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 unsigned int sysctl_sched_min_granularity __read_mostly
= 2000000ULL;
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: 25 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
= 25000000UL;
70 * SCHED_OTHER wake-up granularity.
71 * (default: 1 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
= 2000000UL;
79 unsigned int sysctl_sched_runtime_limit __read_mostly
;
81 extern struct sched_class fair_sched_class
;
83 /**************************************************************
84 * CFS operations on generic schedulable entities:
87 #ifdef CONFIG_FAIR_GROUP_SCHED
89 /* cpu runqueue to which this cfs_rq is attached */
90 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
95 /* An entity is a task if it doesn't "own" a runqueue */
96 #define entity_is_task(se) (!se->my_q)
98 #else /* CONFIG_FAIR_GROUP_SCHED */
100 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
102 return container_of(cfs_rq
, struct rq
, cfs
);
105 #define entity_is_task(se) 1
107 #endif /* CONFIG_FAIR_GROUP_SCHED */
109 static inline struct task_struct
*task_of(struct sched_entity
*se
)
111 return container_of(se
, struct task_struct
, se
);
115 /**************************************************************
116 * Scheduling class tree data structure manipulation methods:
120 set_leftmost(struct cfs_rq
*cfs_rq
, struct rb_node
*leftmost
)
122 struct sched_entity
*se
;
124 cfs_rq
->rb_leftmost
= leftmost
;
126 se
= rb_entry(leftmost
, struct sched_entity
, run_node
);
127 cfs_rq
->min_vruntime
= max(se
->vruntime
,
128 cfs_rq
->min_vruntime
);
133 * Enqueue an entity into the rb-tree:
136 __enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
138 struct rb_node
**link
= &cfs_rq
->tasks_timeline
.rb_node
;
139 struct rb_node
*parent
= NULL
;
140 struct sched_entity
*entry
;
141 s64 key
= se
->fair_key
;
145 * Find the right place in the rbtree:
149 entry
= rb_entry(parent
, struct sched_entity
, run_node
);
151 * We dont care about collisions. Nodes with
152 * the same key stay together.
154 if (key
- entry
->fair_key
< 0) {
155 link
= &parent
->rb_left
;
157 link
= &parent
->rb_right
;
163 * Maintain a cache of leftmost tree entries (it is frequently
167 set_leftmost(cfs_rq
, &se
->run_node
);
169 rb_link_node(&se
->run_node
, parent
, link
);
170 rb_insert_color(&se
->run_node
, &cfs_rq
->tasks_timeline
);
171 update_load_add(&cfs_rq
->load
, se
->load
.weight
);
172 cfs_rq
->nr_running
++;
175 schedstat_add(cfs_rq
, wait_runtime
, se
->wait_runtime
);
179 __dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
181 if (cfs_rq
->rb_leftmost
== &se
->run_node
)
182 set_leftmost(cfs_rq
, rb_next(&se
->run_node
));
184 rb_erase(&se
->run_node
, &cfs_rq
->tasks_timeline
);
185 update_load_sub(&cfs_rq
->load
, se
->load
.weight
);
186 cfs_rq
->nr_running
--;
189 schedstat_add(cfs_rq
, wait_runtime
, -se
->wait_runtime
);
192 static inline struct rb_node
*first_fair(struct cfs_rq
*cfs_rq
)
194 return cfs_rq
->rb_leftmost
;
197 static struct sched_entity
*__pick_next_entity(struct cfs_rq
*cfs_rq
)
199 return rb_entry(first_fair(cfs_rq
), struct sched_entity
, run_node
);
202 /**************************************************************
203 * Scheduling class statistics methods:
206 static u64
__sched_period(unsigned long nr_running
)
208 u64 period
= sysctl_sched_latency
;
209 unsigned long nr_latency
=
210 sysctl_sched_latency
/ sysctl_sched_min_granularity
;
212 if (unlikely(nr_running
> nr_latency
)) {
213 period
*= nr_running
;
214 do_div(period
, nr_latency
);
220 static u64
sched_slice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
222 u64 period
= __sched_period(cfs_rq
->nr_running
);
224 period
*= se
->load
.weight
;
225 do_div(period
, cfs_rq
->load
.weight
);
231 limit_wait_runtime(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
233 long limit
= sysctl_sched_runtime_limit
;
236 * Niced tasks have the same history dynamic range as
239 if (unlikely(se
->wait_runtime
> limit
)) {
240 se
->wait_runtime
= limit
;
241 schedstat_inc(se
, wait_runtime_overruns
);
242 schedstat_inc(cfs_rq
, wait_runtime_overruns
);
244 if (unlikely(se
->wait_runtime
< -limit
)) {
245 se
->wait_runtime
= -limit
;
246 schedstat_inc(se
, wait_runtime_underruns
);
247 schedstat_inc(cfs_rq
, wait_runtime_underruns
);
252 __add_wait_runtime(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, long delta
)
254 se
->wait_runtime
+= delta
;
255 schedstat_add(se
, sum_wait_runtime
, delta
);
256 limit_wait_runtime(cfs_rq
, se
);
260 add_wait_runtime(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, long delta
)
262 schedstat_add(cfs_rq
, wait_runtime
, -se
->wait_runtime
);
263 __add_wait_runtime(cfs_rq
, se
, delta
);
264 schedstat_add(cfs_rq
, wait_runtime
, se
->wait_runtime
);
268 * Update the current task's runtime statistics. Skip current tasks that
269 * are not in our scheduling class.
