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sched: re-instate vruntime based wakeup preemption
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1/*
2 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
3 *
4 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
5 *
6 * Interactivity improvements by Mike Galbraith
7 * (C) 2007 Mike Galbraith <efault@gmx.de>
8 *
9 * Various enhancements by Dmitry Adamushko.
10 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
11 *
12 * Group scheduling enhancements by Srivatsa Vaddagiri
13 * Copyright IBM Corporation, 2007
14 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
15 *
16 * Scaled math optimizations by Thomas Gleixner
17 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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18 *
19 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra
20 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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21 */
22
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23#include <linux/latencytop.h>
24
bf0f6f24 25/*
21805085 26 * Targeted preemption latency for CPU-bound tasks:
722aab0c 27 * (default: 20ms * (1 + ilog(ncpus)), units: nanoseconds)
bf0f6f24 28 *
21805085 29 * NOTE: this latency value is not the same as the concept of
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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.
bf0f6f24 33 *
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34 * (to see the precise effective timeslice length of your workload,
35 * run vmstat and monitor the context-switches (cs) field)
bf0f6f24 36 */
19978ca6 37unsigned int sysctl_sched_latency = 20000000ULL;
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38
39/*
b2be5e96 40 * Minimal preemption granularity for CPU-bound tasks:
722aab0c 41 * (default: 4 msec * (1 + ilog(ncpus)), units: nanoseconds)
2bd8e6d4 42 */
722aab0c 43unsigned int sysctl_sched_min_granularity = 4000000ULL;
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44
45/*
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46 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
47 */
722aab0c 48static unsigned int sched_nr_latency = 5;
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49
50/*
51 * After fork, child runs first. (default) If set to 0 then
52 * parent will (try to) run first.
21805085 53 */
b2be5e96 54const_debug unsigned int sysctl_sched_child_runs_first = 1;
bf0f6f24 55
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56/*
57 * sys_sched_yield() compat mode
58 *
59 * This option switches the agressive yield implementation of the
60 * old scheduler back on.
61 */
62unsigned int __read_mostly sysctl_sched_compat_yield;
63
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64/*
65 * SCHED_OTHER wake-up granularity.
103638d9 66 * (default: 5 msec * (1 + ilog(ncpus)), units: nanoseconds)
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67 *
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.
71 */
103638d9 72unsigned int sysctl_sched_wakeup_granularity = 5000000UL;
bf0f6f24 73
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74const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
75
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76static const struct sched_class fair_sched_class;
77
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78/**************************************************************
79 * CFS operations on generic schedulable entities:
80 */
81
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82static inline struct task_struct *task_of(struct sched_entity *se)
83{
84 return container_of(se, struct task_struct, se);
85}
86
62160e3f 87#ifdef CONFIG_FAIR_GROUP_SCHED
bf0f6f24 88
62160e3f 89/* cpu runqueue to which this cfs_rq is attached */
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90static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
91{
62160e3f 92 return cfs_rq->rq;
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93}
94
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95/* An entity is a task if it doesn't "own" a runqueue */
96#define entity_is_task(se) (!se->my_q)
bf0f6f24 97
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98/* Walk up scheduling entities hierarchy */
99#define for_each_sched_entity(se) \
100 for (; se; se = se->parent)
101
102static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
103{
104 return p->se.cfs_rq;
105}
106
107/* runqueue on which this entity is (to be) queued */
108static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
109{
110 return se->cfs_rq;
111}
112
113/* runqueue "owned" by this group */
114static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
115{
116 return grp->my_q;
117}
118
119/* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on
120 * another cpu ('this_cpu')
121 */
122static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
123{
124 return cfs_rq->tg->cfs_rq[this_cpu];
125}
126
127/* Iterate thr' all leaf cfs_rq's on a runqueue */
128#define for_each_leaf_cfs_rq(rq, cfs_rq) \
129 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
130
131/* Do the two (enqueued) entities belong to the same group ? */
132static inline int
133is_same_group(struct sched_entity *se, struct sched_entity *pse)
134{
135 if (se->cfs_rq == pse->cfs_rq)
136 return 1;
137
138 return 0;
139}
140
141static inline struct sched_entity *parent_entity(struct sched_entity *se)
142{
143 return se->parent;
144}
145
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146/* return depth at which a sched entity is present in the hierarchy */
147static inline int depth_se(struct sched_entity *se)
148{
149 int depth = 0;
150
151 for_each_sched_entity(se)
152 depth++;
153
154 return depth;
155}
156
157static void
158find_matching_se(struct sched_entity **se, struct sched_entity **pse)
159{
160 int se_depth, pse_depth;
161
162 /*
163 * preemption test can be made between sibling entities who are in the
164 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
165 * both tasks until we find their ancestors who are siblings of common
166 * parent.
167 */
168
169 /* First walk up until both entities are at same depth */
170 se_depth = depth_se(*se);
171 pse_depth = depth_se(*pse);
172
173 while (se_depth > pse_depth) {
174 se_depth--;
175 *se = parent_entity(*se);
176 }
177
178 while (pse_depth > se_depth) {
179 pse_depth--;
180 *pse = parent_entity(*pse);
181 }
182
183 while (!is_same_group(*se, *pse)) {
184 *se = parent_entity(*se);
185 *pse = parent_entity(*pse);
186 }
187}
188
62160e3f 189#else /* CONFIG_FAIR_GROUP_SCHED */
bf0f6f24 190
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191static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
192{
193 return container_of(cfs_rq, struct rq, cfs);
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194}
195
196#define entity_is_task(se) 1
197
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198#define for_each_sched_entity(se) \
199 for (; se; se = NULL)
bf0f6f24 200
b758149c 201static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
bf0f6f24 202{
b758149c 203 return &task_rq(p)->cfs;
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204}
205
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206static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
207{
208 struct task_struct *p = task_of(se);
209 struct rq *rq = task_rq(p);
210
211 return &rq->cfs;
212}
213
214/* runqueue "owned" by this group */
215static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
216{
217 return NULL;
218}
219
220static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
221{
222 return &cpu_rq(this_cpu)->cfs;
223}
224
225#define for_each_leaf_cfs_rq(rq, cfs_rq) \
226 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
227
228static inline int
229is_same_group(struct sched_entity *se, struct sched_entity *pse)
230{
231 return 1;
232}
233
234static inline struct sched_entity *parent_entity(struct sched_entity *se)
235{
236 return NULL;
237}
238
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239static inline void
240find_matching_se(struct sched_entity **se, struct sched_entity **pse)
241{
242}
243
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244#endif /* CONFIG_FAIR_GROUP_SCHED */
245
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246
247/**************************************************************
248 * Scheduling class tree data structure manipulation methods:
249 */
250
0702e3eb 251static inline u64 max_vruntime(u64 min_vruntime, u64 vruntime)
02e0431a 252{
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253 s64 delta = (s64)(vruntime - min_vruntime);
254 if (delta > 0)
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255 min_vruntime = vruntime;
256
257 return min_vruntime;
258}
259
0702e3eb 260static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
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261{
262 s64 delta = (s64)(vruntime - min_vruntime);
263 if (delta < 0)
264 min_vruntime = vruntime;
265
266 return min_vruntime;
267}
268
0702e3eb 269static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
9014623c 270{
30cfdcfc 271 return se->vruntime - cfs_rq->min_vruntime;
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272}
273
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274static void update_min_vruntime(struct cfs_rq *cfs_rq)
275{
276 u64 vruntime = cfs_rq->min_vruntime;
277
278 if (cfs_rq->curr)
279 vruntime = cfs_rq->curr->vruntime;
280
281 if (cfs_rq->rb_leftmost) {
282 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
283 struct sched_entity,
284 run_node);
285
286 if (vruntime == cfs_rq->min_vruntime)
287 vruntime = se->vruntime;
288 else
289 vruntime = min_vruntime(vruntime, se->vruntime);
290 }
291
292 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
293}
294
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295/*
296 * Enqueue an entity into the rb-tree:
297 */
0702e3eb 298static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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299{
300 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
301 struct rb_node *parent = NULL;
302 struct sched_entity *entry;
9014623c 303 s64 key = entity_key(cfs_rq, se);
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304 int leftmost = 1;
305
306 /*
307 * Find the right place in the rbtree:
308 */
309 while (*link) {
310 parent = *link;
311 entry = rb_entry(parent, struct sched_entity, run_node);
312 /*
313 * We dont care about collisions. Nodes with
314 * the same key stay together.
