * exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED
436 *
437 * Proof of (2):
438 * Solve (factor)**(power) =~ .1 given factor == (b/(b+1)):
439 * solving for power,
440 * power*ln(b/(b+1)) =~ -2.30, or
441 * power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED
442 *
443 * Actual power values for the implemented algorithm are as follows:
444 * loadav: 1 2 3 4
445 * power: 5.68 10.32 14.94 19.55
446 */
447
448 /* calculations for digital decay to forget 90% of usage in 5*loadav sec */
449 #define loadfactor(loadav) (2 * (loadav))
450 #define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE))
451
452 /* decay 95% of `ts_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */
453 static fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
454 SYSCTL_UINT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
455
456 /*
457 * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the
458 * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below
459 * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT).
460 *
461 * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used:
462 * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits).
463 *
464 * If you don't want to bother with the faster/more-accurate formula, you
465 * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate
466 * (more general) method of calculating the %age of CPU used by a process.
467 */
468 #define CCPU_SHIFT 11
469
470 /*
471 * Recompute process priorities, every hz ticks.
472 * MP-safe, called without the Giant mutex.
473 */
474 /* ARGSUSED */
475 static void
476 schedcpu(void)
477 {
478 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
479 struct thread *td;
480 struct proc *p;
481 struct td_sched *ts;
482 int awake;
483
484 sx_slock(&allproc_lock);
485 FOREACH_PROC_IN_SYSTEM(p) {
486 PROC_LOCK(p);
487 if (p->p_state == PRS_NEW) {
488 PROC_UNLOCK(p);
489 continue;
490 }
491 FOREACH_THREAD_IN_PROC(p, td) {
492 awake = 0;
493 thread_lock(td);
494 ts = td->td_sched;
495 /*
496 * Increment sleep time (if sleeping). We
497 * ignore overflow, as above.
498 */
499 /*
500 * The td_sched slptimes are not touched in wakeup
501 * because the thread may not HAVE everything in
502 * memory? XXX I think this is out of date.
503 */
504 if (TD_ON_RUNQ(td)) {
505 awake = 1;
506 td->td_flags &= ~TDF_DIDRUN;
507 } else if (TD_IS_RUNNING(td)) {
508 awake = 1;
509 /* Do not clear TDF_DIDRUN */
510 } else if (td->td_flags & TDF_DIDRUN) {
511 awake = 1;
512 td->td_flags &= ~TDF_DIDRUN;
513 }
514
515 /*
516 * ts_pctcpu is only for ps and ttyinfo().
517 */
518 ts->ts_pctcpu = (ts->ts_pctcpu * ccpu) >> FSHIFT;
519 /*
520 * If the td_sched has been idle the entire second,
521 * stop recalculating its priority until
522 * it wakes up.
523 */
524 if (ts->ts_cpticks != 0) {
525 #if (FSHIFT >= CCPU_SHIFT)
526 ts->ts_pctcpu += (realstathz == 100)
527 ? ((fixpt_t) ts->ts_cpticks) <<
528 (FSHIFT - CCPU_SHIFT) :
529 100 * (((fixpt_t) ts->ts_cpticks)
530 << (FSHIFT - CCPU_SHIFT)) / realstathz;
531 #else
532 ts->ts_pctcpu += ((FSCALE - ccpu) *
533 (ts->ts_cpticks *
534 FSCALE / realstathz)) >> FSHIFT;
535 #endif
536 ts->ts_cpticks = 0;
537 }
538 /*
539 * If there are ANY running threads in this process,
540 * then don't count it as sleeping.
541 * XXX: this is broken.
542 */
543 if (awake) {
544 if (ts->ts_slptime > 1) {
545 /*
546 * In an ideal world, this should not
547 * happen, because whoever woke us
548 * up from the long sleep should have
549 * unwound the slptime and reset our
550 * priority before we run at the stale
551 * priority. Should KASSERT at some
552 * point when all the cases are fixed.
553 */
554 updatepri(td);
555 }
556 ts->ts_slptime = 0;
557 } else
558 ts->ts_slptime++;
559 if (ts->ts_slptime > 1) {
560 thread_unlock(td);
561 continue;
562 }
563 td->td_estcpu = decay_cpu(loadfac, td->td_estcpu);
564 resetpriority(td);
565 resetpriority_thread(td);
566 thread_unlock(td);
567 }
568 PROC_UNLOCK(p);
569 }
570 sx_sunlock(&allproc_lock);
571 }
572
573 /*
574 * Main loop for a kthread that executes schedcpu once a second.
575 */
576 static void
577 schedcpu_thread(void)
578 {
579
580 for (;;) {
581 schedcpu();
582 pause("-", hz);
583 }
584 }
585
586 /*
587 * Recalculate the priority of a process after it has slept for a while.
588 * For all load averages >= 1 and max td_estcpu of 255, sleeping for at
589 * least six times the loadfactor will decay td_estcpu to zero.
590 */
591 static void
592 updatepri(struct thread *td)
593 {
594 struct td_sched *ts;
595 fixpt_t loadfac;
596 unsigned int newcpu;
597
598 ts = td->td_sched;
599 loadfac = loadfactor(averunnable.ldavg[0]);
600 if (ts->ts_slptime > 5 * loadfac)
601 td->td_estcpu = 0;
602 else {
603 newcpu = td->td_estcpu;
604 ts->ts_slptime--; /* was incremented in schedcpu() */
605 while (newcpu && --ts->ts_slptime)
606 newcpu = decay_cpu(loadfac, newcpu);
607 td->td_estcpu = newcpu;
608 }
609 }
610
611 /*
612 * Compute the priority of a process when running in user mode.
