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>
24 * Targeted preemption latency for CPU-bound tasks:
25 * (default: 20ms, units: nanoseconds)
27 * NOTE: this latency value is not the same as the concept of
28 * 'timeslice length' - timeslices in CFS are of variable length.
29 * (to see the precise effective timeslice length of your workload,
30 * run vmstat and monitor the context-switches field)
32 * On SMP systems the value of this is multiplied by the log2 of the
33 * number of CPUs. (i.e. factor 2x on 2-way systems, 3x on 4-way
34 * systems, 4x on 8-way systems, 5x on 16-way systems, etc.)
35 * Targeted preemption latency for CPU-bound tasks:
37 const_debug unsigned int sysctl_sched_latency = 20000000ULL;
40 * After fork, child runs first. (default) If set to 0 then
41 * parent will (try to) run first.
43 const_debug unsigned int sysctl_sched_child_runs_first = 1;
46 * Minimal preemption granularity for CPU-bound tasks:
47 * (default: 2 msec, units: nanoseconds)
49 const_debug unsigned int sysctl_sched_nr_latency = 20;
52 * sys_sched_yield() compat mode
54 * This option switches the agressive yield implementation of the
55 * old scheduler back on.
57 unsigned int __read_mostly sysctl_sched_compat_yield;
60 * SCHED_BATCH wake-up granularity.
61 * (default: 10 msec, units: nanoseconds)
63 * This option delays the preemption effects of decoupled workloads
64 * and reduces their over-scheduling. Synchronous workloads will still
65 * have immediate wakeup/sleep latencies.
67 const_debug unsigned int sysctl_sched_batch_wakeup_granularity = 10000000UL;
70 * SCHED_OTHER wake-up granularity.
71 * (default: 10 msec, units: nanoseconds)
73 * This option delays the preemption effects of decoupled workloads
74 * and reduces their over-scheduling. Synchronous workloads will still
75 * have immediate wakeup/sleep latencies.
77 const_debug unsigned int sysctl_sched_wakeup_granularity = 10000000UL;
79 /**************************************************************
80 * CFS operations on generic schedulable entities:
83 #ifdef CONFIG_FAIR_GROUP_SCHED
85 /* cpu runqueue to which this cfs_rq is attached */
86 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
91 /* An entity is a task if it doesn't "own" a runqueue */
92 #define entity_is_task(se) (!se->my_q)
94 #else /* CONFIG_FAIR_GROUP_SCHED */
96 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
98 return container_of(cfs_rq, struct rq, cfs);
101 #define entity_is_task(se) 1
103 #endif /* CONFIG_FAIR_GROUP_SCHED */
105 static inline struct task_struct *task_of(struct sched_entity *se)
107 return container_of(se, struct task_struct, se);
111 /**************************************************************
112 * Scheduling class tree data structure manipulation methods:
116 max_vruntime(u64 min_vruntime, u64 vruntime)
118 s64 delta = (s64)(vruntime - min_vruntime);
120 min_vruntime = vruntime;
126 min_vruntime(u64 min_vruntime, u64 vruntime)
128 s64 delta = (s64)(vruntime - min_vruntime);
130 min_vruntime = vruntime;
136 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
138 return se->vruntime - cfs_rq->min_vruntime;
142 * Enqueue an entity into the rb-tree:
145 __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
147 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
148 struct rb_node *parent = NULL;
149 struct sched_entity *entry;
150 s64 key = entity_key(cfs_rq, se);
154 * Find the right place in the rbtree:
158 entry = rb_entry(parent, struct sched_entity, run_node);
160 * We dont care about collisions. Nodes with
161 * the same key stay together.