315 */
9014623c 316 if (key < entity_key(cfs_rq, entry)) {
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317 link = &parent->rb_left;
318 } else {
319 link = &parent->rb_right;
320 leftmost = 0;
321 }
322 }
323
324 /*
325 * Maintain a cache of leftmost tree entries (it is frequently
326 * used):
327 */
1af5f730 328 if (leftmost)
57cb499d 329 cfs_rq->rb_leftmost = &se->run_node;
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330
331 rb_link_node(&se->run_node, parent, link);
332 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
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333}
334
0702e3eb 335static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
bf0f6f24 336{
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337 if (cfs_rq->rb_leftmost == &se->run_node) {
338 struct rb_node *next_node;
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339
340 next_node = rb_next(&se->run_node);
341 cfs_rq->rb_leftmost = next_node;
3fe69747 342 }
e9acbff6 343
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344 if (cfs_rq->next == se)
345 cfs_rq->next = NULL;
346
bf0f6f24 347 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
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348}
349
350static inline struct rb_node *first_fair(struct cfs_rq *cfs_rq)
351{
352 return cfs_rq->rb_leftmost;
353}
354
355static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
356{
357 return rb_entry(first_fair(cfs_rq), struct sched_entity, run_node);
358}
359
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360static inline struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
361{
7eee3e67 362 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
aeb73b04 363
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364 if (!last)
365 return NULL;
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366
367 return rb_entry(last, struct sched_entity, run_node);
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368}
369
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370/**************************************************************
371 * Scheduling class statistics methods:
372 */
373
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374#ifdef CONFIG_SCHED_DEBUG
375int sched_nr_latency_handler(struct ctl_table *table, int write,
376 struct file *filp, void __user *buffer, size_t *lenp,
377 loff_t *ppos)
378{
379 int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
380
381 if (ret || !write)
382 return ret;
383
384 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
385 sysctl_sched_min_granularity);
386
387 return 0;
388}
389#endif
647e7cac 390
a7be37ac 391/*
f9c0b095 392 * delta *= P[w / rw]
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393 */
394static inline unsigned long
395calc_delta_weight(unsigned long delta, struct sched_entity *se)
396{
397 for_each_sched_entity(se) {
398 delta = calc_delta_mine(delta,
399 se->load.weight, &cfs_rq_of(se)->load);
400 }
401
402 return delta;
403}
404
405/*
f9c0b095 406 * delta /= w
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407 */
408static inline unsigned long
409calc_delta_fair(unsigned long delta, struct sched_entity *se)
410{
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411 if (unlikely(se->load.weight != NICE_0_LOAD))
412 delta = calc_delta_mine(delta, NICE_0_LOAD, &se->load);
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413
414 return delta;
415}
416
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417/*
418 * The idea is to set a period in which each task runs once.
419 *
420 * When there are too many tasks (sysctl_sched_nr_latency) we have to stretch
421 * this period because otherwise the slices get too small.
422 *
423 * p = (nr <= nl) ? l : l*nr/nl
424 */
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425static u64 __sched_period(unsigned long nr_running)
426{
427 u64 period = sysctl_sched_latency;
b2be5e96 428 unsigned long nr_latency = sched_nr_latency;
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429
430 if (unlikely(nr_running > nr_latency)) {
4bf0b771 431 period = sysctl_sched_min_granularity;
4d78e7b6 432 period *= nr_running;
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433 }
434
435 return period;
436}
437
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438/*
439 * We calculate the wall-time slice from the period by taking a part
440 * proportional to the weight.
441 *
f9c0b095 442 * s = p*P[w/rw]
647e7cac 443 */
6d0f0ebd 444static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
21805085 445{
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446 unsigned long nr_running = cfs_rq->nr_running;
447
448 if (unlikely(!se->on_rq))
449 nr_running++;
450
451 return calc_delta_weight(__sched_period(nr_running), se);
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452}
453
647e7cac 454/*
ac884dec 455 * We calculate the vruntime slice of a to be inserted task
647e7cac 456 *
f9c0b095 457 * vs = s/w
647e7cac 458 */
f9c0b095 459static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
67e9fb2a 460{
f9c0b095 461 return calc_delta_fair(sched_slice(cfs_rq, se), se);
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462}
463
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464/*
465 * Update the current task's runtime statistics. Skip current tasks that
466 * are not in our scheduling class.
467 */
468static inline void
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469__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
470 unsigned long delta_exec)
bf0f6f24 471{
bbdba7c0 472 unsigned long delta_exec_weighted;
bf0f6f24 473
8179ca23 474 schedstat_set(curr->exec_max, max((u64)delta_exec, curr->exec_max));
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475
476 curr->sum_exec_runtime += delta_exec;
7a62eabc 477 schedstat_add(cfs_rq, exec_clock, delta_exec);
a7be37ac 478 delta_exec_weighted = calc_delta_fair(delta_exec, curr);
e9acbff6 479 curr->vruntime += delta_exec_weighted;
1af5f730 480 update_min_vruntime(cfs_rq);
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481}
482
b7cc0896 483static void update_curr(struct cfs_rq *cfs_rq)
bf0f6f24 484{
429d43bc 485 struct sched_entity *curr = cfs_rq->curr;
8ebc91d9 486 u64 now = rq_of(cfs_rq)->clock;
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487 unsigned long delta_exec;
488
489 if (unlikely(!curr))
490 return;
491
492 /*
493 * Get the amount of time the current task was running
494 * since the last time we changed load (this cannot
495 * overflow on 32 bits):
496 */
8ebc91d9 497 delta_exec = (unsigned long)(now - curr->exec_start);
bf0f6f24 498
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499 __update_curr(cfs_rq, curr, delta_exec);
500 curr->exec_start = now;
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501
502 if (entity_is_task(curr)) {
503 struct task_struct *curtask = task_of(curr);
504
505 cpuacct_charge(curtask, delta_exec);
f06febc9 506 account_group_exec_runtime(curtask, delta_exec);
d842de87 507 }
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508}
509
510static inline void
5870db5b 511update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
bf0f6f24 512{
d281918d 513 schedstat_set(se->wait_start, rq_of(cfs_rq)->clock);
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514}
515
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516/*
517 * Task is being enqueued - update stats:
518 */
d2417e5a 519static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
bf0f6f24 520{
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521 /*
522 * Are we enqueueing a waiting task? (for current tasks
523 * a dequeue/enqueue event is a NOP)
524 */
429d43bc 525 if (se != cfs_rq->curr)
5870db5b 526 update_stats_wait_start(cfs_rq, se);
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527}
528
bf0f6f24 529static void
9ef0a961 530update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
bf0f6f24 531{
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532 schedstat_set(se->wait_max, max(se->wait_max,
533 rq_of(cfs_rq)->clock - se->wait_start));
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534 schedstat_set(se->wait_count, se->wait_count + 1);
535 schedstat_set(se->wait_sum, se->wait_sum +
536 rq_of(cfs_rq)->clock - se->wait_start);
6cfb0d5d 537 schedstat_set(se->wait_start, 0);
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538}
539
540static inline void
