linux/kernel/sched/cpufreq_schedutil.c

656 lines
17 KiB
C

/*
* CPUFreq governor based on scheduler-provided CPU utilization data.
*
* Copyright (C) 2016, Intel Corporation
* Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/cpufreq.h>
#include <linux/kthread.h>
#include <linux/slab.h>
#include <trace/events/power.h>
#include "sched.h"
#define SUGOV_KTHREAD_PRIORITY 50
struct sugov_tunables {
struct gov_attr_set attr_set;
unsigned int rate_limit_us;
};
struct sugov_policy {
struct cpufreq_policy *policy;
struct sugov_tunables *tunables;
struct list_head tunables_hook;
raw_spinlock_t update_lock; /* For shared policies */
u64 last_freq_update_time;
s64 freq_update_delay_ns;
unsigned int next_freq;
/* The next fields are only needed if fast switch cannot be used. */
struct irq_work irq_work;
struct kthread_work work;
struct mutex work_lock;
struct kthread_worker worker;
struct task_struct *thread;
bool work_in_progress;
bool need_freq_update;
};
struct sugov_cpu {
struct update_util_data update_util;
struct sugov_policy *sg_policy;
unsigned int cached_raw_freq;
unsigned long iowait_boost;
unsigned long iowait_boost_max;
u64 last_update;
/* The fields below are only needed when sharing a policy. */
unsigned long util;
unsigned long max;
unsigned int flags;
};
static DEFINE_PER_CPU(struct sugov_cpu, sugov_cpu);
/************************ Governor internals ***********************/
static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
{
s64 delta_ns;
if (sg_policy->work_in_progress)
return false;
if (unlikely(sg_policy->need_freq_update)) {
sg_policy->need_freq_update = false;
/*
* This happens when limits change, so forget the previous
* next_freq value and force an update.
*/
sg_policy->next_freq = UINT_MAX;
return true;
}
delta_ns = time - sg_policy->last_freq_update_time;
return delta_ns >= sg_policy->freq_update_delay_ns;
}
static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
unsigned int next_freq)
{
struct cpufreq_policy *policy = sg_policy->policy;
sg_policy->last_freq_update_time = time;
if (policy->fast_switch_enabled) {
if (sg_policy->next_freq == next_freq) {
trace_cpu_frequency(policy->cur, smp_processor_id());
return;
}
sg_policy->next_freq = next_freq;
next_freq = cpufreq_driver_fast_switch(policy, next_freq);
if (next_freq == CPUFREQ_ENTRY_INVALID)
return;
policy->cur = next_freq;
trace_cpu_frequency(next_freq, smp_processor_id());
} else if (sg_policy->next_freq != next_freq) {
sg_policy->next_freq = next_freq;
sg_policy->work_in_progress = true;
irq_work_queue(&sg_policy->irq_work);
}
}
/**
* get_next_freq - Compute a new frequency for a given cpufreq policy.
* @sg_cpu: schedutil cpu object to compute the new frequency for.
* @util: Current CPU utilization.
* @max: CPU capacity.
*
* If the utilization is frequency-invariant, choose the new frequency to be
* proportional to it, that is
*
* next_freq = C * max_freq * util / max
*
* Otherwise, approximate the would-be frequency-invariant utilization by
* util_raw * (curr_freq / max_freq) which leads to
*
* next_freq = C * curr_freq * util_raw / max
*
* Take C = 1.25 for the frequency tipping point at (util / max) = 0.8.
*
* The lowest driver-supported frequency which is equal or greater than the raw
* next_freq (as calculated above) is returned, subject to policy min/max and
* cpufreq driver limitations.
*/
static unsigned int get_next_freq(struct sugov_cpu *sg_cpu, unsigned long util,
unsigned long max)
{
struct sugov_policy *sg_policy = sg_cpu->sg_policy;
struct cpufreq_policy *policy = sg_policy->policy;
unsigned int freq = arch_scale_freq_invariant() ?
