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/*
* drivers/cpufreq/cpufreq_governor.c
*
* CPUFREQ governors common code
*
* Copyright (C) 2001 Russell King
* (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
* (C) 2003 Jun Nakajima <jun.nakajima@intel.com>
* (C) 2009 Alexander Clouter <alex@digriz.org.uk>
* (c) 2012 Viresh Kumar <viresh.kumar@linaro.org>
*
* 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/export.h>
#include <linux/kernel_stat.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include "cpufreq_governor.h"
static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs);
static DEFINE_MUTEX(gov_dbs_data_mutex);
/* Common sysfs tunables */
/**
* store_sampling_rate - update sampling rate effective immediately if needed.
*
* If new rate is smaller than the old, simply updating
* dbs.sampling_rate might not be appropriate. For example, if the
* original sampling_rate was 1 second and the requested new sampling rate is 10
* ms because the user needs immediate reaction from ondemand governor, but not
* sure if higher frequency will be required or not, then, the governor may
* change the sampling rate too late; up to 1 second later. Thus, if we are
* reducing the sampling rate, we need to make the new value effective
* immediately.
*
* This must be called with dbs_data->mutex held, otherwise traversing
* policy_dbs_list isn't safe.
*/
ssize_t store_sampling_rate(struct dbs_data *dbs_data, const char *buf,
size_t count)
{
struct policy_dbs_info *policy_dbs;
unsigned int rate;
int ret;
ret = sscanf(buf, "%u", &rate);
if (ret != 1)
return -EINVAL;
dbs_data->sampling_rate = max(rate, dbs_data->min_sampling_rate);
/*
* We are operating under dbs_data->mutex and so the list and its
* entries can't be freed concurrently.
*/
list_for_each_entry(policy_dbs, &dbs_data->policy_dbs_list, list) {
mutex_lock(&policy_dbs->timer_mutex);
/*
* On 32-bit architectures this may race with the
* sample_delay_ns read in dbs_update_util_handler(), but that
* really doesn't matter. If the read returns a value that's
* too big, the sample will be skipped, but the next invocation
* of dbs_update_util_handler() (when the update has been
* completed) will take a sample.
*
* If this runs in parallel with dbs_work_handler(), we may end
* up overwriting the sample_delay_ns value that it has just
* written, but it will be corrected next time a sample is
* taken, so it shouldn't be significant.
*/
gov_update_sample_delay(policy_dbs, 0);
mutex_unlock(&policy_dbs->timer_mutex);
}
return count;
}
EXPORT_SYMBOL_GPL(store_sampling_rate);
/**
* gov_update_cpu_data - Update CPU load data.
* @dbs_data: Top-level governor data pointer.
*
* Update CPU load data for all CPUs in the domain governed by @dbs_data
* (that may be a single policy or a bunch of them if governor tunables are
* system-wide).
*
* Call under the @dbs_data mutex.
*/
void gov_update_cpu_data(struct dbs_data *dbs_data)
{
struct policy_dbs_info *policy_dbs;
list_for_each_entry(policy_dbs, &dbs_data->policy_dbs_list, list) {
unsigned int j;
for_each_cpu(j, policy_dbs->policy->cpus) {
struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_cpu_wall,
dbs_data->io_is_busy);
if (dbs_data->ignore_nice_load)
j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
}
}
}
EXPORT_SYMBOL_GPL(gov_update_cpu_data);
static inline struct dbs_data *to_dbs_data(struct kobject *kobj)
{
return container_of(kobj, struct dbs_data, kobj);
}
static inline struct governor_attr *to_gov_attr(struct attribute *attr)
{
return container_of(attr, struct governor_attr, attr);
}
static ssize_t governor_show(struct kobject *kobj, struct attribute *attr,
char *buf)
{
struct dbs_data *dbs_data = to_dbs_data(kobj);
struct governor_attr *gattr = to_gov_attr(attr);
return gattr->show(dbs_data, buf);
}
static ssize_t governor_store(struct kobject *kobj, struct attribute *attr,
const char *buf, size_t count)
{
struct dbs_data *dbs_data = to_dbs_data(kobj);
struct governor_attr *gattr = to_gov_attr(attr);
int ret = -EBUSY;
mutex_lock(&dbs_data->mutex);
if (dbs_data->usage_count)
ret = gattr->store(dbs_data, buf, count);
mutex_unlock(&dbs_data->mutex);
return ret;
}
/*
* Sysfs Ops for accessing governor attributes.