19b6a2e3 541update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
bf0f6f24 542{
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543 /*
544 * Mark the end of the wait period if dequeueing a
545 * waiting task:
546 */
429d43bc 547 if (se != cfs_rq->curr)
9ef0a961 548 update_stats_wait_end(cfs_rq, se);
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549}
550
551/*
552 * We are picking a new current task - update its stats:
553 */
554static inline void
79303e9e 555update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
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556{
557 /*
558 * We are starting a new run period:
559 */
d281918d 560 se->exec_start = rq_of(cfs_rq)->clock;
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561}
562
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563/**************************************************
564 * Scheduling class queueing methods:
565 */
566
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567#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
568static void
569add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight)
570{
571 cfs_rq->task_weight += weight;
572}
573#else
574static inline void
575add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight)
576{
577}
578#endif
579
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580static void
581account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
582{
583 update_load_add(&cfs_rq->load, se->load.weight);
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584 if (!parent_entity(se))
585 inc_cpu_load(rq_of(cfs_rq), se->load.weight);
b87f1724 586 if (entity_is_task(se)) {
c09595f6 587 add_cfs_task_weight(cfs_rq, se->load.weight);
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588 list_add(&se->group_node, &cfs_rq->tasks);
589 }
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590 cfs_rq->nr_running++;
591 se->on_rq = 1;
592}
593
594static void
595account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
596{
597 update_load_sub(&cfs_rq->load, se->load.weight);
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598 if (!parent_entity(se))
599 dec_cpu_load(rq_of(cfs_rq), se->load.weight);
b87f1724 600 if (entity_is_task(se)) {
c09595f6 601 add_cfs_task_weight(cfs_rq, -se->load.weight);
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602 list_del_init(&se->group_node);
603 }
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604 cfs_rq->nr_running--;
605 se->on_rq = 0;
606}
607
2396af69 608static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
bf0f6f24 609{
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610#ifdef CONFIG_SCHEDSTATS
611 if (se->sleep_start) {
d281918d 612 u64 delta = rq_of(cfs_rq)->clock - se->sleep_start;
9745512c 613 struct task_struct *tsk = task_of(se);
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614
615 if ((s64)delta < 0)
616 delta = 0;
617
618 if (unlikely(delta > se->sleep_max))
619 se->sleep_max = delta;
620
621 se->sleep_start = 0;
622 se->sum_sleep_runtime += delta;
9745512c
AV
623
624 account_scheduler_latency(tsk, delta >> 10, 1);
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625 }
626 if (se->block_start) {
d281918d 627 u64 delta = rq_of(cfs_rq)->clock - se->block_start;
9745512c 628 struct task_struct *tsk = task_of(se);
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629
630 if ((s64)delta < 0)
631 delta = 0;
632
633 if (unlikely(delta > se->block_max))
634 se->block_max = delta;
635
636 se->block_start = 0;
637 se->sum_sleep_runtime += delta;
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IM
638
639 /*
640 * Blocking time is in units of nanosecs, so shift by 20 to
641 * get a milliseconds-range estimation of the amount of
642 * time that the task spent sleeping:
643 */
644 if (unlikely(prof_on == SLEEP_PROFILING)) {
e22f5bbf 645
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646 profile_hits(SLEEP_PROFILING, (void *)get_wchan(tsk),
647 delta >> 20);
648 }
9745512c 649 account_scheduler_latency(tsk, delta >> 10, 0);
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650 }
651#endif
652}
653
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654static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
655{
656#ifdef CONFIG_SCHED_DEBUG
657 s64 d = se->vruntime - cfs_rq->min_vruntime;
658
659 if (d < 0)
660 d = -d;
661
662 if (d > 3*sysctl_sched_latency)
663 schedstat_inc(cfs_rq, nr_spread_over);
664#endif
665}
666
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667static void
668place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
669{
1af5f730 670 u64 vruntime = cfs_rq->min_vruntime;
94dfb5e7 671
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672 /*
673 * The 'current' period is already promised to the current tasks,
674 * however the extra weight of the new task will slow them down a
675 * little, place the new task so that it fits in the slot that
676 * stays open at the end.
677 */
94dfb5e7 678 if (initial && sched_feat(START_DEBIT))
f9c0b095 679 vruntime += sched_vslice(cfs_rq, se);
aeb73b04 680
8465e792 681 if (!initial) {
2cb8600e 682 /* sleeps upto a single latency don't count. */
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683 if (sched_feat(NEW_FAIR_SLEEPERS)) {
684 unsigned long thresh = sysctl_sched_latency;
685
686 /*
687 * convert the sleeper threshold into virtual time
688 */
689 if (sched_feat(NORMALIZED_SLEEPER))
690 thresh = calc_delta_fair(thresh, se);
691
692 vruntime -= thresh;
693 }
94359f05 694
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695 /* ensure we never gain time by being placed backwards. */
696 vruntime = max_vruntime(se->vruntime, vruntime);
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697 }
698
67e9fb2a 699 se->vruntime = vruntime;
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700}
701
bf0f6f24 702static void
83b699ed 703enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
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704{
705 /*
a2a2d680 706 * Update run-time statistics of the 'current'.
bf0f6f24 707 */
b7cc0896 708 update_curr(cfs_rq);
a992241d 709 account_entity_enqueue(cfs_rq, se);
bf0f6f24 710
e9acbff6 711 if (wakeup) {
aeb73b04 712 place_entity(cfs_rq, se, 0);
2396af69 713 enqueue_sleeper(cfs_rq, se);
e9acbff6 714 }
bf0f6f24 715
d2417e5a 716 update_stats_enqueue(cfs_rq, se);
ddc97297 717 check_spread(cfs_rq, se);
83b699ed
SV
718 if (se != cfs_rq->curr)
719 __enqueue_entity(cfs_rq, se);
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720}
721
722static void
525c2716 723dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
bf0f6f24 724{
a2a2d680
DA
725 /*
726 * Update run-time statistics of the 'current'.
727 */
728 update_curr(cfs_rq);
729
19b6a2e3 730 update_stats_dequeue(cfs_rq, se);
db36cc7d 731 if (sleep) {
67e9fb2a 732#ifdef CONFIG_SCHEDSTATS
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733 if (entity_is_task(se)) {
734 struct task_struct *tsk = task_of(se);
735
736 if (tsk->state & TASK_INTERRUPTIBLE)
d281918d 737 se->sleep_start = rq_of(cfs_rq)->clock;
bf0f6f24 738 if (tsk->state & TASK_UNINTERRUPTIBLE)
d281918d 739 se->block_start = rq_of(cfs_rq)->clock;
bf0f6f24 740 }
db36cc7d 741#endif
67e9fb2a
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742 }
743
83b699ed 744 if (se != cfs_rq->curr)
30cfdcfc
DA
745 __dequeue_entity(cfs_rq, se);
746 account_entity_dequeue(cfs_rq, se);
1af5f730 747 update_min_vruntime(cfs_rq);
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748}
749
750/*
751 * Preempt the current task with a newly woken task if needed:
752 */
7c92e54f 753static void
2e09bf55 754check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
bf0f6f24 755{
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756 unsigned long ideal_runtime, delta_exec;
757
6d0f0ebd 758 ideal_runtime = sched_slice(cfs_rq, curr);
11697830 759 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3e3e13f3 760 if (delta_exec > ideal_runtime)
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761 resched_task(rq_of(cfs_rq)->curr);
762}
763
83b699ed 764static void
8494f412 765set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
bf0f6f24 766{
83b699ed
SV
767 /* 'current' is not kept within the tree. */
768 if (se->on_rq) {
769 /*
770 * Any task has to be enqueued before it get to execute on
771 * a CPU. So account for the time it spent waiting on the
772 * runqueue.
