2 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
4 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
6 * Interactivity improvements by Mike Galbraith
7 * (C) 2007 Mike Galbraith <efault@gmx.de>
9 * Various enhancements by Dmitry Adamushko.
10 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
12 * Group scheduling enhancements by Srivatsa Vaddagiri
13 * Copyright IBM Corporation, 2007
14 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
16 * Scaled math optimizations by Thomas Gleixner
17 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
21 * Preemption granularity:
22 * (default: 10 msec, units: nanoseconds)
24 * NOTE: this granularity value is not the same as the concept of
25 * 'timeslice length' - timeslices in CFS will typically be somewhat
26 * larger than this value. (to see the precise effective timeslice
27 * length of your workload, run vmstat and monitor the context-switches
30 * On SMP systems the value of this is multiplied by the log2 of the
31 * number of CPUs. (i.e. factor 2x on 2-way systems, 3x on 4-way
32 * systems, 4x on 8-way systems, 5x on 16-way systems, etc.)
34 unsigned int sysctl_sched_granularity __read_mostly
= 10000000UL;
37 * SCHED_BATCH wake-up granularity.
38 * (default: 25 msec, units: nanoseconds)
40 * This option delays the preemption effects of decoupled workloads
41 * and reduces their over-scheduling. Synchronous workloads will still
42 * have immediate wakeup/sleep latencies.
44 unsigned int sysctl_sched_batch_wakeup_granularity __read_mostly
= 25000000UL;
47 * SCHED_OTHER wake-up granularity.
48 * (default: 1 msec, units: nanoseconds)
50 * This option delays the preemption effects of decoupled workloads
51 * and reduces their over-scheduling. Synchronous workloads will still
52 * have immediate wakeup/sleep latencies.
54 unsigned int sysctl_sched_wakeup_granularity __read_mostly
= 1000000UL;
56 unsigned int sysctl_sched_stat_granularity __read_mostly
;
59 * Initialized in sched_init_granularity() [to 5 times the base granularity]:
61 unsigned int sysctl_sched_runtime_limit __read_mostly
;
64 * Debugging: various feature bits
67 SCHED_FEAT_FAIR_SLEEPERS
= 1,
68 SCHED_FEAT_SLEEPER_AVG
= 2,
69 SCHED_FEAT_SLEEPER_LOAD_AVG
= 4,
70 SCHED_FEAT_PRECISE_CPU_LOAD
= 8,
71 SCHED_FEAT_START_DEBIT
= 16,
72 SCHED_FEAT_SKIP_INITIAL
= 32,
75 unsigned int sysctl_sched_features __read_mostly
=
76 SCHED_FEAT_FAIR_SLEEPERS
*1 |
77 SCHED_FEAT_SLEEPER_AVG
*0 |
78 SCHED_FEAT_SLEEPER_LOAD_AVG
*1 |
79 SCHED_FEAT_PRECISE_CPU_LOAD
*1 |
80 SCHED_FEAT_START_DEBIT
*1 |
81 SCHED_FEAT_SKIP_INITIAL
*0;
83 extern struct sched_class fair_sched_class
;
85 /**************************************************************
86 * CFS operations on generic schedulable entities:
89 #ifdef CONFIG_FAIR_GROUP_SCHED
91 /* cpu runqueue to which this cfs_rq is attached */
92 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
97 /* currently running entity (if any) on this cfs_rq */
98 static inline struct sched_entity
*cfs_rq_curr(struct cfs_rq
*cfs_rq
)
103 /* An entity is a task if it doesn't "own" a runqueue */
104 #define entity_is_task(se) (!se->my_q)
107 set_cfs_rq_curr(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
112 #else /* CONFIG_FAIR_GROUP_SCHED */
114 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
116 return container_of(cfs_rq
, struct rq
, cfs
);
119 static inline struct sched_entity
*cfs_rq_curr(struct cfs_rq
*cfs_rq
)
121 struct rq
*rq
= rq_of(cfs_rq
);
123 if (unlikely(rq
->curr
->sched_class
!= &fair_sched_class
))
126 return &rq
->curr
->se
;
129 #define entity_is_task(se) 1
132 set_cfs_rq_curr(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) { }
134 #endif /* CONFIG_FAIR_GROUP_SCHED */
136 static inline struct task_struct
*task_of(struct sched_entity
*se
)
138 return container_of(se
, struct task_struct
, se
);
142 /**************************************************************
143 * Scheduling class tree data structure manipulation methods:
147 * Enqueue an entity into the rb-tree:
150 __enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
152 struct rb_node
**link
= &cfs_rq
->tasks_timeline
.rb_node
;
153 struct rb_node
*parent
= NULL
;
154 struct sched_entity
*entry
;
155 s64 key
= se
->fair_key
;
159 * Find the right place in the rbtree:
163 entry
= rb_entry(parent
, struct sched_entity
, run_node
);
165 * We dont care about collisions. Nodes with
166 * the same key stay together.