163 if (key < entity_key(cfs_rq, entry)) {
164 link = &parent->rb_left;
166 link = &parent->rb_right;
172 * Maintain a cache of leftmost tree entries (it is frequently
176 cfs_rq->rb_leftmost = &se->run_node;
178 rb_link_node(&se->run_node, parent, link);
179 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
183 __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
185 if (cfs_rq->rb_leftmost == &se->run_node)
186 cfs_rq->rb_leftmost = rb_next(&se->run_node);
188 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
191 static inline struct rb_node *first_fair(struct cfs_rq *cfs_rq)
193 return cfs_rq->rb_leftmost;
196 static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
198 return rb_entry(first_fair(cfs_rq), struct sched_entity, run_node);
201 static inline struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
203 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
204 struct sched_entity *se = NULL;
205 struct rb_node *parent;
209 se = rb_entry(parent, struct sched_entity, run_node);
210 link = &parent->rb_right;
216 /**************************************************************
217 * Scheduling class statistics methods:
222 * The idea is to set a period in which each task runs once.
224 * When there are too many tasks (sysctl_sched_nr_latency) we have to stretch
225 * this period because otherwise the slices get too small.
227 * p = (nr <= nl) ? l : l*nr/nl
229 static u64 __sched_period(unsigned long nr_running)
231 u64 period = sysctl_sched_latency;
232 unsigned long nr_latency = sysctl_sched_nr_latency;
234 if (unlikely(nr_running > nr_latency)) {
235 period *= nr_running;
236 do_div(period, nr_latency);
243 * We calculate the wall-time slice from the period by taking a part
244 * proportional to the weight.
248 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
250 u64 slice = __sched_period(cfs_rq->nr_running);
252 slice *= se->load.weight;
253 do_div(slice, cfs_rq->load.weight);
259 * We calculate the vruntime slice.
263 static u64 __sched_vslice(unsigned long rq_weight, unsigned long nr_running)
265 u64 vslice = __sched_period(nr_running);
267 do_div(vslice, rq_weight);
272 static u64 sched_vslice(struct cfs_rq *cfs_rq)
274 return __sched_vslice(cfs_rq->load.weight, cfs_rq->nr_running);
277 static u64 sched_vslice_add(struct cfs_rq *cfs_rq, struct sched_entity *se)
279 return __sched_vslice(cfs_rq->load.weight + se->load.weight,
280 cfs_rq->nr_running + 1);
284 * Update the current task's runtime statistics. Skip current tasks that
285 * are not in our scheduling class.
288 __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
289 unsigned long delta_exec)
291 unsigned long delta_exec_weighted;
294 schedstat_set(curr->exec_max, max((u64)delta_exec, curr->exec_max));
296 curr->sum_exec_runtime += delta_exec;
297 schedstat_add(cfs_rq, exec_clock, delta_exec);
298 delta_exec_weighted = delta_exec;
299 if (unlikely(curr->load.weight != NICE_0_LOAD)) {
300 delta_exec_weighted = calc_delta_fair(delta_exec_weighted,
303 curr->vruntime += delta_exec_weighted;
306 * maintain cfs_rq->min_vruntime to be a monotonic increasing
307 * value tracking the leftmost vruntime in the tree.
309 if (first_fair(cfs_rq)) {
310 vruntime = min_vruntime(curr->vruntime,
311 __pick_next_entity(cfs_rq)->vruntime);
313 vruntime = curr->vruntime;
315 cfs_rq->min_vruntime =
316 max_vruntime(cfs_rq->min_vruntime, vruntime);
319 static void update_curr(struct cfs_rq *cfs_rq)
321 struct sched_entity *curr = cfs_rq->curr;
322 u64 now = rq_of(cfs_rq)->clock;
323 unsigned long delta_exec;
329 * Get the amount of time the current task was running
330 * since the last time we changed load (this cannot
331 * overflow on 32 bits):
333 delta_exec = (unsigned long)(now - curr->exec_start);
335 __update_curr(cfs_rq, curr, delta_exec);
336 curr->exec_start = now;
340 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
342 schedstat_set(se->wait_start, rq_of(cfs_rq)->clock);
346 * Task is being enqueued - update stats:
348 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
351 * Are we enqueueing a waiting task? (for current tasks
352 * a dequeue/enqueue event is a NOP)
354 if (se != cfs_rq->curr)