613 * Arrange to reschedule if the resulting priority is better
614 * than that of the current process.
615 */
616 static void
617 resetpriority(struct thread *td)
618 {
619 register unsigned int newpriority;
620
621 if (td->td_pri_class == PRI_TIMESHARE) {
622 newpriority = PUSER + td->td_estcpu / INVERSE_ESTCPU_WEIGHT +
623 NICE_WEIGHT * (td->td_proc->p_nice - PRIO_MIN);
624 newpriority = min(max(newpriority, PRI_MIN_TIMESHARE),
625 PRI_MAX_TIMESHARE);
626 sched_user_prio(td, newpriority);
627 }
628 }
629
630 /*
631 * Update the thread's priority when the associated process's user
632 * priority changes.
633 */
634 static void
635 resetpriority_thread(struct thread *td)
636 {
637
638 /* Only change threads with a time sharing user priority. */
639 if (td->td_priority < PRI_MIN_TIMESHARE ||
640 td->td_priority > PRI_MAX_TIMESHARE)
641 return;
642
643 /* XXX the whole needresched thing is broken, but not silly. */
644 maybe_resched(td);
645
646 sched_prio(td, td->td_user_pri);
647 }
648
649 /* ARGSUSED */
650 static void
651 sched_setup(void *dummy)
652 {
653
654 setup_runqs();
655
656 /* Account for thread0. */
657 sched_load_add();
658 }
659
660 /*
661 * This routine determines time constants after stathz and hz are setup.
662 */
663 static void
664 sched_initticks(void *dummy)
665 {
666
667 realstathz = stathz ? stathz : hz;
668 sched_slice = realstathz / 10; /* ~100ms */
669 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
670 realstathz);
671 }
672
673 /* External interfaces start here */
674
675 /*
676 * Very early in the boot some setup of scheduler-specific
677 * parts of proc0 and of some scheduler resources needs to be done.
678 * Called from:
679 * proc0_init()
680 */
681 void
682 schedinit(void)
683 {
684 /*
685 * Set up the scheduler specific parts of proc0.
686 */
687 proc0.p_sched = NULL; /* XXX */
688 thread0.td_sched = &td_sched0;
689 thread0.td_lock = &sched_lock;
690 td_sched0.ts_slice = sched_slice;
691 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE);
692 }
693
694 int
695 sched_runnable(void)
696 {
697 #ifdef SMP
698 return runq_check(&runq) + runq_check(&runq_pcpu[PCPU_GET(cpuid)]);
699 #else
700 return runq_check(&runq);
701 #endif
702 }
703
704 int
705 sched_rr_interval(void)
706 {
707
708 /* Convert sched_slice from stathz to hz. */
709 return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
710 }
711
712 /*
713 * We adjust the priority of the current process. The priority of
714 * a process gets worse as it accumulates CPU time. The cpu usage
715 * estimator (td_estcpu) is increased here. resetpriority() will
716 * compute a different priority each time td_estcpu increases by
717 * INVERSE_ESTCPU_WEIGHT
718 * (until MAXPRI is reached). The cpu usage estimator ramps up
719 * quite quickly when the process is running (linearly), and decays
720 * away exponentially, at a rate which is proportionally slower when
721 * the system is busy. The basic principle is that the system will
722 * 90% forget that the process used a lot of CPU time in 5 * loadav
723 * seconds. This causes the system to favor processes which haven't
724 * run much recently, and to round-robin among other processes.
725 */
726 void
727 sched_clock(struct thread *td)
728 {
729 struct pcpuidlestat *stat;
730 struct td_sched *ts;
731
732 THREAD_LOCK_ASSERT(td, MA_OWNED);
733 ts = td->td_sched;
734
735 ts->ts_cpticks++;
736 td->td_estcpu = ESTCPULIM(td->td_estcpu + 1);
737 if ((td->td_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) {
738 resetpriority(td);
739 resetpriority_thread(td);
740 }
741
742 /*
743 * Force a context switch if the current thread has used up a full
744 * time slice (default is 100ms).
745 */
746 if (!TD_IS_IDLETHREAD(td) && --ts->ts_slice <= 0) {
747 ts->ts_slice = sched_slice;
748 td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND;
749 }
750
751 stat = DPCPU_PTR(idlestat);
752 stat->oldidlecalls = stat->idlecalls;
753 stat->idlecalls = 0;
754 }
755
756 /*
757 * Charge child's scheduling CPU usage to parent.
758 */
759 void
760 sched_exit(struct proc *p, struct thread *td)
761 {
762
763 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "proc exit",
764 "prio:%d", td->td_priority);
765
766 PROC_LOCK_ASSERT(p, MA_OWNED);
767 sched_exit_thread(FIRST_THREAD_IN_PROC(p), td);
768 }
769
770 void
771 sched_exit_thread(struct thread *td, struct thread *child)
772 {
773
774 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "exit",
775 "prio:%d", child->td_priority);
776 thread_lock(td);
777 td->td_estcpu = ESTCPULIM(td->td_estcpu + child->td_estcpu);
778 thread_unlock(td);
779 thread_lock(child);
780 if ((child->td_flags & TDF_NOLOAD) == 0)
781 sched_load_rem();
782 thread_unlock(child);
783 }
784
785 void
786 sched_fork(struct thread *td, struct thread *childtd)
787 {
788 sched_fork_thread(td, childtd);
789 }
790
791 void
792 sched_fork_thread(struct thread *td, struct thread *childtd)
793 {
794 struct td_sched *ts;
795
796 childtd->td_estcpu = td->td_estcpu;
797 childtd->td_lock = &sched_lock;
798 childtd->td_cpuset = cpuset_ref(td->td_cpuset);
799 childtd->td_priority = childtd->td_base_pri;
800 ts = childtd->td_sched;
801 bzero(ts, sizeof(*ts));
802 ts->ts_flags |= (td->td_sched->ts_flags & TSF_AFFINITY);
803 ts->ts_slice = 1;
804 }
805
806 void
807 sched_nice(struct proc *p, int nice)
808 {
809 struct thread *td;
810
811 PROC_LOCK_ASSERT(p, MA_OWNED);
812 p->p_nice = nice;
813 FOREACH_THREAD_IN_PROC(p, td) {
814 thread_lock(td);
815 resetpriority(td);
816 resetpriority_thread(td);
817 thread_unlock(td);
818 }
819 }
820
821 void
822 sched_class(struct thread *td, int class)
823 {
824 THREAD_LOCK_ASSERT(td, MA_OWNED);
825 td->td_pri_class = class;
826 }
827
828 /*
829 * Adjust the priority of a thread.