272 __update_curr(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
,
273 unsigned long delta_exec
)
275 unsigned long delta
, delta_fair
, delta_mine
, delta_exec_weighted
;
276 struct load_weight
*lw
= &cfs_rq
->load
;
277 unsigned long load
= lw
->weight
;
279 schedstat_set(curr
->exec_max
, max((u64
)delta_exec
, curr
->exec_max
));
281 curr
->sum_exec_runtime
+= delta_exec
;
282 cfs_rq
->exec_clock
+= delta_exec
;
283 delta_exec_weighted
= delta_exec
;
284 if (unlikely(curr
->load
.weight
!= NICE_0_LOAD
)) {
285 delta_exec_weighted
= calc_delta_fair(delta_exec_weighted
,
288 curr
->vruntime
+= delta_exec_weighted
;
290 if (!sched_feat(FAIR_SLEEPERS
))
296 delta_fair
= calc_delta_fair(delta_exec
, lw
);
297 delta_mine
= calc_delta_mine(delta_exec
, curr
->load
.weight
, lw
);
299 if (cfs_rq
->sleeper_bonus
> sysctl_sched_min_granularity
) {
300 delta
= min((u64
)delta_mine
, cfs_rq
->sleeper_bonus
);
301 delta
= min(delta
, (unsigned long)(
302 (long)sysctl_sched_runtime_limit
- curr
->wait_runtime
));
303 cfs_rq
->sleeper_bonus
-= delta
;
307 cfs_rq
->fair_clock
+= delta_fair
;
309 * We executed delta_exec amount of time on the CPU,
310 * but we were only entitled to delta_mine amount of
311 * time during that period (if nr_running == 1 then
312 * the two values are equal)
313 * [Note: delta_mine - delta_exec is negative]:
315 add_wait_runtime(cfs_rq
, curr
, delta_mine
- delta_exec
);
318 static void update_curr(struct cfs_rq
*cfs_rq
)
320 struct sched_entity
*curr
= cfs_rq
->curr
;
321 u64 now
= rq_of(cfs_rq
)->clock
;
322 unsigned long delta_exec
;
328 * Get the amount of time the current task was running
329 * since the last time we changed load (this cannot
330 * overflow on 32 bits):
332 delta_exec
= (unsigned long)(now
- curr
->exec_start
);
334 __update_curr(cfs_rq
, curr
, delta_exec
);
335 curr
->exec_start
= now
;
339 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
341 se
->wait_start_fair
= cfs_rq
->fair_clock
;
342 schedstat_set(se
->wait_start
, rq_of(cfs_rq
)->clock
);
345 static inline unsigned long
346 calc_weighted(unsigned long delta
, struct sched_entity
*se
)
348 unsigned long weight
= se
->load
.weight
;
350 if (unlikely(weight
!= NICE_0_LOAD
))
351 return (u64
)delta
* se
->load
.weight
>> NICE_0_SHIFT
;
357 * Task is being enqueued - update stats:
359 static void update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
362 * Are we enqueueing a waiting task? (for current tasks
363 * a dequeue/enqueue event is a NOP)
365 if (se
!= cfs_rq
->curr
)
366 update_stats_wait_start(cfs_rq
, se
);
370 se
->fair_key
= se
->vruntime
;
374 * Note: must be called with a freshly updated rq->fair_clock.
