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)
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)
105 /* runqueue on which this entity is (to be) queued */
106 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
111 /* runqueue "owned" by this group */
112 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
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 ? */
131 is_same_group(struct sched_entity *se, struct sched_entity *pse)
133 if (se->cfs_rq == pse->cfs_rq)
139 static inline struct sched_entity *parent_entity(struct sched_entity *se)
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);
169 /* runqueue "owned" by this group */
170 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
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)
184 is_same_group(struct sched_entity *se, struct sched_entity *pse)
189 static inline struct sched_entity *parent_entity(struct sched_entity *se)
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);
205 min_vruntime = vruntime;
210 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
212 s64 delta = (s64)(vruntime - min_vruntime);
214 min_vruntime = 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);
236 * Find the right place in the rbtree:
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;
248 link = &parent->rb_right;
254 * Maintain a cache of leftmost tree entries (it is frequently
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;
281 next = rb_entry(next_node,
282 struct sched_entity, run_node);
283 cfs_rq->min_vruntime =
284 max_vruntime(cfs_rq->min_vruntime,
289 if (cfs_rq->next == se)
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);
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,
324 int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
329 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
330 sysctl_sched_min_granularity);
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;
358 * We calculate the wall-time slice from the period by taking a part
359 * proportional to the weight.
363 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
365 return calc_delta_mine(__sched_period(cfs_rq->nr_running),
366 se->load.weight, &cfs_rq->load);
370 * We calculate the vruntime slice.
374 static u64 __sched_vslice(unsigned long rq_weight, unsigned long nr_running)
376 u64 vslice = __sched_period(nr_running);
378 vslice *= NICE_0_LOAD;
379 do_div(vslice, rq_weight);
384 static u64 sched_vslice_add(struct cfs_rq *cfs_rq, struct sched_entity *se)
386 return __sched_vslice(cfs_rq->load.weight + se->load.weight,
387 cfs_rq->nr_running + 1);
391 * Update the current task's runtime statistics. Skip current tasks that
392 * are not in our scheduling class.
395 __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
396 unsigned long delta_exec)
398 unsigned long delta_exec_weighted;
400 schedstat_set(curr->exec_max, max((u64)delta_exec, curr->exec_max));
402 curr->sum_exec_runtime += delta_exec;
403 schedstat_add(cfs_rq, exec_clock, delta_exec);
404 delta_exec_weighted = delta_exec;
405 if (unlikely(curr->load.weight != NICE_0_LOAD)) {
406 delta_exec_weighted = calc_delta_fair(delta_exec_weighted,
409 curr->vruntime += delta_exec_weighted;
412 static void update_curr(struct cfs_rq *cfs_rq)
414 struct sched_entity *curr = cfs_rq->curr;
415 u64 now = rq_of(cfs_rq)->clock;
416 unsigned long delta_exec;
422 * Get the amount of time the current task was running
423 * since the last time we changed load (this cannot
424 * overflow on 32 bits):
426 delta_exec = (unsigned long)(now - curr->exec_start);
428 __update_curr(cfs_rq, curr, delta_exec);
429 curr->exec_start = now;
431 if (entity_is_task(curr)) {
432 struct task_struct *curtask = task_of(curr);
434 cpuacct_charge(curtask, delta_exec);
439 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
441 schedstat_set(se->wait_start, rq_of(cfs_rq)->clock);
445 * Task is being enqueued - update stats:
447 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