policy->cpuinfo.max_freq : policy->cur;
freq = (freq + (freq >> 2)) * util / max;
if (freq == sg_cpu->cached_raw_freq && sg_policy->next_freq != UINT_MAX)
return sg_policy->next_freq;
sg_cpu->cached_raw_freq = freq;
return cpufreq_driver_resolve_freq(policy, freq);
}
static void sugov_get_util(unsigned long *util, unsigned long *max)
{
struct rq *rq = this_rq();
unsigned long cfs_max;
cfs_max = arch_scale_cpu_capacity(NULL, smp_processor_id());
*util = min(rq->cfs.avg.util_avg, cfs_max);
*max = cfs_max;
}
static void sugov_set_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
unsigned int flags)
{
if (flags & SCHED_CPUFREQ_IOWAIT) {
sg_cpu->iowait_boost = sg_cpu->iowait_boost_max;
} else if (sg_cpu->iowait_boost) {
s64 delta_ns = time - sg_cpu->last_update;
/* Clear iowait_boost if the CPU apprears to have been idle. */
if (delta_ns > TICK_NSEC)
sg_cpu->iowait_boost = 0;
}
}
static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, unsigned long *util,
unsigned long *max)
{
unsigned long boost_util = sg_cpu->iowait_boost;
unsigned long boost_max = sg_cpu->iowait_boost_max;
if (!boost_util)
return;
if (*util * boost_max < *max * boost_util) {
*util = boost_util;
*max = boost_max;
}
sg_cpu->iowait_boost >>= 1;
}
static void sugov_update_single(struct update_util_data *hook, u64 time,
unsigned int flags)
{
struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
struct sugov_policy *sg_policy = sg_cpu->sg_policy;
struct cpufreq_policy *policy = sg_policy->policy;
unsigned long util, max;
unsigned int next_f;
sugov_set_iowait_boost(sg_cpu, time, flags);
sg_cpu->last_update = time;
if (!sugov_should_update_freq(sg_policy, time))
return;
if (flags & SCHED_CPUFREQ_RT_DL) {
next_f = policy->cpuinfo.max_freq;
} else {
sugov_get_util(&util, &max);
sugov_iowait_boost(sg_cpu, &util, &max);
next_f = get_next_freq(sg_cpu, util, max);
}
sugov_update_commit(sg_policy, time, next_f);
}
static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu,
unsigned long util, unsigned long max,
unsigned int flags)
{
struct sugov_policy *sg_policy = sg_cpu->sg_policy;
struct cpufreq_policy *policy = sg_policy->policy;
unsigned int max_f = policy->cpuinfo.max_freq;
u64 last_freq_update_time = sg_policy->last_freq_update_time;
unsigned int j;
if (flags & SCHED_CPUFREQ_RT_DL)
return max_f;
sugov_iowait_boost(sg_cpu, &util, &max);
for_each_cpu(j, policy->cpus) {
struct sugov_cpu *j_sg_cpu;
unsigned long j_util, j_max;
s64 delta_ns;
if (j == smp_processor_id())
continue;
j_sg_cpu = &per_cpu(sugov_cpu, j);
/*
* If the CPU utilization was last updated before the previous
* frequency update and the time elapsed between the last update
* of the CPU utilization and the last frequency update is long
* enough, don't take the CPU into account as it probably is
* idle now (and clear iowait_boost for it).
*/
delta_ns = last_freq_update_time - j_sg_cpu->last_update;
if (delta_ns > TICK_NSEC) {
j_sg_cpu->iowait_boost = 0;
continue;
}
if (j_sg_cpu->flags & SCHED_CPUFREQ_RT_DL)
return max_f;
j_util = j_sg_cpu->util;
j_max = j_sg_cpu->max;
if (j_util * max > j_max * util) {
util = j_util;
max = j_max;
}
sugov_iowait_boost(j_sg_cpu, &util, &max);
}
return get_next_freq(sg_cpu, util, max);
}
static void sugov_update_shared(struct update_util_data *hook, u64 time,
unsigned int flags)
{
struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
struct sugov_policy *sg_policy = sg_cpu->sg_policy;
unsigned long util, max;
unsigned int next_f;
sugov_get_util(&util, &max);
raw_spin_lock(&sg_policy->update_lock);
sg_cpu->util = util;
sg_cpu->max = max;
sg_cpu->flags = flags;
sugov_set_iowait_boost(sg_cpu, time, flags);
sg_cpu->last_update = time;
if (sugov_should_update_freq(sg_policy, time)) {
next_f = sugov_next_freq_shared(sg_cpu, util, max, flags);
sugov_update_commit(sg_policy, time, next_f);
}
raw_spin_unlock(&sg_policy->update_lock);
}
static void sugov_work(struct kthread_work *work)
{
struct sugov_policy *sg_policy = container_of(work, struct sugov_policy, work);
mutex_lock(&sg_policy->work_lock);
__cpufreq_driver_target(sg_policy->policy, sg_policy->next_freq,
CPUFREQ_RELATION_L);
mutex_unlock(&sg_policy->work_lock);
sg_policy->work_in_progress = false;
}
static void sugov_irq_work(struct irq_work *irq_work)
{
struct sugov_policy *sg_policy;
sg_policy = container_of(irq_work, struct sugov_policy, irq_work);
/*
* For RT and deadline tasks, the schedutil governor shoots the
* frequency to maximum. Special care must be taken to ensure that this
* kthread doesn't result in the same behavior.