830 */
831 static void
832 sched_priority(struct thread *td, u_char prio)
833 {
834
835
836 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "priority change",
837 "prio:%d", td->td_priority, "new prio:%d", prio, KTR_ATTR_LINKED,
838 sched_tdname(curthread));
839 SDT_PROBE3(sched, , , change_pri, td, td->td_proc, prio);
840 if (td != curthread && prio > td->td_priority) {
841 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
842 "lend prio", "prio:%d", td->td_priority, "new prio:%d",
843 prio, KTR_ATTR_LINKED, sched_tdname(td));
844 SDT_PROBE4(sched, , , lend_pri, td, td->td_proc, prio,
845 curthread);
846 }
847 THREAD_LOCK_ASSERT(td, MA_OWNED);
848 if (td->td_priority == prio)
849 return;
850 td->td_priority = prio;
851 if (TD_ON_RUNQ(td) && td->td_rqindex != (prio / RQ_PPQ)) {
852 sched_rem(td);
853 sched_add(td, SRQ_BORING);
854 }
855 }
856
857 /*
858 * Update a thread's priority when it is lent another thread's
859 * priority.
860 */
861 void
862 sched_lend_prio(struct thread *td, u_char prio)
863 {
864
865 td->td_flags |= TDF_BORROWING;
866 sched_priority(td, prio);
867 }
868
869 /*
870 * Restore a thread's priority when priority propagation is
871 * over. The prio argument is the minimum priority the thread
872 * needs to have to satisfy other possible priority lending
873 * requests. If the thread's regulary priority is less
874 * important than prio the thread will keep a priority boost
875 * of prio.
876 */
877 void
878 sched_unlend_prio(struct thread *td, u_char prio)
879 {
880 u_char base_pri;
881
882 if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
883 td->td_base_pri <= PRI_MAX_TIMESHARE)
884 base_pri = td->td_user_pri;
885 else
886 base_pri = td->td_base_pri;
887 if (prio >= base_pri) {
888 td->td_flags &= ~TDF_BORROWING;
889 sched_prio(td, base_pri);
890 } else
891 sched_lend_prio(td, prio);
892 }
893
894 void
895 sched_prio(struct thread *td, u_char prio)
896 {
897 u_char oldprio;
898
899 /* First, update the base priority. */
900 td->td_base_pri = prio;
901
902 /*
903 * If the thread is borrowing another thread's priority, don't ever
904 * lower the priority.
905 */
906 if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
907 return;
908
909 /* Change the real priority. */
910 oldprio = td->td_priority;
911 sched_priority(td, prio);
912
913 /*
914 * If the thread is on a turnstile, then let the turnstile update
915 * its state.
916 */
917 if (TD_ON_LOCK(td) && oldprio != prio)
918 turnstile_adjust(td, oldprio);
919 }
920
921 void
922 sched_user_prio(struct thread *td, u_char prio)
923 {
924
925 THREAD_LOCK_ASSERT(td, MA_OWNED);
926 td->td_base_user_pri = prio;
927 if (td->td_lend_user_pri <= prio)
928 return;
929 td->td_user_pri = prio;
930 }
931
932 void
933 sched_lend_user_prio(struct thread *td, u_char prio)
934 {
935
936 THREAD_LOCK_ASSERT(td, MA_OWNED);
937 td->td_lend_user_pri = prio;
938 td->td_user_pri = min(prio, td->td_base_user_pri);
939 if (td->td_priority > td->td_user_pri)
940 sched_prio(td, td->td_user_pri);
941 else if (td->td_priority != td->td_user_pri)
942 td->td_flags |= TDF_NEEDRESCHED;
943 }
944
945 void
946 sched_sleep(struct thread *td, int pri)
947 {
948
949 THREAD_LOCK_ASSERT(td, MA_OWNED);
950 td->td_slptick = ticks;
951 td->td_sched->ts_slptime = 0;
952 if (pri != 0 && PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
953 sched_prio(td, pri);
954 if (TD_IS_SUSPENDED(td) || pri >= PSOCK)
955 td->td_flags |= TDF_CANSWAP;
956 }
957
958 void
959 sched_switch(struct thread *td, struct thread *newtd, int flags)
960 {
961 struct mtx *tmtx;
962 struct td_sched *ts;
963 struct proc *p;
964 int preempted;
965
966 tmtx = NULL;
967 ts = td->td_sched;
968 p = td->td_proc;
969
970 THREAD_LOCK_ASSERT(td, MA_OWNED);
971
972 /*
973 * Switch to the sched lock to fix things up and pick
974 * a new thread.
975 * Block the td_lock in order to avoid breaking the critical path.