377 __update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
,
378 unsigned long delta_fair
)
380 schedstat_set(se
->wait_max
, max(se
->wait_max
,
381 rq_of(cfs_rq
)->clock
- se
->wait_start
));
383 delta_fair
= calc_weighted(delta_fair
, se
);
385 add_wait_runtime(cfs_rq
, se
, delta_fair
);
389 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
391 unsigned long delta_fair
;
393 if (unlikely(!se
->wait_start_fair
))
396 delta_fair
= (unsigned long)min((u64
)(2*sysctl_sched_runtime_limit
),
397 (u64
)(cfs_rq
->fair_clock
- se
->wait_start_fair
));
399 __update_stats_wait_end(cfs_rq
, se
, delta_fair
);
401 se
->wait_start_fair
= 0;
402 schedstat_set(se
->wait_start
, 0);
406 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
410 * Mark the end of the wait period if dequeueing a
413 if (se
!= cfs_rq
->curr
)
414 update_stats_wait_end(cfs_rq
, se
);
418 * We are picking a new current task - update its stats:
421 update_stats_curr_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
424 * We are starting a new run period:
426 se
->exec_start
= rq_of(cfs_rq
)->clock
;
430 * We are descheduling a task - update its stats:
433 update_stats_curr_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
438 /**************************************************
439 * Scheduling class queueing methods:
442 static void __enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
,
443 unsigned long delta_fair
)
445 unsigned long load
= cfs_rq
->load
.weight
;
449 * Do not boost sleepers if there's too much bonus 'in flight'
452 if (unlikely(cfs_rq
->sleeper_bonus
> sysctl_sched_runtime_limit
))
455 if (sched_feat(SLEEPER_LOAD_AVG
))
456 load
= rq_of(cfs_rq
)->cpu_load
[2];
459 * Fix up delta_fair with the effect of us running
460 * during the whole sleep period:
462 if (sched_feat(SLEEPER_AVG
))
463 delta_fair
= div64_likely32((u64
)delta_fair
* load
,
464 load
+ se
->load
.weight
);
466 delta_fair
= calc_weighted(delta_fair
, se
);
468 prev_runtime
= se
->wait_runtime
;
469 __add_wait_runtime(cfs_rq
, se
, delta_fair
);
470 delta_fair
= se
->wait_runtime
- prev_runtime
;
473 * Track the amount of bonus we've given to sleepers:
475 cfs_rq
->sleeper_bonus
+= delta_fair
;
478 static void enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
480 struct task_struct
*tsk
= task_of(se
);
481 unsigned long delta_fair
;
483 if ((entity_is_task(se
) && tsk
->policy
== SCHED_BATCH
) ||
484 !sched_feat(FAIR_SLEEPERS
))
487 delta_fair
= (unsigned long)min((u64
)(2*sysctl_sched_runtime_limit
),
488 (u64
)(cfs_rq
->fair_clock
- se
->sleep_start_fair
));
490 __enqueue_sleeper(cfs_rq
, se
, delta_fair
);
492 se
->sleep_start_fair
= 0;
494 #ifdef CONFIG_SCHEDSTATS
495 if (se
->sleep_start
) {
496 u64 delta
= rq_of(cfs_rq
)->clock
- se
->sleep_start
;
501 if (unlikely(delta
> se
->sleep_max
))
502 se
->sleep_max
= delta
;
505 se
->sum_sleep_runtime
+= delta
;
507 if (se
->block_start
) {
508 u64 delta
= rq_of(cfs_rq
)->clock
- se
->block_start
;
513 if (unlikely(delta
> se
->block_max
))
514 se
->block_max
= delta
;
517 se
->sum_sleep_runtime
+= delta
;
520 * Blocking time is in units of nanosecs, so shift by 20 to
521 * get a milliseconds-range estimation of the amount of
522 * time that the task spent sleeping:
524 if (unlikely(prof_on
== SLEEP_PROFILING
)) {
525 profile_hits(SLEEP_PROFILING
, (void *)get_wchan(tsk
),
533 enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int wakeup
)
536 * Update the fair clock.
