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[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / sched_fair.c
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1 /*
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>
19 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra
20 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
23 #include <linux/latencytop.h>
26 * Targeted preemption latency for CPU-bound tasks:
27 * (default: 20ms * (1 + ilog(ncpus)), units: nanoseconds)
29 * NOTE: this latency value is not the same as the concept of
30 * 'timeslice length' - timeslices in CFS are of variable length
31 * and have no persistent notion like in traditional, time-slice
32 * based scheduling concepts.
34 * (to see the precise effective timeslice length of your workload,
35 * run vmstat and monitor the context-switches (cs) field)
37 unsigned int sysctl_sched_latency = 20000000ULL;
40 * Minimal preemption granularity for CPU-bound tasks:
41 * (default: 4 msec * (1 + ilog(ncpus)), units: nanoseconds)
43 unsigned int sysctl_sched_min_granularity = 4000000ULL;
46 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
48 static unsigned int sched_nr_latency = 5;
51 * After fork, child runs first. (default) If set to 0 then
52 * parent will (try to) run first.
54 const_debug unsigned int sysctl_sched_child_runs_first = 1;
57 * sys_sched_yield() compat mode
59 * This option switches the agressive yield implementation of the
60 * old scheduler back on.
62 unsigned int __read_mostly sysctl_sched_compat_yield;
65 * SCHED_OTHER wake-up granularity.
66 * (default: 10 msec * (1 + ilog(ncpus)), units: nanoseconds)
68 * This option delays the preemption effects of decoupled workloads
69 * and reduces their over-scheduling. Synchronous workloads will still
70 * have immediate wakeup/sleep latencies.
72 unsigned int sysctl_sched_wakeup_granularity = 10000000UL;
74 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
76 /**************************************************************
77 * CFS operations on generic schedulable entities:
80 static inline struct task_struct *task_of(struct sched_entity *se)
82 return container_of(se, struct task_struct, se);
85 #ifdef CONFIG_FAIR_GROUP_SCHED
87 /* cpu runqueue to which this cfs_rq is attached */
88 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
90 return cfs_rq->rq;
93 /* An entity is a task if it doesn't "own" a runqueue */
94 #define entity_is_task(se) (!se->my_q)
96 /* Walk up scheduling entities hierarchy */
97 #define for_each_sched_entity(se) \
98 for (; se; se = se->parent)
100 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
102 return p->se.cfs_rq;
105 /* runqueue on which this entity is (to be) queued */
106 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
108 return se->cfs_rq;
111 /* runqueue "owned" by this group */
112 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
114 return grp->my_q;
117 /* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on
118 * another cpu ('this_cpu')
120 static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
122 return cfs_rq->tg->cfs_rq[this_cpu];
125 /* Iterate thr' all leaf cfs_rq's on a runqueue */
126 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
127 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
129 /* Do the two (enqueued) entities belong to the same group ? */
130 static inline int
131 is_same_group(struct sched_entity *se, struct sched_entity *pse)
133 if (se->cfs_rq == pse->cfs_rq)
134 return 1;
136 return 0;
139 static inline struct sched_entity *parent_entity(struct sched_entity *se)
141 return se->parent;
144 #else /* CONFIG_FAIR_GROUP_SCHED */
146 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
148 return container_of(cfs_rq, struct rq, cfs);
151 #define entity_is_task(se) 1
153 #define for_each_sched_entity(se) \
154 for (; se; se = NULL)
156 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
158 return &task_rq(p)->cfs;
161 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
163 struct task_struct *p = task_of(se);
164 struct rq *rq = task_rq(p);
166 return &rq->cfs;
169 /* runqueue "owned" by this group */
170 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
172 return NULL;
175 static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
177 return &cpu_rq(this_cpu)->cfs;
180 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
181 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
183 static inline int
184 is_same_group(struct sched_entity *se, struct sched_entity *pse)
186 return 1;
189 static inline struct sched_entity *parent_entity(struct sched_entity *se)
191 return NULL;
194 #endif /* CONFIG_FAIR_GROUP_SCHED */
197 /**************************************************************
198 * Scheduling class tree data structure manipulation methods:
201 static inline u64 max_vruntime(u64 min_vruntime, u64 vruntime)
203 s64 delta = (s64)(vruntime - min_vruntime);
204 if (delta > 0)
205 min_vruntime = vruntime;
207 return min_vruntime;
210 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
212 s64 delta = (s64)(vruntime - min_vruntime);
213 if (delta < 0)
214 min_vruntime = vruntime;
216 return min_vruntime;
219 static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
221 return se->vruntime - cfs_rq->min_vruntime;
225 * Enqueue an entity into the rb-tree:
227 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
229 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
230 struct rb_node *parent = NULL;
231 struct sched_entity *entry;
232 s64 key = entity_key(cfs_rq, se);
233 int leftmost = 1;
236 * Find the right place in the rbtree:
238 while (*link) {
239 parent = *link;
240 entry = rb_entry(parent, struct sched_entity, run_node);
242 * We dont care about collisions. Nodes with
243 * the same key stay together.
