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