Linux 4.12-rc2
[sfrench/cifs-2.6.git] / kernel / sched / cpufreq_schedutil.c
1 /*
2  * CPUFreq governor based on scheduler-provided CPU utilization data.
3  *
4  * Copyright (C) 2016, Intel Corporation
5  * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation.
10  */
11
12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13
14 #include <linux/cpufreq.h>
15 #include <linux/kthread.h>
16 #include <uapi/linux/sched/types.h>
17 #include <linux/slab.h>
18 #include <trace/events/power.h>
19
20 #include "sched.h"
21
22 #define SUGOV_KTHREAD_PRIORITY  50
23
24 struct sugov_tunables {
25         struct gov_attr_set attr_set;
26         unsigned int rate_limit_us;
27 };
28
29 struct sugov_policy {
30         struct cpufreq_policy *policy;
31
32         struct sugov_tunables *tunables;
33         struct list_head tunables_hook;
34
35         raw_spinlock_t update_lock;  /* For shared policies */
36         u64 last_freq_update_time;
37         s64 freq_update_delay_ns;
38         unsigned int next_freq;
39         unsigned int cached_raw_freq;
40
41         /* The next fields are only needed if fast switch cannot be used. */
42         struct irq_work irq_work;
43         struct kthread_work work;
44         struct mutex work_lock;
45         struct kthread_worker worker;
46         struct task_struct *thread;
47         bool work_in_progress;
48
49         bool need_freq_update;
50 };
51
52 struct sugov_cpu {
53         struct update_util_data update_util;
54         struct sugov_policy *sg_policy;
55
56         unsigned long iowait_boost;
57         unsigned long iowait_boost_max;
58         u64 last_update;
59
60         /* The fields below are only needed when sharing a policy. */
61         unsigned long util;
62         unsigned long max;
63         unsigned int flags;
64
65         /* The field below is for single-CPU policies only. */
66 #ifdef CONFIG_NO_HZ_COMMON
67         unsigned long saved_idle_calls;
68 #endif
69 };
70
71 static DEFINE_PER_CPU(struct sugov_cpu, sugov_cpu);
72
73 /************************ Governor internals ***********************/
74
75 static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
76 {
77         s64 delta_ns;
78
79         if (sg_policy->work_in_progress)
80                 return false;
81
82         if (unlikely(sg_policy->need_freq_update)) {
83                 sg_policy->need_freq_update = false;
84                 /*
85                  * This happens when limits change, so forget the previous
86                  * next_freq value and force an update.
87                  */
88                 sg_policy->next_freq = UINT_MAX;
89                 return true;
90         }
91
92         delta_ns = time - sg_policy->last_freq_update_time;
93         return delta_ns >= sg_policy->freq_update_delay_ns;
94 }
95
96 static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
97                                 unsigned int next_freq)
98 {
99         struct cpufreq_policy *policy = sg_policy->policy;
100
101         if (sg_policy->next_freq == next_freq)
102                 return;
103
104         if (sg_policy->next_freq > next_freq)
105                 next_freq = (sg_policy->next_freq + next_freq) >> 1;
106
107         sg_policy->next_freq = next_freq;
108         sg_policy->last_freq_update_time = time;
109
110         if (policy->fast_switch_enabled) {
111                 next_freq = cpufreq_driver_fast_switch(policy, next_freq);
112                 if (next_freq == CPUFREQ_ENTRY_INVALID)
113                         return;
114
115                 policy->cur = next_freq;
116                 trace_cpu_frequency(next_freq, smp_processor_id());
117         } else {
118                 sg_policy->work_in_progress = true;
119                 irq_work_queue(&sg_policy->irq_work);
120         }
121 }
122
123 /**
124  * get_next_freq - Compute a new frequency for a given cpufreq policy.
125  * @sg_policy: schedutil policy object to compute the new frequency for.
126  * @util: Current CPU utilization.
127  * @max: CPU capacity.
128  *
129  * If the utilization is frequency-invariant, choose the new frequency to be
130  * proportional to it, that is
131  *
132  * next_freq = C * max_freq * util / max
133  *
134  * Otherwise, approximate the would-be frequency-invariant utilization by
135  * util_raw * (curr_freq / max_freq) which leads to
136  *
137  * next_freq = C * curr_freq * util_raw / max
138  *
139  * Take C = 1.25 for the frequency tipping point at (util / max) = 0.8.
140  *
141  * The lowest driver-supported frequency which is equal or greater than the raw
142  * next_freq (as calculated above) is returned, subject to policy min/max and
143  * cpufreq driver limitations.
