2 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
4 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
6 * Interactivity improvements by Mike Galbraith
7 * (C) 2007 Mike Galbraith <efault@gmx.de>
9 * Various enhancements by Dmitry Adamushko.
10 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
12 * Group scheduling enhancements by Srivatsa Vaddagiri
13 * Copyright IBM Corporation, 2007
14 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
16 * Scaled math optimizations by Thomas Gleixner
17 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
21 * Preemption granularity:
22 * (default: 2 msec, units: nanoseconds)
24 * NOTE: this granularity value is not the same as the concept of
25 * 'timeslice length' - timeslices in CFS will typically be somewhat
26 * larger than this value. (to see the precise effective timeslice
27 * length of your workload, run vmstat and monitor the context-switches
30 * On SMP systems the value of this is multiplied by the log2 of the
31 * number of CPUs. (i.e. factor 2x on 2-way systems, 3x on 4-way
32 * systems, 4x on 8-way systems, 5x on 16-way systems, etc.)
34 unsigned int sysctl_sched_granularity __read_mostly = 2000000000ULL/HZ;
37 * SCHED_BATCH wake-up granularity.
38 * (default: 10 msec, units: nanoseconds)
40 * This option delays the preemption effects of decoupled workloads
41 * and reduces their over-scheduling. Synchronous workloads will still
42 * have immediate wakeup/sleep latencies.
44 unsigned int sysctl_sched_batch_wakeup_granularity __read_mostly =
48 * SCHED_OTHER wake-up granularity.
49 * (default: 1 msec, units: nanoseconds)
51 * This option delays the preemption effects of decoupled workloads
52 * and reduces their over-scheduling. Synchronous workloads will still
53 * have immediate wakeup/sleep latencies.
55 unsigned int sysctl_sched_wakeup_granularity __read_mostly = 1000000000ULL/HZ;
57 unsigned int sysctl_sched_stat_granularity __read_mostly;
60 * Initialized in sched_init_granularity():
62 unsigned int sysctl_sched_runtime_limit __read_mostly;
65 * Debugging: various feature bits
68 SCHED_FEAT_FAIR_SLEEPERS = 1,
69 SCHED_FEAT_SLEEPER_AVG = 2,
70 SCHED_FEAT_SLEEPER_LOAD_AVG = 4,
71 SCHED_FEAT_PRECISE_CPU_LOAD = 8,
72 SCHED_FEAT_START_DEBIT = 16,
73 SCHED_FEAT_SKIP_INITIAL = 32,
76 unsigned int sysctl_sched_features __read_mostly =
77 SCHED_FEAT_FAIR_SLEEPERS *1 |
78 SCHED_FEAT_SLEEPER_AVG *1 |
79 SCHED_FEAT_SLEEPER_LOAD_AVG *1 |
80 SCHED_FEAT_PRECISE_CPU_LOAD *1 |
81 SCHED_FEAT_START_DEBIT *1 |
82 SCHED_FEAT_SKIP_INITIAL *0;
84 extern struct sched_class fair_sched_class;
86 /**************************************************************
87 * CFS operations on generic schedulable entities:
90 #ifdef CONFIG_FAIR_GROUP_SCHED
92 /* cpu runqueue to which this cfs_rq is attached */
93 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
98 /* currently running entity (if any) on this cfs_rq */
99 static inline struct sched_entity *cfs_rq_curr(struct cfs_rq *cfs_rq)
104 /* An entity is a task if it doesn't "own" a runqueue */
105 #define entity_is_task(se) (!se->my_q)
108 set_cfs_rq_curr(struct cfs_rq *cfs_rq, struct sched_entity *se)
113 #else /* CONFIG_FAIR_GROUP_SCHED */
115 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
117 return container_of(cfs_rq, struct rq, cfs);
120 static inline struct sched_entity *cfs_rq_curr(struct cfs_rq *cfs_rq)
122 struct rq *rq = rq_of(cfs_rq);
124 if (unlikely(rq->curr->sched_class != &fair_sched_class))
127 return &rq->curr->se;
130 #define entity_is_task(se) 1
133 set_cfs_rq_curr(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
135 #endif /* CONFIG_FAIR_GROUP_SCHED */
137 static inline struct task_struct *task_of(struct sched_entity *se)
139 return container_of(se, struct task_struct, se);
143 /**************************************************************
144 * Scheduling class tree data structure manipulation methods:
148 * Enqueue an entity into the rb-tree:
151 __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
153 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
154 struct rb_node *parent = NULL;
155 struct sched_entity *entry;
156 s64 key = se->fair_key;
160 * Find the right place in the rbtree:
164 entry = rb_entry(parent, struct sched_entity, run_node);
166 * We dont care about collisions. Nodes with
167 * the same key stay together.