976 */
977 if (td->td_lock != &sched_lock) {
978 mtx_lock_spin(&sched_lock);
979 tmtx = thread_lock_block(td);
980 }
981
982 if ((td->td_flags & TDF_NOLOAD) == 0)
983 sched_load_rem();
984
985 td->td_lastcpu = td->td_oncpu;
986 preempted = !(td->td_flags & TDF_SLICEEND);
987 td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND);
988 td->td_owepreempt = 0;
989 td->td_oncpu = NOCPU;
990
991 /*
992 * At the last moment, if this thread is still marked RUNNING,
993 * then put it back on the run queue as it has not been suspended
994 * or stopped or any thing else similar. We never put the idle
995 * threads on the run queue, however.
996 */
997 if (td->td_flags & TDF_IDLETD) {
998 TD_SET_CAN_RUN(td);
999 #ifdef SMP
1000 CPU_CLR(PCPU_GET(cpuid), &idle_cpus_mask);
1001 #endif
1002 } else {
1003 if (TD_IS_RUNNING(td)) {
1004 /* Put us back on the run queue. */
1005 sched_add(td, preempted ?
1006 SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
1007 SRQ_OURSELF|SRQ_YIELDING);
1008 }
1009 }
1010 if (newtd) {
1011 /*
1012 * The thread we are about to run needs to be counted
1013 * as if it had been added to the run queue and selected.
1014 * It came from:
1015 * * A preemption
1016 * * An upcall
1017 * * A followon
1018 */
1019 KASSERT((newtd->td_inhibitors == 0),
1020 ("trying to run inhibited thread"));
1021 newtd->td_flags |= TDF_DIDRUN;
1022 TD_SET_RUNNING(newtd);
1023 if ((newtd->td_flags & TDF_NOLOAD) == 0)
1024 sched_load_add();
1025 } else {
1026 newtd = choosethread();
1027 MPASS(newtd->td_lock == &sched_lock);
1028 }
1029
1030 if (td != newtd) {
1031 #ifdef HWPMC_HOOKS
1032 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
1033 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
1034 #endif
1035
1036 SDT_PROBE2(sched, , , off_cpu, td, td->td_proc);
1037
1038 /* I feel sleepy */
1039 lock_profile_release_lock(&sched_lock.lock_object);
1040 #ifdef KDTRACE_HOOKS
1041 /*
1042 * If DTrace has set the active vtime enum to anything
1043 * other than INACTIVE (0), then it should have set the
1044 * function to call.
1045 */
1046 if (dtrace_vtime_active)
1047 (*dtrace_vtime_switch_func)(newtd);
1048 #endif
1049
1050 cpu_switch(td, newtd, tmtx != NULL ? tmtx : td->td_lock);
1051 lock_profile_obtain_lock_success(&sched_lock.lock_object,
1052 0, 0, __FILE__, __LINE__);
1053 /*
1054 * Where am I? What year is it?
1055 * We are in the same thread that went to sleep above,
1056 * but any amount of time may have passed. All our context
1057 * will still be available as will local variables.
1058 * PCPU values however may have changed as we may have
1059 * changed CPU so don't trust cached values of them.
1060 * New threads will go to fork_exit() instead of here
1061 * so if you change things here you may need to change
1062 * things there too.
1063 *
1064 * If the thread above was exiting it will never wake
1065 * up again here, so either it has saved everything it
1066 * needed to, or the thread_wait() or wait() will
1067 * need to reap it.
1068 */
1069
1070 SDT_PROBE0(sched, , , on_cpu);
1071 #ifdef HWPMC_HOOKS
1072 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
1073 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
1074 #endif
1075 } else
1076 SDT_PROBE0(sched, , , remain_cpu);
1077
1078 #ifdef SMP
1079 if (td->td_flags & TDF_IDLETD)
1080 CPU_SET(PCPU_GET(cpuid), &idle_cpus_mask);
1081 #endif
1082 sched_lock.mtx_lock = (uintptr_t)td;
1083 td->td_oncpu = PCPU_GET(cpuid);
1084 MPASS(td->td_lock == &sched_lock);
1085 }
1086
1087 void
1088 sched_wakeup(struct thread *td)
1089 {
1090 struct td_sched *ts;
1091
1092 THREAD_LOCK_ASSERT(td, MA_OWNED);
1093 ts = td->td_sched;
1094 td->td_flags &= ~TDF_CANSWAP;
1095 if (ts->ts_slptime > 1) {
1096 updatepri(td);
1097 resetpriority(td);
1098 }
1099 td->td_slptick = 0;
1100 ts->ts_slptime = 0;
1101 ts->ts_slice = sched_slice;
1102 sched_add(td, SRQ_BORING);
1103 }
1104
1105 #ifdef SMP
1106 static int
1107 forward_wakeup(int cpunum)
1108 {
1109 struct pcpu *pc;
1110 cpuset_t dontuse, map, map2;
1111 u_int id, me;
1112 int iscpuset;
1113
1114 mtx_assert(&sched_lock, MA_OWNED);
1115
1116 CTR0(KTR_RUNQ, "forward_wakeup()");
1117
1118 if ((!forward_wakeup_enabled) ||
1119 (forward_wakeup_use_mask == 0 && forward_wakeup_use_loop == 0))
1120 return (0);
1121 if (!smp_started || cold || panicstr)
1122 return (0);
1123
1124 forward_wakeups_requested++;
1125
1126 /*
1127 * Check the idle mask we received against what we calculated
1128 * before in the old version.