245 if (key < entity_key(cfs_rq, entry)) {
246 link = &parent->rb_left;
247 } else {
248 link = &parent->rb_right;
249 leftmost = 0;
254 * Maintain a cache of leftmost tree entries (it is frequently
255 * used):
257 if (leftmost) {
258 cfs_rq->rb_leftmost = &se->run_node;
260 * maintain cfs_rq->min_vruntime to be a monotonic increasing
261 * value tracking the leftmost vruntime in the tree.
263 cfs_rq->min_vruntime =
264 max_vruntime(cfs_rq->min_vruntime, se->vruntime);
267 rb_link_node(&se->run_node, parent, link);
268 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
271 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
273 if (cfs_rq->rb_leftmost == &se->run_node) {
274 struct rb_node *next_node;
275 struct sched_entity *next;
277 next_node = rb_next(&se->run_node);
278 cfs_rq->rb_leftmost = next_node;
280 if (next_node) {
281 next = rb_entry(next_node,
282 struct sched_entity, run_node);
283 cfs_rq->min_vruntime =
284 max_vruntime(cfs_rq->min_vruntime,
285 next->vruntime);
289 if (cfs_rq->next == se)
290 cfs_rq->next = NULL;
292 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
295 static inline struct rb_node *first_fair(struct cfs_rq *cfs_rq)
297 return cfs_rq->rb_leftmost;
300 static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
302 return rb_entry(first_fair(cfs_rq), struct sched_entity, run_node);
305 static inline struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
307 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
309 if (!last)
310 return NULL;
312 return rb_entry(last, struct sched_entity, run_node);
315 /**************************************************************
316 * Scheduling class statistics methods:
319 #ifdef CONFIG_SCHED_DEBUG
320 int sched_nr_latency_handler(struct ctl_table *table, int write,
321 struct file *filp, void __user *buffer, size_t *lenp,
322 loff_t *ppos)
324 int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
326 if (ret || !write)
327 return ret;
329 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
330 sysctl_sched_min_granularity);
332 return 0;
334 #endif
337 * The idea is to set a period in which each task runs once.
339 * When there are too many tasks (sysctl_sched_nr_latency) we have to stretch
340 * this period because otherwise the slices get too small.
342 * p = (nr <= nl) ? l : l*nr/nl
344 static u64 __sched_period(unsigned long nr_running)
346 u64 period = sysctl_sched_latency;
347 unsigned long nr_latency = sched_nr_latency;
349 if (unlikely(nr_running > nr_latency)) {
350 period = sysctl_sched_min_granularity;
351 period *= nr_running;
354 return period;
358 * We calculate the wall-time slice from the period by taking a part
359 * proportional to the weight.
361 * s = p*w/rw
363 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
365 u64 slice = __sched_period(cfs_rq->nr_running);
367 for_each_sched_entity(se) {
368 cfs_rq = cfs_rq_of(se);
370 slice *= se->load.weight;
371 do_div(slice, cfs_rq->load.weight);
375 return slice;
379 * We calculate the vruntime slice of a to be inserted task
381 * vs = s/w = p/rw
383 static u64 sched_vslice_add(struct cfs_rq *cfs_rq, struct sched_entity *se)
385 unsigned long nr_running = cfs_rq->nr_running;
386 unsigned long weight;
387 u64 vslice;
389 if (!se->on_rq)
390 nr_running++;
392 vslice = __sched_period(nr_running);
394 for_each_sched_entity(se) {
395 cfs_rq = cfs_rq_of(se);
397 weight = cfs_rq->load.weight;
398 if (!se->on_rq)
399 weight += se->load.weight;
401 vslice *= NICE_0_LOAD;
402 do_div(vslice, weight);
405 return vslice;
409 * Update the current task's runtime statistics. Skip current tasks that
410 * are not in our scheduling class.