450 * Are we enqueueing a waiting task? (for current tasks
451 * a dequeue/enqueue event is a NOP)
453 if (se != cfs_rq->curr)
454 update_stats_wait_start(cfs_rq, se);
458 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
460 schedstat_set(se->wait_max, max(se->wait_max,
461 rq_of(cfs_rq)->clock - se->wait_start));
462 schedstat_set(se->wait_count, se->wait_count + 1);
463 schedstat_set(se->wait_sum, se->wait_sum +
464 rq_of(cfs_rq)->clock - se->wait_start);
465 schedstat_set(se->wait_start, 0);
469 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
472 * Mark the end of the wait period if dequeueing a
475 if (se != cfs_rq->curr)
476 update_stats_wait_end(cfs_rq, se);
480 * We are picking a new current task - update its stats:
483 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
486 * We are starting a new run period:
488 se->exec_start = rq_of(cfs_rq)->clock;
491 /**************************************************
492 * Scheduling class queueing methods:
496 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
498 update_load_add(&cfs_rq->load, se->load.weight);
499 cfs_rq->nr_running++;
504 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
506 update_load_sub(&cfs_rq->load, se->load.weight);
507 cfs_rq->nr_running--;
511 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
513 #ifdef CONFIG_SCHEDSTATS
514 if (se->sleep_start) {
515 u64 delta = rq_of(cfs_rq)->clock - se->sleep_start;
516 struct task_struct *tsk = task_of(se);
521 if (unlikely(delta > se->sleep_max))
522 se->sleep_max = delta;
525 se->sum_sleep_runtime += delta;
527 account_scheduler_latency(tsk, delta >> 10, 1);
529 if (se->block_start) {
530 u64 delta = rq_of(cfs_rq)->clock - se->block_start;
531 struct task_struct *tsk = task_of(se);
536 if (unlikely(delta > se->block_max))
537 se->block_max = delta;
540 se->sum_sleep_runtime += delta;
543 * Blocking time is in units of nanosecs, so shift by 20 to
544 * get a milliseconds-range estimation of the amount of
545 * time that the task spent sleeping:
547 if (unlikely(prof_on == SLEEP_PROFILING)) {
549 profile_hits(SLEEP_PROFILING, (void *)get_wchan(tsk),
552 account_scheduler_latency(tsk, delta >> 10, 0);
557 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
559 #ifdef CONFIG_SCHED_DEBUG
560 s64 d = se->vruntime - cfs_rq->min_vruntime;
565 if (d > 3*sysctl_sched_latency)
566 schedstat_inc(cfs_rq, nr_spread_over);
571 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
575 if (first_fair(cfs_rq)) {
576 vruntime = min_vruntime(cfs_rq->min_vruntime,
577 __pick_next_entity(cfs_rq)->vruntime);
579 vruntime = cfs_rq->min_vruntime;
582 * The 'current' period is already promised to the current tasks,
583 * however the extra weight of the new task will slow them down a
584 * little, place the new task so that it fits in the slot that
585 * stays open at the end.
587 if (initial && sched_feat(START_DEBIT))
588 vruntime += sched_vslice_add(cfs_rq, se);
591 /* sleeps upto a single latency don't count. */
592 if (sched_feat(NEW_FAIR_SLEEPERS)) {
593 if (sched_feat(NORMALIZED_SLEEPER))
594 vruntime -= calc_delta_fair(sysctl_sched_latency,
597 vruntime -= sysctl_sched_latency;
600 /* ensure we never gain time by being placed backwards. */
601 vruntime = max_vruntime(se->vruntime, vruntime);
604 se->vruntime = vruntime;
608 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
611 * Update run-time statistics of the 'current'.
616 place_entity(cfs_rq, se, 0);
617 enqueue_sleeper(cfs_rq, se);
620 update_stats_enqueue(cfs_rq, se);
621 check_spread(cfs_rq, se);
622 if (se != cfs_rq->curr)
623 __enqueue_entity(cfs_rq, se);
624 account_entity_enqueue(cfs_rq, se);
627 static void update_avg(u64 *avg, u64 sample)
629 s64 diff = sample - *avg;
633 static void update_avg_stats(struct cfs_rq *cfs_rq, struct sched_entity *se)
635 if (!se->last_wakeup)
638 update_avg(&se->avg_overlap, se->sum_exec_runtime - se->last_wakeup);
643 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
646 * Update run-time statistics of the 'current'.
