2 * CPUFreq governor based on scheduler-provided CPU utilization data.
4 * Copyright (C) 2016, Intel Corporation
5 * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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.
12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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>
22 #define SUGOV_KTHREAD_PRIORITY 50
24 struct sugov_tunables
{
25 struct gov_attr_set attr_set
;
26 unsigned int rate_limit_us
;
30 struct cpufreq_policy
*policy
;
32 struct sugov_tunables
*tunables
;
33 struct list_head tunables_hook
;
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
;
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
;
49 bool need_freq_update
;
53 struct update_util_data update_util
;
54 struct sugov_policy
*sg_policy
;
57 bool iowait_boost_pending
;
58 unsigned int iowait_boost
;
59 unsigned int iowait_boost_max
;
62 /* The fields below are only needed when sharing a policy. */
67 /* The field below is for single-CPU policies only. */
68 #ifdef CONFIG_NO_HZ_COMMON
69 unsigned long saved_idle_calls
;
73 static DEFINE_PER_CPU(struct sugov_cpu
, sugov_cpu
);
75 /************************ Governor internals ***********************/
77 static bool sugov_should_update_freq(struct sugov_policy
*sg_policy
, u64 time
)
82 * Since cpufreq_update_util() is called with rq->lock held for
83 * the @target_cpu, our per-cpu data is fully serialized.
85 * However, drivers cannot in general deal with cross-cpu
86 * requests, so while get_next_freq() will work, our
87 * sugov_update_commit() call may not for the fast switching platforms.
89 * Hence stop here for remote requests if they aren't supported
90 * by the hardware, as calculating the frequency is pointless if
91 * we cannot in fact act on it.
93 * For the slow switching platforms, the kthread is always scheduled on
94 * the right set of CPUs and any CPU can find the next frequency and
95 * schedule the kthread.
97 if (sg_policy
->policy
->fast_switch_enabled
&&
98 !cpufreq_can_do_remote_dvfs(sg_policy
->policy
))
101 if (sg_policy
->work_in_progress
)
104 if (unlikely(sg_policy
->need_freq_update
)) {
105 sg_policy
->need_freq_update
= false;
107 * This happens when limits change, so forget the previous
108 * next_freq value and force an update.
110 sg_policy
->next_freq
= UINT_MAX
;
114 delta_ns
= time
- sg_policy
->last_freq_update_time
;
115 return delta_ns
>= sg_policy
->freq_update_delay_ns
;
118 static void sugov_update_commit(struct sugov_policy
*sg_policy
, u64 time
,
119 unsigned int next_freq
)
121 struct cpufreq_policy
*policy
= sg_policy
->policy
;
123 if (sg_policy
->next_freq
== next_freq
)
126 sg_policy
->next_freq
= next_freq
;
127 sg_policy
->last_freq_update_time
= time
;
129 if (policy
->fast_switch_enabled
) {
130 next_freq
= cpufreq_driver_fast_switch(policy
, next_freq
);
134 policy
->cur
= next_freq
;
135 trace_cpu_frequency(next_freq
, smp_processor_id());
137 sg_policy
->work_in_progress
= true;
138 irq_work_queue(&sg_policy
->irq_work
);
143 * get_next_freq - Compute a new frequency for a given cpufreq policy.
144 * @sg_policy: schedutil policy object to compute the new frequency for.
145 * @util: Current CPU utilization.
146 * @max: CPU capacity.
148 * If the utilization is frequency-invariant, choose the new frequency to be
149 * proportional to it, that is
151 * next_freq = C * max_freq * util / max
153 * Otherwise, approximate the would-be frequency-invariant utilization by
154 * util_raw * (curr_freq / max_freq) which leads to
156 * next_freq = C * curr_freq * util_raw / max
158 * Take C = 1.25 for the frequency tipping point at (util / max) = 0.8.
160 * The lowest driver-supported frequency which is equal or greater than the raw
161 * next_freq (as calculated above) is returned, subject to policy min/max and
162 * cpufreq driver limitations.
164 static unsigned int get_next_freq(struct sugov_policy
*sg_policy
,
165 unsigned long util
, unsigned long max
)
167 struct cpufreq_policy
*policy
= sg_policy
->policy
;
168 unsigned int freq
= arch_scale_freq_invariant() ?
