1 /*
2 * Copyright (c) 2000-2019 Apple Inc. All rights reserved.
3 *
4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
5 *
6 * This file contains Original Code and/or Modifications of Original Code
7 * as defined in and that are subject to the Apple Public Source License
8 * Version 2.0 (the 'License'). You may not use this file except in
9 * compliance with the License. The rights granted to you under the License
10 * may not be used to create, or enable the creation or redistribution of,
11 * unlawful or unlicensed copies of an Apple operating system, or to
12 * circumvent, violate, or enable the circumvention or violation of, any
13 * terms of an Apple operating system software license agreement.
14 *
15 * Please obtain a copy of the License at
16 * http://www.opensource.apple.com/apsl/ and read it before using this file.
17 *
18 * The Original Code and all software distributed under the License are
19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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23 * Please see the License for the specific language governing rights and
24 * limitations under the License.
25 *
26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
27 */
28 /*
29 * @OSF_COPYRIGHT@
30 */
31 /*
32 * Mach Operating System
33 * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
34 * All Rights Reserved.
35 *
36 * Permission to use, copy, modify and distribute this software and its
37 * documentation is hereby granted, provided that both the copyright
38 * notice and this permission notice appear in all copies of the
39 * software, derivative works or modified versions, and any portions
40 * thereof, and that both notices appear in supporting documentation.
41 *
42 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
43 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
44 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
45 *
46 * Carnegie Mellon requests users of this software to return to
47 *
48 * Software Distribution Coordinator or [email protected]
49 * School of Computer Science
50 * Carnegie Mellon University
51 * Pittsburgh PA 15213-3890
52 *
53 * any improvements or extensions that they make and grant Carnegie Mellon
54 * the rights to redistribute these changes.
55 */
56 /*
57 */
58 /*
59 * File: priority.c
60 * Author: Avadis Tevanian, Jr.
61 * Date: 1986
62 *
63 * Priority related scheduler bits.
64 */
65
66 #include <mach/boolean.h>
67 #include <mach/kern_return.h>
68 #include <mach/machine.h>
69 #include <kern/host.h>
70 #include <kern/mach_param.h>
71 #include <kern/sched.h>
72 #include <sys/kdebug.h>
73 #include <kern/spl.h>
74 #include <kern/thread.h>
75 #include <kern/processor.h>
76 #include <kern/ledger.h>
77 #include <kern/monotonic.h>
78 #include <machine/machparam.h>
79 #include <kern/machine.h>
80 #include <kern/policy_internal.h>
81 #include <kern/sched_clutch.h>
82
83 #ifdef CONFIG_MACH_APPROXIMATE_TIME
84 #include <machine/commpage.h> /* for commpage_update_mach_approximate_time */
85 #endif
86
87 /*
88 * thread_quantum_expire:
89 *
90 * Recalculate the quantum and priority for a thread.
91 *
92 * Called at splsched.
93 */
94
95 void
thread_quantum_expire(timer_call_param_t p0,timer_call_param_t p1)96 thread_quantum_expire(
97 timer_call_param_t p0,
98 timer_call_param_t p1)
99 {
100 processor_t processor = p0;
101 thread_t thread = p1;
102 ast_t preempt;
103 uint64_t ctime;
104
105 assert(processor == current_processor());
106 assert(thread == current_thread());
107
108 KDBG_RELEASE(MACHDBG_CODE(
109 DBG_MACH_SCHED, MACH_SCHED_QUANTUM_EXPIRED) | DBG_FUNC_START);
110
111 SCHED_STATS_INC(quantum_timer_expirations);
112
113 /*
114 * We bill CPU time to both the individual thread and its task.
115 *
116 * Because this balance adjustment could potentially attempt to wake this
117 * very thread, we must credit the ledger before taking the thread lock.
118 * The ledger pointers are only manipulated by the thread itself at the ast
119 * boundary.
120 *
121 * TODO: This fails to account for the time between when the timer was
122 * armed and when it fired. It should be based on the system_timer and
123 * running a timer_update operation here.
124 */
125 ledger_credit(thread->t_ledger, task_ledgers.cpu_time, thread->quantum_remaining);
126 ledger_credit(thread->t_threadledger, thread_ledgers.cpu_time, thread->quantum_remaining);
127 if (thread->t_bankledger) {
128 ledger_credit(thread->t_bankledger, bank_ledgers.cpu_time,
129 (thread->quantum_remaining - thread->t_deduct_bank_ledger_time));
130 }
131 thread->t_deduct_bank_ledger_time = 0;
132
133 struct recount_snap snap = { 0 };
134 recount_snapshot(&snap);
135 ctime = snap.rsn_time_mach;
136 check_monotonic_time(ctime);
137 #ifdef CONFIG_MACH_APPROXIMATE_TIME
138 commpage_update_mach_approximate_time(ctime);
139 #endif /* CONFIG_MACH_APPROXIMATE_TIME */
140
141 sched_update_pset_avg_execution_time(processor->processor_set, thread->quantum_remaining, ctime, thread->th_sched_bucket);
142
143 recount_switch_thread(&snap, thread, get_threadtask(thread));
144 recount_log_switch_thread(&snap);
145
146 thread_lock(thread);
147
148 /*
149 * We've run up until our quantum expiration, and will (potentially)
150 * continue without re-entering the scheduler, so update this now.
151 */
152 processor->last_dispatch = ctime;
153 thread->last_run_time = ctime;
154
155 /*
156 * Check for fail-safe trip.