168 if (key
- entry
->fair_key
< 0) {
169 link
= &parent
->rb_left
;
171 link
= &parent
->rb_right
;
177 * Maintain a cache of leftmost tree entries (it is frequently
181 cfs_rq
->rb_leftmost
= &se
->run_node
;
183 rb_link_node(&se
->run_node
, parent
, link
);
184 rb_insert_color(&se
->run_node
, &cfs_rq
->tasks_timeline
);
185 update_load_add(&cfs_rq
->load
, se
->load
.weight
);
186 cfs_rq
->nr_running
++;
191 __dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
193 if (cfs_rq
->rb_leftmost
== &se
->run_node
)
194 cfs_rq
->rb_leftmost
= rb_next(&se
->run_node
);
195 rb_erase(&se
->run_node
, &cfs_rq
->tasks_timeline
);
196 update_load_sub(&cfs_rq
->load
, se
->load
.weight
);
197 cfs_rq
->nr_running
--;
201 static inline struct rb_node
*first_fair(struct cfs_rq
*cfs_rq
)
203 return cfs_rq
->rb_leftmost
;
206 static struct sched_entity
*__pick_next_entity(struct cfs_rq
*cfs_rq
)
208 return rb_entry(first_fair(cfs_rq
), struct sched_entity
, run_node
);
211 /**************************************************************
212 * Scheduling class statistics methods:
216 * We rescale the rescheduling granularity of tasks according to their
217 * nice level, but only linearly, not exponentially:
220 niced_granularity(struct sched_entity
*curr
, unsigned long granularity
)
224 if (likely(curr
->load
.weight
== NICE_0_LOAD
))
227 * Positive nice levels get the same granularity as nice-0:
229 if (likely(curr
->load
.weight
< NICE_0_LOAD
)) {
230 tmp
= curr
->load
.weight
* (u64
)granularity
;
231 return (long) (tmp
>> NICE_0_SHIFT
);
234 * Negative nice level tasks get linearly finer
237 tmp
= curr
->load
.inv_weight
* (u64
)granularity
;
240 * It will always fit into 'long':
242 return (long) (tmp
>> WMULT_SHIFT
);
246 limit_wait_runtime(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
248 long limit
= sysctl_sched_runtime_limit
;
251 * Niced tasks have the same history dynamic range as
254 if (unlikely(se
->wait_runtime
> limit
)) {
255 se
->wait_runtime
= limit
;
256 schedstat_inc(se
, wait_runtime_overruns
);
257 schedstat_inc(cfs_rq
, wait_runtime_overruns
);
259 if (unlikely(se
->wait_runtime
< -limit
)) {
260 se
->wait_runtime
= -limit
;
261 schedstat_inc(se
, wait_runtime_underruns
);
262 schedstat_inc(cfs_rq
, wait_runtime_underruns
);
267 __add_wait_runtime(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, long delta
)
269 se
->wait_runtime
+= delta
;
270 schedstat_add(se
, sum_wait_runtime
, delta
);
271 limit_wait_runtime(cfs_rq
, se
);
275 add_wait_runtime(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, long delta
)
277 schedstat_add(cfs_rq
, wait_runtime
, -se
->wait_runtime
);
278 __add_wait_runtime(cfs_rq
, se
, delta
);
279 schedstat_add(cfs_rq
, wait_runtime
, se
->wait_runtime
);
283 * Update the current task's runtime statistics. Skip current tasks that
284 * are not in our scheduling class.