169 if (key - entry->fair_key < 0) {
170 link = &parent->rb_left;
172 link = &parent->rb_right;
178 * Maintain a cache of leftmost tree entries (it is frequently
182 cfs_rq->rb_leftmost = &se->run_node;
184 rb_link_node(&se->run_node, parent, link);
185 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
186 update_load_add(&cfs_rq->load, se->load.weight);
187 cfs_rq->nr_running++;
192 __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
194 if (cfs_rq->rb_leftmost == &se->run_node)
195 cfs_rq->rb_leftmost = rb_next(&se->run_node);
196 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
197 update_load_sub(&cfs_rq->load, se->load.weight);
198 cfs_rq->nr_running--;
202 static inline struct rb_node *first_fair(struct cfs_rq *cfs_rq)
204 return cfs_rq->rb_leftmost;
207 static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
209 return rb_entry(first_fair(cfs_rq), struct sched_entity, run_node);
212 /**************************************************************
213 * Scheduling class statistics methods:
217 * We rescale the rescheduling granularity of tasks according to their
218 * nice level, but only linearly, not exponentially:
221 niced_granularity(struct sched_entity *curr, unsigned long granularity)
226 * Negative nice levels get the same granularity as nice-0:
228 if (likely(curr->load.weight >= NICE_0_LOAD))
231 * Positive nice level tasks get linearly finer
234 tmp = curr->load.weight * (u64)granularity;
237 * It will always fit into 'long':
239 return (long) (tmp >> NICE_0_SHIFT);
243 limit_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se)
245 long limit = sysctl_sched_runtime_limit;
248 * Niced tasks have the same history dynamic range as
251 if (unlikely(se->wait_runtime > limit)) {
252 se->wait_runtime = limit;
253 schedstat_inc(se, wait_runtime_overruns);
254 schedstat_inc(cfs_rq, wait_runtime_overruns);
256 if (unlikely(se->wait_runtime < -limit)) {
257 se->wait_runtime = -limit;
258 schedstat_inc(se, wait_runtime_underruns);
259 schedstat_inc(cfs_rq, wait_runtime_underruns);
264 __add_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se, long delta)
266 se->wait_runtime += delta;
267 schedstat_add(se, sum_wait_runtime, delta);
268 limit_wait_runtime(cfs_rq, se);
272 add_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se, long delta)
274 schedstat_add(cfs_rq, wait_runtime, -se->wait_runtime);
275 __add_wait_runtime(cfs_rq, se, delta);
276 schedstat_add(cfs_rq, wait_runtime, se->wait_runtime);
280 * Update the current task's runtime statistics. Skip current tasks that
281 * are not in our scheduling class.