1129 */
1130 me = PCPU_GET(cpuid);
1131
1132 /* Don't bother if we should be doing it ourself. */
1133 if (CPU_ISSET(me, &idle_cpus_mask) &&
1134 (cpunum == NOCPU || me == cpunum))
1135 return (0);
1136
1137 CPU_SETOF(me, &dontuse);
1138 CPU_OR(&dontuse, &stopped_cpus);
1139 CPU_OR(&dontuse, &hlt_cpus_mask);
1140 CPU_ZERO(&map2);
1141 if (forward_wakeup_use_loop) {
1142 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
1143 id = pc->pc_cpuid;
1144 if (!CPU_ISSET(id, &dontuse) &&
1145 pc->pc_curthread == pc->pc_idlethread) {
1146 CPU_SET(id, &map2);
1147 }
1148 }
1149 }
1150
1151 if (forward_wakeup_use_mask) {
1152 map = idle_cpus_mask;
1153 CPU_NAND(&map, &dontuse);
1154
1155 /* If they are both on, compare and use loop if different. */
1156 if (forward_wakeup_use_loop) {
1157 if (CPU_CMP(&map, &map2)) {
1158 printf("map != map2, loop method preferred\n");
1159 map = map2;
1160 }
1161 }
1162 } else {
1163 map = map2;
1164 }
1165
1166 /* If we only allow a specific CPU, then mask off all the others. */
1167 if (cpunum != NOCPU) {
1168 KASSERT((cpunum <= mp_maxcpus),("forward_wakeup: bad cpunum."));
1169 iscpuset = CPU_ISSET(cpunum, &map);
1170 if (iscpuset == 0)
1171 CPU_ZERO(&map);
1172 else
1173 CPU_SETOF(cpunum, &map);
1174 }
1175 if (!CPU_EMPTY(&map)) {
1176 forward_wakeups_delivered++;
1177 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
1178 id = pc->pc_cpuid;
1179 if (!CPU_ISSET(id, &map))
1180 continue;
1181 if (cpu_idle_wakeup(pc->pc_cpuid))
1182 CPU_CLR(id, &map);
1183 }
1184 if (!CPU_EMPTY(&map))
1185 ipi_selected(map, IPI_AST);
1186 return (1);
1187 }
1188 if (cpunum == NOCPU)
1189 printf("forward_wakeup: Idle processor not found\n");
1190 return (0);
1191 }
1192
1193 static void
1194 kick_other_cpu(int pri, int cpuid)
1195 {
1196 struct pcpu *pcpu;
1197 int cpri;
1198
1199 pcpu = pcpu_find(cpuid);
1200 if (CPU_ISSET(cpuid, &idle_cpus_mask)) {
1201 forward_wakeups_delivered++;
1202 if (!cpu_idle_wakeup(cpuid))
1203 ipi_cpu(cpuid, IPI_AST);
1204 return;
1205 }
1206
1207 cpri = pcpu->pc_curthread->td_priority;
1208 if (pri >= cpri)
1209 return;
1210
1211 #if defined(IPI_PREEMPTION) && defined(PREEMPTION)
1212 #if !defined(FULL_PREEMPTION)
1213 if (pri <= PRI_MAX_ITHD)
1214 #endif /* ! FULL_PREEMPTION */
1215 {
1216 ipi_cpu(cpuid, IPI_PREEMPT);
1217 return;
1218 }
1219 #endif /* defined(IPI_PREEMPTION) && defined(PREEMPTION) */
1220
1221 pcpu->pc_curthread->td_flags |= TDF_NEEDRESCHED;
1222 ipi_cpu(cpuid, IPI_AST);
1223 return;
1224 }
1225 #endif /* SMP */
1226
1227 #ifdef SMP
1228 static int
1229 sched_pickcpu(struct thread *td)
1230 {
1231 int best, cpu;
1232
1233 mtx_assert(&sched_lock, MA_OWNED);
1234
1235 if (THREAD_CAN_SCHED(td, td->td_lastcpu))
1236 best = td->td_lastcpu;
1237 else
1238 best = NOCPU;
1239 CPU_FOREACH(cpu) {
1240 if (!THREAD_CAN_SCHED(td, cpu))
1241 continue;
1242
1243 if (best == NOCPU)
1244 best = cpu;
1245 else if (runq_length[cpu] < runq_length[best])
1246 best = cpu;
1247 }
1248 KASSERT(best != NOCPU, ("no valid CPUs"));
1249
1250 return (best);
1251 }
1252 #endif
1253
1254 void
1255 sched_add(struct thread *td, int flags)
1256 #ifdef SMP
1257 {
1258 cpuset_t tidlemsk;
1259 struct td_sched *ts;
1260 u_int cpu, cpuid;
1261 int forwarded = 0;
1262 int single_cpu = 0;
1263
1264 ts = td->td_sched;
1265 THREAD_LOCK_ASSERT(td, MA_OWNED);
1266 KASSERT((td->td_inhibitors == 0),
1267 ("sched_add: trying to run inhibited thread"));
1268 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
1269 ("sched_add: bad thread state"));
1270 KASSERT(td->td_flags & TDF_INMEM,
1271 ("sched_add: thread swapped out"));
1272
1273 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
1274 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
1275 sched_tdname(curthread));
1276 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
1277 KTR_ATTR_LINKED, sched_tdname(td));
1278 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL,
1279 flags & SRQ_PREEMPTED);
1280
1281
1282 /*
1283 * Now that the thread is moving to the run-queue, set the lock
1284 * to the scheduler's lock.
1285 */
1286 if (td->td_lock != &sched_lock) {
1287 mtx_lock_spin(&sched_lock);
1288 thread_lock_set(td, &sched_lock);
1289 }
1290 TD_SET_RUNQ(td);
1291
1292 /*
1293 * If SMP is started and the thread is pinned or otherwise limited to
1294 * a specific set of CPUs, queue the thread to a per-CPU run queue.
1295 * Otherwise, queue the thread to the global run queue.