157 */
158 if ((thread->sched_mode == TH_MODE_REALTIME || thread->sched_mode == TH_MODE_FIXED) &&
159 !(thread->sched_flags & TH_SFLAG_PROMOTED) &&
160 !(thread->kern_promotion_schedpri != 0) &&
161 !(thread->sched_flags & TH_SFLAG_PROMOTE_REASON_MASK) &&
162 !(thread->options & TH_OPT_SYSTEM_CRITICAL)) {
163 uint64_t new_computation;
164
165 new_computation = ctime - thread->computation_epoch;
166 new_computation += thread->computation_metered;
167 /*
168 * Remove any time spent handling interrupts outside of the thread's
169 * control.
170 */
171 new_computation -= recount_current_thread_interrupt_time_mach() - thread->computation_interrupt_epoch;
172
173 bool demote = false;
174 switch (thread->sched_mode) {
175 case TH_MODE_REALTIME:
176 if (new_computation > max_unsafe_rt_computation) {
177 thread->safe_release = ctime + sched_safe_rt_duration;
178 demote = true;
179 }
180 break;
181 case TH_MODE_FIXED:
182 if (new_computation > max_unsafe_fixed_computation) {
183 thread->safe_release = ctime + sched_safe_fixed_duration;
184 demote = true;
185 }
186 break;
187 default:
188 panic("unexpected mode: %d", thread->sched_mode);
189 }
190
191 if (demote) {
192 KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SCHED, MACH_FAILSAFE) | DBG_FUNC_NONE,
193 (uintptr_t)thread->sched_pri, (uintptr_t)thread->sched_mode, 0, 0, 0);
194 sched_thread_mode_demote(thread, TH_SFLAG_FAILSAFE);
195 }
196 }
197
198 /*
199 * Recompute scheduled priority if appropriate.
200 */
201 if (SCHED(can_update_priority)(thread)) {
202 SCHED(update_priority)(thread);
203 } else {
204 SCHED(lightweight_update_priority)(thread);
205 }
206
207 if (thread->sched_mode != TH_MODE_REALTIME) {
208 SCHED(quantum_expire)(thread);
209 }
210
211 /*
212 * This quantum is up, give this thread another.
213 */
214 processor->first_timeslice = FALSE;
215
216 thread_quantum_init(thread, ctime);
217
218 timer_update(&thread->runnable_timer, ctime);
219
220 processor->quantum_end = ctime + thread->quantum_remaining;
221
222 /*
223 * Context switch check
224 *
225 * non-urgent flags don't affect kernel threads, so upgrade to urgent
226 * to ensure that rebalancing and non-recommendation kick in quickly.
227 */
228
229 ast_t check_reason = AST_QUANTUM;
230 if (get_threadtask(thread) == kernel_task) {
231 check_reason |= AST_URGENT;
232 }
233
234 if ((preempt = csw_check(thread, processor, check_reason)) != AST_NONE) {
235 ast_on(preempt);
236 }
237
238 /*
239 * AST_KEVENT does not send an IPI when setting the AST,
240 * to avoid waiting for the next context switch to propagate the AST,
241 * the AST is propagated here at quantum expiration.
242 */
243 ast_propagate(thread);
244
245 thread_unlock(thread);
246
247 /* Now that the processor->thread_timer has been updated, evaluate to see if
248 * the workqueue quantum expired and set AST_KEVENT if it has */
249 if (thread_get_tag(thread) & THREAD_TAG_WORKQUEUE) {
250 thread_evaluate_workqueue_quantum_expiry(thread);
251 }
252
253 running_timer_enter(processor, RUNNING_TIMER_QUANTUM, thread,
254 processor->quantum_end, ctime);
255
256 /* Tell platform layer that we are still running this thread */
257 thread_urgency_t urgency = thread_get_urgency(thread, NULL, NULL);
258 machine_thread_going_on_core(thread, urgency, 0, 0, ctime);
259 machine_switch_perfcontrol_state_update(QUANTUM_EXPIRY, ctime,
260 0, thread);
261
262 #if defined(CONFIG_SCHED_TIMESHARE_CORE)
263 sched_timeshare_consider_maintenance(ctime, false);
264 #endif /* CONFIG_SCHED_TIMESHARE_CORE */
265
266 #if __arm64__
267 if (thread->sched_mode == TH_MODE_REALTIME) {
268 sched_consider_recommended_cores(ctime, thread);
269 }
270 #endif /* __arm64__ */
271
272 KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SCHED, MACH_SCHED_QUANTUM_EXPIRED) | DBG_FUNC_END, preempt, 0, 0, 0, 0);
273 }
274
275 /*
276 * sched_set_thread_base_priority:
277 *
278 * Set the base priority of the thread
279 * and reset its scheduled priority.
280 *
281 * This is the only path to change base_pri.
282 *
283 * Called with the thread locked.
284 */
285 void
sched_set_thread_base_priority(thread_t thread,int priority)286 sched_set_thread_base_priority(thread_t thread, int priority)
287 {
288 assert(priority >= MINPRI);
289 uint64_t ctime = 0;
290
291 if (thread->sched_mode == TH_MODE_REALTIME) {
292 assert((priority >= BASEPRI_RTQUEUES) && (priority <= MAXPRI));
293 } else {
294 assert(priority < BASEPRI_RTQUEUES);
295 }
296
297 int old_base_pri = thread->base_pri;
298 thread->req_base_pri = (int16_t)priority;
299 if (thread->sched_flags & TH_SFLAG_BASE_PRI_FROZEN) {
300 priority = MAX(priority, old_base_pri);
301 }
302 thread->base_pri = (int16_t)priority;
303
304 if ((thread->state & TH_RUN) == TH_RUN) {
305 assert(thread->last_made_runnable_time != THREAD_NOT_RUNNABLE);
306 ctime = mach_approximate_time();
307 thread->last_basepri_change_time = ctime;
308 } else {
309 assert(thread->last_basepri_change_time == THREAD_NOT_RUNNABLE);
310 assert(thread->last_made_runnable_time == THREAD_NOT_RUNNABLE);
311 }
312
313 /*
314 * Currently the perfcontrol_attr depends on the base pri of the
315 * thread. Therefore, we use this function as the hook for the
316 * perfcontrol callout.