541 u64 min_runtime
, latency
;
543 min_runtime
= cfs_rq
->min_vruntime
;
544 min_runtime
+= sysctl_sched_latency
/2;
546 if (sched_feat(NEW_FAIR_SLEEPERS
)) {
547 latency
= calc_weighted(sysctl_sched_latency
, se
);
548 if (min_runtime
> latency
)
549 min_runtime
-= latency
;
552 se
->vruntime
= max(se
->vruntime
, min_runtime
);
554 enqueue_sleeper(cfs_rq
, se
);
557 update_stats_enqueue(cfs_rq
, se
);
558 __enqueue_entity(cfs_rq
, se
);
562 dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int sleep
)
564 update_stats_dequeue(cfs_rq
, se
);
566 se
->sleep_start_fair
= cfs_rq
->fair_clock
;
567 #ifdef CONFIG_SCHEDSTATS
568 if (entity_is_task(se
)) {
569 struct task_struct
*tsk
= task_of(se
);
571 if (tsk
->state
& TASK_INTERRUPTIBLE
)
572 se
->sleep_start
= rq_of(cfs_rq
)->clock
;
573 if (tsk
->state
& TASK_UNINTERRUPTIBLE
)
574 se
->block_start
= rq_of(cfs_rq
)->clock
;
578 __dequeue_entity(cfs_rq
, se
);
582 * Preempt the current task with a newly woken task if needed:
585 check_preempt_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
587 unsigned long ideal_runtime
, delta_exec
;
589 ideal_runtime
= sched_slice(cfs_rq
, curr
);
590 delta_exec
= curr
->sum_exec_runtime
- curr
->prev_sum_exec_runtime
;
591 if (delta_exec
> ideal_runtime
)
592 resched_task(rq_of(cfs_rq
)->curr
);
596 set_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
599 * Any task has to be enqueued before it get to execute on
600 * a CPU. So account for the time it spent waiting on the
601 * runqueue. (note, here we rely on pick_next_task() having
602 * done a put_prev_task_fair() shortly before this, which
603 * updated rq->fair_clock - used by update_stats_wait_end())
605 update_stats_wait_end(cfs_rq
, se
);
606 update_stats_curr_start(cfs_rq
, se
);
608 #ifdef CONFIG_SCHEDSTATS
610 * Track our maximum slice length, if the CPU's load is at
611 * least twice that of our own weight (i.e. dont track it
612 * when there are only lesser-weight tasks around):
614 if (rq_of(cfs_rq
)->ls
.load
.weight
>= 2*se
->load
.weight
) {
615 se
->slice_max
= max(se
->slice_max
,
616 se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
);
619 se
->prev_sum_exec_runtime
= se
->sum_exec_runtime
;
622 static struct sched_entity
*pick_next_entity(struct cfs_rq
*cfs_rq
)
624 struct sched_entity
*se
= __pick_next_entity(cfs_rq
);
626 set_next_entity(cfs_rq
, se
);
631 static void put_prev_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*prev
)
634 * If still on the runqueue then deactivate_task()
635 * was not called and update_curr() has to be done:
640 update_stats_curr_end(cfs_rq
, prev
);
643 update_stats_wait_start(cfs_rq
, prev
);
647 static void entity_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
650 * Dequeue and enqueue the task to update its
651 * position within the tree:
653 dequeue_entity(cfs_rq
, curr
, 0);
654 enqueue_entity(cfs_rq
, curr
, 0);
656 if (cfs_rq
->nr_running
> 1)
657 check_preempt_tick(cfs_rq
, curr
);
660 /**************************************************
661 * CFS operations on tasks:
664 #ifdef CONFIG_FAIR_GROUP_SCHED
666 /* Walk up scheduling entities hierarchy */
667 #define for_each_sched_entity(se) \
668 for (; se; se = se->parent)
670 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
675 /* runqueue on which this entity is (to be) queued */
676 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