*
* All show/store invocations for governor specific sysfs attributes, will first
* call the below show/store callbacks and the attribute specific callback will
* be called from within it.
*/
static const struct sysfs_ops governor_sysfs_ops = {
.show = governor_show,
.store = governor_store,
};
unsigned int dbs_update(struct cpufreq_policy *policy)
{
struct policy_dbs_info *policy_dbs = policy->governor_data;
struct dbs_data *dbs_data = policy_dbs->dbs_data;
unsigned int ignore_nice = dbs_data->ignore_nice_load;
unsigned int max_load = 0;
unsigned int sampling_rate, io_busy, j;
/*
* Sometimes governors may use an additional multiplier to increase
* sample delays temporarily. Apply that multiplier to sampling_rate
* so as to keep the wake-up-from-idle detection logic a bit
* conservative.
*/
sampling_rate = dbs_data->sampling_rate * policy_dbs->rate_mult;
/*
* For the purpose of ondemand, waiting for disk IO is an indication
* that you're performance critical, and not that the system is actually
* idle, so do not add the iowait time to the CPU idle time then.
*/
io_busy = dbs_data->io_is_busy;
/* Get Absolute Load */
for_each_cpu(j, policy->cpus) {
struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
u64 cur_wall_time, cur_idle_time;
unsigned int idle_time, wall_time;
unsigned int load;
cur_idle_time = get_cpu_idle_time(j, &cur_wall_time, io_busy);
wall_time = cur_wall_time - j_cdbs->prev_cpu_wall;
j_cdbs->prev_cpu_wall = cur_wall_time;
idle_time = cur_idle_time - j_cdbs->prev_cpu_idle;
j_cdbs->prev_cpu_idle = cur_idle_time;
if (ignore_nice) {
u64 cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
idle_time += cputime_to_usecs(cur_nice - j_cdbs->prev_cpu_nice);
j_cdbs->prev_cpu_nice = cur_nice;
}
if (unlikely(!wall_time || wall_time < idle_time))
continue;
/*
* If the CPU had gone completely idle, and a task just woke up
* on this CPU now, it would be unfair to calculate 'load' the
* usual way for this elapsed time-window, because it will show
* near-zero load, irrespective of how CPU intensive that task
* actually is. This is undesirable for latency-sensitive bursty
* workloads.
*
* To avoid this, we reuse the 'load' from the previous
* time-window and give this task a chance to start with a
* reasonably high CPU frequency. (However, we shouldn't over-do
* this copy, lest we get stuck at a high load (high frequency)
* for too long, even when the current system load has actually
* dropped down. So we perform the copy only once, upon the
* first wake-up from idle.)
*
* Detecting this situation is easy: the governor's utilization
* update handler would not have run during CPU-idle periods.
* Hence, an unusually large 'wall_time' (as compared to the
* sampling rate) indicates this scenario.
*
* prev_load can be zero in two cases and we must recalculate it
* for both cases:
* - during long idle intervals
* - explicitly set to zero
*/
if (unlikely(wall_time > (2 * sampling_rate) &&
j_cdbs->prev_load)) {
load = j_cdbs->prev_load;
/*
* Perform a destructive copy, to ensure that we copy
* the previous load only once, upon the first wake-up
* from idle.
*/
j_cdbs->prev_load = 0;
} else {
load = 100 * (wall_time - idle_time) / wall_time;
j_cdbs->prev_load = load;
}
if (load > max_load)
max_load = load;
}
return max_load;
}
EXPORT_SYMBOL_GPL(dbs_update);
static void gov_set_update_util(struct policy_dbs_info *policy_dbs,
unsigned int delay_us)
{
struct cpufreq_policy *policy = policy_dbs->policy;
int cpu;
gov_update_sample_delay(policy_dbs, delay_us);
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