287 __update_curr(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
289 unsigned long delta
, delta_exec
, delta_fair
, delta_mine
;
290 struct load_weight
*lw
= &cfs_rq
->load
;
291 unsigned long load
= lw
->weight
;
293 delta_exec
= curr
->delta_exec
;
294 schedstat_set(curr
->exec_max
, max((u64
)delta_exec
, curr
->exec_max
));
296 curr
->sum_exec_runtime
+= delta_exec
;
297 cfs_rq
->exec_clock
+= delta_exec
;
302 delta_fair
= calc_delta_fair(delta_exec
, lw
);
303 delta_mine
= calc_delta_mine(delta_exec
, curr
->load
.weight
, lw
);
305 if (cfs_rq
->sleeper_bonus
> sysctl_sched_granularity
) {
306 delta
= calc_delta_mine(delta_exec
, curr
->load
.weight
, lw
);
307 delta
= min((u64
)delta
, cfs_rq
->sleeper_bonus
);
308 delta
= min(delta
, (unsigned long)(
309 (long)sysctl_sched_runtime_limit
- curr
->wait_runtime
));
310 cfs_rq
->sleeper_bonus
-= delta
;
314 cfs_rq
->fair_clock
+= delta_fair
;
316 * We executed delta_exec amount of time on the CPU,
317 * but we were only entitled to delta_mine amount of
318 * time during that period (if nr_running == 1 then
319 * the two values are equal)
320 * [Note: delta_mine - delta_exec is negative]:
322 add_wait_runtime(cfs_rq
, curr
, delta_mine
- delta_exec
);
325 static void update_curr(struct cfs_rq
*cfs_rq
)
327 struct sched_entity
*curr
= cfs_rq_curr(cfs_rq
);
328 unsigned long delta_exec
;
334 * Get the amount of time the current task was running
335 * since the last time we changed load (this cannot
336 * overflow on 32 bits):
338 delta_exec
= (unsigned long)(rq_of(cfs_rq
)->clock
- curr
->exec_start
);
340 curr
->delta_exec
+= delta_exec
;
342 if (unlikely(curr
->delta_exec
> sysctl_sched_stat_granularity
)) {
343 __update_curr(cfs_rq
, curr
);
344 curr
->delta_exec
= 0;
346 curr
->exec_start
= rq_of(cfs_rq
)->clock
;
350 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
352 se
->wait_start_fair
= cfs_rq
->fair_clock
;
353 schedstat_set(se
->wait_start
, rq_of(cfs_rq
)->clock
);
357 * We calculate fair deltas here, so protect against the random effects
358 * of a multiplication overflow by capping it to the runtime limit:
360 #if BITS_PER_LONG == 32
361 static inline unsigned long
362 calc_weighted(unsigned long delta
, unsigned long weight
, int shift
)
364 u64 tmp
= (u64
)delta
* weight
>> shift
;
366 if (unlikely(tmp
> sysctl_sched_runtime_limit
*2))
367 return sysctl_sched_runtime_limit
*2;
371 static inline unsigned long
372 calc_weighted(unsigned long delta
, unsigned long weight
, int shift
)
374 return delta
* weight
>> shift
;
379 * Task is being enqueued - update stats:
381 static void update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
386 * Are we enqueueing a waiting task? (for current tasks
387 * a dequeue/enqueue event is a NOP)
389 if (se
!= cfs_rq_curr(cfs_rq
))
390 update_stats_wait_start(cfs_rq
, se
);
394 key
= cfs_rq
->fair_clock
;
397 * Optimize the common nice 0 case:
399 if (likely(se
->load
.weight
== NICE_0_LOAD
)) {
400 key
-= se
->wait_runtime
;
404 if (se
->wait_runtime
< 0) {
405 tmp
= -se
->wait_runtime
;
406 key
+= (tmp
* se
->load
.inv_weight
) >>
407 (WMULT_SHIFT
- NICE_0_SHIFT
);
409 tmp
= se
->wait_runtime
;
410 key
-= (tmp
* se
->load
.inv_weight
) >>
411 (WMULT_SHIFT
- NICE_0_SHIFT
);
419 * Note: must be called with a freshly updated rq->fair_clock.