681 /* runqueue "owned" by this group */
682 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
687 /* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on
688 * another cpu ('this_cpu')
690 static inline struct cfs_rq
*cpu_cfs_rq(struct cfs_rq
*cfs_rq
, int this_cpu
)
692 /* A later patch will take group into account */
693 return &cpu_rq(this_cpu
)->cfs
;
696 /* Iterate thr' all leaf cfs_rq's on a runqueue */
697 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
698 list_for_each_entry(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
700 /* Do the two (enqueued) tasks belong to the same group ? */
701 static inline int is_same_group(struct task_struct
*curr
, struct task_struct
*p
)
703 if (curr
->se
.cfs_rq
== p
->se
.cfs_rq
)
709 #else /* CONFIG_FAIR_GROUP_SCHED */
711 #define for_each_sched_entity(se) \
712 for (; se; se = NULL)
714 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
716 return &task_rq(p
)->cfs
;
719 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
721 struct task_struct
*p
= task_of(se
);
722 struct rq
*rq
= task_rq(p
);
727 /* runqueue "owned" by this group */
728 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
733 static inline struct cfs_rq
*cpu_cfs_rq(struct cfs_rq
*cfs_rq
, int this_cpu
)
735 return &cpu_rq(this_cpu
)->cfs
;
738 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
739 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
741 static inline int is_same_group(struct task_struct
*curr
, struct task_struct
*p
)
746 #endif /* CONFIG_FAIR_GROUP_SCHED */
749 * The enqueue_task method is called before nr_running is
750 * increased. Here we update the fair scheduling stats and
751 * then put the task into the rbtree:
753 static void enqueue_task_fair(struct rq
*rq
, struct task_struct
*p
, int wakeup
)
755 struct cfs_rq
*cfs_rq
;
756 struct sched_entity
*se
= &p
->se
;
758 for_each_sched_entity(se
) {
761 cfs_rq
= cfs_rq_of(se
);
762 enqueue_entity(cfs_rq
, se
, wakeup
);
767 * The dequeue_task method is called before nr_running is
768 * decreased. We remove the task from the rbtree and
769 * update the fair scheduling stats:
771 static void dequeue_task_fair(struct rq
*rq
, struct task_struct
*p
, int sleep
)
773 struct cfs_rq
*cfs_rq
;
774 struct sched_entity
*se
= &p
->se
;
776 for_each_sched_entity(se
) {
777 cfs_rq
= cfs_rq_of(se
);
778 dequeue_entity(cfs_rq
, se
, sleep
);
779 /* Don't dequeue parent if it has other entities besides us */
780 if (cfs_rq
->load
.weight
)
786 * sched_yield() support is very simple - we dequeue and enqueue.
788 * If compat_yield is turned on then we requeue to the end of the tree.
790 static void yield_task_fair(struct rq
*rq
, struct task_struct
*p
)
792 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
793 struct rb_node
**link
= &cfs_rq
->tasks_timeline
.rb_node
;
794 struct sched_entity
*rightmost
, *se
= &p
->se
;
795 struct rb_node
*parent
;
798 * Are we the only task in the tree?
800 if (unlikely(cfs_rq
->nr_running
== 1))
803 if (likely(!sysctl_sched_compat_yield
)) {
804 __update_rq_clock(rq
);
806 * Dequeue and enqueue the task to update its
807 * position within the tree:
809 dequeue_entity(cfs_rq
, &p
->se
, 0);
810 enqueue_entity(cfs_rq
, &p
->se
, 0);
815 * Find the rightmost entry in the rbtree:
819 link
= &parent
->rb_right
;
822 rightmost
= rb_entry(parent
, struct sched_entity
, run_node
);
824 * Already in the rightmost position?