355 update_stats_wait_start(cfs_rq, se);
359 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
361 schedstat_set(se->wait_max, max(se->wait_max,
362 rq_of(cfs_rq)->clock - se->wait_start));
363 schedstat_set(se->wait_start, 0);
367 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
371 * Mark the end of the wait period if dequeueing a
374 if (se != cfs_rq->curr)
375 update_stats_wait_end(cfs_rq, se);
379 * We are picking a new current task - update its stats:
382 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
385 * We are starting a new run period:
387 se->exec_start = rq_of(cfs_rq)->clock;
391 * We are descheduling a task - update its stats:
394 update_stats_curr_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
399 /**************************************************
400 * Scheduling class queueing methods:
404 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
406 update_load_add(&cfs_rq->load, se->load.weight);
407 cfs_rq->nr_running++;
412 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
414 update_load_sub(&cfs_rq->load, se->load.weight);
415 cfs_rq->nr_running--;
419 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
421 #ifdef CONFIG_SCHEDSTATS
422 if (se->sleep_start) {
423 u64 delta = rq_of(cfs_rq)->clock - se->sleep_start;
428 if (unlikely(delta > se->sleep_max))
429 se->sleep_max = delta;
432 se->sum_sleep_runtime += delta;
434 if (se->block_start) {
435 u64 delta = rq_of(cfs_rq)->clock - se->block_start;
440 if (unlikely(delta > se->block_max))
441 se->block_max = delta;
444 se->sum_sleep_runtime += delta;
447 * Blocking time is in units of nanosecs, so shift by 20 to
448 * get a milliseconds-range estimation of the amount of
449 * time that the task spent sleeping:
451 if (unlikely(prof_on == SLEEP_PROFILING)) {
452 struct task_struct *tsk = task_of(se);
454 profile_hits(SLEEP_PROFILING, (void *)get_wchan(tsk),
461 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
463 #ifdef CONFIG_SCHED_DEBUG
464 s64 d = se->vruntime - cfs_rq->min_vruntime;
469 if (d > 3*sysctl_sched_latency)
470 schedstat_inc(cfs_rq, nr_spread_over);
475 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
479 vruntime = cfs_rq->min_vruntime;
481 if (sched_feat(USE_TREE_AVG)) {
482 struct sched_entity *last = __pick_last_entity(cfs_rq);
484 vruntime += last->vruntime;
487 } else if (sched_feat(APPROX_AVG) && cfs_rq->nr_running)
488 vruntime += sched_vslice(cfs_rq)/2;
490 if (initial && sched_feat(START_DEBIT))
491 vruntime += sched_vslice_add(cfs_rq, se);
494 if (sched_feat(NEW_FAIR_SLEEPERS))
495 vruntime -= sysctl_sched_latency;
497 vruntime = max_t(s64, vruntime, se->vruntime);
500 se->vruntime = vruntime;
505 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
508 * Update the fair clock.
513 place_entity(cfs_rq, se, 0);
514 enqueue_sleeper(cfs_rq, se);
517 update_stats_enqueue(cfs_rq, se);
518 check_spread(cfs_rq, se);
519 if (se != cfs_rq->curr)
520 __enqueue_entity(cfs_rq, se);
521 account_entity_enqueue(cfs_rq, se);
525 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
527 update_stats_dequeue(cfs_rq, se);
529 #ifdef CONFIG_SCHEDSTATS
530 if (entity_is_task(se)) {
531 struct task_struct *tsk = task_of(se);
533 if (tsk->state & TASK_INTERRUPTIBLE)
534 se->sleep_start = rq_of(cfs_rq)->clock;
535 if (tsk->state & TASK_UNINTERRUPTIBLE)
536 se->block_start = rq_of(cfs_rq)->clock;
541 if (se != cfs_rq->curr)
542 __dequeue_entity(cfs_rq, se);
543 account_entity_dequeue(cfs_rq, se);
547 * Preempt the current task with a newly woken task if needed:
550 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
552 unsigned long ideal_runtime, delta_exec;
554 ideal_runtime = sched_slice(cfs_rq, curr);
555 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
556 if (delta_exec > ideal_runtime)
557 resched_task(rq_of(cfs_rq)->curr);
561 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
563 /* 'current' is not kept within the tree. */
566 * Any task has to be enqueued before it get to execute on
567 * a CPU. So account for the time it spent waiting on the
570 update_stats_wait_end(cfs_rq, se);
571 __dequeue_entity(cfs_rq, se);
574 update_stats_curr_start(cfs_rq, se);