144  */
145 static unsigned int get_next_freq(struct sugov_policy *sg_policy,
146                                   unsigned long util, unsigned long max)
147 {
148         struct cpufreq_policy *policy = sg_policy->policy;
149         unsigned int freq = arch_scale_freq_invariant() ?
150                                 policy->cpuinfo.max_freq : policy->cur;
151
152         freq = (freq + (freq >> 2)) * util / max;
153
154         if (freq == sg_policy->cached_raw_freq && sg_policy->next_freq != UINT_MAX)
155                 return sg_policy->next_freq;
156         sg_policy->cached_raw_freq = freq;
157         return cpufreq_driver_resolve_freq(policy, freq);
158 }
159
160 static void sugov_get_util(unsigned long *util, unsigned long *max)
161 {
162         struct rq *rq = this_rq();
163         unsigned long cfs_max;
164
165         cfs_max = arch_scale_cpu_capacity(NULL, smp_processor_id());
166
167         *util = min(rq->cfs.avg.util_avg, cfs_max);
168         *max = cfs_max;
169 }
170
171 static void sugov_set_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
172                                    unsigned int flags)
173 {
174         if (flags & SCHED_CPUFREQ_IOWAIT) {
175                 sg_cpu->iowait_boost = sg_cpu->iowait_boost_max;
176         } else if (sg_cpu->iowait_boost) {
177                 s64 delta_ns = time - sg_cpu->last_update;
178
179                 /* Clear iowait_boost if the CPU apprears to have been idle. */
180                 if (delta_ns > TICK_NSEC)
181                         sg_cpu->iowait_boost = 0;
182         }
183 }
184
185 static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, unsigned long *util,
186                                unsigned long *max)
187 {
188         unsigned long boost_util = sg_cpu->iowait_boost;
189         unsigned long boost_max = sg_cpu->iowait_boost_max;
190
191         if (!boost_util)
192                 return;
193
194         if (*util * boost_max < *max * boost_util) {
195                 *util = boost_util;
196                 *max = boost_max;
197         }
198         sg_cpu->iowait_boost >>= 1;
199 }
200
201 #ifdef CONFIG_NO_HZ_COMMON
202 static bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu)
203 {
204         unsigned long idle_calls = tick_nohz_get_idle_calls();
205         bool ret = idle_calls == sg_cpu->saved_idle_calls;
206
207         sg_cpu->saved_idle_calls = idle_calls;
208         return ret;
209 }
210 #else
211 static inline bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu) { return false; }
212 #endif /* CONFIG_NO_HZ_COMMON */
213
214 static void sugov_update_single(struct update_util_data *hook, u64 time,
215                                 unsigned int flags)
216 {
217         struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
218         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
219         struct cpufreq_policy *policy = sg_policy->policy;
220         unsigned long util, max;
221         unsigned int next_f;
222         bool busy;
223
224         sugov_set_iowait_boost(sg_cpu, time, flags);
225         sg_cpu->last_update = time;
226
227         if (!sugov_should_update_freq(sg_policy, time))
228                 return;
229
230         busy = sugov_cpu_is_busy(sg_cpu);
231
232         if (flags & SCHED_CPUFREQ_RT_DL) {
233                 next_f = policy->cpuinfo.max_freq;
234         } else {
235                 sugov_get_util(&util, &max);
236                 sugov_iowait_boost(sg_cpu, &util, &max);
237                 next_f = get_next_freq(sg_policy, util, max);
238                 /*
239                  * Do not reduce the frequency if the CPU has not been idle
240                  * recently, as the reduction is likely to be premature then.
241                  */
242                 if (busy && next_f < sg_policy->next_freq)
243                         next_f = sg_policy->next_freq;
244         }
245         sugov_update_commit(sg_policy, time, next_f);
246 }
247
248 static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu)
249 {
250         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
251         struct cpufreq_policy *policy = sg_policy->policy;
252         u64 last_freq_update_time = sg_policy->last_freq_update_time;
253         unsigned long util = 0, max = 1;
254         unsigned int j;
255
256         for_each_cpu(j, policy->cpus) {
257                 struct sugov_cpu *j_sg_cpu = &per_cpu(sugov_cpu, j);
258                 unsigned long j_util, j_max;
259                 s64 delta_ns;
260
261                 /*
262                  * If the CPU utilization was last updated before the previous
263                  * frequency update and the time elapsed between the last update
264                  * of the CPU utilization and the last frequency update is long
265                  * enough, don't take the CPU into account as it probably is
266                  * idle now (and clear iowait_boost for it).