422 __update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
424 unsigned long delta_fair
= se
->delta_fair_run
;
426 schedstat_set(se
->wait_max
, max(se
->wait_max
,
427 rq_of(cfs_rq
)->clock
- se
->wait_start
));
429 if (unlikely(se
->load
.weight
!= NICE_0_LOAD
))
430 delta_fair
= calc_weighted(delta_fair
, se
->load
.weight
,
433 add_wait_runtime(cfs_rq
, se
, delta_fair
);
437 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
439 unsigned long delta_fair
;
441 delta_fair
= (unsigned long)min((u64
)(2*sysctl_sched_runtime_limit
),
442 (u64
)(cfs_rq
->fair_clock
- se
->wait_start_fair
));
444 se
->delta_fair_run
+= delta_fair
;
445 if (unlikely(abs(se
->delta_fair_run
) >=
446 sysctl_sched_stat_granularity
)) {
447 __update_stats_wait_end(cfs_rq
, se
);
448 se
->delta_fair_run
= 0;
451 se
->wait_start_fair
= 0;
452 schedstat_set(se
->wait_start
, 0);
456 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
460 * Mark the end of the wait period if dequeueing a
463 if (se
!= cfs_rq_curr(cfs_rq
))
464 update_stats_wait_end(cfs_rq
, se
);
468 * We are picking a new current task - update its stats:
471 update_stats_curr_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
474 * We are starting a new run period:
476 se
->exec_start
= rq_of(cfs_rq
)->clock
;
480 * We are descheduling a task - update its stats:
483 update_stats_curr_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
488 /**************************************************
489 * Scheduling class queueing methods:
492 static void __enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
494 unsigned long load
= cfs_rq
->load
.weight
, delta_fair
;
498 * Do not boost sleepers if there's too much bonus 'in flight'
501 if (unlikely(cfs_rq
->sleeper_bonus
> sysctl_sched_runtime_limit
))
504 if (sysctl_sched_features
& SCHED_FEAT_SLEEPER_LOAD_AVG
)
505 load
= rq_of(cfs_rq
)->cpu_load
[2];
507 delta_fair
= se
->delta_fair_sleep
;
510 * Fix up delta_fair with the effect of us running
511 * during the whole sleep period:
513 if (sysctl_sched_features
& SCHED_FEAT_SLEEPER_AVG
)
514 delta_fair
= div64_likely32((u64
)delta_fair
* load
,
515 load
+ se
->load
.weight
);
517 if (unlikely(se
->load
.weight
!= NICE_0_LOAD
))
518 delta_fair
= calc_weighted(delta_fair
, se
->load
.weight
,
521 prev_runtime
= se
->wait_runtime
;
522 __add_wait_runtime(cfs_rq
, se
, delta_fair
);
523 schedstat_add(cfs_rq
, wait_runtime
, se
->wait_runtime
);
524 delta_fair
= se
->wait_runtime
- prev_runtime
;
527 * Track the amount of bonus we've given to sleepers:
529 cfs_rq
->sleeper_bonus
+= delta_fair
;
532 static void enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
534 struct task_struct
*tsk
= task_of(se
);
535 unsigned long delta_fair
;
537 if ((entity_is_task(se
) && tsk
->policy
== SCHED_BATCH
) ||
538 !(sysctl_sched_features
& SCHED_FEAT_FAIR_SLEEPERS
))
541 delta_fair
= (unsigned long)min((u64
)(2*sysctl_sched_runtime_limit
),
542 (u64
)(cfs_rq
->fair_clock
- se
->sleep_start_fair
));
544 se
->delta_fair_sleep
+= delta_fair
;
545 if (unlikely(abs(se
->delta_fair_sleep
) >=
546 sysctl_sched_stat_granularity