*
* This is (mostly) guaranteed by the work_in_progress flag. The flag is
* updated only at the end of the sugov_work() function and before that
* the schedutil governor rejects all other frequency scaling requests.
*
* There is a very rare case though, where the RT thread yields right
* after the work_in_progress flag is cleared. The effects of that are
* neglected for now.
*/
kthread_queue_work(&sg_policy->worker, &sg_policy->work);
}
/************************** sysfs interface ************************/
static struct sugov_tunables *global_tunables;
static DEFINE_MUTEX(global_tunables_lock);
static inline struct sugov_tunables *to_sugov_tunables(struct gov_attr_set *attr_set)
{
return container_of(attr_set, struct sugov_tunables, attr_set);
}
static ssize_t rate_limit_us_show(struct gov_attr_set *attr_set, char *buf)
{
struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
return sprintf(buf, "%u\n", tunables->rate_limit_us);
}
static ssize_t rate_limit_us_store(struct gov_attr_set *attr_set, const char *buf,
size_t count)
{
struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
struct sugov_policy *sg_policy;
unsigned int rate_limit_us;
if (kstrtouint(buf, 10, &rate_limit_us))
return -EINVAL;
tunables->rate_limit_us = rate_limit_us;
list_for_each_entry(sg_policy, &attr_set->policy_list, tunables_hook)
sg_policy->freq_update_delay_ns = rate_limit_us * NSEC_PER_USEC;
return count;
}
static struct governor_attr rate_limit_us = __ATTR_RW(rate_limit_us);
static struct attribute *sugov_attributes[] = {
&rate_limit_us.attr,
NULL
};
static struct kobj_type sugov_tunables_ktype = {
.default_attrs = sugov_attributes,
.sysfs_ops = &governor_sysfs_ops,
};
/********************** cpufreq governor interface *********************/
static struct cpufreq_governor schedutil_gov;
static struct sugov_policy *sugov_policy_alloc(struct cpufreq_policy *policy)
{
struct sugov_policy *sg_policy;
sg_policy = kzalloc(sizeof(*sg_policy), GFP_KERNEL);
if (!sg_policy)
return NULL;
sg_policy->policy = policy;
raw_spin_lock_init(&sg_policy->update_lock);
return sg_policy;
}
static void sugov_policy_free(struct sugov_policy *sg_policy)
{
kfree(sg_policy);
}
static int sugov_kthread_create(struct sugov_policy *sg_policy)
{
struct task_struct *thread;
struct sched_param param = { .sched_priority = MAX_USER_RT_PRIO / 2 };
struct cpufreq_policy *policy = sg_policy->policy;
int ret;
/* kthread only required for slow path */
if (policy->fast_switch_enabled)
return 0;
kthread_init_work(&sg_policy->work, sugov_work);
kthread_init_worker(&sg_policy->worker);
thread = kthread_create(kthread_worker_fn, &sg_policy->worker,
"sugov:%d",
cpumask_first(policy->related_cpus));
if (IS_ERR(thread)) {
pr_err("failed to create sugov thread: %ld\n", PTR_ERR(thread));
return PTR_ERR(thread);
}
ret = sched_setscheduler_nocheck(thread, SCHED_FIFO, &param);
if (ret) {
kthread_stop(thread);
pr_warn("%s: failed to set SCHED_FIFO\n", __func__);
return ret;
}
sg_policy->thread = thread;
kthread_bind_mask(thread, policy->related_cpus);
init_irq_work(&sg_policy->irq_work, sugov_irq_work);
mutex_init(&sg_policy->work_lock);
wake_up_process(thread);
return 0;
}
static void sugov_kthread_stop(struct sugov_policy *sg_policy)
{
/* kthread only required for slow path */
if (sg_policy->policy->fast_switch_enabled)
return;
kthread_flush_worker(&sg_policy->worker);
kthread_stop(sg_policy->thread);
mutex_destroy(&sg_policy->work_lock);
}
static struct sugov_tunables *sugov_tunables_alloc(struct sugov_policy *sg_policy)
{
struct sugov_tunables *tunables;
tunables = kzalloc(sizeof(*tunables), GFP_KERNEL);
if (tunables) {
gov_attr_set_init(&tunables->attr_set, &sg_policy->tunables_hook);
if (!have_governor_per_policy())
global_tunables = tunables;
}
return tunables;
}
static void sugov_tunables_free(struct sugov_tunables *tunables)
{
if (!have_governor_per_policy())
global_tunables = NULL;
kfree(tunables);
}
static int sugov_init(struct cpufreq_policy *policy)
{
struct sugov_policy *sg_policy;