284 __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr)
286 unsigned long delta, delta_exec, delta_fair, delta_mine;
287 struct load_weight *lw = &cfs_rq->load;
288 unsigned long load = lw->weight;
290 delta_exec = curr->delta_exec;
291 schedstat_set(curr->exec_max, max((u64)delta_exec, curr->exec_max));
293 curr->sum_exec_runtime += delta_exec;
294 cfs_rq->exec_clock += delta_exec;
299 delta_fair = calc_delta_fair(delta_exec, lw);
300 delta_mine = calc_delta_mine(delta_exec, curr->load.weight, lw);
302 if (cfs_rq->sleeper_bonus > sysctl_sched_granularity) {
303 delta = calc_delta_mine(cfs_rq->sleeper_bonus,
304 curr->load.weight, lw);
305 if (unlikely(delta > cfs_rq->sleeper_bonus))
306 delta = cfs_rq->sleeper_bonus;
308 cfs_rq->sleeper_bonus -= delta;
312 cfs_rq->fair_clock += delta_fair;
314 * We executed delta_exec amount of time on the CPU,
315 * but we were only entitled to delta_mine amount of
316 * time during that period (if nr_running == 1 then
317 * the two values are equal)
318 * [Note: delta_mine - delta_exec is negative]:
320 add_wait_runtime(cfs_rq, curr, delta_mine - delta_exec);
323 static void update_curr(struct cfs_rq *cfs_rq)
325 struct sched_entity *curr = cfs_rq_curr(cfs_rq);
326 unsigned long delta_exec;
332 * Get the amount of time the current task was running
333 * since the last time we changed load (this cannot
334 * overflow on 32 bits):
336 delta_exec = (unsigned long)(rq_of(cfs_rq)->clock - curr->exec_start);
338 curr->delta_exec += delta_exec;
340 if (unlikely(curr->delta_exec > sysctl_sched_stat_granularity)) {
341 __update_curr(cfs_rq, curr);
342 curr->delta_exec = 0;
344 curr->exec_start = rq_of(cfs_rq)->clock;
348 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
350 se->wait_start_fair = cfs_rq->fair_clock;
351 schedstat_set(se->wait_start, rq_of(cfs_rq)->clock);
355 * We calculate fair deltas here, so protect against the random effects
356 * of a multiplication overflow by capping it to the runtime limit:
358 #if BITS_PER_LONG == 32
359 static inline unsigned long
360 calc_weighted(unsigned long delta, unsigned long weight, int shift)
362 u64 tmp = (u64)delta * weight >> shift;
364 if (unlikely(tmp > sysctl_sched_runtime_limit*2))
365 return sysctl_sched_runtime_limit*2;
369 static inline unsigned long
370 calc_weighted(unsigned long delta, unsigned long weight, int shift)
372 return delta * weight >> shift;
377 * Task is being enqueued - update stats:
379 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
384 * Are we enqueueing a waiting task? (for current tasks
385 * a dequeue/enqueue event is a NOP)
387 if (se != cfs_rq_curr(cfs_rq))
388 update_stats_wait_start(cfs_rq, se);
392 key = cfs_rq->fair_clock;
395 * Optimize the common nice 0 case:
397 if (likely(se->load.weight == NICE_0_LOAD)) {
398 key -= se->wait_runtime;
402 if (se->wait_runtime < 0) {
403 tmp = -se->wait_runtime;
404 key += (tmp * se->load.inv_weight) >>
405 (WMULT_SHIFT - NICE_0_SHIFT);
407 tmp = se->wait_runtime;
408 key -= (tmp * se->load.weight) >> NICE_0_SHIFT;
416 * Note: must be called with a freshly updated rq->fair_clock.
419 __update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
421 unsigned long delta_fair = se->delta_fair_run;
423 schedstat_set(se->wait_max, max(se->wait_max,
424 rq_of(cfs_rq)->clock - se->wait_start));
426 if (unlikely(se->load.weight != NICE_0_LOAD))
427 delta_fair = calc_weighted(delta_fair, se->load.weight,
430 add_wait_runtime(cfs_rq, se, delta_fair);
434 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
436 unsigned long delta_fair;
438 delta_fair = (unsigned long)min((u64)(2*sysctl_sched_runtime_limit),
439 (u64)(cfs_rq->fair_clock - se->wait_start_fair));
441 se->delta_fair_run += delta_fair;
442 if (unlikely(abs(se->delta_fair_run) >=