826 if (unlikely(rightmost
== se
))
830 * Minimally necessary key value to be last in the tree:
832 se
->fair_key
= rightmost
->fair_key
+ 1;
834 if (cfs_rq
->rb_leftmost
== &se
->run_node
)
835 cfs_rq
->rb_leftmost
= rb_next(&se
->run_node
);
837 * Relink the task to the rightmost position:
839 rb_erase(&se
->run_node
, &cfs_rq
->tasks_timeline
);
840 rb_link_node(&se
->run_node
, parent
, link
);
841 rb_insert_color(&se
->run_node
, &cfs_rq
->tasks_timeline
);
845 * Preempt the current task with a newly woken task if needed:
847 static void check_preempt_wakeup(struct rq
*rq
, struct task_struct
*p
)
849 struct task_struct
*curr
= rq
->curr
;
850 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
852 if (unlikely(rt_prio(p
->prio
))) {
858 if (is_same_group(curr
, p
)) {
859 s64 delta
= curr
->se
.vruntime
- p
->se
.vruntime
;
861 if (delta
> (s64
)sysctl_sched_wakeup_granularity
)
866 static struct task_struct
*pick_next_task_fair(struct rq
*rq
)
868 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
869 struct sched_entity
*se
;
871 if (unlikely(!cfs_rq
->nr_running
))
875 se
= pick_next_entity(cfs_rq
);
876 cfs_rq
= group_cfs_rq(se
);
883 * Account for a descheduled task:
885 static void put_prev_task_fair(struct rq
*rq
, struct task_struct
*prev
)
887 struct sched_entity
*se
= &prev
->se
;
888 struct cfs_rq
*cfs_rq
;
890 for_each_sched_entity(se
) {
891 cfs_rq
= cfs_rq_of(se
);
892 put_prev_entity(cfs_rq
, se
);
896 /**************************************************
897 * Fair scheduling class load-balancing methods:
901 * Load-balancing iterator. Note: while the runqueue stays locked
902 * during the whole iteration, the current task might be
903 * dequeued so the iterator has to be dequeue-safe. Here we
904 * achieve that by always pre-iterating before returning
907 static inline struct task_struct
*
908 __load_balance_iterator(struct cfs_rq
*cfs_rq
, struct rb_node
*curr
)
910 struct task_struct
*p
;
915 p
= rb_entry(curr
, struct task_struct
, se
.run_node
);
916 cfs_rq
->rb_load_balance_curr
= rb_next(curr
);
921 static struct task_struct
*load_balance_start_fair(void *arg
)
923 struct cfs_rq
*cfs_rq
= arg
;
925 return __load_balance_iterator(cfs_rq
, first_fair(cfs_rq
));
928 static struct task_struct
*load_balance_next_fair(void *arg
)
930 struct cfs_rq
*cfs_rq
= arg
;
932 return __load_balance_iterator(cfs_rq
, cfs_rq
->rb_load_balance_curr
);
935 #ifdef CONFIG_FAIR_GROUP_SCHED
936 static int cfs_rq_best_prio(struct cfs_rq
*cfs_rq
)
938 struct sched_entity
*curr
;
939 struct task_struct
*p
;
941 if (!cfs_rq
->nr_running
)
944 curr
= __pick_next_entity(cfs_rq
);
952 load_balance_fair(struct rq
*this_rq
, int this_cpu
, struct rq
*busiest
,
953 unsigned long max_nr_move
, unsigned long max_load_move
,
954 struct sched_domain
*sd
, enum cpu_idle_type idle
,
955 int *all_pinned
, int *this_best_prio
)
957 struct cfs_rq
*busy_cfs_rq
;
958 unsigned long load_moved
, total_nr_moved
= 0, nr_moved
;
959 long rem_load_move
= max_load_move
;
960 struct rq_iterator cfs_rq_iterator
;
962 cfs_rq_iterator
.start
= load_balance_start_fair
;
963 cfs_rq_iterator
.next
= load_balance_next_fair
;
965 for_each_leaf_cfs_rq(busiest
, busy_cfs_rq
) {
966 #ifdef CONFIG_FAIR_GROUP_SCHED
967 struct cfs_rq
*this_cfs_rq
;
969 unsigned long maxload
;
971 this_cfs_rq
= cpu_cfs_rq(busy_cfs_rq
, this_cpu
);
973 imbalance
= busy_cfs_rq
->load
.weight
- this_cfs_rq
->load
.weight
;
974 /* Don't pull if this_cfs_rq has more load than busy_cfs_rq */
978 /* Don't pull more than imbalance/2 */