412 static inline void
413 __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
414 unsigned long delta_exec)
416 unsigned long delta_exec_weighted;
418 schedstat_set(curr->exec_max, max((u64)delta_exec, curr->exec_max));
420 curr->sum_exec_runtime += delta_exec;
421 schedstat_add(cfs_rq, exec_clock, delta_exec);
422 delta_exec_weighted = delta_exec;
423 if (unlikely(curr->load.weight != NICE_0_LOAD)) {
424 delta_exec_weighted = calc_delta_fair(delta_exec_weighted,
425 &curr->load);
427 curr->vruntime += delta_exec_weighted;
430 static void update_curr(struct cfs_rq *cfs_rq)
432 struct sched_entity *curr = cfs_rq->curr;
433 u64 now = rq_of(cfs_rq)->clock;
434 unsigned long delta_exec;
436 if (unlikely(!curr))
437 return;
440 * Get the amount of time the current task was running
441 * since the last time we changed load (this cannot
442 * overflow on 32 bits):
444 delta_exec = (unsigned long)(now - curr->exec_start);
446 __update_curr(cfs_rq, curr, delta_exec);
447 curr->exec_start = now;
449 if (entity_is_task(curr)) {
450 struct task_struct *curtask = task_of(curr);
452 cpuacct_charge(curtask, delta_exec);
456 static inline void
457 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
459 schedstat_set(se->wait_start, rq_of(cfs_rq)->clock);
463 * Task is being enqueued - update stats:
465 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
468 * Are we enqueueing a waiting task? (for current tasks
469 * a dequeue/enqueue event is a NOP)
471 if (se != cfs_rq->curr)
472 update_stats_wait_start(cfs_rq, se);
475 static void
476 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
478 schedstat_set(se->wait_max, max(se->wait_max,
479 rq_of(cfs_rq)->clock - se->wait_start));
480 schedstat_set(se->wait_count, se->wait_count + 1);
481 schedstat_set(se->wait_sum, se->wait_sum +
482 rq_of(cfs_rq)->clock - se->wait_start);
483 schedstat_set(se->wait_start, 0);
486 static inline void
487 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
490 * Mark the end of the wait period if dequeueing a
491 * waiting task:
493 if (se != cfs_rq->curr)
494 update_stats_wait_end(cfs_rq, se);
498 * We are picking a new current task - update its stats:
500 static inline void
501 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
504 * We are starting a new run period:
506 se->exec_start = rq_of(cfs_rq)->clock;
509 /**************************************************
510 * Scheduling class queueing methods:
513 static void
514 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
516 update_load_add(&cfs_rq->load, se->load.weight);
517 cfs_rq->nr_running++;
518 se->on_rq = 1;
519 list_add(&se->group_node, &cfs_rq->tasks);
522 static void
523 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
525 update_load_sub(&cfs_rq->load, se->load.weight);
526 cfs_rq->nr_running--;
527 se->on_rq = 0;
528 list_del_init(&se->group_node);
531 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
533 #ifdef CONFIG_SCHEDSTATS
534 if (se->sleep_start) {
535 u64 delta = rq_of(cfs_rq)->clock - se->sleep_start;
536 struct task_struct *tsk = task_of(se);
538 if ((s64)delta < 0)
539 delta = 0;
541 if (unlikely(delta > se->sleep_max))
542 se->sleep_max = delta;
544 se->sleep_start = 0;
545 se->sum_sleep_runtime += delta;
547 account_scheduler_latency(tsk, delta >> 10, 1);
549 if (se->block_start) {
550 u64 delta = rq_of(cfs_rq)->clock - se->block_start;
551 struct task_struct *tsk = task_of(se);
553 if ((s64)delta < 0)
554 delta = 0;
556 if (unlikely(delta > se->block_max))
557 se->block_max = delta;
559 se->block_start = 0;
560 se->sum_sleep_runtime += delta;
563 * Blocking time is in units of nanosecs, so shift by 20 to
564 * get a milliseconds-range estimation of the amount of
565 * time that the task spent sleeping:
567 if (unlikely(prof_on == SLEEP_PROFILING)) {
569 profile_hits(SLEEP_PROFILING, (void *)get_wchan(tsk),
570 delta >> 20);
572 account_scheduler_latency(tsk, delta >> 10, 0);
574 #endif
577 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
579 #ifdef CONFIG_SCHED_DEBUG
580 s64 d = se->vruntime - cfs_rq->min_vruntime;
582 if (d < 0)
583 d = -d;
585 if (d > 3*sysctl_sched_latency)
586 schedstat_inc(cfs_rq, nr_spread_over);
587 #endif
590 static void
591 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
593 u64 vruntime;
595 if (first_fair(cfs_rq)) {
596 vruntime = min_vruntime(cfs_rq->min_vruntime,
597 __pick_next_entity(cfs_rq)->vruntime);
598 } else
599 vruntime = cfs_rq->min_vruntime;
602 * The 'current' period is already promised to the current tasks,
603 * however the extra weight of the new task will slow them down a
604 * little, place the new task so that it fits in the slot that
605 * stays open at the end.
607 if (initial && sched_feat(START_DEBIT))
608 vruntime += sched_vslice_add(cfs_rq, se);
610 if (!initial) {
611 /* sleeps upto a single latency don't count. */
612 if (sched_feat(NEW_FAIR_SLEEPERS))
613 vruntime -= sysctl_sched_latency;
615 /* ensure we never gain time by being placed backwards. */
616 vruntime = max_vruntime(se->vruntime, vruntime);
619 se->vruntime = vruntime;
622 static void
623 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
626 * Update run-time statistics of the 'current'.
628 update_curr(cfs_rq);
629 account_entity_enqueue(cfs_rq, se);
631 if (wakeup) {
632 place_entity(cfs_rq, se, 0);
633 enqueue_sleeper(cfs_rq, se);
636 update_stats_enqueue(cfs_rq, se);
637 check_spread(cfs_rq, se);
638 if (se != cfs_rq->curr)
639 __enqueue_entity(cfs_rq, se);
642 static void update_avg(u64 *avg, u64 sample)
644 s64 diff = sample - *avg;
645 *avg += diff >> 3;
648 static void update_avg_stats(struct cfs_rq *cfs_rq, struct sched_entity *se)
650 if (!se->last_wakeup)
651 return;
653 update_avg(&se->avg_overlap, se->sum_exec_runtime - se->last_wakeup);
654 se->last_wakeup = 0;
657 static void
658 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
661 * Update run-time statistics of the 'current'.