)) {
547 __enqueue_sleeper(cfs_rq
, se
);
548 se
->delta_fair_sleep
= 0;
551 se
->sleep_start_fair
= 0;
553 #ifdef CONFIG_SCHEDSTATS
554 if (se
->sleep_start
) {
555 u64 delta
= rq_of(cfs_rq
)->clock
- se
->sleep_start
;
560 if (unlikely(delta
> se
->sleep_max
))
561 se
->sleep_max
= delta
;
564 se
->sum_sleep_runtime
+= delta
;
566 if (se
->block_start
) {
567 u64 delta
= rq_of(cfs_rq
)->clock
- se
->block_start
;
572 if (unlikely(delta
> se
->block_max
))
573 se
->block_max
= delta
;
576 se
->sum_sleep_runtime
+= delta
;
582 enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int wakeup
)
585 * Update the fair clock.
590 enqueue_sleeper(cfs_rq
, se
);
592 update_stats_enqueue(cfs_rq
, se
);
593 __enqueue_entity(cfs_rq
, se
);
597 dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int sleep
)
599 update_stats_dequeue(cfs_rq
, se
);
601 se
->sleep_start_fair
= cfs_rq
->fair_clock
;
602 #ifdef CONFIG_SCHEDSTATS
603 if (entity_is_task(se
)) {
604 struct task_struct
*tsk
= task_of(se
);
606 if (tsk
->state
& TASK_INTERRUPTIBLE
)
607 se
->sleep_start
= rq_of(cfs_rq
)->clock
;
608 if (tsk
->state
& TASK_UNINTERRUPTIBLE
)
609 se
->block_start
= rq_of(cfs_rq
)->clock
;
611 cfs_rq
->wait_runtime
-= se
->wait_runtime
;
614 __dequeue_entity(cfs_rq
, se
);
618 * Preempt the current task with a newly woken task if needed:
621 __check_preempt_curr_fair(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
,
622 struct sched_entity
*curr
, unsigned long granularity
)
624 s64 __delta
= curr
->fair_key
- se
->fair_key
;
627 * Take scheduling granularity into account - do not
628 * preempt the current task unless the best task has
629 * a larger than sched_granularity fairness advantage:
631 if (__delta
> niced_granularity(curr
, granularity
))
632 resched_task(rq_of(cfs_rq
)->curr
);
636 set_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
639 * Any task has to be enqueued before it get to execute on
640 * a CPU. So account for the time it spent waiting on the
641 * runqueue. (note, here we rely on pick_next_task() having
642 * done a put_prev_task_fair() shortly before this, which
643 * updated rq->fair_clock - used by update_stats_wait_end())
645 update_stats_wait_end(cfs_rq
, se
);
646 update_stats_curr_start(cfs_rq
, se
);
647 set_cfs_rq_curr(cfs_rq
, se
);
650 static struct sched_entity
*pick_next_entity(struct cfs_rq
*cfs_rq
)
652 struct sched_entity
*se
= __pick_next_entity(cfs_rq
);
654 set_next_entity(cfs_rq
, se
);
659 static void put_prev_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*prev
)
662 * If still on the runqueue then deactivate_task()
663 * was not called and update_curr() has to be done:
668 update_stats_curr_end(cfs_rq
, prev
);
671 update_stats_wait_start(cfs_rq
, prev
);
672 set_cfs_rq_curr(cfs_rq
, NULL
);
675 static void entity_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
677 struct sched_entity
*next
;
680 * Dequeue and enqueue the task to update its
681 * position within the tree:
683 dequeue_entity(cfs_rq
, curr
, 0);
684 enqueue_entity(cfs_rq
, curr
, 0);
687 * Reschedule if another task tops the current one.