struct sugov_tunables *tunables;
unsigned int lat;
int ret = 0;
/* State should be equivalent to EXIT */
if (policy->governor_data)
return -EBUSY;
cpufreq_enable_fast_switch(policy);
sg_policy = sugov_policy_alloc(policy);
if (!sg_policy) {
ret = -ENOMEM;
goto disable_fast_switch;
}
ret = sugov_kthread_create(sg_policy);
if (ret)
goto free_sg_policy;
mutex_lock(&global_tunables_lock);
if (global_tunables) {
if (WARN_ON(have_governor_per_policy())) {
ret = -EINVAL;
goto stop_kthread;
}
policy->governor_data = sg_policy;
sg_policy->tunables = global_tunables;
gov_attr_set_get(&global_tunables->attr_set, &sg_policy->tunables_hook);
goto out;
}
tunables = sugov_tunables_alloc(sg_policy);
if (!tunables) {
ret = -ENOMEM;
goto stop_kthread;
}
tunables->rate_limit_us = LATENCY_MULTIPLIER;
lat = policy->cpuinfo.transition_latency / NSEC_PER_USEC;
if (lat)
tunables->rate_limit_us *= lat;
policy->governor_data = sg_policy;
sg_policy->tunables = tunables;
ret = kobject_init_and_add(&tunables->attr_set.kobj, &sugov_tunables_ktype,
get_governor_parent_kobj(policy), "%s",
schedutil_gov.name);
if (ret)
goto fail;
out:
mutex_unlock(&global_tunables_lock);
return 0;
fail:
policy->governor_data = NULL;
sugov_tunables_free(tunables);
stop_kthread:
sugov_kthread_stop(sg_policy);
free_sg_policy:
mutex_unlock(&global_tunables_lock);
sugov_policy_free(sg_policy);
disable_fast_switch:
cpufreq_disable_fast_switch(policy);
pr_err("initialization failed (error %d)\n", ret);
return ret;
}
static void sugov_exit(struct cpufreq_policy *policy)
{
struct sugov_policy *sg_policy = policy->governor_data;
struct sugov_tunables *tunables = sg_policy->tunables;
unsigned int count;
mutex_lock(&global_tunables_lock);
count = gov_attr_set_put(&tunables->attr_set, &sg_policy->tunables_hook);
policy->governor_data = NULL;
if (!count)
sugov_tunables_free(tunables);
mutex_unlock(&global_tunables_lock);
sugov_kthread_stop(sg_policy);
sugov_policy_free(sg_policy);
cpufreq_disable_fast_switch(policy);
}
static int sugov_start(struct cpufreq_policy *policy)
{
struct sugov_policy *sg_policy = policy->governor_data;
unsigned int cpu;
sg_policy->freq_update_delay_ns = sg_policy->tunables->rate_limit_us * NSEC_PER_USEC;
sg_policy->last_freq_update_time = 0;
sg_policy->next_freq = UINT_MAX;
sg_policy->work_in_progress = false;
sg_policy->need_freq_update = false;
for_each_cpu(cpu, policy->cpus) {
struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu);
sg_cpu->sg_policy = sg_policy;
if (policy_is_shared(policy)) {
sg_cpu->util = 0;
sg_cpu->max = 0;
sg_cpu->flags = SCHED_CPUFREQ_RT;
sg_cpu->last_update = 0;
sg_cpu->cached_raw_freq = 0;
sg_cpu->iowait_boost = 0;
sg_cpu->iowait_boost_max = policy->cpuinfo.max_freq;
cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util,
sugov_update_shared);
} else {
cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util,
sugov_update_single);
}
}
return 0;
}
static void sugov_stop(struct cpufreq_policy *policy)
{
struct sugov_policy *sg_policy = policy->governor_data;
unsigned int cpu;
for_each_cpu(cpu, policy->cpus)
cpufreq_remove_update_util_hook(cpu);
synchronize_sched();
if (!policy->fast_switch_enabled) {
irq_work_sync(&sg_policy->irq_work);
kthread_cancel_work_sync(&sg_policy->work);
}
}
static void sugov_limits(struct cpufreq_policy *policy)
{
struct sugov_policy *sg_policy = policy->governor_data;
if (!policy->fast_switch_enabled) {
mutex_lock(&sg_policy->work_lock);
cpufreq_policy_apply_limits(policy);
mutex_unlock(&sg_policy->work_lock);
}
sg_policy->need_freq_update = true;
}
static struct cpufreq_governor schedutil_gov = {
.name = "schedutil",
.owner = THIS_MODULE,
.init = sugov_init,
.exit = sugov_exit,
.start = sugov_start,
.stop = sugov_stop,
.limits = sugov_limits,
};
#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL
struct cpufreq_governor *cpufreq_default_governor(void)
{
return &schedutil_gov;
}
#endif
static int __init sugov_register(void)
{
return cpufreq_register_governor(&schedutil_gov);
}
fs_initcall(sugov_register);