317 */
318 if (thread == current_thread() && old_base_pri != priority) {
319 if (!ctime) {
320 ctime = mach_approximate_time();
321 }
322 machine_switch_perfcontrol_state_update(PERFCONTROL_ATTR_UPDATE,
323 ctime, PERFCONTROL_CALLOUT_WAKE_UNSAFE, thread);
324 }
325 #if !CONFIG_SCHED_CLUTCH
326 /* For the clutch scheduler, this operation is done in set_sched_pri() */
327 SCHED(update_thread_bucket)(thread);
328 #endif /* !CONFIG_SCHED_CLUTCH */
329
330 thread_recompute_sched_pri(thread, SETPRI_DEFAULT);
331 }
332
333 /*
334 * sched_set_kernel_thread_priority:
335 *
336 * Set the absolute base priority of the thread
337 * and reset its scheduled priority.
338 *
339 * Called with the thread unlocked.
340 */
341 void
sched_set_kernel_thread_priority(thread_t thread,int new_priority)342 sched_set_kernel_thread_priority(thread_t thread, int new_priority)
343 {
344 spl_t s = splsched();
345
346 thread_lock(thread);
347
348 assert(thread->sched_mode != TH_MODE_REALTIME);
349 assert(thread->effective_policy.thep_qos == THREAD_QOS_UNSPECIFIED);
350
351 if (new_priority > thread->max_priority) {
352 new_priority = thread->max_priority;
353 }
354 #if !defined(XNU_TARGET_OS_OSX)
355 if (new_priority < MAXPRI_THROTTLE) {
356 new_priority = MAXPRI_THROTTLE;
357 }
358 #endif /* !defined(XNU_TARGET_OS_OSX) */
359
360 thread->importance = new_priority - thread->task_priority;
361
362 sched_set_thread_base_priority(thread, new_priority);
363
364 thread_unlock(thread);
365 splx(s);
366 }
367
368 /*
369 * thread_recompute_sched_pri:
370 *
371 * Reset the scheduled priority of the thread
372 * according to its base priority if the
373 * thread has not been promoted or depressed.
374 *
375 * This is the only way to push base_pri changes into sched_pri,
376 * or to recalculate the appropriate sched_pri after changing
377 * a promotion or depression.
378 *
379 * Called at splsched with the thread locked.
380 *
381 * TODO: Add an 'update urgency' flag to avoid urgency callouts on every rwlock operation
382 */
383 void
thread_recompute_sched_pri(thread_t thread,set_sched_pri_options_t options)384 thread_recompute_sched_pri(thread_t thread, set_sched_pri_options_t options)
385 {
386 uint32_t sched_flags = thread->sched_flags;
387 sched_mode_t sched_mode = thread->sched_mode;
388
389 int16_t priority = thread->base_pri;
390
391 if (sched_mode == TH_MODE_TIMESHARE) {
392 priority = (int16_t)SCHED(compute_timeshare_priority)(thread);
393 }
394
395 if (sched_flags & TH_SFLAG_DEPRESS) {
396 /* thread_yield_internal overrides kernel mutex promotion */
397 priority = DEPRESSPRI;
398 } else {
399 /* poll-depress is overridden by mutex promotion and promote-reasons */
400 if ((sched_flags & TH_SFLAG_POLLDEPRESS)) {
401 priority = DEPRESSPRI;
402 }
403
404 if (thread->kern_promotion_schedpri > 0) {
405 priority = MAX(priority, thread->kern_promotion_schedpri);
406
407 if (sched_mode != TH_MODE_REALTIME) {
408 priority = MIN(priority, MAXPRI_PROMOTE);
409 }
410 }
411
412 if (sched_flags & TH_SFLAG_PROMOTED) {
413 priority = MAX(priority, thread->promotion_priority);
414
415 if (sched_mode != TH_MODE_REALTIME) {
416 priority = MIN(priority, MAXPRI_PROMOTE);
417 }
418 }
419
420 if (sched_flags & TH_SFLAG_PROMOTE_REASON_MASK) {
421 if (sched_flags & TH_SFLAG_RW_PROMOTED) {
422 priority = MAX(priority, MINPRI_RWLOCK);
423 }
424
425 if (sched_flags & TH_SFLAG_WAITQ_PROMOTED) {
426 priority = MAX(priority, MINPRI_WAITQ);
427 }
428
429 if (sched_flags & TH_SFLAG_EXEC_PROMOTED) {
430 priority = MAX(priority, MINPRI_EXEC);
431 }
432
433 if (sched_flags & TH_SFLAG_FLOOR_PROMOTED) {
434 priority = MAX(priority, MINPRI_FLOOR);
435 }
436 }
437 }
438
439 set_sched_pri(thread, priority, options);
440 }
441
442 void
sched_default_quantum_expire(thread_t thread __unused)443 sched_default_quantum_expire(thread_t thread __unused)
444 {
445 /*
446 * No special behavior when a timeshare, fixed, or realtime thread
447 * uses up its entire quantum
448 */
449 }
450
451 int smt_timeshare_enabled = 1;
452 int smt_sched_bonus_16ths = 8;
453
454 #if defined(CONFIG_SCHED_TIMESHARE_CORE)
455
456 /*
457 * lightweight_update_priority:
458 *
459 * Update the scheduled priority for
460 * a timesharing thread.
461 *
462 * Only for use on the current thread.
463 *
464 * Called with the thread locked.