689 next
= __pick_next_entity(cfs_rq
);
693 __check_preempt_curr_fair(cfs_rq
, next
, curr
, sysctl_sched_granularity
);
696 /**************************************************
697 * CFS operations on tasks:
700 #ifdef CONFIG_FAIR_GROUP_SCHED
702 /* Walk up scheduling entities hierarchy */
703 #define for_each_sched_entity(se) \
704 for (; se; se = se->parent)
706 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
711 /* runqueue on which this entity is (to be) queued */
712 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
717 /* runqueue "owned" by this group */
718 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
723 /* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on
724 * another cpu ('this_cpu')
726 static inline struct cfs_rq
*cpu_cfs_rq(struct cfs_rq
*cfs_rq
, int this_cpu
)
728 /* A later patch will take group into account */
729 return &cpu_rq(this_cpu
)->cfs
;
732 /* Iterate thr' all leaf cfs_rq's on a runqueue */
733 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
734 list_for_each_entry(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
736 /* Do the two (enqueued) tasks belong to the same group ? */
737 static inline int is_same_group(struct task_struct
*curr
, struct task_struct
*p
)
739 if (curr
->se
.cfs_rq
== p
->se
.cfs_rq
)
745 #else /* CONFIG_FAIR_GROUP_SCHED */
747 #define for_each_sched_entity(se) \
748 for (; se; se = NULL)
750 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
752 return &task_rq(p
)->cfs
;
755 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
757 struct task_struct
*p
= task_of(se
);
758 struct rq
*rq
= task_rq(p
);
763 /* runqueue "owned" by this group */
764 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
769 static inline struct cfs_rq
*cpu_cfs_rq(struct cfs_rq
*cfs_rq
, int this_cpu
)
771 return &cpu_rq(this_cpu
)->cfs
;
774 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
775 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
777 static inline int is_same_group(struct task_struct
*curr
, struct task_struct
*p
)
782 #endif /* CONFIG_FAIR_GROUP_SCHED */
785 * The enqueue_task method is called before nr_running is
786 * increased. Here we update the fair scheduling stats and
787 * then put the task into the rbtree:
789 static void enqueue_task_fair(struct rq
*rq
, struct task_struct
*p
, int wakeup
)
791 struct cfs_rq
*cfs_rq
;
792 struct sched_entity
*se
= &p
->se
;
794 for_each_sched_entity(se
) {
797 cfs_rq
= cfs_rq_of(se
);
798 enqueue_entity(cfs_rq
, se
, wakeup
);
803 * The dequeue_task method is called before nr_running is
804 * decreased. We remove the task from the rbtree and
805 * update the fair scheduling stats:
807 static void dequeue_task_fair(struct rq
*rq
, struct task_struct
*p
, int sleep
)
809 struct cfs_rq
*cfs_rq
;
810 struct sched_entity
*se
= &p
->se
;
812 for_each_sched_entity(se
) {
813 cfs_rq
= cfs_rq_of(se
);
814 dequeue_entity(cfs_rq
, se
, sleep
);
815 /* Don't dequeue parent if it has other entities besides us */
816 if (cfs_rq
->load
.weight
)
822 * sched_yield() support is very simple - we dequeue and enqueue
824 static void yield_task_fair(struct rq
*rq
, struct task_struct
*p
)
826 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
828 __update_rq_clock(rq
);
830 * Dequeue and enqueue the task to update its