1296 *
1297 * If SMP has not yet been started we must use the global run queue
1298 * as per-CPU state may not be initialized yet and we may crash if we
1299 * try to access the per-CPU run queues.
1300 */
1301 if (smp_started && (td->td_pinned != 0 || td->td_flags & TDF_BOUND ||
1302 ts->ts_flags & TSF_AFFINITY)) {
1303 if (td->td_pinned != 0)
1304 cpu = td->td_lastcpu;
1305 else if (td->td_flags & TDF_BOUND) {
1306 /* Find CPU from bound runq. */
1307 KASSERT(SKE_RUNQ_PCPU(ts),
1308 ("sched_add: bound td_sched not on cpu runq"));
1309 cpu = ts->ts_runq - &runq_pcpu[0];
1310 } else
1311 /* Find a valid CPU for our cpuset */
1312 cpu = sched_pickcpu(td);
1313 ts->ts_runq = &runq_pcpu[cpu];
1314 single_cpu = 1;
1315 CTR3(KTR_RUNQ,
1316 "sched_add: Put td_sched:%p(td:%p) on cpu%d runq", ts, td,
1317 cpu);
1318 } else {
1319 CTR2(KTR_RUNQ,
1320 "sched_add: adding td_sched:%p (td:%p) to gbl runq", ts,
1321 td);
1322 cpu = NOCPU;
1323 ts->ts_runq = &runq;
1324 }
1325
1326 cpuid = PCPU_GET(cpuid);
1327 if (single_cpu && cpu != cpuid) {
1328 kick_other_cpu(td->td_priority, cpu);
1329 } else {
1330 if (!single_cpu) {
1331 tidlemsk = idle_cpus_mask;
1332 CPU_NAND(&tidlemsk, &hlt_cpus_mask);
1333 CPU_CLR(cpuid, &tidlemsk);
1334
1335 if (!CPU_ISSET(cpuid, &idle_cpus_mask) &&
1336 ((flags & SRQ_INTR) == 0) &&
1337 !CPU_EMPTY(&tidlemsk))
1338 forwarded = forward_wakeup(cpu);
1339 }
1340
1341 if (!forwarded) {
1342 if ((flags & SRQ_YIELDING) == 0 && maybe_preempt(td))
1343 return;
1344 else
1345 maybe_resched(td);
1346 }
1347 }
1348
1349 if ((td->td_flags & TDF_NOLOAD) == 0)
1350 sched_load_add();
1351 runq_add(ts->ts_runq, td, flags);
1352 if (cpu != NOCPU)
1353 runq_length[cpu]++;
1354 }
1355 #else /* SMP */
1356 {
1357 struct td_sched *ts;
1358
1359 ts = td->td_sched;
1360 THREAD_LOCK_ASSERT(td, MA_OWNED);
1361 KASSERT((td->td_inhibitors == 0),
1362 ("sched_add: trying to run inhibited thread"));
1363 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
1364 ("sched_add: bad thread state"));
1365 KASSERT(td->td_flags & TDF_INMEM,
1366 ("sched_add: thread swapped out"));
1367 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
1368 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
1369 sched_tdname(curthread));
1370 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
1371 KTR_ATTR_LINKED, sched_tdname(td));
1372 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL,
1373 flags & SRQ_PREEMPTED);
1374
1375 /*
1376 * Now that the thread is moving to the run-queue, set the lock
1377 * to the scheduler's lock.
1378 */
1379 if (td->td_lock != &sched_lock) {
1380 mtx_lock_spin(&sched_lock);
1381 thread_lock_set(td, &sched_lock);
1382 }
1383 TD_SET_RUNQ(td);
1384 CTR2(KTR_RUNQ, "sched_add: adding td_sched:%p (td:%p) to runq", ts, td);
1385 ts->ts_runq = &runq;
1386
1387 /*
1388 * If we are yielding (on the way out anyhow) or the thread
1389 * being saved is US, then don't try be smart about preemption
1390 * or kicking off another CPU as it won't help and may hinder.
1391 * In the YIEDLING case, we are about to run whoever is being
1392 * put in the queue anyhow, and in the OURSELF case, we are
1393 * puting ourself on the run queue which also only happens
1394 * when we are about to yield.
1395 */
1396 if ((flags & SRQ_YIELDING) == 0) {
1397 if (maybe_preempt(td))
1398 return;
1399 }
1400 if ((td->td_flags & TDF_NOLOAD) == 0)
1401 sched_load_add();
1402 runq_add(ts->ts_runq, td, flags);
1403 maybe_resched(td);
1404 }
1405 #endif /* SMP */
1406
1407 void
1408 sched_rem(struct thread *td)
1409 {
1410 struct td_sched *ts;
1411
1412 ts = td->td_sched;
1413 KASSERT(td->td_flags & TDF_INMEM,
1414 ("sched_rem: thread swapped out"));
1415 KASSERT(TD_ON_RUNQ(td),
1416 ("sched_rem: thread not on run queue"));
1417 mtx_assert(&sched_lock, MA_OWNED);
1418 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
1419 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
1420 sched_tdname(curthread));
1421 SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
1422
1423 if ((td->td_flags & TDF_NOLOAD) == 0)
1424 sched_load_rem();
1425 #ifdef SMP
1426 if (ts->ts_runq != &runq)
1427 runq_length[ts->ts_runq - runq_pcpu]--;
1428 #endif
1429 runq_remove(ts->ts_runq, td);
1430 TD_SET_CAN_RUN(td);
1431 }
1432
1433 /*
1434 * Select threads to run. Note that running threads still consume a
1435 * slot.