663 update_curr(cfs_rq);
665 update_stats_dequeue(cfs_rq, se);
666 if (sleep) {
667 update_avg_stats(cfs_rq, se);
668 #ifdef CONFIG_SCHEDSTATS
669 if (entity_is_task(se)) {
670 struct task_struct *tsk = task_of(se);
672 if (tsk->state & TASK_INTERRUPTIBLE)
673 se->sleep_start = rq_of(cfs_rq)->clock;
674 if (tsk->state & TASK_UNINTERRUPTIBLE)
675 se->block_start = rq_of(cfs_rq)->clock;
677 #endif
680 if (se != cfs_rq->curr)
681 __dequeue_entity(cfs_rq, se);
682 account_entity_dequeue(cfs_rq, se);
686 * Preempt the current task with a newly woken task if needed:
688 static void
689 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
691 unsigned long ideal_runtime, delta_exec;
693 ideal_runtime = sched_slice(cfs_rq, curr);
694 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
695 if (delta_exec > ideal_runtime)
696 resched_task(rq_of(cfs_rq)->curr);
699 static void
700 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
702 /* 'current' is not kept within the tree. */
703 if (se->on_rq) {
705 * Any task has to be enqueued before it get to execute on
706 * a CPU. So account for the time it spent waiting on the
707 * runqueue.
709 update_stats_wait_end(cfs_rq, se);
710 __dequeue_entity(cfs_rq, se);
713 update_stats_curr_start(cfs_rq, se);
714 cfs_rq->curr = se;
715 #ifdef CONFIG_SCHEDSTATS
717 * Track our maximum slice length, if the CPU's load is at
718 * least twice that of our own weight (i.e. dont track it
719 * when there are only lesser-weight tasks around):
721 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
722 se->slice_max = max(se->slice_max,
723 se->sum_exec_runtime - se->prev_sum_exec_runtime);
725 #endif
726 se->prev_sum_exec_runtime = se->sum_exec_runtime;
729 static int
730 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
732 static struct sched_entity *
733 pick_next(struct cfs_rq *cfs_rq, struct sched_entity *se)
735 if (!cfs_rq->next)
736 return se;
738 if (wakeup_preempt_entity(cfs_rq->next, se) != 0)
739 return se;
741 return cfs_rq->next;
744 static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
746 struct sched_entity *se = NULL;
748 if (first_fair(cfs_rq)) {
749 se = __pick_next_entity(cfs_rq);
750 se = pick_next(cfs_rq, se);
751 set_next_entity(cfs_rq, se);
754 return se;
757 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
760 * If still on the runqueue then deactivate_task()
761 * was not called and update_curr() has to be done:
763 if (prev->on_rq)
764 update_curr(cfs_rq);
766 check_spread(cfs_rq, prev);
767 if (prev->on_rq) {
768 update_stats_wait_start(cfs_rq, prev);
769 /* Put 'current' back into the tree. */
770 __enqueue_entity(cfs_rq, prev);
772 cfs_rq->curr = NULL;
775 static void
776 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
779 * Update run-time statistics of the 'current'.
781 update_curr(cfs_rq);
783 #ifdef CONFIG_SCHED_HRTICK
785 * queued ticks are scheduled to match the slice, so don't bother
786 * validating it and just reschedule.
788 if (queued) {
789 resched_task(rq_of(cfs_rq)->curr);
790 return;
793 * don't let the period tick interfere with the hrtick preemption
795 if (!sched_feat(DOUBLE_TICK) &&
796 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
797 return;
798 #endif
800 if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
801 check_preempt_tick(cfs_rq, curr);
804 /**************************************************
805 * CFS operations on tasks:
808 #ifdef CONFIG_SCHED_HRTICK
809 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
811 int requeue = rq->curr == p;
812 struct sched_entity *se = &p->se;
813 struct cfs_rq *cfs_rq = cfs_rq_of(se);
815 WARN_ON(task_rq(p) != rq);
817 if (hrtick_enabled(rq) && cfs_rq->nr_running > 1) {
818 u64 slice = sched_slice(cfs_rq, se);
819 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
820 s64 delta = slice - ran;
822 if (delta < 0) {
823 if (rq->curr == p)
824 resched_task(p);
825 return;
829 * Don't schedule slices shorter than 10000ns, that just
830 * doesn't make sense. Rely on vruntime for fairness.