576 #ifdef CONFIG_SCHEDSTATS
578 * Track our maximum slice length, if the CPU's load is at
579 * least twice that of our own weight (i.e. dont track it
580 * when there are only lesser-weight tasks around):
582 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
583 se->slice_max = max(se->slice_max,
584 se->sum_exec_runtime - se->prev_sum_exec_runtime);
587 se->prev_sum_exec_runtime = se->sum_exec_runtime;
590 static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
592 struct sched_entity *se = NULL;
594 if (first_fair(cfs_rq)) {
595 se = __pick_next_entity(cfs_rq);
596 set_next_entity(cfs_rq, se);
602 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
605 * If still on the runqueue then deactivate_task()
606 * was not called and update_curr() has to be done:
611 update_stats_curr_end(cfs_rq, prev);
613 check_spread(cfs_rq, prev);
615 update_stats_wait_start(cfs_rq, prev);
616 /* Put 'current' back into the tree. */
617 __enqueue_entity(cfs_rq, prev);
622 static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
625 * Update run-time statistics of the 'current'.
629 if (cfs_rq->nr_running > 1)
630 check_preempt_tick(cfs_rq, curr);
633 /**************************************************
634 * CFS operations on tasks:
637 #ifdef CONFIG_FAIR_GROUP_SCHED
639 /* Walk up scheduling entities hierarchy */
640 #define for_each_sched_entity(se) \
641 for (; se; se = se->parent)
643 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
648 /* runqueue on which this entity is (to be) queued */
649 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
654 /* runqueue "owned" by this group */
655 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
660 /* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on
661 * another cpu ('this_cpu')
663 static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
665 return cfs_rq->tg->cfs_rq[this_cpu];
668 /* Iterate thr' all leaf cfs_rq's on a runqueue */
669 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
670 list_for_each_entry(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
672 /* Do the two (enqueued) entities belong to the same group ? */
674 is_same_group(struct sched_entity *se, struct sched_entity *pse)
676 if (se->cfs_rq == pse->cfs_rq)
682 static inline struct sched_entity *parent_entity(struct sched_entity *se)
687 #else /* CONFIG_FAIR_GROUP_SCHED */
689 #define for_each_sched_entity(se) \
690 for (; se; se = NULL)
692 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
694 return &task_rq(p)->cfs;
697 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
699 struct task_struct *p = task_of(se);
700 struct rq *rq = task_rq(p);
705 /* runqueue "owned" by this group */
706 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
711 static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
713 return &cpu_rq(this_cpu)->cfs;
716 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
717 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
720 is_same_group(struct sched_entity *se, struct sched_entity *pse)
725 static inline struct sched_entity *parent_entity(struct sched_entity *se)
730 #endif /* CONFIG_FAIR_GROUP_SCHED */
733 * The enqueue_task method is called before nr_running is
734 * increased. Here we update the fair scheduling stats and
735 * then put the task into the rbtree:
737 static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
739 struct cfs_rq *cfs_rq;
740 struct sched_entity *se = &p->se;
742 for_each_sched_entity(se) {
745 cfs_rq = cfs_rq_of(se);
746 enqueue_entity(cfs_rq, se, wakeup);
752 * The dequeue_task method is called before nr_running is
753 * decreased. We remove the task from the rbtree and
754 * update the fair scheduling stats:
756 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
758 struct cfs_rq *cfs_rq;
759 struct sched_entity *se = &p->se;
761 for_each_sched_entity(se) {
762 cfs_rq = cfs_rq_of(se);
763 dequeue_entity(cfs_rq, se, sleep);
764 /* Don't dequeue parent if it has other entities besides us */
765 if (cfs_rq->load.weight)
772 * sched_yield() support is very simple - we dequeue and enqueue.
774 * If compat_yield is turned on then we requeue to the end of the tree.