773 */
774 update_stats_wait_end(cfs_rq, se);
775 __dequeue_entity(cfs_rq, se);
776 }
777
79303e9e 778 update_stats_curr_start(cfs_rq, se);
429d43bc 779 cfs_rq->curr = se;
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780#ifdef CONFIG_SCHEDSTATS
781 /*
782 * Track our maximum slice length, if the CPU's load is at
783 * least twice that of our own weight (i.e. dont track it
784 * when there are only lesser-weight tasks around):
785 */
495eca49 786 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
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787 se->slice_max = max(se->slice_max,
788 se->sum_exec_runtime - se->prev_sum_exec_runtime);
789 }
790#endif
4a55b450 791 se->prev_sum_exec_runtime = se->sum_exec_runtime;
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792}
793
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794static struct sched_entity *
795pick_next(struct cfs_rq *cfs_rq, struct sched_entity *se)
796{
103638d9
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797 struct rq *rq = rq_of(cfs_rq);
798 u64 pair_slice = rq->clock - cfs_rq->pair_start;
aa2ac252 799
b0aa51b9 800 if (!cfs_rq->next || pair_slice > sysctl_sched_min_granularity) {
103638d9 801 cfs_rq->pair_start = rq->clock;
aa2ac252 802 return se;
103638d9 803 }
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804
805 return cfs_rq->next;
806}
807
9948f4b2 808static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
bf0f6f24 809{
08ec3df5 810 struct sched_entity *se = NULL;
bf0f6f24 811
08ec3df5
DA
812 if (first_fair(cfs_rq)) {
813 se = __pick_next_entity(cfs_rq);
aa2ac252 814 se = pick_next(cfs_rq, se);
08ec3df5
DA
815 set_next_entity(cfs_rq, se);
816 }
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817
818 return se;
819}
820
ab6cde26 821static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
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822{
823 /*
824 * If still on the runqueue then deactivate_task()
825 * was not called and update_curr() has to be done:
826 */
827 if (prev->on_rq)
b7cc0896 828 update_curr(cfs_rq);
bf0f6f24 829
ddc97297 830 check_spread(cfs_rq, prev);
30cfdcfc 831 if (prev->on_rq) {
5870db5b 832 update_stats_wait_start(cfs_rq, prev);
30cfdcfc
DA
833 /* Put 'current' back into the tree. */
834 __enqueue_entity(cfs_rq, prev);
835 }
429d43bc 836 cfs_rq->curr = NULL;
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IM
837}
838
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839static void
840entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
bf0f6f24 841{
bf0f6f24 842 /*
30cfdcfc 843 * Update run-time statistics of the 'current'.
bf0f6f24 844 */
30cfdcfc 845 update_curr(cfs_rq);
bf0f6f24 846
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847#ifdef CONFIG_SCHED_HRTICK
848 /*
849 * queued ticks are scheduled to match the slice, so don't bother
850 * validating it and just reschedule.
851 */
983ed7a6
HH
852 if (queued) {
853 resched_task(rq_of(cfs_rq)->curr);
854 return;
855 }
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856 /*
857 * don't let the period tick interfere with the hrtick preemption
858 */
859 if (!sched_feat(DOUBLE_TICK) &&
860 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
861 return;
862#endif
863
ce6c1311 864 if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
2e09bf55 865 check_preempt_tick(cfs_rq, curr);
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866}
867
868/**************************************************
869 * CFS operations on tasks:
870 */
871
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872#ifdef CONFIG_SCHED_HRTICK
873static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
874{
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875 struct sched_entity *se = &p->se;
876 struct cfs_rq *cfs_rq = cfs_rq_of(se);
877
878 WARN_ON(task_rq(p) != rq);
879
880 if (hrtick_enabled(rq) && cfs_rq->nr_running > 1) {
881 u64 slice = sched_slice(cfs_rq, se);
882 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
883 s64 delta = slice - ran;
884
885 if (delta < 0) {
886 if (rq->curr == p)
887 resched_task(p);
888 return;
889 }
890
891 /*
892 * Don't schedule slices shorter than 10000ns, that just
893 * doesn't make sense. Rely on vruntime for fairness.
894 */
31656519 895 if (rq->curr != p)
157124c1 896 delta = max_t(s64, 10000LL, delta);
8f4d37ec 897
31656519 898 hrtick_start(rq, delta);
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899 }
900}
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901
902/*
903 * called from enqueue/dequeue and updates the hrtick when the
904 * current task is from our class and nr_running is low enough
905 * to matter.
906 */
907static void hrtick_update(struct rq *rq)
908{
909 struct task_struct *curr = rq->curr;
910
911 if (curr->sched_class != &fair_sched_class)
912 return;
913
914 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
915 hrtick_start_fair(rq, curr);
916}
55e12e5e 917#else /* !CONFIG_SCHED_HRTICK */
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918static inline void
919hrtick_start_fair(struct rq *rq, struct task_struct *p)
920{
921}
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922
923static inline void hrtick_update(struct rq *rq)
924{
925}
8f4d37ec
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926#endif
927
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928/*
929 * The enqueue_task method is called before nr_running is
930 * increased. Here we update the fair scheduling stats and
931 * then put the task into the rbtree:
932 */
fd390f6a 933static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
bf0f6f24
IM
934{
935 struct cfs_rq *cfs_rq;
62fb1851 936 struct sched_entity *se = &p->se;
bf0f6f24
IM
937
938 for_each_sched_entity(se) {
62fb1851 939 if (se->on_rq)
bf0f6f24
IM
940 break;
941 cfs_rq = cfs_rq_of(se);
83b699ed 942 enqueue_entity(cfs_rq, se, wakeup);
b9fa3df3 943 wakeup = 1;
bf0f6f24 944 }
8f4d37ec 945
a4c2f00f 946 hrtick_update(rq);
bf0f6f24
IM
947}
948
949/*
950 * The dequeue_task method is called before nr_running is
951 * decreased. We remove the task from the rbtree and
952 * update the fair scheduling stats:
953 */
f02231e5 954static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
bf0f6f24
IM
955{
956 struct cfs_rq *cfs_rq;
62fb1851 957 struct sched_entity *se = &p->se;
bf0f6f24
IM
958
959 for_each_sched_entity(se) {
960 cfs_rq = cfs_rq_of(se);
525c2716 961 dequeue_entity(cfs_rq, se, sleep);
bf0f6f24 962 /* Don't dequeue parent if it has other entities besides us */
62fb1851 963 if (cfs_rq->load.weight)
bf0f6f24 964 break;
b9fa3df3 965 sleep = 1;
bf0f6f24 966 }
8f4d37ec 967
a4c2f00f 968 hrtick_update(rq);
bf0f6f24
IM
969}
970
971/*
1799e35d
IM
972 * sched_yield() support is very simple - we dequeue and enqueue.