267                  */
268                 delta_ns = last_freq_update_time - j_sg_cpu->last_update;
269                 if (delta_ns > TICK_NSEC) {
270                         j_sg_cpu->iowait_boost = 0;
271                         continue;
272                 }
273                 if (j_sg_cpu->flags & SCHED_CPUFREQ_RT_DL)
274                         return policy->cpuinfo.max_freq;
275
276                 j_util = j_sg_cpu->util;
277                 j_max = j_sg_cpu->max;
278                 if (j_util * max > j_max * util) {
279                         util = j_util;
280                         max = j_max;
281                 }
282
283                 sugov_iowait_boost(j_sg_cpu, &util, &max);
284         }
285
286         return get_next_freq(sg_policy, util, max);
287 }
288
289 static void sugov_update_shared(struct update_util_data *hook, u64 time,
290                                 unsigned int flags)
291 {
292         struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
293         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
294         unsigned long util, max;
295         unsigned int next_f;
296
297         sugov_get_util(&util, &max);
298
299         raw_spin_lock(&sg_policy->update_lock);
300
301         sg_cpu->util = util;
302         sg_cpu->max = max;
303         sg_cpu->flags = flags;
304
305         sugov_set_iowait_boost(sg_cpu, time, flags);
306         sg_cpu->last_update = time;
307
308         if (sugov_should_update_freq(sg_policy, time)) {
309                 if (flags & SCHED_CPUFREQ_RT_DL)
310                         next_f = sg_policy->policy->cpuinfo.max_freq;
311                 else
312                         next_f = sugov_next_freq_shared(sg_cpu);
313
314                 sugov_update_commit(sg_policy, time, next_f);
315         }
316
317         raw_spin_unlock(&sg_policy->update_lock);
318 }
319
320 static void sugov_work(struct kthread_work *work)
321 {
322         struct sugov_policy *sg_policy = container_of(work, struct sugov_policy, work);
323
324         mutex_lock(&sg_policy->work_lock);
325         __cpufreq_driver_target(sg_policy->policy, sg_policy->next_freq,
326                                 CPUFREQ_RELATION_L);
327         mutex_unlock(&sg_policy->work_lock);
328
329         sg_policy->work_in_progress = false;
330 }
331
332 static void sugov_irq_work(struct irq_work *irq_work)
333 {
334         struct sugov_policy *sg_policy;
335
336         sg_policy = container_of(irq_work, struct sugov_policy, irq_work);
337
338         /*
339          * For RT and deadline tasks, the schedutil governor shoots the
340          * frequency to maximum. Special care must be taken to ensure that this
341          * kthread doesn't result in the same behavior.
342          *
343          * This is (mostly) guaranteed by the work_in_progress flag. The flag is
344          * updated only at the end of the sugov_work() function and before that
345          * the schedutil governor rejects all other frequency scaling requests.
346          *
347          * There is a very rare case though, where the RT thread yields right
348          * after the work_in_progress flag is cleared. The effects of that are
349          * neglected for now.
350          */
351         kthread_queue_work(&sg_policy->worker, &sg_policy->work);
352 }
353
354 /************************** sysfs interface ************************/
355
356 static struct sugov_tunables *global_tunables;
357 static DEFINE_MUTEX(global_tunables_lock);
358
359 static inline struct sugov_tunables *to_sugov_tunables(struct gov_attr_set *attr_set)
360 {
361         return container_of(attr_set, struct sugov_tunables, attr_set);
362 }
363
364 static ssize_t rate_limit_us_show(struct gov_attr_set *attr_set, char *buf)
365 {
366         struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
367
368         return sprintf(buf, "%u\n", tunables->rate_limit_us);
369 }
370
371 static ssize_t rate_limit_us_store(struct gov_attr_set *attr_set, const char *buf,
372                                    size_t count)
373 {
374         struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
375         struct sugov_policy *sg_policy;
376         unsigned int rate_limit_us;
377
378         if (kstrtouint(buf, 10, &rate_limit_us))
379                 return -EINVAL;
380
381         tunables->rate_limit_us = rate_limit_us;
382
383         list_for_each_entry(sg_policy, &attr_set->policy_list, tunables_hook)
384                 sg_policy->freq_update_delay_ns = rate_limit_us * NSEC_PER_USEC;
385
386         return count;
387 }
388
389 static struct governor_attr rate_limit_us = __ATTR_RW(rate_limit_us);
390
391 static struct attribute *sugov_attributes[] = {
392         &rate_limit_us.attr,
393         NULL