776 static void yield_task_fair(struct rq *rq)
778 struct cfs_rq *cfs_rq = task_cfs_rq(rq->curr);
779 struct sched_entity *rightmost, *se = &rq->curr->se;
782 * Are we the only task in the tree?
784 if (unlikely(cfs_rq->nr_running == 1))
787 if (likely(!sysctl_sched_compat_yield)) {
788 __update_rq_clock(rq);
790 * Dequeue and enqueue the task to update its
791 * position within the tree:
798 * Find the rightmost entry in the rbtree:
800 rightmost = __pick_last_entity(cfs_rq);
802 * Already in the rightmost position?
804 if (unlikely(rightmost->vruntime < se->vruntime))
808 * Minimally necessary key value to be last in the tree:
809 * Upon rescheduling, sched_class::put_prev_task() will place
810 * 'current' within the tree based on its new key value.
812 se->vruntime = rightmost->vruntime + 1;
816 * Preempt the current task with a newly woken task if needed:
818 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
820 struct task_struct *curr = rq->curr;
821 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
822 struct sched_entity *se = &curr->se, *pse = &p->se;
825 if (unlikely(rt_prio(p->prio))) {
832 while (!is_same_group(se, pse)) {
833 se = parent_entity(se);
834 pse = parent_entity(pse);
837 delta = se->vruntime - pse->vruntime;
839 if (delta > (s64)sysctl_sched_wakeup_granularity)
843 static struct task_struct *pick_next_task_fair(struct rq *rq)
845 struct cfs_rq *cfs_rq = &rq->cfs;
846 struct sched_entity *se;
848 if (unlikely(!cfs_rq->nr_running))
852 se = pick_next_entity(cfs_rq);
853 cfs_rq = group_cfs_rq(se);
860 * Account for a descheduled task:
862 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
864 struct sched_entity *se = &prev->se;
865 struct cfs_rq *cfs_rq;
867 for_each_sched_entity(se) {
868 cfs_rq = cfs_rq_of(se);
869 put_prev_entity(cfs_rq, se);
873 /**************************************************
874 * Fair scheduling class load-balancing methods:
878 * Load-balancing iterator. Note: while the runqueue stays locked
879 * during the whole iteration, the current task might be
880 * dequeued so the iterator has to be dequeue-safe. Here we
881 * achieve that by always pre-iterating before returning
884 static struct task_struct *
885 __load_balance_iterator(struct cfs_rq *cfs_rq, struct rb_node *curr)
887 struct task_struct *p;
892 p = rb_entry(curr, struct task_struct, se.run_node);
893 cfs_rq->rb_load_balance_curr = rb_next(curr);
898 static struct task_struct *load_balance_start_fair(void *arg)
900 struct cfs_rq *cfs_rq = arg;
902 return __load_balance_iterator(cfs_rq, first_fair(cfs_rq));
905 static struct task_struct *load_balance_next_fair(void *arg)
907 struct cfs_rq *cfs_rq = arg;
909 return __load_balance_iterator(cfs_rq, cfs_rq->rb_load_balance_curr);
912 #ifdef CONFIG_FAIR_GROUP_SCHED
913 static int cfs_rq_best_prio(struct cfs_rq *cfs_rq)
915 struct sched_entity *curr;
916 struct task_struct *p;
918 if (!cfs_rq->nr_running)
923 curr = __pick_next_entity(cfs_rq);
932 load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
933 unsigned long max_nr_move, unsigned long max_load_move,
934 struct sched_domain *sd, enum cpu_idle_type idle,
935 int *all_pinned, int *this_best_prio)
937 struct cfs_rq *busy_cfs_rq;
938 unsigned long load_moved, total_nr_moved = 0, nr_moved;
939 long rem_load_move = max_load_move;
940 struct rq_iterator cfs_rq_iterator;
942 cfs_rq_iterator.start = load_balance_start_fair;
943 cfs_rq_iterator.next = load_balance_next_fair;
945 for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