169 policy
->cpuinfo
.max_freq
: policy
->cur
;
171 freq
= (freq
+ (freq
>> 2)) * util
/ max
;
173 if (freq
== sg_policy
->cached_raw_freq
&& sg_policy
->next_freq
!= UINT_MAX
)
174 return sg_policy
->next_freq
;
175 sg_policy
->cached_raw_freq
= freq
;
176 return cpufreq_driver_resolve_freq(policy
, freq
);
179 static void sugov_get_util(unsigned long *util
, unsigned long *max
, int cpu
)
181 struct rq
*rq
= cpu_rq(cpu
);
182 unsigned long cfs_max
;
184 cfs_max
= arch_scale_cpu_capacity(NULL
, cpu
);
186 *util
= min(rq
->cfs
.avg
.util_avg
, cfs_max
);
190 static void sugov_set_iowait_boost(struct sugov_cpu
*sg_cpu
, u64 time
,
193 if (flags
& SCHED_CPUFREQ_IOWAIT
) {
194 if (sg_cpu
->iowait_boost_pending
)
197 sg_cpu
->iowait_boost_pending
= true;
199 if (sg_cpu
->iowait_boost
) {
200 sg_cpu
->iowait_boost
<<= 1;
201 if (sg_cpu
->iowait_boost
> sg_cpu
->iowait_boost_max
)
202 sg_cpu
->iowait_boost
= sg_cpu
->iowait_boost_max
;
204 sg_cpu
->iowait_boost
= sg_cpu
->sg_policy
->policy
->min
;
206 } else if (sg_cpu
->iowait_boost
) {
207 s64 delta_ns
= time
- sg_cpu
->last_update
;
209 /* Clear iowait_boost if the CPU apprears to have been idle. */
210 if (delta_ns
> TICK_NSEC
) {
211 sg_cpu
->iowait_boost
= 0;
212 sg_cpu
->iowait_boost_pending
= false;
217 static void sugov_iowait_boost(struct sugov_cpu
*sg_cpu
, unsigned long *util
,
220 unsigned int boost_util
, boost_max
;
222 if (!sg_cpu
->iowait_boost
)
225 if (sg_cpu
->iowait_boost_pending
) {
226 sg_cpu
->iowait_boost_pending
= false;
228 sg_cpu
->iowait_boost
>>= 1;
229 if (sg_cpu
->iowait_boost
< sg_cpu
->sg_policy
->policy
->min
) {
230 sg_cpu
->iowait_boost
= 0;
235 boost_util
= sg_cpu
->iowait_boost
;
236 boost_max
= sg_cpu
->iowait_boost_max
;
238 if (*util
* boost_max
< *max
* boost_util
) {
244 #ifdef CONFIG_NO_HZ_COMMON
245 static bool sugov_cpu_is_busy(struct sugov_cpu
*sg_cpu
)
247 unsigned long idle_calls
= tick_nohz_get_idle_calls_cpu(sg_cpu
->cpu
);
248 bool ret
= idle_calls
== sg_cpu
->saved_idle_calls
;
250 sg_cpu
->saved_idle_calls
= idle_calls
;
254 static inline bool sugov_cpu_is_busy(struct sugov_cpu
*sg_cpu
) { return false; }
255 #endif /* CONFIG_NO_HZ_COMMON */
257 static void sugov_update_single(struct update_util_data
*hook
, u64 time
,
260 struct sugov_cpu
*sg_cpu
= container_of(hook
, struct sugov_cpu
, update_util
);
261 struct sugov_policy
*sg_policy
= sg_cpu
->sg_policy
;
262 struct cpufreq_policy
*policy
= sg_policy
->policy
;
263 unsigned long util
, max
;
267 sugov_set_iowait_boost(sg_cpu
, time
, flags
);
268 sg_cpu
->last_update
= time
;
270 if (!sugov_should_update_freq(sg_policy
, time
))
273 busy
= sugov_cpu_is_busy(sg_cpu
);
275 if (flags
& SCHED_CPUFREQ_RT_DL
) {
276 next_f
= policy
->cpuinfo
.max_freq
;
278 sugov_get_util(&util
, &max
, sg_cpu
->cpu
);
279 sugov_iowait_boost(sg_cpu
, &util
, &max
);
280 next_f
= get_next_freq(sg_policy
, util
, max
);
282 * Do not reduce the frequency if the CPU has not been idle
283 * recently, as the reduction is likely to be premature then.