1436 */
1437 struct thread *
1438 sched_choose(void)
1439 {
1440 struct thread *td;
1441 struct runq *rq;
1442
1443 mtx_assert(&sched_lock, MA_OWNED);
1444 #ifdef SMP
1445 struct thread *tdcpu;
1446
1447 rq = &runq;
1448 td = runq_choose_fuzz(&runq, runq_fuzz);
1449 tdcpu = runq_choose(&runq_pcpu[PCPU_GET(cpuid)]);
1450
1451 if (td == NULL ||
1452 (tdcpu != NULL &&
1453 tdcpu->td_priority < td->td_priority)) {
1454 CTR2(KTR_RUNQ, "choosing td %p from pcpu runq %d", tdcpu,
1455 PCPU_GET(cpuid));
1456 td = tdcpu;
1457 rq = &runq_pcpu[PCPU_GET(cpuid)];
1458 } else {
1459 CTR1(KTR_RUNQ, "choosing td_sched %p from main runq", td);
1460 }
1461
1462 #else
1463 rq = &runq;
1464 td = runq_choose(&runq);
1465 #endif
1466
1467 if (td) {
1468 #ifdef SMP
1469 if (td == tdcpu)
1470 runq_length[PCPU_GET(cpuid)]--;
1471 #endif
1472 runq_remove(rq, td);
1473 td->td_flags |= TDF_DIDRUN;
1474
1475 KASSERT(td->td_flags & TDF_INMEM,
1476 ("sched_choose: thread swapped out"));
1477 return (td);
1478 }
1479 return (PCPU_GET(idlethread));
1480 }
1481
1482 void
1483 sched_preempt(struct thread *td)
1484 {
1485
1486 SDT_PROBE2(sched, , , surrender, td, td->td_proc);
1487 thread_lock(td);
1488 if (td->td_critnest > 1)
1489 td->td_owepreempt = 1;
1490 else
1491 mi_switch(SW_INVOL | SW_PREEMPT | SWT_PREEMPT, NULL);
1492 thread_unlock(td);
1493 }
1494
1495 void
1496 sched_userret(struct thread *td)
1497 {
1498 /*
1499 * XXX we cheat slightly on the locking here to avoid locking in
1500 * the usual case. Setting td_priority here is essentially an
1501 * incomplete workaround for not setting it properly elsewhere.
1502 * Now that some interrupt handlers are threads, not setting it
1503 * properly elsewhere can clobber it in the window between setting
1504 * it here and returning to user mode, so don't waste time setting
1505 * it perfectly here.
1506 */
1507 KASSERT((td->td_flags & TDF_BORROWING) == 0,
1508 ("thread with borrowed priority returning to userland"));
1509 if (td->td_priority != td->td_user_pri) {
1510 thread_lock(td);
1511 td->td_priority = td->td_user_pri;
1512 td->td_base_pri = td->td_user_pri;
1513 thread_unlock(td);
1514 }
1515 }
1516
1517 void
1518 sched_bind(struct thread *td, int cpu)
1519 {
1520 struct td_sched *ts;
1521
1522 THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
1523 KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
1524
1525 ts = td->td_sched;
1526
1527 td->td_flags |= TDF_BOUND;
1528 #ifdef SMP
1529 ts->ts_runq = &runq_pcpu[cpu];
1530 if (PCPU_GET(cpuid) == cpu)
1531 return;
1532
1533 mi_switch(SW_VOL, NULL);
1534 #endif
1535 }
1536
1537 void
1538 sched_unbind(struct thread* td)
1539 {
1540 THREAD_LOCK_ASSERT(td, MA_OWNED);
1541 KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
1542 td->td_flags &= ~TDF_BOUND;
1543 }
1544
1545 int
1546 sched_is_bound(struct thread *td)
1547 {
1548 THREAD_LOCK_ASSERT(td, MA_OWNED);
1549 return (td->td_flags & TDF_BOUND);
1550 }
1551
1552 void
1553 sched_relinquish(struct thread *td)
1554 {
1555 thread_lock(td);
1556 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
1557 thread_unlock(td);
1558 }
1559
1560 int
1561 sched_load(void)
1562 {
1563 return (sched_tdcnt);
1564 }
1565
1566 int
1567 sched_sizeof_proc(void)
1568 {
1569 return (sizeof(struct proc));
1570 }
1571
1572 int
1573 sched_sizeof_thread(void)
1574 {
1575 return (sizeof(struct thread) + sizeof(struct td_sched));
1576 }
1577
1578 fixpt_t
1579 sched_pctcpu(struct thread *td)
1580 {
1581 struct td_sched *ts;
1582
1583 THREAD_LOCK_ASSERT(td, MA_OWNED);
1584 ts = td->td_sched;
1585 return (ts->ts_pctcpu);
1586 }
1587
1588 #ifdef RACCT
1589 /*
1590 * Calculates the contribution to the thread cpu usage for the latest
1591 * (unfinished) second.
1592 */
1593 fixpt_t
1594 sched_pctcpu_delta(struct thread *td)
1595 {
1596 struct td_sched *ts;
1597 fixpt_t delta;
1598 int realstathz;
1599
1600 THREAD_LOCK_ASSERT(td, MA_OWNED);
1601 ts = td->td_sched;
1602 delta = 0;
1603 realstathz = stathz ? stathz : hz;
1604 if (ts->ts_cpticks != 0) {
1605 #if (FSHIFT >= CCPU_SHIFT)
1606 delta = (realstathz == 100)
1607 ? ((fixpt_t) ts->ts_cpticks) <<
1608 (FSHIFT - CCPU_SHIFT) :
1609 100 * (((fixpt_t) ts->ts_cpticks)
1610 << (FSHIFT - CCPU_SHIFT)) / realstathz;
1611 #else
1612 delta = ((FSCALE - ccpu) *
1613 (ts->ts_cpticks *
1614 FSCALE / realstathz)) >> FSHIFT;
1615 #endif
1616 }
1617
1618 return (delta);
1619 }
1620 #endif
1621
1622 void
1623 sched_tick(int cnt)
1624 {
1625 }
1626
1627 /*
1628 * The actual idle process.