973 *
974 * If compat_yield is turned on then we requeue to the end of the tree.
bf0f6f24 975 */
4530d7ab 976static void yield_task_fair(struct rq *rq)
bf0f6f24 977{
db292ca3
IM
978 struct task_struct *curr = rq->curr;
979 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
980 struct sched_entity *rightmost, *se = &curr->se;
bf0f6f24
IM
981
982 /*
1799e35d
IM
983 * Are we the only task in the tree?
984 */
985 if (unlikely(cfs_rq->nr_running == 1))
986 return;
987
db292ca3 988 if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {
3e51f33f 989 update_rq_clock(rq);
1799e35d 990 /*
a2a2d680 991 * Update run-time statistics of the 'current'.
1799e35d 992 */
2b1e315d 993 update_curr(cfs_rq);
1799e35d
IM
994
995 return;
996 }
997 /*
998 * Find the rightmost entry in the rbtree:
bf0f6f24 999 */
2b1e315d 1000 rightmost = __pick_last_entity(cfs_rq);
1799e35d
IM
1001 /*
1002 * Already in the rightmost position?
1003 */
79b3feff 1004 if (unlikely(!rightmost || rightmost->vruntime < se->vruntime))
1799e35d
IM
1005 return;
1006
1007 /*
1008 * Minimally necessary key value to be last in the tree:
2b1e315d
DA
1009 * Upon rescheduling, sched_class::put_prev_task() will place
1010 * 'current' within the tree based on its new key value.
1799e35d 1011 */
30cfdcfc 1012 se->vruntime = rightmost->vruntime + 1;
bf0f6f24
IM
1013}
1014
e7693a36
GH
1015/*
1016 * wake_idle() will wake a task on an idle cpu if task->cpu is
1017 * not idle and an idle cpu is available. The span of cpus to
1018 * search starts with cpus closest then further out as needed,
1019 * so we always favor a closer, idle cpu.
e761b772
MK
1020 * Domains may include CPUs that are not usable for migration,
1021 * hence we need to mask them out (cpu_active_map)
e7693a36
GH
1022 *
1023 * Returns the CPU we should wake onto.
1024 */
1025#if defined(ARCH_HAS_SCHED_WAKE_IDLE)
1026static int wake_idle(int cpu, struct task_struct *p)
1027{
1028 cpumask_t tmp;
1029 struct sched_domain *sd;
1030 int i;
1031
1032 /*
1033 * If it is idle, then it is the best cpu to run this task.
1034 *
1035 * This cpu is also the best, if it has more than one task already.
1036 * Siblings must be also busy(in most cases) as they didn't already
1037 * pickup the extra load from this cpu and hence we need not check
1038 * sibling runqueue info. This will avoid the checks and cache miss
1039 * penalities associated with that.
1040 */
104f6454 1041 if (idle_cpu(cpu) || cpu_rq(cpu)->cfs.nr_running > 1)
e7693a36
GH
1042 return cpu;
1043
1044 for_each_domain(cpu, sd) {
1d3504fc
HS
1045 if ((sd->flags & SD_WAKE_IDLE)
1046 || ((sd->flags & SD_WAKE_IDLE_FAR)
1047 && !task_hot(p, task_rq(p)->clock, sd))) {
e7693a36 1048 cpus_and(tmp, sd->span, p->cpus_allowed);
e761b772 1049 cpus_and(tmp, tmp, cpu_active_map);
363ab6f1 1050 for_each_cpu_mask_nr(i, tmp) {
e7693a36
GH
1051 if (idle_cpu(i)) {
1052 if (i != task_cpu(p)) {
1053 schedstat_inc(p,
1054 se.nr_wakeups_idle);
1055 }
1056 return i;
1057 }
1058 }
1059 } else {
1060 break;
1061 }
1062 }
1063 return cpu;
1064}
55e12e5e 1065#else /* !ARCH_HAS_SCHED_WAKE_IDLE*/
e7693a36
GH
1066static inline int wake_idle(int cpu, struct task_struct *p)
1067{
1068 return cpu;
1069}
1070#endif
1071
1072#ifdef CONFIG_SMP
098fb9db 1073
bb3469ac 1074#ifdef CONFIG_FAIR_GROUP_SCHED
f5bfb7d9
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1075/*
1076 * effective_load() calculates the load change as seen from the root_task_group
1077 *
1078 * Adding load to a group doesn't make a group heavier, but can cause movement
1079 * of group shares between cpus. Assuming the shares were perfectly aligned one
1080 * can calculate the shift in shares.
1081 *
1082 * The problem is that perfectly aligning the shares is rather expensive, hence
1083 * we try to avoid doing that too often - see update_shares(), which ratelimits
1084 * this change.
1085 *
1086 * We compensate this by not only taking the current delta into account, but
1087 * also considering the delta between when the shares were last adjusted and
1088 * now.
1089 *
1090 * We still saw a performance dip, some tracing learned us that between
1091 * cgroup:/ and cgroup:/foo balancing the number of affine wakeups increased
1092 * significantly. Therefore try to bias the error in direction of failing
1093 * the affine wakeup.
1094 *
1095 */
f1d239f7
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1096static long effective_load(struct task_group *tg, int cpu,
1097 long wl, long wg)
bb3469ac 1098{
4be9daaa 1099 struct sched_entity *se = tg->se[cpu];
f1d239f7
PZ
1100
1101 if (!tg->parent)
1102 return wl;
1103
f5bfb7d9
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1104 /*
1105 * By not taking the decrease of shares on the other cpu into
1106 * account our error leans towards reducing the affine wakeups.
1107 */
1108 if (!wl && sched_feat(ASYM_EFF_LOAD))
1109 return wl;
1110
4be9daaa 1111 for_each_sched_entity(se) {
cb5ef42a 1112 long S, rw, s, a, b;
940959e9
PZ
1113 long more_w;
1114
1115 /*
1116 * Instead of using this increment, also add the difference
1117 * between when the shares were last updated and now.
1118 */
1119 more_w = se->my_q->load.weight - se->my_q->rq_weight;
1120 wl += more_w;
1121 wg += more_w;
4be9daaa
PZ
1122
1123 S = se->my_q->tg->shares;
1124 s = se->my_q->shares;
f1d239f7 1125 rw = se->my_q->rq_weight;
bb3469ac 1126
cb5ef42a
PZ
1127 a = S*(rw + wl);
1128 b = S*rw + s*wg;
4be9daaa 1129
940959e9
PZ
1130 wl = s*(a-b);
1131
1132 if (likely(b))
1133 wl /= b;
1134
83378269
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1135 /*
1136 * Assume the group is already running and will
1137 * thus already be accounted for in the weight.
1138 *
1139 * That is, moving shares between CPUs, does not
1140 * alter the group weight.