832 if (!requeue)
833 delta = max(10000LL, delta);
835 hrtick_start(rq, delta, requeue);
838 #else
839 static inline void
840 hrtick_start_fair(struct rq *rq, struct task_struct *p)
843 #endif
846 * The enqueue_task method is called before nr_running is
847 * increased. Here we update the fair scheduling stats and
848 * then put the task into the rbtree:
850 static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
852 struct cfs_rq *cfs_rq;
853 struct sched_entity *se = &p->se;
855 for_each_sched_entity(se) {
856 if (se->on_rq)
857 break;
858 cfs_rq = cfs_rq_of(se);
859 enqueue_entity(cfs_rq, se, wakeup);
860 wakeup = 1;
863 hrtick_start_fair(rq, rq->curr);
867 * The dequeue_task method is called before nr_running is
868 * decreased. We remove the task from the rbtree and
869 * update the fair scheduling stats:
871 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
873 struct cfs_rq *cfs_rq;
874 struct sched_entity *se = &p->se;
876 for_each_sched_entity(se) {
877 cfs_rq = cfs_rq_of(se);
878 dequeue_entity(cfs_rq, se, sleep);
879 /* Don't dequeue parent if it has other entities besides us */
880 if (cfs_rq->load.weight)
881 break;
882 sleep = 1;
885 hrtick_start_fair(rq, rq->curr);
889 * sched_yield() support is very simple - we dequeue and enqueue.
891 * If compat_yield is turned on then we requeue to the end of the tree.
893 static void yield_task_fair(struct rq *rq)
895 struct task_struct *curr = rq->curr;
896 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
897 struct sched_entity *rightmost, *se = &curr->se;
900 * Are we the only task in the tree?
902 if (unlikely(cfs_rq->nr_running == 1))
903 return;
905 if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {
906 update_rq_clock(rq);
908 * Update run-time statistics of the 'current'.
910 update_curr(cfs_rq);
912 return;
915 * Find the rightmost entry in the rbtree:
917 rightmost = __pick_last_entity(cfs_rq);
919 * Already in the rightmost position?
921 if (unlikely(!rightmost || rightmost->vruntime < se->vruntime))
922 return;
925 * Minimally necessary key value to be last in the tree:
926 * Upon rescheduling, sched_class::put_prev_task() will place
927 * 'current' within the tree based on its new key value.
929 se->vruntime = rightmost->vruntime + 1;
933 * wake_idle() will wake a task on an idle cpu if task->cpu is
934 * not idle and an idle cpu is available. The span of cpus to
935 * search starts with cpus closest then further out as needed,
936 * so we always favor a closer, idle cpu.
938 * Returns the CPU we should wake onto.
940 #if defined(ARCH_HAS_SCHED_WAKE_IDLE)
941 static int wake_idle(int cpu, struct task_struct *p)
943 cpumask_t tmp;
944 struct sched_domain *sd;
945 int i;
948 * If it is idle, then it is the best cpu to run this task.
950 * This cpu is also the best, if it has more than one task already.
951 * Siblings must be also busy(in most cases) as they didn't already
952 * pickup the extra load from this cpu and hence we need not check
953 * sibling runqueue info. This will avoid the checks and cache miss
954 * penalities associated with that.
956 if (idle_cpu(cpu) || cpu_rq(cpu)->cfs.nr_running > 1)
957 return cpu;
959 for_each_domain(cpu, sd) {
960 if ((sd->flags & SD_WAKE_IDLE)
961 || ((sd->flags & SD_WAKE_IDLE_FAR)
962 && !task_hot(p, task_rq(p)->clock, sd))) {
963 cpus_and(tmp, sd->span, p->cpus_allowed);
964 for_each_cpu_mask(i, tmp) {
965 if (idle_cpu(i)) {
966 if (i != task_cpu(p)) {
967 schedstat_inc(p,
968 se.nr_wakeups_idle);
970 return i;
973 } else {
974 break;
977 return cpu;
979 #else
980 static inline int wake_idle(int cpu, struct task_struct *p)
982 return cpu;
984 #endif
986 #ifdef CONFIG_SMP
988 static const struct sched_class fair_sched_class;
990 static int
991 wake_affine(struct rq *rq, struct sched_domain *this_sd, struct rq *this_rq,
992 struct task_struct *p, int prev_cpu, int this_cpu, int sync,
993 int idx, unsigned long load, unsigned long this_load,
994 unsigned int imbalance)
996 struct task_struct *curr = this_rq->curr;
997 unsigned long tl = this_load;
998 unsigned long tl_per_task;
999 int balanced;
1001 if (!(this_sd->flags & SD_WAKE_AFFINE) || !sched_feat(AFFINE_WAKEUPS))
1002 return 0;
1005 * If sync wakeup then subtract the (maximum possible)
1006 * effect of the currently running task from the load
1007 * of the current CPU:
1009 if (sync)
1010 tl -= current->se.load.weight;
1012 balanced = 100*(tl + p->se.load.weight) <= imbalance*load;
1015 * If the currently running task will sleep within
1016 * a reasonable amount of time then attract this newly
1017 * woken task:
1019 if (sync && balanced && curr->sched_class == &fair_sched_class) {
1020 if (curr->se.avg_overlap < sysctl_sched_migration_cost &&
1021 p->se.avg_overlap < sysctl_sched_migration_cost)
1022 return 1;
1025 schedstat_inc(p, se.nr_wakeups_affine_attempts);
1026 tl_per_task = cpu_avg_load_per_task(this_cpu);
1028 if ((tl <= load && tl + target_load(prev_cpu, idx) <= tl_per_task) ||
1029 balanced) {
1031 * This domain has SD_WAKE_AFFINE and
1032 * p is cache cold in this domain, and
1033 * there is no bad imbalance.