650 update_stats_dequeue(cfs_rq, se);
652 update_avg_stats(cfs_rq, se);
653 #ifdef CONFIG_SCHEDSTATS
654 if (entity_is_task(se)) {
655 struct task_struct *tsk = task_of(se);
657 if (tsk->state & TASK_INTERRUPTIBLE)
658 se->sleep_start = rq_of(cfs_rq)->clock;
659 if (tsk->state & TASK_UNINTERRUPTIBLE)
660 se->block_start = rq_of(cfs_rq)->clock;
665 if (se != cfs_rq->curr)
666 __dequeue_entity(cfs_rq, se);
667 account_entity_dequeue(cfs_rq, se);
671 * Preempt the current task with a newly woken task if needed:
674 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
676 unsigned long ideal_runtime, delta_exec;
678 ideal_runtime = sched_slice(cfs_rq, curr);
679 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
680 if (delta_exec > ideal_runtime)
681 resched_task(rq_of(cfs_rq)->curr);
685 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
687 /* 'current' is not kept within the tree. */
690 * Any task has to be enqueued before it get to execute on
691 * a CPU. So account for the time it spent waiting on the
694 update_stats_wait_end(cfs_rq, se);
695 __dequeue_entity(cfs_rq, se);
698 update_stats_curr_start(cfs_rq, se);
700 #ifdef CONFIG_SCHEDSTATS
702 * Track our maximum slice length, if the CPU's load is at
703 * least twice that of our own weight (i.e. dont track it
704 * when there are only lesser-weight tasks around):
706 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
707 se->slice_max = max(se->slice_max,
708 se->sum_exec_runtime - se->prev_sum_exec_runtime);
711 se->prev_sum_exec_runtime = se->sum_exec_runtime;
715 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
717 static struct sched_entity *
718 pick_next(struct cfs_rq *cfs_rq, struct sched_entity *se)
723 if (wakeup_preempt_entity(cfs_rq->next, se) != 0)
729 static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
731 struct sched_entity *se = NULL;
733 if (first_fair(cfs_rq)) {
734 se = __pick_next_entity(cfs_rq);
735 se = pick_next(cfs_rq, se);
736 set_next_entity(cfs_rq, se);
742 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
745 * If still on the runqueue then deactivate_task()
746 * was not called and update_curr() has to be done:
751 check_spread(cfs_rq, prev);
753 update_stats_wait_start(cfs_rq, prev);
754 /* Put 'current' back into the tree. */
755 __enqueue_entity(cfs_rq, prev);
761 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
764 * Update run-time statistics of the 'current'.
768 #ifdef CONFIG_SCHED_HRTICK
770 * queued ticks are scheduled to match the slice, so don't bother
771 * validating it and just reschedule.
774 return resched_task(rq_of(cfs_rq)->curr);
776 * don't let the period tick interfere with the hrtick preemption
778 if (!sched_feat(DOUBLE_TICK) &&
779 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
783 if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
784 check_preempt_tick(cfs_rq, curr);
787 /**************************************************
788 * CFS operations on tasks:
791 #ifdef CONFIG_SCHED_HRTICK
792 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
794 int requeue = rq->curr == p;
795 struct sched_entity *se = &p->se;
796 struct cfs_rq *cfs_rq = cfs_rq_of(se);
798 WARN_ON(task_rq(p) != rq);
800 if (hrtick_enabled(rq) && cfs_rq->nr_running > 1) {
801 u64 slice = sched_slice(cfs_rq, se);
802 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
803 s64 delta = slice - ran;
812 * Don't schedule slices shorter than 10000ns, that just
813 * doesn't make sense. Rely on vruntime for fairness.
816 delta = max(10000LL, delta);
818 hrtick_start(rq, delta, requeue);
823 hrtick_start_fair(struct rq *rq, struct task_struct *p)
829 * The enqueue_task method is called before nr_running is
830 * increased. Here we update the fair scheduling stats and
831 * then put the task into the rbtree:
833 static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
835 struct cfs_rq *cfs_rq;
836 struct sched_entity *se = &p->se;
838 for_each_sched_entity(se) {
841 cfs_rq = cfs_rq_of(se);
842 enqueue_entity(cfs_rq, se, wakeup);
846 hrtick_start_fair(rq, rq->curr);
850 * The dequeue_task method is called before nr_running is
851 * decreased. We remove the task from the rbtree and
852 * update the fair scheduling stats:
854 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
856 struct cfs_rq *cfs_rq;
857 struct sched_entity *se = &p->se;
859 for_each_sched_entity(se) {
860 cfs_rq = cfs_rq_of(se);
861 dequeue_entity(cfs_rq, se, sleep);
862 /* Don't dequeue parent if it has other entities besides us */
863 if (cfs_rq->load.weight)
868 hrtick_start_fair(rq, rq->curr);
872 * sched_yield() support is very simple - we dequeue and enqueue.