285 if (busy
&& next_f
< sg_policy
->next_freq
&&
286 sg_policy
->next_freq
!= UINT_MAX
) {
287 next_f
= sg_policy
->next_freq
;
289 /* Reset cached freq as next_freq has changed */
290 sg_policy
->cached_raw_freq
= 0;
293 sugov_update_commit(sg_policy
, time
, next_f
);
296 static unsigned int sugov_next_freq_shared(struct sugov_cpu
*sg_cpu
, u64 time
)
298 struct sugov_policy
*sg_policy
= sg_cpu
->sg_policy
;
299 struct cpufreq_policy
*policy
= sg_policy
->policy
;
300 unsigned long util
= 0, max
= 1;
303 for_each_cpu(j
, policy
->cpus
) {
304 struct sugov_cpu
*j_sg_cpu
= &per_cpu(sugov_cpu
, j
);
305 unsigned long j_util
, j_max
;
309 * If the CPU utilization was last updated before the previous
310 * frequency update and the time elapsed between the last update
311 * of the CPU utilization and the last frequency update is long
312 * enough, don't take the CPU into account as it probably is
313 * idle now (and clear iowait_boost for it).
315 delta_ns
= time
- j_sg_cpu
->last_update
;
316 if (delta_ns
> TICK_NSEC
) {
317 j_sg_cpu
->iowait_boost
= 0;
318 j_sg_cpu
->iowait_boost_pending
= false;
321 if (j_sg_cpu
->flags
& SCHED_CPUFREQ_RT_DL
)
322 return policy
->cpuinfo
.max_freq
;
324 j_util
= j_sg_cpu
->util
;
325 j_max
= j_sg_cpu
->max
;
326 if (j_util
* max
> j_max
* util
) {
331 sugov_iowait_boost(j_sg_cpu
, &util
, &max
);
334 return get_next_freq(sg_policy
, util
, max
);
337 static void sugov_update_shared(struct update_util_data
*hook
, u64 time
,
340 struct sugov_cpu
*sg_cpu
= container_of(hook
, struct sugov_cpu
, update_util
);
341 struct sugov_policy
*sg_policy
= sg_cpu
->sg_policy
;
342 unsigned long util
, max
;
345 sugov_get_util(&util
, &max
, sg_cpu
->cpu
);
347 raw_spin_lock(&sg_policy
->update_lock
);
351 sg_cpu
->flags
= flags
;
353 sugov_set_iowait_boost(sg_cpu
, time
, flags
);
354 sg_cpu
->last_update
= time
;
356 if (sugov_should_update_freq(sg_policy
, time
)) {
357 if (flags
& SCHED_CPUFREQ_RT_DL
)
358 next_f
= sg_policy
->policy
->cpuinfo
.max_freq
;
360 next_f
= sugov_next_freq_shared(sg_cpu
, time
);
362 sugov_update_commit(sg_policy
, time
, next_f
);
365 raw_spin_unlock(&sg_policy
->update_lock
);
368 static void sugov_work(struct kthread_work
*work
)
370 struct sugov_policy
*sg_policy
= container_of(work
, struct sugov_policy
, work
);
372 mutex_lock(&sg_policy
->work_lock
);
373 __cpufreq_driver_target(sg_policy
->policy
, sg_policy
->next_freq
,
375 mutex_unlock(&sg_policy
->work_lock
);
377 sg_policy
->work_in_progress
= false;
380 static void sugov_irq_work(struct irq_work
*irq_work
)
382 struct sugov_policy
*sg_policy
;
384 sg_policy
= container_of(irq_work
, struct sugov_policy
, irq_work
);
387 * For RT and deadline tasks, the schedutil governor shoots the
388 * frequency to maximum. Special care must be taken to ensure that this
389 * kthread doesn't result in the same behavior.
391 * This is (mostly) guaranteed by the work_in_progress flag. The flag is
392 * updated only at the end of the sugov_work() function and before that
393 * the schedutil governor rejects all other frequency scaling requests.