1035 schedstat_inc(this_sd, ttwu_move_affine);
1036 schedstat_inc(p, se.nr_wakeups_affine);
1038 return 1;
1040 return 0;
1043 static int select_task_rq_fair(struct task_struct *p, int sync)
1045 struct sched_domain *sd, *this_sd = NULL;
1046 int prev_cpu, this_cpu, new_cpu;
1047 unsigned long load, this_load;
1048 struct rq *rq, *this_rq;
1049 unsigned int imbalance;
1050 int idx;
1052 prev_cpu = task_cpu(p);
1053 rq = task_rq(p);
1054 this_cpu = smp_processor_id();
1055 this_rq = cpu_rq(this_cpu);
1056 new_cpu = prev_cpu;
1059 * 'this_sd' is the first domain that both
1060 * this_cpu and prev_cpu are present in:
1062 for_each_domain(this_cpu, sd) {
1063 if (cpu_isset(prev_cpu, sd->span)) {
1064 this_sd = sd;
1065 break;
1069 if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
1070 goto out;
1073 * Check for affine wakeup and passive balancing possibilities.
1075 if (!this_sd)
1076 goto out;
1078 idx = this_sd->wake_idx;
1080 imbalance = 100 + (this_sd->imbalance_pct - 100) / 2;
1082 load = source_load(prev_cpu, idx);
1083 this_load = target_load(this_cpu, idx);
1085 if (wake_affine(rq, this_sd, this_rq, p, prev_cpu, this_cpu, sync, idx,
1086 load, this_load, imbalance))
1087 return this_cpu;
1089 if (prev_cpu == this_cpu)
1090 goto out;
1093 * Start passive balancing when half the imbalance_pct
1094 * limit is reached.
1096 if (this_sd->flags & SD_WAKE_BALANCE) {
1097 if (imbalance*this_load <= 100*load) {
1098 schedstat_inc(this_sd, ttwu_move_balance);
1099 schedstat_inc(p, se.nr_wakeups_passive);
1100 return this_cpu;
1104 out:
1105 return wake_idle(new_cpu, p);
1107 #endif /* CONFIG_SMP */
1109 static unsigned long wakeup_gran(struct sched_entity *se)
1111 unsigned long gran = sysctl_sched_wakeup_granularity;
1114 * More easily preempt - nice tasks, while not making
1115 * it harder for + nice tasks.
1117 if (unlikely(se->load.weight > NICE_0_LOAD))
1118 gran = calc_delta_fair(gran, &se->load);
1120 return gran;
1124 * Should 'se' preempt 'curr'.
1126 * |s1
1127 * |s2
1128 * |s3
1130 * |<--->|c
1132 * w(c, s1) = -1
1133 * w(c, s2) = 0
1134 * w(c, s3) = 1
1137 static int
1138 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
1140 s64 gran, vdiff = curr->vruntime - se->vruntime;
1142 if (vdiff < 0)
1143 return -1;
1145 gran = wakeup_gran(curr);
1146 if (vdiff > gran)
1147 return 1;
1149 return 0;
1152 /* return depth at which a sched entity is present in the hierarchy */
1153 static inline int depth_se(struct sched_entity *se)
1155 int depth = 0;
1157 for_each_sched_entity(se)
1158 depth++;
1160 return depth;
1164 * Preempt the current task with a newly woken task if needed:
1166 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
1168 struct task_struct *curr = rq->curr;
1169 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
1170 struct sched_entity *se = &curr->se, *pse = &p->se;
1171 int se_depth, pse_depth;
1173 if (unlikely(rt_prio(p->prio))) {
1174 update_rq_clock(rq);
1175 update_curr(cfs_rq);
1176 resched_task(curr);
1177 return;
1180 se->last_wakeup = se->sum_exec_runtime;
1181 if (unlikely(se == pse))
1182 return;
1184 cfs_rq_of(pse)->next = pse;
1187 * Batch tasks do not preempt (their preemption is driven by
1188 * the tick):
1190 if (unlikely(p->policy == SCHED_BATCH))
1191 return;
1193 if (!sched_feat(WAKEUP_PREEMPT))
1194 return;
1197 * preemption test can be made between sibling entities who are in the
1198 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
1199 * both tasks until we find their ancestors who are siblings of common
1200 * parent.