874 * If compat_yield is turned on then we requeue to the end of the tree.
876 static void yield_task_fair(struct rq *rq)
878 struct task_struct *curr = rq->curr;
879 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
880 struct sched_entity *rightmost, *se = &curr->se;
883 * Are we the only task in the tree?
885 if (unlikely(cfs_rq->nr_running == 1))
888 if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {
889 __update_rq_clock(rq);
891 * Update run-time statistics of the 'current'.
898 * Find the rightmost entry in the rbtree:
900 rightmost = __pick_last_entity(cfs_rq);
902 * Already in the rightmost position?
904 if (unlikely(!rightmost || rightmost->vruntime < se->vruntime))
908 * Minimally necessary key value to be last in the tree:
909 * Upon rescheduling, sched_class::put_prev_task() will place
910 * 'current' within the tree based on its new key value.
912 se->vruntime = rightmost->vruntime + 1;
916 * wake_idle() will wake a task on an idle cpu if task->cpu is
917 * not idle and an idle cpu is available. The span of cpus to
918 * search starts with cpus closest then further out as needed,
919 * so we always favor a closer, idle cpu.
921 * Returns the CPU we should wake onto.
923 #if defined(ARCH_HAS_SCHED_WAKE_IDLE)
924 static int wake_idle(int cpu, struct task_struct *p)
927 struct sched_domain *sd;
931 * If it is idle, then it is the best cpu to run this task.
933 * This cpu is also the best, if it has more than one task already.
934 * Siblings must be also busy(in most cases) as they didn't already
935 * pickup the extra load from this cpu and hence we need not check
936 * sibling runqueue info. This will avoid the checks and cache miss
937 * penalities associated with that.
939 if (idle_cpu(cpu) || cpu_rq(cpu)->nr_running > 1)
942 for_each_domain(cpu, sd) {
943 if (sd->flags & SD_WAKE_IDLE) {
944 cpus_and(tmp, sd->span, p->cpus_allowed);
945 for_each_cpu_mask(i, tmp) {
947 if (i != task_cpu(p)) {
961 static inline int wake_idle(int cpu, struct task_struct *p)
969 static const struct sched_class fair_sched_class;
972 wake_affine(struct rq *rq, struct sched_domain *this_sd, struct rq *this_rq,
973 struct task_struct *p, int prev_cpu, int this_cpu, int sync,
974 int idx, unsigned long load, unsigned long this_load,
975 unsigned int imbalance)
977 struct task_struct *curr = this_rq->curr;
978 unsigned long tl = this_load;
979 unsigned long tl_per_task;
981 if (!(this_sd->flags & SD_WAKE_AFFINE))
985 * If the currently running task will sleep within
986 * a reasonable amount of time then attract this newly
989 if (sync && curr->sched_class == &fair_sched_class) {
990 if (curr->se.avg_overlap < sysctl_sched_migration_cost &&
991 p->se.avg_overlap < sysctl_sched_migration_cost)
995 schedstat_inc(p, se.nr_wakeups_affine_attempts);
996 tl_per_task = cpu_avg_load_per_task(this_cpu);
999 * If sync wakeup then subtract the (maximum possible)
1000 * effect of the currently running task from the load
1001 * of the current CPU:
1004 tl -= current->se.load.weight;
1006 if ((tl <= load && tl + target_load(prev_cpu, idx) <= tl_per_task) ||
1007 100*(tl + p->se.load.weight) <= imbalance*load) {
1009 * This domain has SD_WAKE_AFFINE and
1010 * p is cache cold in this domain, and
1011 * there is no bad imbalance.