946 #ifdef CONFIG_FAIR_GROUP_SCHED
947 struct cfs_rq *this_cfs_rq;
949 unsigned long maxload;
951 this_cfs_rq = cpu_cfs_rq(busy_cfs_rq, this_cpu);
953 imbalance = busy_cfs_rq->load.weight - this_cfs_rq->load.weight;
954 /* Don't pull if this_cfs_rq has more load than busy_cfs_rq */
958 /* Don't pull more than imbalance/2 */
960 maxload = min(rem_load_move, imbalance);
962 *this_best_prio = cfs_rq_best_prio(this_cfs_rq);
964 # define maxload rem_load_move
966 /* pass busy_cfs_rq argument into
967 * load_balance_[start|next]_fair iterators
969 cfs_rq_iterator.arg = busy_cfs_rq;
970 nr_moved = balance_tasks(this_rq, this_cpu, busiest,
971 max_nr_move, maxload, sd, idle, all_pinned,
972 &load_moved, this_best_prio, &cfs_rq_iterator);
974 total_nr_moved += nr_moved;
975 max_nr_move -= nr_moved;
976 rem_load_move -= load_moved;
978 if (max_nr_move <= 0 || rem_load_move <= 0)
982 return max_load_move - rem_load_move;
986 * scheduler tick hitting a task of our scheduling class:
988 static void task_tick_fair(struct rq *rq, struct task_struct *curr)
990 struct cfs_rq *cfs_rq;
991 struct sched_entity *se = &curr->se;
993 for_each_sched_entity(se) {
994 cfs_rq = cfs_rq_of(se);
995 entity_tick(cfs_rq, se);
999 #define swap(a,b) do { typeof(a) tmp = (a); (a) = (b); (b) = tmp; } while (0)
1002 * Share the fairness runtime between parent and child, thus the
1003 * total amount of pressure for CPU stays equal - new tasks
1004 * get a chance to run but frequent forkers are not allowed to
1005 * monopolize the CPU. Note: the parent runqueue is locked,
1006 * the child is not running yet.
1008 static void task_new_fair(struct rq *rq, struct task_struct *p)
1010 struct cfs_rq *cfs_rq = task_cfs_rq(p);
1011 struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
1013 sched_info_queued(p);
1015 update_curr(cfs_rq);
1016 place_entity(cfs_rq, se, 1);
1018 if (sysctl_sched_child_runs_first &&
1019 curr->vruntime < se->vruntime) {
1021 * Upon rescheduling, sched_class::put_prev_task() will place
1022 * 'current' within the tree based on its new key value.
1024 swap(curr->vruntime, se->vruntime);
1027 update_stats_enqueue(cfs_rq, se);
1028 check_spread(cfs_rq, se);
1029 check_spread(cfs_rq, curr);
1030 __enqueue_entity(cfs_rq, se);
1031 account_entity_enqueue(cfs_rq, se);
1032 resched_task(rq->curr);
1035 /* Account for a task changing its policy or group.
1037 * This routine is mostly called to set cfs_rq->curr field when a task
1038 * migrates between groups/classes.
1040 static void set_curr_task_fair(struct rq *rq)
1042 struct sched_entity *se = &rq->curr->se;
1044 for_each_sched_entity(se)
1045 set_next_entity(cfs_rq_of(se), se);
1049 * All the scheduling class methods:
1051 static const struct sched_class fair_sched_class = {
1052 .next = &idle_sched_class,
1053 .enqueue_task = enqueue_task_fair,
1054 .dequeue_task = dequeue_task_fair,
1055 .yield_task = yield_task_fair,
1057 .check_preempt_curr = check_preempt_wakeup,
1059 .pick_next_task = pick_next_task_fair,
1060 .put_prev_task = put_prev_task_fair,
1062 .load_balance = load_balance_fair,
1064 .set_curr_task = set_curr_task_fair,
1065 .task_tick = task_tick_fair,
1066 .task_new = task_new_fair,
1069 #ifdef CONFIG_SCHED_DEBUG
1070 static void print_cfs_stats(struct seq_file *m, int cpu)
1072 struct cfs_rq *cfs_rq;
1074 #ifdef CONFIG_FAIR_GROUP_SCHED
1075 print_cfs_rq(m, cpu, &cpu_rq(cpu)->cfs);
1077 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
1078 print_cfs_rq(m, cpu, cfs_rq);