1203 /* First walk up until both entities are at same depth */
1204 se_depth = depth_se(se);
1205 pse_depth = depth_se(pse);
1207 while (se_depth > pse_depth) {
1208 se_depth--;
1209 se = parent_entity(se);
1212 while (pse_depth > se_depth) {
1213 pse_depth--;
1214 pse = parent_entity(pse);
1217 while (!is_same_group(se, pse)) {
1218 se = parent_entity(se);
1219 pse = parent_entity(pse);
1222 if (wakeup_preempt_entity(se, pse) == 1)
1223 resched_task(curr);
1226 static struct task_struct *pick_next_task_fair(struct rq *rq)
1228 struct task_struct *p;
1229 struct cfs_rq *cfs_rq = &rq->cfs;
1230 struct sched_entity *se;
1232 if (unlikely(!cfs_rq->nr_running))
1233 return NULL;
1235 do {
1236 se = pick_next_entity(cfs_rq);
1237 cfs_rq = group_cfs_rq(se);
1238 } while (cfs_rq);
1240 p = task_of(se);
1241 hrtick_start_fair(rq, p);
1243 return p;
1247 * Account for a descheduled task:
1249 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
1251 struct sched_entity *se = &prev->se;
1252 struct cfs_rq *cfs_rq;
1254 for_each_sched_entity(se) {
1255 cfs_rq = cfs_rq_of(se);
1256 put_prev_entity(cfs_rq, se);
1260 #ifdef CONFIG_SMP
1261 /**************************************************
1262 * Fair scheduling class load-balancing methods:
1266 * Load-balancing iterator. Note: while the runqueue stays locked
1267 * during the whole iteration, the current task might be
1268 * dequeued so the iterator has to be dequeue-safe. Here we
1269 * achieve that by always pre-iterating before returning
1270 * the current task:
1272 static struct task_struct *
1273 __load_balance_iterator(struct cfs_rq *cfs_rq, struct list_head *next)
1275 struct task_struct *p = NULL;
1276 struct sched_entity *se;
1278 if (next == &cfs_rq->tasks)
1279 return NULL;
1281 /* Skip over entities that are not tasks */
1282 do {
1283 se = list_entry(next, struct sched_entity, group_node);
1284 next = next->next;
1285 } while (next != &cfs_rq->tasks && !entity_is_task(se));
1287 if (next == &cfs_rq->tasks)
1288 return NULL;
1290 cfs_rq->balance_iterator = next;
1292 if (entity_is_task(se))
1293 p = task_of(se);
1295 return p;
1298 static struct task_struct *load_balance_start_fair(void *arg)
1300 struct cfs_rq *cfs_rq = arg;
1302 return __load_balance_iterator(cfs_rq, cfs_rq->tasks.next);
1305 static struct task_struct *load_balance_next_fair(void *arg)
1307 struct cfs_rq *cfs_rq = arg;
1309 return __load_balance_iterator(cfs_rq, cfs_rq->balance_iterator);
1312 #ifdef CONFIG_FAIR_GROUP_SCHED
1313 static int cfs_rq_best_prio(struct cfs_rq *cfs_rq)
1315 struct sched_entity *curr;
1316 struct task_struct *p;
1318 if (!cfs_rq->nr_running || !first_fair(cfs_rq))
1319 return MAX_PRIO;
1321 curr = cfs_rq->curr;
1322 if (!curr)
1323 curr = __pick_next_entity(cfs_rq);
1325 p = task_of(curr);
1327 return p->prio;
1329 #endif
1331 static unsigned long
1332 load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
1333 unsigned long max_load_move,
1334 struct sched_domain *sd, enum cpu_idle_type idle,
1335 int *all_pinned, int *this_best_prio)
1337 struct cfs_rq *busy_cfs_rq;
1338 long rem_load_move = max_load_move;
1339 struct rq_iterator cfs_rq_iterator;
1341 cfs_rq_iterator.start = load_balance_start_fair;
1342 cfs_rq_iterator.next = load_balance_next_fair;
1344 for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
1345 #ifdef CONFIG_FAIR_GROUP_SCHED
1346 struct cfs_rq *this_cfs_rq;
1347 long imbalance;
1348 unsigned long maxload;
1350 this_cfs_rq = cpu_cfs_rq(busy_cfs_rq, this_cpu);
1352 imbalance = busy_cfs_rq->load.weight - this_cfs_rq->load.weight;
1353 /* Don't pull if this_cfs_rq has more load than busy_cfs_rq */
1354 if (imbalance <= 0)
1355 continue;
1357 /* Don't pull more than imbalance/2 */
1358 imbalance /= 2;
1359 maxload = min(rem_load_move, imbalance);
1361 *this_best_prio = cfs_rq_best_prio(this_cfs_rq);
1362 #else
1363 # define maxload rem_load_move
1364 #endif
1366 * pass busy_cfs_rq argument into
1367 * load_balance_[start|next]_fair iterators
1369 cfs_rq_iterator.arg = busy_cfs_rq;
1370 rem_load_move -= balance_tasks(this_rq, this_cpu, busiest,
1371 maxload, sd, idle, all_pinned,
1372 this_best_prio,
1373 &cfs_rq_iterator);
1375 if (rem_load_move <= 0)
1376 break;
1379 return max_load_move - rem_load_move;
1382 static int
1383 move_one_task_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
1384 struct sched_domain *sd, enum cpu_idle_type idle)
1386 struct cfs_rq *busy_cfs_rq;
1387 struct rq_iterator cfs_rq_iterator;
1389 cfs_rq_iterator.start = load_balance_start_fair;
1390 cfs_rq_iterator.next = load_balance_next_fair;
1392 for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
1394 * pass busy_cfs_rq argument into
1395 * load_balance_[start|next]_fair iterators
1397 cfs_rq_iterator.arg = busy_cfs_rq;
1398 if (iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
1399 &cfs_rq_iterator))
1400 return 1;
1403 return 0;
1405 #endif
1408 * scheduler tick hitting a task of our scheduling class:
1410 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
1412 struct cfs_rq *cfs_rq;
1413 struct sched_entity *se = &curr->se;
1415 for_each_sched_entity(se) {
1416 cfs_rq = cfs_rq_of(se);
1417 entity_tick(cfs_rq, se, queued);
1421 #define swap(a, b) do { typeof(a) tmp = (a); (a) = (b); (b) = tmp; } while (0)
1424 * Share the fairness runtime between parent and child, thus the
1425 * total amount of pressure for CPU stays equal - new tasks
1426 * get a chance to run but frequent forkers are not allowed to
1427 * monopolize the CPU. Note: the parent runqueue is locked,
1428 * the child is not running yet.