465 */
466 void
lightweight_update_priority(thread_t thread)467 lightweight_update_priority(thread_t thread)
468 {
469 thread_assert_runq_null(thread);
470 assert(thread == current_thread());
471
472 if (thread->sched_mode == TH_MODE_TIMESHARE) {
473 int priority;
474 uint32_t delta;
475
476 sched_tick_delta(thread, delta);
477
478 /*
479 * Accumulate timesharing usage only
480 * during contention for processor
481 * resources.
482 */
483 if (thread->pri_shift < INT8_MAX) {
484 if (thread_no_smt(thread) && smt_timeshare_enabled) {
485 thread->sched_usage += (delta + ((delta * smt_sched_bonus_16ths) >> 4));
486 } else {
487 thread->sched_usage += delta;
488 }
489 }
490
491 thread->cpu_delta += delta;
492
493 #if CONFIG_SCHED_CLUTCH
494 /*
495 * Update the CPU usage for the thread group to which the thread belongs.
496 * The implementation assumes that the thread ran for the entire delta
497 * as part of the same thread group.
498 */
499 sched_clutch_cpu_usage_update(thread, delta);
500 #endif /* CONFIG_SCHED_CLUTCH */
501
502 priority = sched_compute_timeshare_priority(thread);
503
504 if (priority != thread->sched_pri) {
505 thread_recompute_sched_pri(thread, SETPRI_LAZY);
506 }
507 }
508 }
509
510 /*
511 * Define shifts for simulating (5/8) ** n
512 *
513 * Shift structures for holding update shifts. Actual computation
514 * is usage = (usage >> shift1) +/- (usage >> abs(shift2)) where the
515 * +/- is determined by the sign of shift 2.
516 */
517
518 const struct shift_data sched_decay_shifts[SCHED_DECAY_TICKS] = {
519 { .shift1 = 1, .shift2 = 1 },
520 { .shift1 = 1, .shift2 = 3 },
521 { .shift1 = 1, .shift2 = -3 },
522 { .shift1 = 2, .shift2 = -7 },
523 { .shift1 = 3, .shift2 = 5 },
524 { .shift1 = 3, .shift2 = -5 },
525 { .shift1 = 4, .shift2 = -8 },
526 { .shift1 = 5, .shift2 = 7 },
527 { .shift1 = 5, .shift2 = -7 },
528 { .shift1 = 6, .shift2 = -10 },
529 { .shift1 = 7, .shift2 = 10 },
530 { .shift1 = 7, .shift2 = -9 },
531 { .shift1 = 8, .shift2 = -11 },
532 { .shift1 = 9, .shift2 = 12 },
533 { .shift1 = 9, .shift2 = -11 },
534 { .shift1 = 10, .shift2 = -13 },
535 { .shift1 = 11, .shift2 = 14 },
536 { .shift1 = 11, .shift2 = -13 },
537 { .shift1 = 12, .shift2 = -15 },
538 { .shift1 = 13, .shift2 = 17 },
539 { .shift1 = 13, .shift2 = -15 },
540 { .shift1 = 14, .shift2 = -17 },
541 { .shift1 = 15, .shift2 = 19 },
542 { .shift1 = 16, .shift2 = 18 },
543 { .shift1 = 16, .shift2 = -19 },
544 { .shift1 = 17, .shift2 = 22 },
545 { .shift1 = 18, .shift2 = 20 },
546 { .shift1 = 18, .shift2 = -20 },
547 { .shift1 = 19, .shift2 = 26 },
548 { .shift1 = 20, .shift2 = 22 },
549 { .shift1 = 20, .shift2 = -22 },
550 { .shift1 = 21, .shift2 = -27 }
551 };
552
553 /*
554 * sched_compute_timeshare_priority:
555 *
556 * Calculate the timesharing priority based upon usage and load.
557 */
558 extern int sched_pri_decay_band_limit;
559
560
561 /* Only use the decay floor logic on non-macOS and non-clutch schedulers */
562 #if !defined(XNU_TARGET_OS_OSX) && !CONFIG_SCHED_CLUTCH
563
564 int
sched_compute_timeshare_priority(thread_t thread)565 sched_compute_timeshare_priority(thread_t thread)
566 {
567 int decay_amount;
568 int decay_limit = sched_pri_decay_band_limit;
569
570 if (thread->base_pri > BASEPRI_FOREGROUND) {
571 decay_limit += (thread->base_pri - BASEPRI_FOREGROUND);
572 }
573
574 if (thread->pri_shift == INT8_MAX) {
575 decay_amount = 0;
576 } else {
577 decay_amount = (thread->sched_usage >> thread->pri_shift);
578 }
579
580 if (decay_amount > decay_limit) {
581 decay_amount = decay_limit;
582 }
583
584 /* start with base priority */
585 int priority = thread->base_pri - decay_amount;
586
587 if (priority < MAXPRI_THROTTLE) {
588 if (get_threadtask(thread)->max_priority > MAXPRI_THROTTLE) {
589 priority = MAXPRI_THROTTLE;
590 } else if (priority < MINPRI_USER) {
591 priority = MINPRI_USER;
592 }
593 } else if (priority > MAXPRI_KERNEL) {
594 priority = MAXPRI_KERNEL;
595 }
596
597 return priority;
598 }
599
600 #else /* !defined(XNU_TARGET_OS_OSX) && !CONFIG_SCHED_CLUTCH */
601
602 int
sched_compute_timeshare_priority(thread_t thread)603 sched_compute_timeshare_priority(thread_t thread)
604 {
605 /* start with base priority */
606 int priority = thread->base_pri;
607
608 if (thread->pri_shift != INT8_MAX) {
609 priority -= (thread->sched_usage >> thread->pri_shift);
610 }
611
612 if (priority < MINPRI_USER) {
613 priority = MINPRI_USER;
614 } else if (priority > MAXPRI_KERNEL) {
615 priority = MAXPRI_KERNEL;
616 }
617
618 return priority;
619 }
620
621 #endif /* !defined(XNU_TARGET_OS_OSX) && !CONFIG_SCHED_CLUTCH */
622
623 /*
624 * can_update_priority
625 *
626 * Make sure we don't do re-dispatches more frequently than a scheduler tick.