443 sysctl_sched_stat_granularity)) {
444 __update_stats_wait_end(cfs_rq, se);
445 se->delta_fair_run = 0;
448 se->wait_start_fair = 0;
449 schedstat_set(se->wait_start, 0);
453 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
457 * Mark the end of the wait period if dequeueing a
460 if (se != cfs_rq_curr(cfs_rq))
461 update_stats_wait_end(cfs_rq, se);
465 * We are picking a new current task - update its stats:
468 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
471 * We are starting a new run period:
473 se->exec_start = rq_of(cfs_rq)->clock;
477 * We are descheduling a task - update its stats:
480 update_stats_curr_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
485 /**************************************************
486 * Scheduling class queueing methods:
489 static void __enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
491 unsigned long load = cfs_rq->load.weight, delta_fair;
494 if (sysctl_sched_features & SCHED_FEAT_SLEEPER_LOAD_AVG)
495 load = rq_of(cfs_rq)->cpu_load[2];
497 delta_fair = se->delta_fair_sleep;
500 * Fix up delta_fair with the effect of us running
501 * during the whole sleep period:
503 if (sysctl_sched_features & SCHED_FEAT_SLEEPER_AVG)
504 delta_fair = div64_likely32((u64)delta_fair * load,
505 load + se->load.weight);
507 if (unlikely(se->load.weight != NICE_0_LOAD))
508 delta_fair = calc_weighted(delta_fair, se->load.weight,
511 prev_runtime = se->wait_runtime;
512 __add_wait_runtime(cfs_rq, se, delta_fair);
513 delta_fair = se->wait_runtime - prev_runtime;
516 * Track the amount of bonus we've given to sleepers:
518 cfs_rq->sleeper_bonus += delta_fair;
520 schedstat_add(cfs_rq, wait_runtime, se->wait_runtime);
524 enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now)
526 struct task_struct *tsk = task_of(se);
527 unsigned long delta_fair;
529 if ((entity_is_task(se) && tsk->policy == SCHED_BATCH) ||
530 !(sysctl_sched_features & SCHED_FEAT_FAIR_SLEEPERS))
533 delta_fair = (unsigned long)min((u64)(2*sysctl_sched_runtime_limit),
534 (u64)(cfs_rq->fair_clock - se->sleep_start_fair));
536 se->delta_fair_sleep += delta_fair;
537 if (unlikely(abs(se->delta_fair_sleep) >=
538 sysctl_sched_stat_granularity)) {
539 __enqueue_sleeper(cfs_rq, se);
540 se->delta_fair_sleep = 0;
543 se->sleep_start_fair = 0;
545 #ifdef CONFIG_SCHEDSTATS
546 if (se->sleep_start) {
547 u64 delta = rq_of(cfs_rq)->clock - se->sleep_start;
552 if (unlikely(delta > se->sleep_max))
553 se->sleep_max = delta;
556 se->sum_sleep_runtime += delta;
558 if (se->block_start) {
559 u64 delta = rq_of(cfs_rq)->clock - se->block_start;
564 if (unlikely(delta > se->block_max))
565 se->block_max = delta;
568 se->sum_sleep_runtime += delta;
574 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
578 * Update the fair clock.
583 enqueue_sleeper(cfs_rq, se, now);
585 update_stats_enqueue(cfs_rq, se);
586 __enqueue_entity(cfs_rq, se);
590 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
593 update_stats_dequeue(cfs_rq, se);
595 se->sleep_start_fair = cfs_rq->fair_clock;
596 #ifdef CONFIG_SCHEDSTATS
597 if (entity_is_task(se)) {
598 struct task_struct *tsk = task_of(se);
600 if (tsk->state & TASK_INTERRUPTIBLE)
601 se->sleep_start = rq_of(cfs_rq)->clock;
602 if (tsk->state & TASK_UNINTERRUPTIBLE)
603 se->block_start = rq_of(cfs_rq)->clock;
605 cfs_rq->wait_runtime -= se->wait_runtime;
608 __dequeue_entity(cfs_rq, se);
612 * Preempt the current task with a newly woken task if needed:
615 __check_preempt_curr_fair(struct cfs_rq *cfs_rq, struct sched_entity *se,
616 struct sched_entity *curr, unsigned long granularity)
618 s64 __delta = curr->fair_key - se->fair_key;
621 * Take scheduling granularity into account - do not
622 * preempt the current task unless the best task has
623 * a larger than sched_granularity fairness advantage:
625 if (__delta > niced_granularity(curr, granularity))
626 resched_task(rq_of(cfs_rq)->curr);
630 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now)
633 * Any task has to be enqueued before it get to execute on
634 * a CPU. So account for the time it spent waiting on the
635 * runqueue. (note, here we rely on pick_next_task() having
636 * done a put_prev_task_fair() shortly before this, which
637 * updated rq->fair_clock - used by update_stats_wait_end())
639 update_stats_wait_end(cfs_rq, se);
640 update_stats_curr_start(cfs_rq, se);
641 set_cfs_rq_curr(cfs_rq, se);
644 static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq, u64 now)
646 struct sched_entity *se = __pick_next_entity(cfs_rq);
648 set_next_entity(cfs_rq, se, now);
654 put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev, u64 now)
657 * If still on the runqueue then deactivate_task()
658 * was not called and update_curr() has to be done:
663 update_stats_curr_end(cfs_rq, prev);
666 update_stats_wait_start(cfs_rq, prev);
667 set_cfs_rq_curr(cfs_rq, NULL);
670 static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
672 struct rq *rq = rq_of(cfs_rq);
673 struct sched_entity *next;
676 __update_rq_clock(rq);
680 * Dequeue and enqueue the task to update its
681 * position within the tree:
683 dequeue_entity(cfs_rq, curr, 0, now);
684 enqueue_entity(cfs_rq, curr, 0, now);
687 * Reschedule if another task tops the current one.
689 next = __pick_next_entity(cfs_rq);
693 __check_preempt_curr_fair(cfs_rq, next, curr, sysctl_sched_granularity);
696 /**************************************************
697 * CFS operations on tasks:
700 #ifdef CONFIG_FAIR_GROUP_SCHED
702 /* Walk up scheduling entities hierarchy */
703 #define for_each_sched_entity(se) \
704 for (; se; se = se->parent)
706 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
711 /* runqueue on which this entity is (to be) queued */
712 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
717 /* runqueue "owned" by this group */
718 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
723 /* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on
724 * another cpu ('this_cpu')
726 static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
728 /* A later patch will take group into account */
729 return &cpu_rq(this_cpu)->cfs;
732 /* Iterate thr' all leaf cfs_rq's on a runqueue */
733 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
734 list_for_each_entry(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
736 /* Do the two (enqueued) tasks belong to the same group ? */
737 static inline int is_same_group(struct task_struct *curr, struct task_struct *p)
739 if (curr->se.cfs_rq == p->se.cfs_rq)
745 #else /* CONFIG_FAIR_GROUP_SCHED */
747 #define for_each_sched_entity(se) \
748 for (; se; se = NULL)
750 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
752 return &task_rq(p)->cfs;
755 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
757 struct task_struct *p = task_of(se);
758 struct rq *rq = task_rq(p);
763 /* runqueue "owned" by this group */
764 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
769 static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
771 return &cpu_rq(this_cpu)->cfs;
774 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
775 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
777 static inline int is_same_group(struct task_struct *curr, struct task_struct *p)
782 #endif /* CONFIG_FAIR_GROUP_SCHED */
785 * The enqueue_task method is called before nr_running is
786 * increased. Here we update the fair scheduling stats and
787 * then put the task into the rbtree:
790 enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup, u64 now)
792 struct cfs_rq *cfs_rq;
793 struct sched_entity *se = &p->se;