1141 */
4be9daaa 1142 wg = 0;
4be9daaa 1143 }
bb3469ac 1144
4be9daaa 1145 return wl;
bb3469ac 1146}
4be9daaa 1147
bb3469ac 1148#else
4be9daaa 1149
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1150static inline unsigned long effective_load(struct task_group *tg, int cpu,
1151 unsigned long wl, unsigned long wg)
4be9daaa 1152{
83378269 1153 return wl;
bb3469ac 1154}
4be9daaa 1155
bb3469ac
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1156#endif
1157
098fb9db 1158static int
64b9e029 1159wake_affine(struct sched_domain *this_sd, struct rq *this_rq,
4ae7d5ce
IM
1160 struct task_struct *p, int prev_cpu, int this_cpu, int sync,
1161 int idx, unsigned long load, unsigned long this_load,
098fb9db
IM
1162 unsigned int imbalance)
1163{
4ae7d5ce 1164 struct task_struct *curr = this_rq->curr;
83378269 1165 struct task_group *tg;
098fb9db
IM
1166 unsigned long tl = this_load;
1167 unsigned long tl_per_task;
83378269 1168 unsigned long weight;
b3137bc8 1169 int balanced;
098fb9db 1170
b3137bc8 1171 if (!(this_sd->flags & SD_WAKE_AFFINE) || !sched_feat(AFFINE_WAKEUPS))
098fb9db
IM
1172 return 0;
1173
0d13033b
MG
1174 if (sync && (curr->se.avg_overlap > sysctl_sched_migration_cost ||
1175 p->se.avg_overlap > sysctl_sched_migration_cost))
1176 sync = 0;
2fb7635c 1177
b3137bc8
MG
1178 /*
1179 * If sync wakeup then subtract the (maximum possible)
1180 * effect of the currently running task from the load
1181 * of the current CPU:
1182 */
83378269
PZ
1183 if (sync) {
1184 tg = task_group(current);
1185 weight = current->se.load.weight;
1186
1187 tl += effective_load(tg, this_cpu, -weight, -weight);
1188 load += effective_load(tg, prev_cpu, 0, -weight);
1189 }
b3137bc8 1190
83378269
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1191 tg = task_group(p);
1192 weight = p->se.load.weight;
b3137bc8 1193
83378269
PZ
1194 balanced = 100*(tl + effective_load(tg, this_cpu, weight, weight)) <=
1195 imbalance*(load + effective_load(tg, prev_cpu, 0, weight));
b3137bc8 1196
098fb9db 1197 /*
4ae7d5ce
IM
1198 * If the currently running task will sleep within
1199 * a reasonable amount of time then attract this newly
1200 * woken task:
098fb9db 1201 */
2fb7635c
PZ
1202 if (sync && balanced)
1203 return 1;
098fb9db
IM
1204
1205 schedstat_inc(p, se.nr_wakeups_affine_attempts);
1206 tl_per_task = cpu_avg_load_per_task(this_cpu);
1207
64b9e029
AA
1208 if (balanced || (tl <= load && tl + target_load(prev_cpu, idx) <=
1209 tl_per_task)) {
098fb9db
IM
1210 /*
1211 * This domain has SD_WAKE_AFFINE and
1212 * p is cache cold in this domain, and
1213 * there is no bad imbalance.
1214 */
1215 schedstat_inc(this_sd, ttwu_move_affine);
1216 schedstat_inc(p, se.nr_wakeups_affine);
1217
1218 return 1;
1219 }
1220 return 0;
1221}
1222
e7693a36
GH
1223static int select_task_rq_fair(struct task_struct *p, int sync)
1224{
e7693a36 1225 struct sched_domain *sd, *this_sd = NULL;
ac192d39 1226 int prev_cpu, this_cpu, new_cpu;
098fb9db 1227 unsigned long load, this_load;
64b9e029 1228 struct rq *this_rq;
098fb9db 1229 unsigned int imbalance;
098fb9db 1230 int idx;
e7693a36 1231
ac192d39 1232 prev_cpu = task_cpu(p);
ac192d39 1233 this_cpu = smp_processor_id();
4ae7d5ce 1234 this_rq = cpu_rq(this_cpu);
ac192d39 1235 new_cpu = prev_cpu;
e7693a36 1236
64b9e029
AA
1237 if (prev_cpu == this_cpu)
1238 goto out;
ac192d39
IM
1239 /*
1240 * 'this_sd' is the first domain that both
1241 * this_cpu and prev_cpu are present in:
1242 */
e7693a36 1243 for_each_domain(this_cpu, sd) {
ac192d39 1244 if (cpu_isset(prev_cpu, sd->span)) {
e7693a36
GH
1245 this_sd = sd;
1246 break;
1247 }
1248 }
1249
1250 if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
f4827386 1251 goto out;
e7693a36
GH
1252
1253 /*
1254 * Check for affine wakeup and passive balancing possibilities.
1255 */
098fb9db 1256 if (!this_sd)
f4827386 1257 goto out;
e7693a36 1258
098fb9db
IM
1259 idx = this_sd->wake_idx;
1260
1261 imbalance = 100 + (this_sd->imbalance_pct - 100) / 2;
1262
ac192d39 1263 load = source_load(prev_cpu, idx);
098fb9db
IM
1264 this_load = target_load(this_cpu, idx);
1265
64b9e029 1266 if (wake_affine(this_sd, this_rq, p, prev_cpu, this_cpu, sync, idx,
4ae7d5ce
IM
1267 load, this_load, imbalance))
1268 return this_cpu;
1269
098fb9db
IM
1270 /*
1271 * Start passive balancing when half the imbalance_pct
1272 * limit is reached.
1273 */
1274 if (this_sd->flags & SD_WAKE_BALANCE) {
1275 if (imbalance*this_load <= 100*load) {
1276 schedstat_inc(this_sd, ttwu_move_balance);
1277 schedstat_inc(p, se.nr_wakeups_passive);
4ae7d5ce 1278 return this_cpu;
e7693a36
GH
1279 }
1280 }
1281
f4827386 1282out:
e7693a36
GH
1283 return wake_idle(new_cpu, p);
1284}
1285#endif /* CONFIG_SMP */
1286
0bbd3336
PZ
1287static unsigned long wakeup_gran(struct sched_entity *se)
1288{
1289 unsigned long gran = sysctl_sched_wakeup_granularity;
1290
1291 /*
a7be37ac
PZ
1292 * More easily preempt - nice tasks, while not making it harder for
1293 * + nice tasks.
0bbd3336 1294 */
464b7527
PZ
1295 if (!sched_feat(ASYM_GRAN) || se->load.weight > NICE_0_LOAD)
1296 gran = calc_delta_fair(sysctl_sched_wakeup_granularity, se);
0bbd3336
PZ
1297
1298 return gran;
1299}
1300
464b7527
PZ
1301/*
1302 * Should 'se' preempt 'curr'.
1303 *
1304 * |s1
1305 * |s2
1306 * |s3
1307 * g
1308 * |<--->|c
1309 *
1310 * w(c, s1) = -1
1311 * w(c, s2) = 0
1312 * w(c, s3) = 1
1313 *
1314 */
1315static int
1316wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
1317{
1318 s64 gran, vdiff = curr->vruntime - se->vruntime;
1319
1320 if (vdiff <= 0)
1321 return -1;
1322
1323 gran = wakeup_gran(curr);
1324 if (vdiff > gran)
1325 return 1;
1326
1327 return 0;
1328}
1329
bf0f6f24
IM
1330/*
1331 * Preempt the current task with a newly woken task if needed:
1332 */
15afe09b 1333static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
bf0f6f24
IM
1334{
1335 struct task_struct *curr = rq->curr;
fad095a7 1336 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
8651a86c 1337 struct sched_entity *se = &curr->se, *pse = &p->se;
bf0f6f24
IM
1338
1339 if (unlikely(rt_prio(p->prio))) {
a8e504d2 1340 update_rq_clock(rq);
b7cc0896 1341 update_curr(cfs_rq);
bf0f6f24
IM
1342 resched_task(curr);
1343 return;
1344 }
aa2ac252 1345
4ae7d5ce
IM
1346 if (unlikely(se == pse))
1347 return;
1348
57fdc26d
PZ
1349 cfs_rq_of(pse)->next = pse;
1350
aec0a514
BR
1351 /*
1352 * We can come here with TIF_NEED_RESCHED already set from new task
1353 * wake up path.