1013 schedstat_inc(this_sd, ttwu_move_affine);
1014 schedstat_inc(p, se.nr_wakeups_affine);
1021 static int select_task_rq_fair(struct task_struct *p, int sync)
1023 struct sched_domain *sd, *this_sd = NULL;
1024 int prev_cpu, this_cpu, new_cpu;
1025 unsigned long load, this_load;
1026 struct rq *rq, *this_rq;
1027 unsigned int imbalance;
1030 prev_cpu = task_cpu(p);
1032 this_cpu = smp_processor_id();
1033 this_rq = cpu_rq(this_cpu);
1037 * 'this_sd' is the first domain that both
1038 * this_cpu and prev_cpu are present in:
1040 for_each_domain(this_cpu, sd) {
1041 if (cpu_isset(prev_cpu, sd->span)) {
1047 if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
1051 * Check for affine wakeup and passive balancing possibilities.
1056 idx = this_sd->wake_idx;
1058 imbalance = 100 + (this_sd->imbalance_pct - 100) / 2;
1060 load = source_load(prev_cpu, idx);
1061 this_load = target_load(this_cpu, idx);
1063 if (wake_affine(rq, this_sd, this_rq, p, prev_cpu, this_cpu, sync, idx,
1064 load, this_load, imbalance))
1067 if (prev_cpu == this_cpu)
1071 * Start passive balancing when half the imbalance_pct
1074 if (this_sd->flags & SD_WAKE_BALANCE) {
1075 if (imbalance*this_load <= 100*load) {
1076 schedstat_inc(this_sd, ttwu_move_balance);
1077 schedstat_inc(p, se.nr_wakeups_passive);
1083 return wake_idle(new_cpu, p);
1085 #endif /* CONFIG_SMP */
1087 static unsigned long wakeup_gran(struct sched_entity *se)
1089 unsigned long gran = sysctl_sched_wakeup_granularity;
1092 * More easily preempt - nice tasks, while not making
1093 * it harder for + nice tasks.
1095 if (unlikely(se->load.weight > NICE_0_LOAD))
1096 gran = calc_delta_fair(gran, &se->load);
1102 * Should 'se' preempt 'curr'.
1116 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
1118 s64 gran, vdiff = curr->vruntime - se->vruntime;
1123 gran = wakeup_gran(curr);
1130 /* return depth at which a sched entity is present in the hierarchy */
1131 static inline int depth_se(struct sched_entity *se)
1135 for_each_sched_entity(se)
1142 * Preempt the current task with a newly woken task if needed:
1144 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
1146 struct task_struct *curr = rq->curr;
1147 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
1148 struct sched_entity *se = &curr->se, *pse = &p->se;
1149 int se_depth, pse_depth;
1151 if (unlikely(rt_prio(p->prio))) {
1152 update_rq_clock(rq);
1153 update_curr(cfs_rq);
1158 se->last_wakeup = se->sum_exec_runtime;
1159 if (unlikely(se == pse))
1162 cfs_rq_of(pse)->next = pse;
1165 * Batch tasks do not preempt (their preemption is driven by
1168 if (unlikely(p->policy == SCHED_BATCH))
1171 if (!sched_feat(WAKEUP_PREEMPT))
1175 * preemption test can be made between sibling entities who are in the
1176 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
1177 * both tasks until we find their ancestors who are siblings of common
1181 /* First walk up until both entities are at same depth */
1182 se_depth = depth_se(se);
1183 pse_depth = depth_se(pse);
1185 while (se_depth > pse_depth) {
1187 se = parent_entity(se);
1190 while (pse_depth > se_depth) {
1192 pse = parent_entity(pse);
1195 while (!is_same_group(se, pse)) {
1196 se = parent_entity(se);
1197 pse = parent_entity(pse);
1200 if (wakeup_preempt_entity(se, pse) == 1)
1204 static struct task_struct *pick_next_task_fair(struct rq *rq)
1206 struct task_struct *p;
1207 struct cfs_rq *cfs_rq = &rq->cfs;
1208 struct sched_entity *se;
1210 if (unlikely(!cfs_rq->nr_running))
1214 se = pick_next_entity(cfs_rq);
1215 cfs_rq = group_cfs_rq(se);
1219 hrtick_start_fair(rq, p);
1225 * Account for a descheduled task:
1227 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
1229 struct sched_entity *se = &prev->se;
1230 struct cfs_rq *cfs_rq;
1232 for_each_sched_entity(se) {
1233 cfs_rq = cfs_rq_of(se);
1234 put_prev_entity(cfs_rq, se);