795 for_each_sched_entity(se) {
798 cfs_rq = cfs_rq_of(se);
799 enqueue_entity(cfs_rq, se, wakeup, now);
804 * The dequeue_task method is called before nr_running is
805 * decreased. We remove the task from the rbtree and
806 * update the fair scheduling stats:
809 dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep, u64 now)
811 struct cfs_rq *cfs_rq;
812 struct sched_entity *se = &p->se;
814 for_each_sched_entity(se) {
815 cfs_rq = cfs_rq_of(se);
816 dequeue_entity(cfs_rq, se, sleep, now);
817 /* Don't dequeue parent if it has other entities besides us */
818 if (cfs_rq->load.weight)
824 * sched_yield() support is very simple - we dequeue and enqueue
826 static void yield_task_fair(struct rq *rq, struct task_struct *p)
828 struct cfs_rq *cfs_rq = task_cfs_rq(p);
831 __update_rq_clock(rq);
834 * Dequeue and enqueue the task to update its
835 * position within the tree:
837 dequeue_entity(cfs_rq, &p->se, 0, now);
838 enqueue_entity(cfs_rq, &p->se, 0, now);
842 * Preempt the current task with a newly woken task if needed:
844 static void check_preempt_curr_fair(struct rq *rq, struct task_struct *p)
846 struct task_struct *curr = rq->curr;
847 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
850 if (unlikely(rt_prio(p->prio))) {
857 gran = sysctl_sched_wakeup_granularity;
859 * Batch tasks prefer throughput over latency:
861 if (unlikely(p->policy == SCHED_BATCH))
862 gran = sysctl_sched_batch_wakeup_granularity;
864 if (is_same_group(curr, p))
865 __check_preempt_curr_fair(cfs_rq, &p->se, &curr->se, gran);
868 static struct task_struct *pick_next_task_fair(struct rq *rq, u64 now)
870 struct cfs_rq *cfs_rq = &rq->cfs;
871 struct sched_entity *se;
873 if (unlikely(!cfs_rq->nr_running))
877 se = pick_next_entity(cfs_rq, now);
878 cfs_rq = group_cfs_rq(se);
885 * Account for a descheduled task:
887 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev, u64 now)
889 struct sched_entity *se = &prev->se;
890 struct cfs_rq *cfs_rq;
892 for_each_sched_entity(se) {
893 cfs_rq = cfs_rq_of(se);
894 put_prev_entity(cfs_rq, se, now);
898 /**************************************************
899 * Fair scheduling class load-balancing methods:
903 * Load-balancing iterator. Note: while the runqueue stays locked
904 * during the whole iteration, the current task might be
905 * dequeued so the iterator has to be dequeue-safe. Here we
906 * achieve that by always pre-iterating before returning
909 static inline struct task_struct *
910 __load_balance_iterator(struct cfs_rq *cfs_rq, struct rb_node *curr)
912 struct task_struct *p;
917 p = rb_entry(curr, struct task_struct, se.run_node);
918 cfs_rq->rb_load_balance_curr = rb_next(curr);
923 static struct task_struct *load_balance_start_fair(void *arg)
925 struct cfs_rq *cfs_rq = arg;
927 return __load_balance_iterator(cfs_rq, first_fair(cfs_rq));
930 static struct task_struct *load_balance_next_fair(void *arg)
932 struct cfs_rq *cfs_rq = arg;
934 return __load_balance_iterator(cfs_rq, cfs_rq->rb_load_balance_curr);
937 #ifdef CONFIG_FAIR_GROUP_SCHED
938 static int cfs_rq_best_prio(struct cfs_rq *cfs_rq)
940 struct sched_entity *curr;
941 struct task_struct *p;
943 if (!cfs_rq->nr_running)
946 curr = __pick_next_entity(cfs_rq);
954 load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
955 unsigned long max_nr_move, unsigned long max_load_move,
956 struct sched_domain *sd, enum cpu_idle_type idle,
957 int *all_pinned, int *this_best_prio)
959 struct cfs_rq *busy_cfs_rq;
960 unsigned long load_moved, total_nr_moved = 0, nr_moved;
961 long rem_load_move = max_load_move;
962 struct rq_iterator cfs_rq_iterator;
964 cfs_rq_iterator.start = load_balance_start_fair;
965 cfs_rq_iterator.next = load_balance_next_fair;
967 for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