627 *
628 * Called with the thread locked.
629 */
630 boolean_t
can_update_priority(thread_t thread)631 can_update_priority(
632 thread_t thread)
633 {
634 if (sched_tick == thread->sched_stamp) {
635 return FALSE;
636 } else {
637 return TRUE;
638 }
639 }
640
641 /*
642 * update_priority
643 *
644 * Perform housekeeping operations driven by scheduler tick.
645 *
646 * Called with the thread locked.
647 */
648 void
update_priority(thread_t thread)649 update_priority(
650 thread_t thread)
651 {
652 uint32_t ticks, delta;
653
654 ticks = sched_tick - thread->sched_stamp;
655 assert(ticks != 0);
656
657 thread->sched_stamp += ticks;
658
659 /* If requested, accelerate aging of sched_usage */
660 if (sched_decay_usage_age_factor > 1) {
661 ticks *= sched_decay_usage_age_factor;
662 }
663
664 /*
665 * Gather cpu usage data.
666 */
667 sched_tick_delta(thread, delta);
668 if (ticks < SCHED_DECAY_TICKS) {
669 /*
670 * Accumulate timesharing usage only during contention for processor
671 * resources. Use the pri_shift from the previous tick window to
672 * determine if the system was in a contended state.
673 */
674 if (thread->pri_shift < INT8_MAX) {
675 if (thread_no_smt(thread) && smt_timeshare_enabled) {
676 thread->sched_usage += (delta + ((delta * smt_sched_bonus_16ths) >> 4));
677 } else {
678 thread->sched_usage += delta;
679 }
680 }
681
682 thread->cpu_usage += delta + thread->cpu_delta;
683 thread->cpu_delta = 0;
684
685 #if CONFIG_SCHED_CLUTCH
686 /*
687 * Update the CPU usage for the thread group to which the thread belongs.
688 * The implementation assumes that the thread ran for the entire delta
689 * as part of the same thread group.
690 */
691 sched_clutch_cpu_usage_update(thread, delta);
692 #endif /* CONFIG_SCHED_CLUTCH */
693
694 const struct shift_data *shiftp = &sched_decay_shifts[ticks];
695
696 if (shiftp->shift2 > 0) {
697 thread->cpu_usage = (thread->cpu_usage >> shiftp->shift1) +
698 (thread->cpu_usage >> shiftp->shift2);
699 thread->sched_usage = (thread->sched_usage >> shiftp->shift1) +
700 (thread->sched_usage >> shiftp->shift2);
701 } else {
702 thread->cpu_usage = (thread->cpu_usage >> shiftp->shift1) -
703 (thread->cpu_usage >> -(shiftp->shift2));
704 thread->sched_usage = (thread->sched_usage >> shiftp->shift1) -
705 (thread->sched_usage >> -(shiftp->shift2));
706 }
707 } else {
708 thread->cpu_usage = thread->cpu_delta = 0;
709 thread->sched_usage = 0;
710 }
711
712 /*
713 * Check for fail-safe release.
714 */
715 if ((thread->sched_flags & TH_SFLAG_FAILSAFE) &&
716 mach_absolute_time() >= thread->safe_release) {
717 sched_thread_mode_undemote(thread, TH_SFLAG_FAILSAFE);
718 }
719
720 /*
721 * Now that the thread's CPU usage has been accumulated and aged
722 * based on contention of the previous tick window, update the
723 * pri_shift of the thread to match the current global load/shift
724 * values. The updated pri_shift would be used to calculate the
725 * new priority of the thread.
726 */
727 #if CONFIG_SCHED_CLUTCH
728 thread->pri_shift = sched_clutch_thread_pri_shift(thread, thread->th_sched_bucket);
729 #else /* CONFIG_SCHED_CLUTCH */
730 thread->pri_shift = sched_pri_shifts[thread->th_sched_bucket];
731 #endif /* CONFIG_SCHED_CLUTCH */
732
733 /* Recompute scheduled priority if appropriate. */
734 if (thread->sched_mode == TH_MODE_TIMESHARE) {
735 thread_recompute_sched_pri(thread, SETPRI_LAZY);
736 }
737 }
738
739 #endif /* CONFIG_SCHED_TIMESHARE_CORE */
740
741
742 /*
743 * TH_BUCKET_RUN is a count of *all* runnable non-idle threads.
744 * Each other bucket is a count of the runnable non-idle threads
745 * with that property. All updates to these counts should be
746 * performed with os_atomic_* operations.
747 *
748 * For the clutch scheduler, this global bucket is used only for
749 * keeping the total global run count.