980 maxload
= min(rem_load_move
, imbalance
);
982 *this_best_prio
= cfs_rq_best_prio(this_cfs_rq
);
984 # define maxload rem_load_move
986 /* pass busy_cfs_rq argument into
987 * load_balance_[start|next]_fair iterators
989 cfs_rq_iterator
.arg
= busy_cfs_rq
;
990 nr_moved
= balance_tasks(this_rq
, this_cpu
, busiest
,
991 max_nr_move
, maxload
, sd
, idle
, all_pinned
,
992 &load_moved
, this_best_prio
, &cfs_rq_iterator
);
994 total_nr_moved
+= nr_moved
;
995 max_nr_move
-= nr_moved
;
996 rem_load_move
-= load_moved
;
998 if (max_nr_move
<= 0 || rem_load_move
<= 0)
1002 return max_load_move
- rem_load_move
;
1006 * scheduler tick hitting a task of our scheduling class:
1008 static void task_tick_fair(struct rq
*rq
, struct task_struct
*curr
)
1010 struct cfs_rq
*cfs_rq
;
1011 struct sched_entity
*se
= &curr
->se
;
1013 for_each_sched_entity(se
) {
1014 cfs_rq
= cfs_rq_of(se
);
1015 entity_tick(cfs_rq
, se
);
1019 #define swap(a,b) do { typeof(a) tmp = (a); (a) = (b); (b) = tmp; } while (0)
1022 * Share the fairness runtime between parent and child, thus the
1023 * total amount of pressure for CPU stays equal - new tasks
1024 * get a chance to run but frequent forkers are not allowed to
1025 * monopolize the CPU. Note: the parent runqueue is locked,
1026 * the child is not running yet.
1028 static void task_new_fair(struct rq
*rq
, struct task_struct
*p
)
1030 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
1031 struct sched_entity
*se
= &p
->se
, *curr
= cfs_rq
->curr
;
1033 sched_info_queued(p
);
1035 update_curr(cfs_rq
);
1036 se
->vruntime
= cfs_rq
->min_vruntime
;
1037 update_stats_enqueue(cfs_rq
, se
);
1040 * The first wait is dominated by the child-runs-first logic,
1041 * so do not credit it with that waiting time yet:
1043 if (sched_feat(SKIP_INITIAL
))
1044 se
->wait_start_fair
= 0;
1047 * The statistical average of wait_runtime is about
1048 * -granularity/2, so initialize the task with that:
1050 if (sched_feat(START_DEBIT
))
1051 se
->wait_runtime
= -(__sched_period(cfs_rq
->nr_running
+1) / 2);
1053 if (sysctl_sched_child_runs_first
&&
1054 curr
->vruntime
< se
->vruntime
) {
1056 dequeue_entity(cfs_rq
, curr
, 0);
1057 swap(curr
->vruntime
, se
->vruntime
);
1058 enqueue_entity(cfs_rq
, curr
, 0);
1061 update_stats_enqueue(cfs_rq
, se
);
1062 __enqueue_entity(cfs_rq
, se
);
1063 resched_task(rq
->curr
);
1066 #ifdef CONFIG_FAIR_GROUP_SCHED
1067 /* Account for a task changing its policy or group.
1069 * This routine is mostly called to set cfs_rq->curr field when a task
1070 * migrates between groups/classes.
1072 static void set_curr_task_fair(struct rq
*rq
)
1074 struct sched_entity
*se
= &rq
->curr
->se
;
1076 for_each_sched_entity(se
)
1077 set_next_entity(cfs_rq_of(se
), se
);
1080 static void set_curr_task_fair(struct rq
*rq
)
1086 * All the scheduling class methods:
1088 struct sched_class fair_sched_class __read_mostly
= {
1089 .enqueue_task
= enqueue_task_fair
,
1090 .dequeue_task
= dequeue_task_fair
,
1091 .yield_task
= yield_task_fair
,
1093 .check_preempt_curr
= check_preempt_wakeup
,
1095 .pick_next_task
= pick_next_task_fair
,
1096 .put_prev_task
= put_prev_task_fair
,
1098 .load_balance
= load_balance_fair
,
1100 .set_curr_task
= set_curr_task_fair
,
1101 .task_tick
= task_tick_fair
,
1102 .task_new
= task_new_fair
,
1105 #ifdef CONFIG_SCHED_DEBUG
1106 static void print_cfs_stats(struct seq_file
*m
, int cpu
)
1108 struct cfs_rq
*cfs_rq
;
1110 for_each_leaf_cfs_rq(cpu_rq(cpu
), cfs_rq
)
1111 print_cfs_rq(m
, cpu
, cfs_rq
);