1430 static void task_new_fair(struct rq *rq, struct task_struct *p)
1432 struct cfs_rq *cfs_rq = task_cfs_rq(p);
1433 struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
1434 int this_cpu = smp_processor_id();
1436 sched_info_queued(p);
1438 update_curr(cfs_rq);
1439 place_entity(cfs_rq, se, 1);
1441 /* 'curr' will be NULL if the child belongs to a different group */
1442 if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
1443 curr && curr->vruntime < se->vruntime) {
1445 * Upon rescheduling, sched_class::put_prev_task() will place
1446 * 'current' within the tree based on its new key value.
1448 swap(curr->vruntime, se->vruntime);
1451 enqueue_task_fair(rq, p, 0);
1452 resched_task(rq->curr);
1456 * Priority of the task has changed. Check to see if we preempt
1457 * the current task.
1459 static void prio_changed_fair(struct rq *rq, struct task_struct *p,
1460 int oldprio, int running)
1463 * Reschedule if we are currently running on this runqueue and
1464 * our priority decreased, or if we are not currently running on
1465 * this runqueue and our priority is higher than the current's
1467 if (running) {
1468 if (p->prio > oldprio)
1469 resched_task(rq->curr);
1470 } else
1471 check_preempt_curr(rq, p);
1475 * We switched to the sched_fair class.
1477 static void switched_to_fair(struct rq *rq, struct task_struct *p,
1478 int running)
1481 * We were most likely switched from sched_rt, so
1482 * kick off the schedule if running, otherwise just see
1483 * if we can still preempt the current task.
1485 if (running)
1486 resched_task(rq->curr);
1487 else
1488 check_preempt_curr(rq, p);
1491 /* Account for a task changing its policy or group.
1493 * This routine is mostly called to set cfs_rq->curr field when a task
1494 * migrates between groups/classes.
1496 static void set_curr_task_fair(struct rq *rq)
1498 struct sched_entity *se = &rq->curr->se;
1500 for_each_sched_entity(se)
1501 set_next_entity(cfs_rq_of(se), se);
1504 #ifdef CONFIG_FAIR_GROUP_SCHED
1505 static void moved_group_fair(struct task_struct *p)
1507 struct cfs_rq *cfs_rq = task_cfs_rq(p);
1509 update_curr(cfs_rq);
1510 place_entity(cfs_rq, &p->se, 1);
1512 #endif
1515 * All the scheduling class methods:
1517 static const struct sched_class fair_sched_class = {
1518 .next = &idle_sched_class,
1519 .enqueue_task = enqueue_task_fair,
1520 .dequeue_task = dequeue_task_fair,
1521 .yield_task = yield_task_fair,
1522 #ifdef CONFIG_SMP
1523 .select_task_rq = select_task_rq_fair,
1524 #endif /* CONFIG_SMP */
1526 .check_preempt_curr = check_preempt_wakeup,
1528 .pick_next_task = pick_next_task_fair,
1529 .put_prev_task = put_prev_task_fair,
1531 #ifdef CONFIG_SMP
1532 .load_balance = load_balance_fair,
1533 .move_one_task = move_one_task_fair,
1534 #endif
1536 .set_curr_task = set_curr_task_fair,
1537 .task_tick = task_tick_fair,
1538 .task_new = task_new_fair,
1540 .prio_changed = prio_changed_fair,
1541 .switched_to = switched_to_fair,
1543 #ifdef CONFIG_FAIR_GROUP_SCHED
1544 .moved_group = moved_group_fair,
1545 #endif
1548 #ifdef CONFIG_SCHED_DEBUG
1549 static void print_cfs_stats(struct seq_file *m, int cpu)
1551 struct cfs_rq *cfs_rq;
1553 rcu_read_lock();
1554 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
1555 print_cfs_rq(m, cpu, cfs_rq);
1556 rcu_read_unlock();
1558 #endif