750 */
751 uint32_t sched_run_buckets[TH_BUCKET_MAX];
752
753 static void
sched_incr_bucket(sched_bucket_t bucket)754 sched_incr_bucket(sched_bucket_t bucket)
755 {
756 assert(bucket >= TH_BUCKET_FIXPRI &&
757 bucket <= TH_BUCKET_SHARE_BG);
758
759 os_atomic_inc(&sched_run_buckets[bucket], relaxed);
760 }
761
762 static void
sched_decr_bucket(sched_bucket_t bucket)763 sched_decr_bucket(sched_bucket_t bucket)
764 {
765 assert(bucket >= TH_BUCKET_FIXPRI &&
766 bucket <= TH_BUCKET_SHARE_BG);
767
768 assert(os_atomic_load(&sched_run_buckets[bucket], relaxed) > 0);
769
770 os_atomic_dec(&sched_run_buckets[bucket], relaxed);
771 }
772
773 static void
sched_add_bucket(sched_bucket_t bucket,uint8_t run_weight)774 sched_add_bucket(sched_bucket_t bucket, uint8_t run_weight)
775 {
776 assert(bucket >= TH_BUCKET_FIXPRI &&
777 bucket <= TH_BUCKET_SHARE_BG);
778
779 os_atomic_add(&sched_run_buckets[bucket], run_weight, relaxed);
780 }
781
782 static void
sched_sub_bucket(sched_bucket_t bucket,uint8_t run_weight)783 sched_sub_bucket(sched_bucket_t bucket, uint8_t run_weight)
784 {
785 assert(bucket >= TH_BUCKET_FIXPRI &&
786 bucket <= TH_BUCKET_SHARE_BG);
787
788 assert(os_atomic_load(&sched_run_buckets[bucket], relaxed) > 0);
789
790 os_atomic_sub(&sched_run_buckets[bucket], run_weight, relaxed);
791 }
792
793 uint32_t
sched_run_incr(thread_t thread)794 sched_run_incr(thread_t thread)
795 {
796 assert((thread->state & (TH_RUN | TH_IDLE)) == TH_RUN);
797
798 uint32_t new_count = os_atomic_inc(&sched_run_buckets[TH_BUCKET_RUN], relaxed);
799
800 sched_incr_bucket(thread->th_sched_bucket);
801
802 return new_count;
803 }
804
805 uint32_t
sched_run_decr(thread_t thread)806 sched_run_decr(thread_t thread)
807 {
808 assert((thread->state & (TH_RUN | TH_IDLE)) != TH_RUN);
809
810 sched_decr_bucket(thread->th_sched_bucket);
811
812 uint32_t new_count = os_atomic_dec(&sched_run_buckets[TH_BUCKET_RUN], relaxed);
813
814 return new_count;
815 }
816
817 uint32_t
sched_smt_run_incr(thread_t thread)818 sched_smt_run_incr(thread_t thread)
819 {
820 assert((thread->state & (TH_RUN | TH_IDLE)) == TH_RUN);
821
822 uint8_t run_weight = (thread_no_smt(thread) && smt_timeshare_enabled) ? 2 : 1;
823 thread->sched_saved_run_weight = run_weight;
824
825 uint32_t new_count = os_atomic_add(&sched_run_buckets[TH_BUCKET_RUN], run_weight, relaxed);
826
827 sched_add_bucket(thread->th_sched_bucket, run_weight);
828
829 return new_count;
830 }
831
832 uint32_t
sched_smt_run_decr(thread_t thread)833 sched_smt_run_decr(thread_t thread)
834 {
835 assert((thread->state & (TH_RUN | TH_IDLE)) != TH_RUN);
836
837 uint8_t run_weight = thread->sched_saved_run_weight;
838
839 sched_sub_bucket(thread->th_sched_bucket, run_weight);
840
841 uint32_t new_count = os_atomic_sub(&sched_run_buckets[TH_BUCKET_RUN], run_weight, relaxed);
842
843 return new_count;
844 }
845
846 void
sched_update_thread_bucket(thread_t thread)847 sched_update_thread_bucket(thread_t thread)
848 {
849 sched_bucket_t old_bucket = thread->th_sched_bucket;
850 sched_bucket_t new_bucket = TH_BUCKET_RUN;
851
852 switch (thread->sched_mode) {
853 case TH_MODE_FIXED:
854 case TH_MODE_REALTIME:
855 new_bucket = TH_BUCKET_FIXPRI;
856 break;
857
858 case TH_MODE_TIMESHARE:
859 if (thread->base_pri > BASEPRI_DEFAULT) {
860 new_bucket = TH_BUCKET_SHARE_FG;
861 } else if (thread->base_pri > BASEPRI_UTILITY) {
862 new_bucket = TH_BUCKET_SHARE_DF;
863 } else if (thread->base_pri > MAXPRI_THROTTLE) {
864 new_bucket = TH_BUCKET_SHARE_UT;
865 } else {
866 new_bucket = TH_BUCKET_SHARE_BG;
867 }
868 break;
869
870 default:
871 panic("unexpected mode: %d", thread->sched_mode);
872 break;
873 }
874
875 if (old_bucket != new_bucket) {
876 thread->th_sched_bucket = new_bucket;
877 thread->pri_shift = sched_pri_shifts[new_bucket];
878
879 if ((thread->state & (TH_RUN | TH_IDLE)) == TH_RUN) {
880 sched_decr_bucket(old_bucket);
881 sched_incr_bucket(new_bucket);
882 }
883 }
884 }
885
886 void
sched_smt_update_thread_bucket(thread_t thread)887 sched_smt_update_thread_bucket(thread_t thread)
888 {
889 sched_bucket_t old_bucket = thread->th_sched_bucket;
890 sched_bucket_t new_bucket = TH_BUCKET_RUN;
891
892 switch (thread->sched_mode) {
893 case TH_MODE_FIXED:
894 case TH_MODE_REALTIME:
895 new_bucket = TH_BUCKET_FIXPRI;
896 break;
897
898 case TH_MODE_TIMESHARE:
899 if (thread->base_pri > BASEPRI_DEFAULT) {
900 new_bucket = TH_BUCKET_SHARE_FG;
901 } else if (thread->base_pri > BASEPRI_UTILITY) {
902 new_bucket = TH_BUCKET_SHARE_DF;
903 } else if (thread->base_pri > MAXPRI_THROTTLE) {
904 new_bucket = TH_BUCKET_SHARE_UT;
905 } else {
906 new_bucket = TH_BUCKET_SHARE_BG;
907 }
908 break;
909
910 default:
911 panic("unexpected mode: %d", thread->sched_mode);
912 break;
913 }
914
915 if (old_bucket != new_bucket) {
916 thread->th_sched_bucket = new_bucket;
917 thread->pri_shift = sched_pri_shifts[new_bucket];
918
919 if ((thread->state & (TH_RUN | TH_IDLE)) == TH_RUN) {
920 sched_sub_bucket(old_bucket, thread->sched_saved_run_weight);
921 sched_add_bucket(new_bucket, thread->sched_saved_run_weight);
922 }
923 }
924 }
925
926 static inline void
sched_validate_mode(sched_mode_t mode)927 sched_validate_mode(sched_mode_t mode)
928 {
929 switch (mode) {
930 case TH_MODE_FIXED:
931 case TH_MODE_REALTIME:
932 case TH_MODE_TIMESHARE:
933 break;
934
935 default:
936 panic("unexpected mode: %d", mode);
937 break;
938 }
939 }
940
941 /*
942 * Set the thread's true scheduling mode
943 * Called with thread mutex and thread locked
944 * The thread has already been removed from the runqueue.