395 * There is a very rare case though, where the RT thread yields right
396 * after the work_in_progress flag is cleared. The effects of that are
399 kthread_queue_work(&sg_policy
->worker
, &sg_policy
->work
);
402 /************************** sysfs interface ************************/
404 static struct sugov_tunables
*global_tunables
;
405 static DEFINE_MUTEX(global_tunables_lock
);
407 static inline struct sugov_tunables
*to_sugov_tunables(struct gov_attr_set
*attr_set
)
409 return container_of(attr_set
, struct sugov_tunables
, attr_set
);
412 static ssize_t
rate_limit_us_show(struct gov_attr_set
*attr_set
, char *buf
)
414 struct sugov_tunables
*tunables
= to_sugov_tunables(attr_set
);
416 return sprintf(buf
, "%u\n", tunables
->rate_limit_us
);
419 static ssize_t
rate_limit_us_store(struct gov_attr_set
*attr_set
, const char *buf
,
422 struct sugov_tunables
*tunables
= to_sugov_tunables(attr_set
);
423 struct sugov_policy
*sg_policy
;
424 unsigned int rate_limit_us
;
426 if (kstrtouint(buf
, 10, &rate_limit_us
))
429 tunables
->rate_limit_us
= rate_limit_us
;
431 list_for_each_entry(sg_policy
, &attr_set
->policy_list
, tunables_hook
)
432 sg_policy
->freq_update_delay_ns
= rate_limit_us
* NSEC_PER_USEC
;
437 static struct governor_attr rate_limit_us
= __ATTR_RW(rate_limit_us
);
439 static struct attribute
*sugov_attributes
[] = {
444 static struct kobj_type sugov_tunables_ktype
= {
445 .default_attrs
= sugov_attributes
,
446 .sysfs_ops
= &governor_sysfs_ops
,
449 /********************** cpufreq governor interface *********************/
451 static struct cpufreq_governor schedutil_gov
;
453 static struct sugov_policy
*sugov_policy_alloc(struct cpufreq_policy
*policy
)
455 struct sugov_policy
*sg_policy
;
457 sg_policy
= kzalloc(sizeof(*sg_policy
), GFP_KERNEL
);
461 sg_policy
->policy
= policy
;
462 raw_spin_lock_init(&sg_policy
->update_lock
);
466 static void sugov_policy_free(struct sugov_policy
*sg_policy
)
471 static int sugov_kthread_create(struct sugov_policy
*sg_policy
)
473 struct task_struct
*thread
;
474 struct sched_param param
= { .sched_priority
= MAX_USER_RT_PRIO
/ 2 };
475 struct cpufreq_policy
*policy
= sg_policy
->policy
;
478 /* kthread only required for slow path */
479 if (policy
->fast_switch_enabled
)
482 kthread_init_work(&sg_policy
->work
, sugov_work
);
483 kthread_init_worker(&sg_policy
->worker
);
484 thread
= kthread_create(kthread_worker_fn
, &sg_policy
->worker
,
486 cpumask_first(policy
->related_cpus
));
487 if (IS_ERR(thread
)) {
488 pr_err("failed to create sugov thread: %ld\n", PTR_ERR(thread
));
489 return PTR_ERR(thread
);
492 ret
= sched_setscheduler_nocheck(thread
, SCHED_FIFO
, ¶m
);
494 kthread_stop(thread
);
495 pr_warn("%s: failed to set SCHED_FIFO\n", __func__
);
499 sg_policy
->thread
= thread
;
501 /* Kthread is bound to all CPUs by default */
502 if (!policy
->dvfs_possible_from_any_cpu
)
503 kthread_bind_mask(thread
, policy
->related_cpus
);
505 init_irq_work(&sg_policy
->irq_work
, sugov_irq_work
);
506 mutex_init(&sg_policy
->work_lock
);
508 wake_up_process(thread
);
513 static void sugov_kthread_stop(struct sugov_policy
*sg_policy
)
515 /* kthread only required for slow path */
516 if (sg_policy
->policy
->fast_switch_enabled
)
519 kthread_flush_worker(&sg_policy
->worker
);
520 kthread_stop(sg_policy
->thread
);
521 mutex_destroy(&sg_policy
->work_lock
);
524 static struct sugov_tunables
*sugov_tunables_alloc(struct sugov_policy
*sg_policy
)
526 struct sugov_tunables
*tunables
;
528 tunables
= kzalloc(sizeof(*tunables
), GFP_KERNEL
);
530 gov_attr_set_init(&tunables
->attr_set
, &sg_policy
->tunables_hook
);
531 if (!have_governor_per_policy())
532 global_tunables
= tunables
;
537 static void sugov_tunables_free(struct sugov_tunables
*tunables
)
539 if (!have_governor_per_policy())
540 global_tunables
= NULL
;
545 static int sugov_init(struct cpufreq_policy
*policy