831 * position within the tree:
833 dequeue_entity(cfs_rq
, &p
->se
, 0);
834 enqueue_entity(cfs_rq
, &p
->se
, 0);
838 * Preempt the current task with a newly woken task if needed:
840 static void check_preempt_curr_fair(struct rq
*rq
, struct task_struct
*p
)
842 struct task_struct
*curr
= rq
->curr
;
843 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
846 if (unlikely(rt_prio(p
->prio
))) {
853 gran
= sysctl_sched_wakeup_granularity
;
855 * Batch tasks prefer throughput over latency:
857 if (unlikely(p
->policy
== SCHED_BATCH
))
858 gran
= sysctl_sched_batch_wakeup_granularity
;
860 if (is_same_group(curr
, p
))
861 __check_preempt_curr_fair(cfs_rq
, &p
->se
, &curr
->se
, gran
);
864 static struct task_struct
*pick_next_task_fair(struct rq
*rq
)
866 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
867 struct sched_entity
*se
;
869 if (unlikely(!cfs_rq
->nr_running
))
873 se
= pick_next_entity(cfs_rq
);
874 cfs_rq
= group_cfs_rq(se
);
881 * Account for a descheduled task:
883 static void put_prev_task_fair(struct rq
*rq
, struct task_struct
*prev
)
885 struct sched_entity
*se
= &prev
->se
;
886 struct cfs_rq
*cfs_rq
;
888 for_each_sched_entity(se
) {
889 cfs_rq
= cfs_rq_of(se
);
890 put_prev_entity(cfs_rq
, se
);
894 /**************************************************
895 * Fair scheduling class load-balancing methods:
899 * Load-balancing iterator. Note: while the runqueue stays locked
900 * during the whole iteration, the current task might be
901 * dequeued so the iterator has to be dequeue-safe. Here we
902 * achieve that by always pre-iterating before returning
905 static inline struct task_struct
*
906 __load_balance_iterator(struct cfs_rq
*cfs_rq
, struct rb_node
*curr
)
908 struct task_struct
*p
;
913 p
= rb_entry(curr
, struct task_struct
, se
.run_node
);
914 cfs_rq
->rb_load_balance_curr
= rb_next(curr
);
919 static struct task_struct
*load_balance_start_fair(void *arg
)
921 struct cfs_rq
*cfs_rq
= arg
;
923 return __load_balance_iterator(cfs_rq
, first_fair(cfs_rq
));
926 static struct task_struct
*load_balance_next_fair(void *arg
)
928 struct cfs_rq
*cfs_rq
= arg
;
930 return __load_balance_iterator(cfs_rq
, cfs_rq
->rb_load_balance_curr
);
933 #ifdef CONFIG_FAIR_GROUP_SCHED
934 static int cfs_rq_best_prio(struct cfs_rq
*cfs_rq
)
936 struct sched_entity
*curr
;
937 struct task_struct
*p
;
939 if (!cfs_rq
->nr_running
)
942 curr
= __pick_next_entity(cfs_rq
);
950 load_balance_fair(struct rq
*this_rq
, int this_cpu
, struct rq
*busiest
,
951 unsigned long max_nr_move
, unsigned long max_load_move
,
952 struct sched_domain
*sd
, enum cpu_idle_type idle
,
953 int *all_pinned
, int *this_best_prio
)
955 struct cfs_rq
*busy_cfs_rq
;
956 unsigned long load_moved
, total_nr_moved
= 0, nr_moved
;
957 long rem_load_move
= max_load_move
;
958 struct rq_iterator cfs_rq_iterator
;
960 cfs_rq_iterator
.start
= load_balance_start_fair
;
961 cfs_rq_iterator
.next
= load_balance_next_fair
;
963 for_each_leaf_cfs_rq(busiest
, busy_cfs_rq
) {
964 #ifdef CONFIG_FAIR_GROUP_SCHED
965 struct cfs_rq
*this_cfs_rq
;
967 unsigned long maxload
;
969 this_cfs_rq
= cpu_cfs_rq(busy_cfs_rq
, this_cpu
);
971 imbalance
= busy_cfs_rq
->load
.weight
- this_cfs_rq
->load
.weight
;
972 /* Don't pull if this_cfs_rq has more load than busy_cfs_rq */