945 *
946 * (saved_mode is handled before this point)
947 */
948 void
sched_set_thread_mode(thread_t thread,sched_mode_t new_mode)949 sched_set_thread_mode(thread_t thread, sched_mode_t new_mode)
950 {
951 thread_assert_runq_null(thread);
952
953 sched_validate_mode(new_mode);
954
955 #if CONFIG_SCHED_AUTO_JOIN
956 /*
957 * Realtime threads might have auto-joined a work interval based on
958 * make runnable relationships. If such an RT thread is now being demoted
959 * to non-RT, unjoin the thread from the work interval.
960 */
961 if ((thread->sched_flags & TH_SFLAG_THREAD_GROUP_AUTO_JOIN) && (new_mode != TH_MODE_REALTIME)) {
962 assert((thread->sched_mode == TH_MODE_REALTIME) || (thread->th_work_interval_flags & TH_WORK_INTERVAL_FLAGS_AUTO_JOIN_LEAK));
963 work_interval_auto_join_demote(thread);
964 }
965 #endif /* CONFIG_SCHED_AUTO_JOIN */
966
967 thread->sched_mode = new_mode;
968
969 SCHED(update_thread_bucket)(thread);
970 }
971
972 /*
973 * TODO: Instead of having saved mode, have 'user mode' and 'true mode'.
974 * That way there's zero confusion over which the user wants
975 * and which the kernel wants.
976 */
977 void
sched_set_thread_mode_user(thread_t thread,sched_mode_t new_mode)978 sched_set_thread_mode_user(thread_t thread, sched_mode_t new_mode)
979 {
980 thread_assert_runq_null(thread);
981
982 sched_validate_mode(new_mode);
983
984 /* If demoted, only modify the saved mode. */
985 if (thread->sched_flags & TH_SFLAG_DEMOTED_MASK) {
986 thread->saved_mode = new_mode;
987 } else {
988 sched_set_thread_mode(thread, new_mode);
989 }
990 }
991
992 sched_mode_t
sched_get_thread_mode_user(thread_t thread)993 sched_get_thread_mode_user(thread_t thread)
994 {
995 if (thread->sched_flags & TH_SFLAG_DEMOTED_MASK) {
996 return thread->saved_mode;
997 } else {
998 return thread->sched_mode;
999 }
1000 }
1001
1002 /*
1003 * Demote the true scheduler mode to timeshare (called with the thread locked)
1004 */
1005 void
sched_thread_mode_demote(thread_t thread,uint32_t reason)1006 sched_thread_mode_demote(thread_t thread, uint32_t reason)
1007 {
1008 assert(reason & TH_SFLAG_DEMOTED_MASK);
1009 assert((thread->sched_flags & reason) != reason);
1010
1011 if (thread->policy_reset) {
1012 return;
1013 }
1014
1015 switch (reason) {
1016 case TH_SFLAG_THROTTLED:
1017 KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_MODE_DEMOTE_THROTTLED),
1018 thread_tid(thread), thread->sched_flags);
1019 break;
1020 case TH_SFLAG_FAILSAFE:
1021 KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_MODE_DEMOTE_FAILSAFE),
1022 thread_tid(thread), thread->sched_flags);
1023 break;
1024 case TH_SFLAG_RT_DISALLOWED:
1025 KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_MODE_DEMOTE_RT_DISALLOWED),
1026 thread_tid(thread), thread->sched_flags);
1027 break;
1028 }
1029
1030 if (thread->sched_flags & TH_SFLAG_DEMOTED_MASK) {
1031 /* Another demotion reason is already active */
1032 thread->sched_flags |= reason;
1033 return;
1034 }
1035
1036 assert(thread->saved_mode == TH_MODE_NONE);
1037
1038 boolean_t removed = thread_run_queue_remove(thread);
1039
1040 thread->sched_flags |= reason;
1041
1042 thread->saved_mode = thread->sched_mode;
1043
1044 sched_set_thread_mode(thread, TH_MODE_TIMESHARE);
1045
1046 thread_recompute_priority(thread);
1047
1048 if (removed) {
1049 thread_run_queue_reinsert(thread, SCHED_TAILQ);
1050 }
1051 }
1052
1053 /*
1054 * Return true if the thread is demoted for the specified reason
1055 */
1056 bool
sched_thread_mode_has_demotion(thread_t thread,uint32_t reason)1057 sched_thread_mode_has_demotion(thread_t thread, uint32_t reason)
1058 {
1059 assert(reason & TH_SFLAG_DEMOTED_MASK);
1060 return (thread->sched_flags & reason) != 0;
1061 }
1062
1063 /*
1064 * Un-demote the true scheduler mode back to the saved mode (called with the thread locked)
1065 */
1066 void
sched_thread_mode_undemote(thread_t thread,uint32_t reason)1067 sched_thread_mode_undemote(thread_t thread, uint32_t reason)
1068 {
1069 assert(reason & TH_SFLAG_DEMOTED_MASK);
1070 assert((thread->sched_flags & reason) == reason);
1071 assert(thread->saved_mode != TH_MODE_NONE);
1072 assert(thread->sched_mode == TH_MODE_TIMESHARE);