)
547 struct sugov_policy
*sg_policy
;
548 struct sugov_tunables
*tunables
;
551 /* State should be equivalent to EXIT */
552 if (policy
->governor_data
)
555 cpufreq_enable_fast_switch(policy
);
557 sg_policy
= sugov_policy_alloc(policy
);
560 goto disable_fast_switch
;
563 ret
= sugov_kthread_create(sg_policy
);
567 mutex_lock(&global_tunables_lock
);
569 if (global_tunables
) {
570 if (WARN_ON(have_governor_per_policy())) {
574 policy
->governor_data
= sg_policy
;
575 sg_policy
->tunables
= global_tunables
;
577 gov_attr_set_get(&global_tunables
->attr_set
, &sg_policy
->tunables_hook
);
581 tunables
= sugov_tunables_alloc(sg_policy
);
587 tunables
->rate_limit_us
= cpufreq_policy_transition_delay_us(policy
);
589 policy
->governor_data
= sg_policy
;
590 sg_policy
->tunables
= tunables
;
592 ret
= kobject_init_and_add(&tunables
->attr_set
.kobj
, &sugov_tunables_ktype
,
593 get_governor_parent_kobj(policy
), "%s",
599 mutex_unlock(&global_tunables_lock
);
603 kobject_put(&tunables
->attr_set
.kobj
);
604 policy
->governor_data
= NULL
;
605 sugov_tunables_free(tunables
);
608 sugov_kthread_stop(sg_policy
);
609 mutex_unlock(&global_tunables_lock
);
612 sugov_policy_free(sg_policy
);
615 cpufreq_disable_fast_switch(policy
);
617 pr_err("initialization failed (error %d)\n", ret
);
621 static void sugov_exit(struct cpufreq_policy
*policy
)
623 struct sugov_policy
*sg_policy
= policy
->governor_data
;
624 struct sugov_tunables
*tunables
= sg_policy
->tunables
;
627 mutex_lock(&global_tunables_lock
);
629 count
= gov_attr_set_put(&tunables
->attr_set
, &sg_policy
->tunables_hook
);
630 policy
->governor_data
= NULL
;
632 sugov_tunables_free(tunables
);
634 mutex_unlock(&global_tunables_lock
);
636 sugov_kthread_stop(sg_policy
);
637 sugov_policy_free(sg_policy
);
638 cpufreq_disable_fast_switch(policy
);
641 static int sugov_start(struct cpufreq_policy
*policy
)
643 struct sugov_policy
*sg_policy
= policy
->governor_data
;
646 sg_policy
->freq_update_delay_ns
= sg_policy
->tunables
->rate_limit_us
* NSEC_PER_USEC
;
647 sg_policy
->last_freq_update_time
= 0;
648 sg_policy
->next_freq
= UINT_MAX
;
649 sg_policy
->work_in_progress
= false;
650 sg_policy
->need_freq_update
= false;
651 sg_policy
->cached_raw_freq
= 0;
653 for_each_cpu(cpu
, policy
->cpus
) {
654 struct sugov_cpu
*sg_cpu
= &per_cpu(sugov_cpu
, cpu
);
656 memset(sg_cpu
, 0, sizeof(*sg_cpu
));
658 sg_cpu
->sg_policy
= sg_policy
;
659 sg_cpu
->flags
= SCHED_CPUFREQ_RT
;
660 sg_cpu
->iowait_boost_max
= policy
->cpuinfo
.max_freq
;
663 for_each_cpu(cpu
, policy
->cpus
) {
664 struct sugov_cpu
*sg_cpu
= &per_cpu(sugov_cpu
, cpu
);
666 cpufreq_add_update_util_hook(cpu
, &sg_cpu
->update_util
,
667 policy_is_shared(policy
) ?
668 sugov_update_shared
:
669 sugov_update_single
);
674 static void sugov_stop(struct cpufreq_policy
*policy
)
676 struct sugov_policy
*sg_policy
= policy
->governor_data
;
679 for_each_cpu(cpu
, policy
->cpus
)
680 cpufreq_remove_update_util_hook(cpu
);
684 if (!policy
->fast_switch_enabled
) {
685 irq_work_sync(&sg_policy
->irq_work
);
686 kthread_cancel_work_sync(&sg_policy
->work
);
690 static void sugov_limits(struct cpufreq_policy
*policy
)
692 struct sugov_policy
*sg_policy
= policy
->governor_data
;
694 if (!policy
->fast_switch_enabled
) {
695 mutex_lock(&sg_policy
->work_lock
);
696 cpufreq_policy_apply_limits(policy
);
697 mutex_unlock(&sg_policy
->work_lock
);
700 sg_policy
->need_freq_update
= true;
703 static struct cpufreq_governor schedutil_gov
= {
705 .owner
= THIS_MODULE
,
706 .dynamic_switching
= true,
709 .start
= sugov_start
,
711 .limits
= sugov_limits
,
714 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL
715 struct cpufreq_governor
*cpufreq_default_governor(void)
717 return &schedutil_gov
;
721 static int __init
sugov_register(void)
723 return cpufreq_register_governor(&schedutil_gov
);
725 fs_initcall(sugov_register
);