394 };
395
396 static struct kobj_type sugov_tunables_ktype = {
397         .default_attrs = sugov_attributes,
398         .sysfs_ops = &governor_sysfs_ops,
399 };
400
401 /********************** cpufreq governor interface *********************/
402
403 static struct cpufreq_governor schedutil_gov;
404
405 static struct sugov_policy *sugov_policy_alloc(struct cpufreq_policy *policy)
406 {
407         struct sugov_policy *sg_policy;
408
409         sg_policy = kzalloc(sizeof(*sg_policy), GFP_KERNEL);
410         if (!sg_policy)
411                 return NULL;
412
413         sg_policy->policy = policy;
414         raw_spin_lock_init(&sg_policy->update_lock);
415         return sg_policy;
416 }
417
418 static void sugov_policy_free(struct sugov_policy *sg_policy)
419 {
420         kfree(sg_policy);
421 }
422
423 static int sugov_kthread_create(struct sugov_policy *sg_policy)
424 {
425         struct task_struct *thread;
426         struct sched_param param = { .sched_priority = MAX_USER_RT_PRIO / 2 };
427         struct cpufreq_policy *policy = sg_policy->policy;
428         int ret;
429
430         /* kthread only required for slow path */
431         if (policy->fast_switch_enabled)
432                 return 0;
433
434         kthread_init_work(&sg_policy->work, sugov_work);
435         kthread_init_worker(&sg_policy->worker);
436         thread = kthread_create(kthread_worker_fn, &sg_policy->worker,
437                                 "sugov:%d",
438                                 cpumask_first(policy->related_cpus));
439         if (IS_ERR(thread)) {
440                 pr_err("failed to create sugov thread: %ld\n", PTR_ERR(thread));
441                 return PTR_ERR(thread);
442         }
443
444         ret = sched_setscheduler_nocheck(thread, SCHED_FIFO, &param);
445         if (ret) {
446                 kthread_stop(thread);
447                 pr_warn("%s: failed to set SCHED_FIFO\n", __func__);
448                 return ret;
449         }
450
451         sg_policy->thread = thread;
452         kthread_bind_mask(thread, policy->related_cpus);
453         init_irq_work(&sg_policy->irq_work, sugov_irq_work);
454         mutex_init(&sg_policy->work_lock);
455
456         wake_up_process(thread);
457
458         return 0;
459 }
460
461 static void sugov_kthread_stop(struct sugov_policy *sg_policy)
462 {
463         /* kthread only required for slow path */
464         if (sg_policy->policy->fast_switch_enabled)
465                 return;
466
467         kthread_flush_worker(&sg_policy->worker);
468         kthread_stop(sg_policy->thread);
469         mutex_destroy(&sg_policy->work_lock);
470 }
471
472 static struct sugov_tunables *sugov_tunables_alloc(struct sugov_policy *sg_policy)
473 {
474         struct sugov_tunables *tunables;
475
476         tunables = kzalloc(sizeof(*tunables), GFP_KERNEL);
477         if (tunables) {
478                 gov_attr_set_init(&tunables->attr_set, &sg_policy->tunables_hook);
479                 if (!have_governor_per_policy())
480                         global_tunables = tunables;
481         }
482         return tunables;
483 }
484
485 static void sugov_tunables_free(struct sugov_tunables *tunables)
486 {
487         if (!have_governor_per_policy())
488                 global_tunables = NULL;
489
490         kfree(tunables);
491 }
492
493 static int sugov_init(struct cpufreq_policy *policy)
494 {
495         struct sugov_policy *sg_policy;
496         struct sugov_tunables *tunables;
497         int ret = 0;
498
499         /* State should be equivalent to EXIT */
500         if (policy->governor_data)
501                 return -EBUSY;
502
503         cpufreq_enable_fast_switch(policy);
504
505         sg_policy = sugov_policy_alloc(policy);
506         if (!sg_policy) {
507                 ret = -ENOMEM;
508                 goto disable_fast_switch;
509         }
510
511         ret = sugov_kthread_create(sg_policy);
512         if (ret)
513                 goto free_sg_policy;
514
515         mutex_lock(&global_tunables_lock);
516
517         if (global_tunables) {
518                 if (WARN_ON(have_governor_per_policy())) {
519                         ret = -EINVAL;
520                         goto stop_kthread;
521                 }
522                 policy->governor_data = sg_policy;
523                 sg_policy->tunables = global_tunables;
524
525                 gov_attr_set_get(&global_tunables->attr_set, &sg_policy->tunables_hook);
526                 goto out;
527         }
528
529         tunables = sugov_tunables_alloc(sg_policy);
530         if (!tunables) {
531                 ret = -ENOMEM;
532                 goto stop_kthread;
533         }
534
535         if (policy->transition_delay_us) {