1073 assert(thread->policy_reset == 0);
1074
1075 switch (reason) {
1076 case TH_SFLAG_THROTTLED:
1077 KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_MODE_UNDEMOTE_THROTTLED),
1078 thread_tid(thread), thread->sched_flags);
1079 break;
1080 case TH_SFLAG_FAILSAFE:
1081 KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_MODE_UNDEMOTE_FAILSAFE),
1082 thread_tid(thread), thread->sched_flags);
1083 break;
1084 case TH_SFLAG_RT_DISALLOWED:
1085 KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_MODE_UNDEMOTE_RT_DISALLOWED),
1086 thread_tid(thread), thread->sched_flags);
1087 break;
1088 }
1089
1090 thread->sched_flags &= ~reason;
1091
1092 if (thread->sched_flags & TH_SFLAG_DEMOTED_MASK) {
1093 /* Another demotion reason is still active */
1094 return;
1095 }
1096
1097 boolean_t removed = thread_run_queue_remove(thread);
1098
1099 sched_set_thread_mode(thread, thread->saved_mode);
1100
1101 thread->saved_mode = TH_MODE_NONE;
1102
1103 thread_recompute_priority(thread);
1104
1105 if (removed) {
1106 thread_run_queue_reinsert(thread, SCHED_TAILQ);
1107 }
1108 }
1109
1110 /*
1111 * Promote thread to have a sched pri floor for a specific reason
1112 *
1113 * Promotion must not last past syscall boundary
1114 * Clients must always pair promote and demote 1:1,
1115 * Handling nesting of the same promote reason is the client's responsibility
1116 *
1117 * Called at splsched with thread locked
1118 */
1119 void
sched_thread_promote_reason(thread_t thread,uint32_t reason,__kdebug_only uintptr_t trace_obj)1120 sched_thread_promote_reason(thread_t thread,
1121 uint32_t reason,
1122 __kdebug_only uintptr_t trace_obj /* already unslid */)
1123 {
1124 assert(reason & TH_SFLAG_PROMOTE_REASON_MASK);
1125 assert((thread->sched_flags & reason) != reason);
1126
1127 switch (reason) {
1128 case TH_SFLAG_RW_PROMOTED:
1129 KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_RW_PROMOTE),
1130 thread_tid(thread), thread->sched_pri,
1131 thread->base_pri, trace_obj);
1132 break;
1133 case TH_SFLAG_WAITQ_PROMOTED:
1134 KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_WAITQ_PROMOTE),
1135 thread_tid(thread), thread->sched_pri,
1136 thread->base_pri, trace_obj);
1137 break;
1138 case TH_SFLAG_EXEC_PROMOTED:
1139 KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_EXEC_PROMOTE),
1140 thread_tid(thread), thread->sched_pri,
1141 thread->base_pri, trace_obj);
1142 break;
1143 case TH_SFLAG_FLOOR_PROMOTED:
1144 KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_FLOOR_PROMOTE),
1145 thread_tid(thread), thread->sched_pri,
1146 thread->base_pri, trace_obj);
1147 break;
1148 }
1149
1150 thread->sched_flags |= reason;
1151 thread_recompute_sched_pri(thread, SETPRI_DEFAULT);
1152 }
1153
1154 /*
1155 * End a specific promotion reason
1156 * Demotes a thread back to its expected priority without the promotion in place
1157 *
1158 * Called at splsched with thread locked
1159 */
1160 void
sched_thread_unpromote_reason(thread_t thread,uint32_t reason,__kdebug_only uintptr_t trace_obj)1161 sched_thread_unpromote_reason(thread_t thread,
1162 uint32_t reason,
1163 __kdebug_only uintptr_t trace_obj /* already unslid */)
1164 {
1165 assert(reason & TH_SFLAG_PROMOTE_REASON_MASK);
1166 assert((thread->sched_flags & reason) == reason);
1167
1168 switch (reason) {
1169 case TH_SFLAG_RW_PROMOTED:
1170 KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_RW_DEMOTE),
1171 thread_tid(thread), thread->sched_pri,
1172 thread->base_pri, trace_obj);
1173 break;
1174 case TH_SFLAG_WAITQ_PROMOTED:
1175 KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_WAITQ_DEMOTE),
1176 thread_tid(thread), thread->sched_pri,
1177 thread->base_pri, trace_obj);
1178 break;
1179 case TH_SFLAG_EXEC_PROMOTED:
1180 KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_EXEC_DEMOTE),
1181 thread_tid(thread), thread->sched_pri,
1182 thread->base_pri, trace_obj);
1183 break;
1184 case TH_SFLAG_FLOOR_PROMOTED:
1185 KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_FLOOR_DEMOTE),
1186 thread_tid(thread), thread->sched_pri,
1187 thread->base_pri, trace_obj);
1188 break;
1189 }
1190
1191 thread->sched_flags &= ~reason;
1192
1193 thread_recompute_sched_pri(thread, SETPRI_DEFAULT);
1194 }
1195