1629 */
1630 void
1631 sched_idletd(void *dummy)
1632 {
1633 struct pcpuidlestat *stat;
1634
1635 THREAD_NO_SLEEPING();
1636 stat = DPCPU_PTR(idlestat);
1637 for (;;) {
1638 mtx_assert(&Giant, MA_NOTOWNED);
1639
1640 while (sched_runnable() == 0) {
1641 cpu_idle(stat->idlecalls + stat->oldidlecalls > 64);
1642 stat->idlecalls++;
1643 }
1644
1645 mtx_lock_spin(&sched_lock);
1646 mi_switch(SW_VOL | SWT_IDLE, NULL);
1647 mtx_unlock_spin(&sched_lock);
1648 }
1649 }
1650
1651 /*
1652 * A CPU is entering for the first time or a thread is exiting.
1653 */
1654 void
1655 sched_throw(struct thread *td)
1656 {
1657 /*
1658 * Correct spinlock nesting. The idle thread context that we are
1659 * borrowing was created so that it would start out with a single
1660 * spin lock (sched_lock) held in fork_trampoline(). Since we've
1661 * explicitly acquired locks in this function, the nesting count
1662 * is now 2 rather than 1. Since we are nested, calling
1663 * spinlock_exit() will simply adjust the counts without allowing
1664 * spin lock using code to interrupt us.
1665 */
1666 if (td == NULL) {
1667 mtx_lock_spin(&sched_lock);
1668 spinlock_exit();
1669 PCPU_SET(switchtime, cpu_ticks());
1670 PCPU_SET(switchticks, ticks);
1671 } else {
1672 lock_profile_release_lock(&sched_lock.lock_object);
1673 MPASS(td->td_lock == &sched_lock);
1674 }
1675 mtx_assert(&sched_lock, MA_OWNED);
1676 KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
1677 cpu_throw(td, choosethread()); /* doesn't return */
1678 }
1679
1680 void
1681 sched_fork_exit(struct thread *td)
1682 {
1683
1684 /*
1685 * Finish setting up thread glue so that it begins execution in a
1686 * non-nested critical section with sched_lock held but not recursed.
1687 */
1688 td->td_oncpu = PCPU_GET(cpuid);
1689 sched_lock.mtx_lock = (uintptr_t)td;
1690 lock_profile_obtain_lock_success(&sched_lock.lock_object,
1691 0, 0, __FILE__, __LINE__);
1692 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
1693 }
1694
1695 char *
1696 sched_tdname(struct thread *td)
1697 {
1698 #ifdef KTR
1699 struct td_sched *ts;
1700
1701 ts = td->td_sched;
1702 if (ts->ts_name[0] == '\0')
1703 snprintf(ts->ts_name, sizeof(ts->ts_name),
1704 "%s tid %d", td->td_name, td->td_tid);
1705 return (ts->ts_name);
1706 #else
1707 return (td->td_name);
1708 #endif
1709 }
1710
1711 #ifdef KTR
1712 void
1713 sched_clear_tdname(struct thread *td)
1714 {
1715 struct td_sched *ts;
1716
1717 ts = td->td_sched;
1718 ts->ts_name[0] = '\0';
1719 }
1720 #endif
1721
1722 void
1723 sched_affinity(struct thread *td)
1724 {
1725 #ifdef SMP
1726 struct td_sched *ts;
1727 int cpu;
1728
1729 THREAD_LOCK_ASSERT(td, MA_OWNED);
1730
1731 /*
1732 * Set the TSF_AFFINITY flag if there is at least one CPU this
1733 * thread can't run on.
1734 */
1735 ts = td->td_sched;
1736 ts->ts_flags &= ~TSF_AFFINITY;
1737 CPU_FOREACH(cpu) {
1738 if (!THREAD_CAN_SCHED(td, cpu)) {
1739 ts->ts_flags |= TSF_AFFINITY;
1740 break;
1741 }
1742 }
1743
1744 /*
1745 * If this thread can run on all CPUs, nothing else to do.
1746 */
1747 if (!(ts->ts_flags & TSF_AFFINITY))
1748 return;
1749
1750 /* Pinned threads and bound threads should be left alone. */
1751 if (td->td_pinned != 0 || td->td_flags & TDF_BOUND)
1752 return;
1753
1754 switch (td->td_state) {
1755 case TDS_RUNQ:
1756 /*
1757 * If we are on a per-CPU runqueue that is in the set,
1758 * then nothing needs to be done.
1759 */
1760 if (ts->ts_runq != &runq &&
1761 THREAD_CAN_SCHED(td, ts->ts_runq - runq_pcpu))
1762 return;
1763
1764 /* Put this thread on a valid per-CPU runqueue. */
1765 sched_rem(td);
1766 sched_add(td, SRQ_BORING);
1767 break;
1768 case TDS_RUNNING:
1769 /*
1770 * See if our current CPU is in the set. If not, force a
1771 * context switch.
1772 */
1773 if (THREAD_CAN_SCHED(td, td->td_oncpu))
1774 return;
1775
1776 td->td_flags |= TDF_NEEDRESCHED;
1777 if (td != curthread)
1778 ipi_cpu(cpu, IPI_AST);
1779 break;
1780 default:
1781 break;
1782 }
1783 #endif
1784 }
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