1354 */
1355 if (test_tsk_need_resched(curr))
1356 return;
1357
91c234b4
IM
1358 /*
1359 * Batch tasks do not preempt (their preemption is driven by
1360 * the tick):
1361 */
1362 if (unlikely(p->policy == SCHED_BATCH))
1363 return;
bf0f6f24 1364
77d9cc44
IM
1365 if (!sched_feat(WAKEUP_PREEMPT))
1366 return;
8651a86c 1367
2fb7635c
PZ
1368 if (sched_feat(WAKEUP_OVERLAP) && (sync ||
1369 (se->avg_overlap < sysctl_sched_migration_cost &&
1370 pse->avg_overlap < sysctl_sched_migration_cost))) {
15afe09b
PZ
1371 resched_task(curr);
1372 return;
1373 }
1374
464b7527
PZ
1375 find_matching_se(&se, &pse);
1376
1377 while (se) {
1378 BUG_ON(!pse);
1379
1380 if (wakeup_preempt_entity(se, pse) == 1) {
1381 resched_task(curr);
1382 break;
1383 }
1384
1385 se = parent_entity(se);
1386 pse = parent_entity(pse);
1387 }
bf0f6f24
IM
1388}
1389
fb8d4724 1390static struct task_struct *pick_next_task_fair(struct rq *rq)
bf0f6f24 1391{
8f4d37ec 1392 struct task_struct *p;
bf0f6f24
IM
1393 struct cfs_rq *cfs_rq = &rq->cfs;
1394 struct sched_entity *se;
1395
1396 if (unlikely(!cfs_rq->nr_running))
1397 return NULL;
1398
1399 do {
9948f4b2 1400 se = pick_next_entity(cfs_rq);
bf0f6f24
IM
1401 cfs_rq = group_cfs_rq(se);
1402 } while (cfs_rq);
1403
8f4d37ec
PZ
1404 p = task_of(se);
1405 hrtick_start_fair(rq, p);
1406
1407 return p;
bf0f6f24
IM
1408}
1409
1410/*
1411 * Account for a descheduled task:
1412 */
31ee529c 1413static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
bf0f6f24
IM
1414{
1415 struct sched_entity *se = &prev->se;
1416 struct cfs_rq *cfs_rq;
1417
1418 for_each_sched_entity(se) {
1419 cfs_rq = cfs_rq_of(se);
ab6cde26 1420 put_prev_entity(cfs_rq, se);
bf0f6f24
IM
1421 }
1422}
1423
681f3e68 1424#ifdef CONFIG_SMP
bf0f6f24
IM
1425/**************************************************
1426 * Fair scheduling class load-balancing methods:
1427 */
1428
1429/*
1430 * Load-balancing iterator. Note: while the runqueue stays locked
1431 * during the whole iteration, the current task might be
1432 * dequeued so the iterator has to be dequeue-safe. Here we
1433 * achieve that by always pre-iterating before returning
1434 * the current task:
1435 */
a9957449 1436static struct task_struct *
4a55bd5e 1437__load_balance_iterator(struct cfs_rq *cfs_rq, struct list_head *next)
bf0f6f24 1438{
354d60c2
DG
1439 struct task_struct *p = NULL;
1440 struct sched_entity *se;
bf0f6f24 1441
77ae6513
MG
1442 if (next == &cfs_rq->tasks)
1443 return NULL;
1444
b87f1724
BR
1445 se = list_entry(next, struct sched_entity, group_node);
1446 p = task_of(se);
1447 cfs_rq->balance_iterator = next->next;
77ae6513 1448
bf0f6f24
IM
1449 return p;
1450}
1451
1452static struct task_struct *load_balance_start_fair(void *arg)
1453{
1454 struct cfs_rq *cfs_rq = arg;
1455
4a55bd5e 1456 return __load_balance_iterator(cfs_rq, cfs_rq->tasks.next);
bf0f6f24
IM
1457}
1458
1459static struct task_struct *load_balance_next_fair(void *arg)
1460{
1461 struct cfs_rq *cfs_rq = arg;
1462
4a55bd5e 1463 return __load_balance_iterator(cfs_rq, cfs_rq->balance_iterator);
bf0f6f24
IM
1464}
1465
c09595f6
PZ
1466static unsigned long
1467__load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
1468 unsigned long max_load_move, struct sched_domain *sd,
1469 enum cpu_idle_type idle, int *all_pinned, int *this_best_prio,
1470 struct cfs_rq *cfs_rq)
62fb1851 1471{
c09595f6 1472 struct rq_iterator cfs_rq_iterator;
62fb1851 1473
c09595f6
PZ
1474 cfs_rq_iterator.start = load_balance_start_fair;
1475 cfs_rq_iterator.next = load_balance_next_fair;
1476 cfs_rq_iterator.arg = cfs_rq;
62fb1851 1477
c09595f6
PZ
1478 return balance_tasks(this_rq, this_cpu, busiest,
1479 max_load_move, sd, idle, all_pinned,
1480 this_best_prio, &cfs_rq_iterator);
62fb1851 1481}
62fb1851 1482
c09595f6 1483#ifdef CONFIG_FAIR_GROUP_SCHED
43010659 1484static unsigned long
bf0f6f24 1485load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
e1d1484f 1486 unsigned long max_load_move,
a4ac01c3
PW
1487 struct sched_domain *sd, enum cpu_idle_type idle,
1488 int *all_pinned, int *this_best_prio)
bf0f6f24 1489{
bf0f6f24 1490 long rem_load_move = max_load_move;
c09595f6
PZ
1491 int busiest_cpu = cpu_of(busiest);
1492 struct task_group *tg;
18d95a28 1493
c09595f6 1494 rcu_read_lock();
c8cba857 1495 update_h_load(busiest_cpu);
18d95a28 1496
caea8a03 1497 list_for_each_entry_rcu(tg, &task_groups, list) {
c8cba857 1498 struct cfs_rq *busiest_cfs_rq = tg->cfs_rq[busiest_cpu];
42a3ac7d
PZ
1499 unsigned long busiest_h_load = busiest_cfs_rq->h_load;
1500 unsigned long busiest_weight = busiest_cfs_rq->load.weight;
243e0e7b 1501 u64 rem_load, moved_load;
18d95a28 1502
c09595f6
PZ
1503 /*
1504 * empty group
1505 */
c8cba857 1506 if (!busiest_cfs_rq->task_weight)
bf0f6f24
IM
1507 continue;
1508
243e0e7b
SV
1509 rem_load = (u64)rem_load_move * busiest_weight;
1510 rem_load = div_u64(rem_load, busiest_h_load + 1);
bf0f6f24 1511
c09595f6 1512 moved_load = __load_balance_fair(this_rq, this_cpu, busiest,
53fecd8a 1513 rem_load, sd, idle, all_pinned, this_best_prio,
c09595f6 1514 tg->cfs_rq[busiest_cpu]);
bf0f6f24 1515
c09595f6 1516 if (!moved_load)
bf0f6f24
IM
1517 continue;
1518
42a3ac7d 1519 moved_load *= busiest_h_load;
243e0e7b 1520 moved_load = div_u64(moved_load, busiest_weight + 1);
bf0f6f24 1521
c09595f6
PZ
1522 rem_load_move -= moved_load;
1523 if (rem_load_move < 0)
bf0f6f24
IM
1524 break;
1525 }
c09595f6 1526 rcu_read_unlock();
bf0f6f24 1527
43010659 1528 return max_load_move - rem_load_move;
bf0f6f24 1529}
c09595f6
PZ
1530#else
1531static unsigned long
1532load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
1533 unsigned long max_load_move,
1534 struct sched_domain *sd, enum cpu_idle_type idle,
1535 int *all_pinned, int *this_best_prio)
1536{
1537 return __load_balance_fair(this_rq, this_cpu, busiest,