968 #ifdef CONFIG_FAIR_GROUP_SCHED
969 struct cfs_rq *this_cfs_rq;
971 unsigned long maxload;
973 this_cfs_rq = cpu_cfs_rq(busy_cfs_rq, this_cpu);
975 imbalance = busy_cfs_rq->load.weight -
976 this_cfs_rq->load.weight;
977 /* Don't pull if this_cfs_rq has more load than busy_cfs_rq */
981 /* Don't pull more than imbalance/2 */
983 maxload = min(rem_load_move, imbalance);
985 *this_best_prio = cfs_rq_best_prio(this_cfs_rq);
987 #define maxload rem_load_move
989 /* pass busy_cfs_rq argument into
990 * load_balance_[start|next]_fair iterators
992 cfs_rq_iterator.arg = busy_cfs_rq;
993 nr_moved = balance_tasks(this_rq, this_cpu, busiest,
994 max_nr_move, maxload, sd, idle, all_pinned,
995 &load_moved, this_best_prio, &cfs_rq_iterator);
997 total_nr_moved += nr_moved;
998 max_nr_move -= nr_moved;
999 rem_load_move -= load_moved;
1001 if (max_nr_move <= 0 || rem_load_move <= 0)
1005 return max_load_move - rem_load_move;
1009 * scheduler tick hitting a task of our scheduling class:
1011 static void task_tick_fair(struct rq *rq, struct task_struct *curr)
1013 struct cfs_rq *cfs_rq;
1014 struct sched_entity *se = &curr->se;
1016 for_each_sched_entity(se) {
1017 cfs_rq = cfs_rq_of(se);
1018 entity_tick(cfs_rq, se);
1023 * Share the fairness runtime between parent and child, thus the
1024 * total amount of pressure for CPU stays equal - new tasks
1025 * get a chance to run but frequent forkers are not allowed to
1026 * monopolize the CPU. Note: the parent runqueue is locked,
1027 * the child is not running yet.
1029 static void task_new_fair(struct rq *rq, struct task_struct *p, u64 now)
1031 struct cfs_rq *cfs_rq = task_cfs_rq(p);
1032 struct sched_entity *se = &p->se;
1034 sched_info_queued(p);
1036 update_stats_enqueue(cfs_rq, se);
1038 * Child runs first: we let it run before the parent
1039 * until it reschedules once. We set up the key so that
1040 * it will preempt the parent:
1042 p->se.fair_key = current->se.fair_key -
1043 niced_granularity(&rq->curr->se, sysctl_sched_granularity) - 1;
1045 * The first wait is dominated by the child-runs-first logic,
1046 * so do not credit it with that waiting time yet:
1048 if (sysctl_sched_features & SCHED_FEAT_SKIP_INITIAL)
1049 p->se.wait_start_fair = 0;
1052 * The statistical average of wait_runtime is about
1053 * -granularity/2, so initialize the task with that:
1055 if (sysctl_sched_features & SCHED_FEAT_START_DEBIT)
1056 p->se.wait_runtime = -(sysctl_sched_granularity / 2);
1058 __enqueue_entity(cfs_rq, se);
1061 #ifdef CONFIG_FAIR_GROUP_SCHED
1062 /* Account for a task changing its policy or group.
1064 * This routine is mostly called to set cfs_rq->curr field when a task
1065 * migrates between groups/classes.
1067 static void set_curr_task_fair(struct rq *rq)
1069 struct task_struct *curr = rq->curr;
1070 struct sched_entity *se = &curr->se;
1072 struct cfs_rq *cfs_rq;
1074 update_rq_clock(rq);
1077 for_each_sched_entity(se) {
1078 cfs_rq = cfs_rq_of(se);
1079 set_next_entity(cfs_rq, se, now);
1083 static void set_curr_task_fair(struct rq *rq)
1089 * All the scheduling class methods:
1091 struct sched_class fair_sched_class __read_mostly = {
1092 .enqueue_task = enqueue_task_fair,
1093 .dequeue_task = dequeue_task_fair,
1094 .yield_task = yield_task_fair,
1096 .check_preempt_curr = check_preempt_curr_fair,
1098 .pick_next_task = pick_next_task_fair,
1099 .put_prev_task = put_prev_task_fair,
1101 .load_balance = load_balance_fair,
1103 .set_curr_task = set_curr_task_fair,
1104 .task_tick = task_tick_fair,
1105 .task_new = task_new_fair,
1108 #ifdef CONFIG_SCHED_DEBUG
1109 static void print_cfs_stats(struct seq_file *m, int cpu)
1111 struct rq *rq = cpu_rq(cpu);
1112 struct cfs_rq *cfs_rq;
1114 for_each_leaf_cfs_rq(rq, cfs_rq)
1115 print_cfs_rq(m, cpu, cfs_rq);