536                 tunables->rate_limit_us = policy->transition_delay_us;
537         } else {
538                 unsigned int lat;
539
540                 tunables->rate_limit_us = LATENCY_MULTIPLIER;
541                 lat = policy->cpuinfo.transition_latency / NSEC_PER_USEC;
542                 if (lat)
543                         tunables->rate_limit_us *= lat;
544         }
545
546         policy->governor_data = sg_policy;
547         sg_policy->tunables = tunables;
548
549         ret = kobject_init_and_add(&tunables->attr_set.kobj, &sugov_tunables_ktype,
550                                    get_governor_parent_kobj(policy), "%s",
551                                    schedutil_gov.name);
552         if (ret)
553                 goto fail;
554
555 out:
556         mutex_unlock(&global_tunables_lock);
557         return 0;
558
559 fail:
560         policy->governor_data = NULL;
561         sugov_tunables_free(tunables);
562
563 stop_kthread:
564         sugov_kthread_stop(sg_policy);
565
566 free_sg_policy:
567         mutex_unlock(&global_tunables_lock);
568
569         sugov_policy_free(sg_policy);
570
571 disable_fast_switch:
572         cpufreq_disable_fast_switch(policy);
573
574         pr_err("initialization failed (error %d)\n", ret);
575         return ret;
576 }
577
578 static void sugov_exit(struct cpufreq_policy *policy)
579 {
580         struct sugov_policy *sg_policy = policy->governor_data;
581         struct sugov_tunables *tunables = sg_policy->tunables;
582         unsigned int count;
583
584         mutex_lock(&global_tunables_lock);
585
586         count = gov_attr_set_put(&tunables->attr_set, &sg_policy->tunables_hook);
587         policy->governor_data = NULL;
588         if (!count)
589                 sugov_tunables_free(tunables);
590
591         mutex_unlock(&global_tunables_lock);
592
593         sugov_kthread_stop(sg_policy);
594         sugov_policy_free(sg_policy);
595         cpufreq_disable_fast_switch(policy);
596 }
597
598 static int sugov_start(struct cpufreq_policy *policy)
599 {
600         struct sugov_policy *sg_policy = policy->governor_data;
601         unsigned int cpu;
602
603         sg_policy->freq_update_delay_ns = sg_policy->tunables->rate_limit_us * NSEC_PER_USEC;
604         sg_policy->last_freq_update_time = 0;
605         sg_policy->next_freq = UINT_MAX;
606         sg_policy->work_in_progress = false;
607         sg_policy->need_freq_update = false;
608         sg_policy->cached_raw_freq = 0;
609
610         for_each_cpu(cpu, policy->cpus) {
611                 struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu);
612
613                 memset(sg_cpu, 0, sizeof(*sg_cpu));
614                 sg_cpu->sg_policy = sg_policy;
615                 sg_cpu->flags = SCHED_CPUFREQ_RT;
616                 sg_cpu->iowait_boost_max = policy->cpuinfo.max_freq;
617                 cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util,
618                                              policy_is_shared(policy) ?
619                                                         sugov_update_shared :
620                                                         sugov_update_single);
621         }
622         return 0;
623 }
624
625 static void sugov_stop(struct cpufreq_policy *policy)
626 {
627         struct sugov_policy *sg_policy = policy->governor_data;
628         unsigned int cpu;
629
630         for_each_cpu(cpu, policy->cpus)
631                 cpufreq_remove_update_util_hook(cpu);
632
633         synchronize_sched();
634
635         if (!policy->fast_switch_enabled) {
636                 irq_work_sync(&sg_policy->irq_work);
637                 kthread_cancel_work_sync(&sg_policy->work);
638         }
639 }
640
641 static void sugov_limits(struct cpufreq_policy *policy)
642 {
643         struct sugov_policy *sg_policy = policy->governor_data;
644
645         if (!policy->fast_switch_enabled) {
646                 mutex_lock(&sg_policy->work_lock);
647                 cpufreq_policy_apply_limits(policy);
648                 mutex_unlock(&sg_policy->work_lock);
649         }
650
651         sg_policy->need_freq_update = true;
652 }
653
654 static struct cpufreq_governor schedutil_gov = {
655         .name = "schedutil",
656         .owner = THIS_MODULE,
657         .init = sugov_init,
658         .exit = sugov_exit,
659         .start = sugov_start,
660         .stop = sugov_stop,
661         .limits = sugov_limits,
662 };
663
664 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL
665 struct cpufreq_governor *cpufreq_default_governor(void)
666 {
667         return &schedutil_gov;
668 }
669 #endif
670
671 static int __init sugov_register(void)
672 {
673         return cpufreq_register_governor(&schedutil_gov);
674 }
675 fs_initcall(sugov_register);