1538 max_load_move, sd, idle, all_pinned,
1539 this_best_prio, &busiest->cfs);
1540}
1541#endif
bf0f6f24 1542
e1d1484f
PW
1543static int
1544move_one_task_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
1545 struct sched_domain *sd, enum cpu_idle_type idle)
1546{
1547 struct cfs_rq *busy_cfs_rq;
1548 struct rq_iterator cfs_rq_iterator;
1549
1550 cfs_rq_iterator.start = load_balance_start_fair;
1551 cfs_rq_iterator.next = load_balance_next_fair;
1552
1553 for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
1554 /*
1555 * pass busy_cfs_rq argument into
1556 * load_balance_[start|next]_fair iterators
1557 */
1558 cfs_rq_iterator.arg = busy_cfs_rq;
1559 if (iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
1560 &cfs_rq_iterator))
1561 return 1;
1562 }
1563
1564 return 0;
1565}
55e12e5e 1566#endif /* CONFIG_SMP */
e1d1484f 1567
bf0f6f24
IM
1568/*
1569 * scheduler tick hitting a task of our scheduling class:
1570 */
8f4d37ec 1571static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
bf0f6f24
IM
1572{
1573 struct cfs_rq *cfs_rq;
1574 struct sched_entity *se = &curr->se;
1575
1576 for_each_sched_entity(se) {
1577 cfs_rq = cfs_rq_of(se);
8f4d37ec 1578 entity_tick(cfs_rq, se, queued);
bf0f6f24
IM
1579 }
1580}
1581
8eb172d9 1582#define swap(a, b) do { typeof(a) tmp = (a); (a) = (b); (b) = tmp; } while (0)
4d78e7b6 1583
bf0f6f24
IM
1584/*
1585 * Share the fairness runtime between parent and child, thus the
1586 * total amount of pressure for CPU stays equal - new tasks
1587 * get a chance to run but frequent forkers are not allowed to
1588 * monopolize the CPU. Note: the parent runqueue is locked,
1589 * the child is not running yet.
1590 */
ee0827d8 1591static void task_new_fair(struct rq *rq, struct task_struct *p)
bf0f6f24
IM
1592{
1593 struct cfs_rq *cfs_rq = task_cfs_rq(p);
429d43bc 1594 struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
00bf7bfc 1595 int this_cpu = smp_processor_id();
bf0f6f24
IM
1596
1597 sched_info_queued(p);
1598
7109c442 1599 update_curr(cfs_rq);
aeb73b04 1600 place_entity(cfs_rq, se, 1);
4d78e7b6 1601
3c90e6e9 1602 /* 'curr' will be NULL if the child belongs to a different group */
00bf7bfc 1603 if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
3c90e6e9 1604 curr && curr->vruntime < se->vruntime) {
87fefa38 1605 /*
edcb60a3
IM
1606 * Upon rescheduling, sched_class::put_prev_task() will place
1607 * 'current' within the tree based on its new key value.
1608 */
4d78e7b6 1609 swap(curr->vruntime, se->vruntime);
aec0a514 1610 resched_task(rq->curr);
4d78e7b6 1611 }
bf0f6f24 1612
b9dca1e0 1613 enqueue_task_fair(rq, p, 0);
bf0f6f24
IM
1614}
1615
cb469845
SR
1616/*
1617 * Priority of the task has changed. Check to see if we preempt
1618 * the current task.
1619 */
1620static void prio_changed_fair(struct rq *rq, struct task_struct *p,
1621 int oldprio, int running)
1622{
1623 /*
1624 * Reschedule if we are currently running on this runqueue and
1625 * our priority decreased, or if we are not currently running on
1626 * this runqueue and our priority is higher than the current's
1627 */
1628 if (running) {
1629 if (p->prio > oldprio)
1630 resched_task(rq->curr);
1631 } else
15afe09b 1632 check_preempt_curr(rq, p, 0);
cb469845
SR
1633}
1634
1635/*
1636 * We switched to the sched_fair class.
1637 */
1638static void switched_to_fair(struct rq *rq, struct task_struct *p,
1639 int running)
1640{
1641 /*
1642 * We were most likely switched from sched_rt, so
1643 * kick off the schedule if running, otherwise just see
1644 * if we can still preempt the current task.
1645 */
1646 if (running)
1647 resched_task(rq->curr);
1648 else
15afe09b 1649 check_preempt_curr(rq, p, 0);
cb469845
SR
1650}
1651
83b699ed
SV
1652/* Account for a task changing its policy or group.
1653 *
1654 * This routine is mostly called to set cfs_rq->curr field when a task
1655 * migrates between groups/classes.
1656 */
1657static void set_curr_task_fair(struct rq *rq)
1658{
1659 struct sched_entity *se = &rq->curr->se;
1660
1661 for_each_sched_entity(se)
1662 set_next_entity(cfs_rq_of(se), se);
1663}
1664
810b3817
PZ
1665#ifdef CONFIG_FAIR_GROUP_SCHED
1666static void moved_group_fair(struct task_struct *p)
1667{
1668 struct cfs_rq *cfs_rq = task_cfs_rq(p);
1669
1670 update_curr(cfs_rq);
1671 place_entity(cfs_rq, &p->se, 1);
1672}
1673#endif
1674
bf0f6f24
IM
1675/*
1676 * All the scheduling class methods:
1677 */
5522d5d5
IM
1678static const struct sched_class fair_sched_class = {
1679 .next = &idle_sched_class,
bf0f6f24
IM
1680 .enqueue_task = enqueue_task_fair,
1681 .dequeue_task = dequeue_task_fair,
1682 .yield_task = yield_task_fair,
1683
2e09bf55 1684 .check_preempt_curr = check_preempt_wakeup,
bf0f6f24
IM
1685
1686 .pick_next_task = pick_next_task_fair,
1687 .put_prev_task = put_prev_task_fair,
1688
681f3e68 1689#ifdef CONFIG_SMP
4ce72a2c
LZ
1690 .select_task_rq = select_task_rq_fair,
1691
bf0f6f24 1692 .load_balance = load_balance_fair,
e1d1484f 1693 .move_one_task = move_one_task_fair,
681f3e68 1694#endif
bf0f6f24 1695
83b699ed 1696 .set_curr_task = set_curr_task_fair,
bf0f6f24
IM
1697 .task_tick = task_tick_fair,
1698 .task_new = task_new_fair,
cb469845
SR
1699
1700 .prio_changed = prio_changed_fair,
1701 .switched_to = switched_to_fair,
810b3817
PZ
1702
1703#ifdef CONFIG_FAIR_GROUP_SCHED
1704 .moved_group = moved_group_fair,
1705#endif
bf0f6f24
IM
1706};
1707
1708#ifdef CONFIG_SCHED_DEBUG
5cef9eca 1709static void print_cfs_stats(struct seq_file *m, int cpu)
bf0f6f24 1710{
bf0f6f24
IM
1711 struct cfs_rq *cfs_rq;
1712
5973e5b9 1713 rcu_read_lock();
c3b64f1e 1714 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
5cef9eca 1715 print_cfs_rq(m, cpu, cfs_rq);
5973e5b9 1716 rcu_read_unlock();
bf0f6f24
IM
1717}
1718#endif