1239 /**************************************************
1240 * Fair scheduling class load-balancing methods:
1244 * Load-balancing iterator. Note: while the runqueue stays locked
1245 * during the whole iteration, the current task might be
1246 * dequeued so the iterator has to be dequeue-safe. Here we
1247 * achieve that by always pre-iterating before returning
1250 static struct task_struct *
1251 __load_balance_iterator(struct cfs_rq *cfs_rq, struct rb_node *curr)
1253 struct task_struct *p = NULL;
1254 struct sched_entity *se;
1259 /* Skip over entities that are not tasks */
1261 se = rb_entry(curr, struct sched_entity, run_node);
1262 curr = rb_next(curr);
1263 } while (curr && !entity_is_task(se));
1265 cfs_rq->rb_load_balance_curr = curr;
1267 if (entity_is_task(se))
1273 static struct task_struct *load_balance_start_fair(void *arg)
1275 struct cfs_rq *cfs_rq = arg;
1277 return __load_balance_iterator(cfs_rq, first_fair(cfs_rq));
1280 static struct task_struct *load_balance_next_fair(void *arg)
1282 struct cfs_rq *cfs_rq = arg;
1284 return __load_balance_iterator(cfs_rq, cfs_rq->rb_load_balance_curr);
1287 #ifdef CONFIG_FAIR_GROUP_SCHED
1288 static int cfs_rq_best_prio(struct cfs_rq *cfs_rq)
1290 struct sched_entity *curr;
1291 struct task_struct *p;
1293 if (!cfs_rq->nr_running || !first_fair(cfs_rq))
1296 curr = cfs_rq->curr;
1298 curr = __pick_next_entity(cfs_rq);
1306 static unsigned long
1307 load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
1308 unsigned long max_load_move,
1309 struct sched_domain *sd, enum cpu_idle_type idle,
1310 int *all_pinned, int *this_best_prio)
1312 struct cfs_rq *busy_cfs_rq;
1313 long rem_load_move = max_load_move;
1314 struct rq_iterator cfs_rq_iterator;
1316 cfs_rq_iterator.start = load_balance_start_fair;
1317 cfs_rq_iterator.next = load_balance_next_fair;
1319 for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
1320 #ifdef CONFIG_FAIR_GROUP_SCHED
1321 struct cfs_rq *this_cfs_rq;
1323 unsigned long maxload;
1325 this_cfs_rq = cpu_cfs_rq(busy_cfs_rq, this_cpu);
1327 imbalance = busy_cfs_rq->load.weight - this_cfs_rq->load.weight;
1328 /* Don't pull if this_cfs_rq has more load than busy_cfs_rq */
1332 /* Don't pull more than imbalance/2 */
1334 maxload = min(rem_load_move, imbalance);
1336 *this_best_prio = cfs_rq_best_prio(this_cfs_rq);
1338 # define maxload rem_load_move
1341 * pass busy_cfs_rq argument into
1342 * load_balance_[start|next]_fair iterators
1344 cfs_rq_iterator.arg = busy_cfs_rq;
1345 rem_load_move -= balance_tasks(this_rq, this_cpu, busiest,
1346 maxload, sd, idle, all_pinned,
1350 if (rem_load_move <= 0)
1354 return max_load_move - rem_load_move;
1358 move_one_task_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
1359 struct sched_domain *sd, enum cpu_idle_type idle)
1361 struct cfs_rq *busy_cfs_rq;
1362 struct rq_iterator cfs_rq_iterator;
1364 cfs_rq_iterator.start = load_balance_start_fair;
1365 cfs_rq_iterator.next = load_balance_next_fair;
1367 for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
1369 * pass busy_cfs_rq argument into
1370 * load_balance_[start|next]_fair iterators
1372 cfs_rq_iterator.arg = busy_cfs_rq;
1373 if (iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
1383 * scheduler tick hitting a task of our scheduling class:
1385 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
1387 struct cfs_rq *cfs_rq;
1388 struct sched_entity *se = &curr->se;
1390 for_each_sched_entity(se) {
1391 cfs_rq = cfs_rq_of(se);
1392 entity_tick(cfs_rq, se, queued);
1396 #define swap(a, b) do { typeof(a) tmp = (a); (a) = (b); (b) = tmp; } while (0)
1399 * Share the fairness runtime between parent and child, thus the
1400 * total amount of pressure for CPU stays equal - new tasks
1401 * get a chance to run but frequent forkers are not allowed to
1402 * monopolize the CPU. Note: the parent runqueue is locked,
1403 * the child is not running yet.
