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/*
* 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.
*/
#include <linux/cpufreq.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <trace/events/power.h>
#include "sched.h"
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 work_struct work;
struct mutex work_lock;
bool work_in_progress;
bool need_freq_update;
};
struct sugov_cpu {
struct update_util_data update_util;
struct sugov_policy *sg_policy;
/* The fields below are only needed when sharing a policy. */
unsigned long util;
unsigned long max;
u64 last_update;
};
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.
* @policy: cpufreq policy 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.
*/
static unsigned int get_next_freq(struct cpufreq_policy *policy,
unsigned long util, unsigned long max)
{
unsigned int freq = arch_scale_freq_invariant() ?
policy->cpuinfo.max_freq : policy->cur;
return (freq + (freq >> 2)) * util / max;
}
static void sugov_update_single(struct update_util_data *hook, u64 time,
unsigned long util, unsigned long max)
{
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 int next_f;
if (!sugov_should_update_freq(sg_policy, time))
return;
next_f = util == ULONG_MAX ? policy->cpuinfo.max_freq :
get_next_freq(policy, util, max);
sugov_update_commit(sg_policy, time, next_f);
}
static unsigned int sugov_next_freq_shared(struct sugov_policy *sg_policy,
unsigned long util, unsigned long max)
{
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 (util == ULONG_MAX)
return max_f;
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.
*/
delta_ns = last_freq_update_time - j_sg_cpu->last_update;
if (delta_ns > TICK_NSEC)
continue;
j_util = j_sg_cpu->util;
if (j_util == ULONG_MAX)
return max_f;
j_max = j_sg_cpu->max;
if (j_util * max > j_max * util) {
util = j_util;
max = j_max;
}
}
return get_next_freq(policy, util, max);
}
static void sugov_update_shared(struct update_util_data *hook, u64 time,
unsigned long util, unsigned long max)
{
struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
struct sugov_policy *sg_policy = sg_cpu->sg_policy;
unsigned int next_f;
raw_spin_lock(&sg_policy->update_lock);
sg_cpu->util = util;
sg_cpu->max = max;
sg_cpu->last_update = time;
if (sugov_should_update_freq(sg_policy, time)) {
next_f = sugov_next_freq_shared(sg_policy, util, max);
sugov_update_commit(sg_policy, time, next_f);
}
raw_spin_unlock(&sg_policy->update_lock);
}
static void sugov_work(struct work_struct *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);
schedule_work_on(smp_processor_id(), &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"
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