976 /* Don't pull more than imbalance/2 */
978 maxload
= min(rem_load_move
, imbalance
);
980 *this_best_prio
= cfs_rq_best_prio(this_cfs_rq
);
982 # define maxload rem_load_move
984 /* pass busy_cfs_rq argument into
985 * load_balance_[start|next]_fair iterators
987 cfs_rq_iterator
.arg
= busy_cfs_rq
;
988 nr_moved
= balance_tasks(this_rq
, this_cpu
, busiest
,
989 max_nr_move
, maxload
, sd
, idle
, all_pinned
,
990 &load_moved
, this_best_prio
, &cfs_rq_iterator
);
992 total_nr_moved
+= nr_moved
;
993 max_nr_move
-= nr_moved
;
994 rem_load_move
-= load_moved
;
996 if (max_nr_move
<= 0 || rem_load_move
<= 0)
1000 return max_load_move
- rem_load_move
;
1004 * scheduler tick hitting a task of our scheduling class:
1006 static void task_tick_fair(struct rq
*rq
, struct task_struct
*curr
)
1008 struct cfs_rq
*cfs_rq
;
1009 struct sched_entity
*se
= &curr
->se
;
1011 for_each_sched_entity(se
) {
1012 cfs_rq
= cfs_rq_of(se
);
1013 entity_tick(cfs_rq
, se
);
1018 * Share the fairness runtime between parent and child, thus the
1019 * total amount of pressure for CPU stays equal - new tasks
1020 * get a chance to run but frequent forkers are not allowed to
1021 * monopolize the CPU. Note: the parent runqueue is locked,
1022 * the child is not running yet.
1024 static void task_new_fair(struct rq
*rq
, struct task_struct
*p
)
1026 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
1027 struct sched_entity
*se
= &p
->se
;
1029 sched_info_queued(p
);
1031 update_stats_enqueue(cfs_rq
, se
);
1033 * Child runs first: we let it run before the parent
1034 * until it reschedules once. We set up the key so that
1035 * it will preempt the parent:
1037 p
->se
.fair_key
= current
->se
.fair_key
-
1038 niced_granularity(&rq
->curr
->se
, sysctl_sched_granularity
) - 1;
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 (sysctl_sched_features
& SCHED_FEAT_SKIP_INITIAL
)
1044 p
->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 (sysctl_sched_features
& SCHED_FEAT_START_DEBIT
)
1051 p
->se
.wait_runtime
= -(sysctl_sched_granularity
/ 2);
1053 __enqueue_entity(cfs_rq
, se
);
1056 #ifdef CONFIG_FAIR_GROUP_SCHED
1057 /* Account for a task changing its policy or group.
1059 * This routine is mostly called to set cfs_rq->curr field when a task
1060 * migrates between groups/classes.
1062 static void set_curr_task_fair(struct rq
*rq
)
1064 struct sched_entity
*se
= &rq
->curr
->se
;
1066 for_each_sched_entity(se
)
1067 set_next_entity(cfs_rq_of(se
), se
);
1070 static void set_curr_task_fair(struct rq
*rq
)
1076 * All the scheduling class methods:
1078 struct sched_class fair_sched_class __read_mostly
= {
1079 .enqueue_task
= enqueue_task_fair
,
1080 .dequeue_task
= dequeue_task_fair
,
1081 .yield_task
= yield_task_fair
,
1083 .check_preempt_curr
= check_preempt_curr_fair
,
1085 .pick_next_task
= pick_next_task_fair
,
1086 .put_prev_task
= put_prev_task_fair
,
1088 .load_balance
= load_balance_fair
,
1090 .set_curr_task
= set_curr_task_fair
,
1091 .task_tick
= task_tick_fair
,
1092 .task_new
= task_new_fair
,
1095 #ifdef CONFIG_SCHED_DEBUG
1096 static void print_cfs_stats(struct seq_file
*m
, int cpu
)
1098 struct cfs_rq
*cfs_rq
;
1100 for_each_leaf_cfs_rq(cpu_rq(cpu
), cfs_rq
)
1101 print_cfs_rq(m
, cpu
, cfs_rq
);