1405 static void task_new_fair(struct rq *rq, struct task_struct *p)
1407 struct cfs_rq *cfs_rq = task_cfs_rq(p);
1408 struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
1409 int this_cpu = smp_processor_id();
1411 sched_info_queued(p);
1413 update_curr(cfs_rq);
1414 place_entity(cfs_rq, se, 1);
1416 /* 'curr' will be NULL if the child belongs to a different group */
1417 if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
1418 curr && curr->vruntime < se->vruntime) {
1420 * Upon rescheduling, sched_class::put_prev_task() will place
1421 * 'current' within the tree based on its new key value.
1423 swap(curr->vruntime, se->vruntime);
1426 enqueue_task_fair(rq, p, 0);
1427 resched_task(rq->curr);
1431 * Priority of the task has changed. Check to see if we preempt
1434 static void prio_changed_fair(struct rq *rq, struct task_struct *p,
1435 int oldprio, int running)
1438 * Reschedule if we are currently running on this runqueue and
1439 * our priority decreased, or if we are not currently running on
1440 * this runqueue and our priority is higher than the current's
1443 if (p->prio > oldprio)
1444 resched_task(rq->curr);
1446 check_preempt_curr(rq, p);
1450 * We switched to the sched_fair class.
1452 static void switched_to_fair(struct rq *rq, struct task_struct *p,
1456 * We were most likely switched from sched_rt, so
1457 * kick off the schedule if running, otherwise just see
1458 * if we can still preempt the current task.
1461 resched_task(rq->curr);
1463 check_preempt_curr(rq, p);
1466 /* Account for a task changing its policy or group.
1468 * This routine is mostly called to set cfs_rq->curr field when a task
1469 * migrates between groups/classes.
1471 static void set_curr_task_fair(struct rq *rq)
1473 struct sched_entity *se = &rq->curr->se;
1475 for_each_sched_entity(se)
1476 set_next_entity(cfs_rq_of(se), se);
1479 #ifdef CONFIG_FAIR_GROUP_SCHED
1480 static void moved_group_fair(struct task_struct *p)
1482 struct cfs_rq *cfs_rq = task_cfs_rq(p);
1484 update_curr(cfs_rq);
1485 place_entity(cfs_rq, &p->se, 1);
1490 * All the scheduling class methods:
1492 static const struct sched_class fair_sched_class = {
1493 .next = &idle_sched_class,
1494 .enqueue_task = enqueue_task_fair,
1495 .dequeue_task = dequeue_task_fair,
1496 .yield_task = yield_task_fair,
1498 .select_task_rq = select_task_rq_fair,
1499 #endif /* CONFIG_SMP */
1501 .check_preempt_curr = check_preempt_wakeup,
1503 .pick_next_task = pick_next_task_fair,
1504 .put_prev_task = put_prev_task_fair,
1507 .load_balance = load_balance_fair,
1508 .move_one_task = move_one_task_fair,
1511 .set_curr_task = set_curr_task_fair,
1512 .task_tick = task_tick_fair,
1513 .task_new = task_new_fair,
1515 .prio_changed = prio_changed_fair,
1516 .switched_to = switched_to_fair,
1518 #ifdef CONFIG_FAIR_GROUP_SCHED
1519 .moved_group = moved_group_fair,
1523 #ifdef CONFIG_SCHED_DEBUG
1524 static void print_cfs_stats(struct seq_file *m, int cpu)
1526 struct cfs_rq *cfs_rq;
1529 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
1530 print_cfs_rq(m, cpu, cfs_rq);