linux/drivers/cpufreq/cpufreq_ondemand.c

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/*
* drivers/cpufreq/cpufreq_ondemand.c
*
* Copyright (C) 2001 Russell King
* (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
* Jun Nakajima <jun.nakajima@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/kernel.h>
#include <linux/module.h>
#include <linux/smp.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/ctype.h>
#include <linux/cpufreq.h>
#include <linux/sysctl.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/sysfs.h>
#include <linux/sched.h>
#include <linux/kmod.h>
#include <linux/workqueue.h>
#include <linux/jiffies.h>
#include <linux/kernel_stat.h>
#include <linux/percpu.h>
/*
* dbs is used in this file as a shortform for demandbased switching
* It helps to keep variable names smaller, simpler
*/
#define DEF_FREQUENCY_UP_THRESHOLD (80)
#define MIN_FREQUENCY_UP_THRESHOLD (11)
#define MAX_FREQUENCY_UP_THRESHOLD (100)
/*
* The polling frequency of this governor depends on the capability of
* the processor. Default polling frequency is 1000 times the transition
* latency of the processor. The governor will work on any processor with
* transition latency <= 10mS, using appropriate sampling
* rate.
* For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
* this governor will not work.
* All times here are in uS.
*/
static unsigned int def_sampling_rate;
#define MIN_SAMPLING_RATE_RATIO (2)
/* for correct statistics, we need at least 10 ticks between each measure */
#define MIN_STAT_SAMPLING_RATE (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
#define MIN_SAMPLING_RATE (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
#define MAX_SAMPLING_RATE (500 * def_sampling_rate)
#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000)
#define DEF_SAMPLING_DOWN_FACTOR (1)
#define MAX_SAMPLING_DOWN_FACTOR (10)
#define TRANSITION_LATENCY_LIMIT (10 * 1000)
static void do_dbs_timer(void *data);
struct cpu_dbs_info_s {
struct cpufreq_policy *cur_policy;
unsigned int prev_cpu_idle_up;
unsigned int prev_cpu_idle_down;
unsigned int enable;
};
static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
static unsigned int dbs_enable; /* number of CPUs using this policy */
static DECLARE_MUTEX (dbs_sem);
static DECLARE_WORK (dbs_work, do_dbs_timer, NULL);
struct dbs_tuners {
unsigned int sampling_rate;
unsigned int sampling_down_factor;
unsigned int up_threshold;
unsigned int ignore_nice;
};
static struct dbs_tuners dbs_tuners_ins = {
.up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
.sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
};
static inline unsigned int get_cpu_idle_time(unsigned int cpu)
{
return kstat_cpu(cpu).cpustat.idle +
kstat_cpu(cpu).cpustat.iowait +
( !dbs_tuners_ins.ignore_nice ?
kstat_cpu(cpu).cpustat.nice :
0);
}
/************************** sysfs interface ************************/
static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
{
return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
}
static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
{
return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
}
#define define_one_ro(_name) \
static struct freq_attr _name = \
__ATTR(_name, 0444, show_##_name, NULL)
define_one_ro(sampling_rate_max);
define_one_ro(sampling_rate_min);
/* cpufreq_ondemand Governor Tunables */
#define show_one(file_name, object) \
static ssize_t show_##file_name \
(struct cpufreq_policy *unused, char *buf) \
{ \
return sprintf(buf, "%u\n", dbs_tuners_ins.object); \
}
show_one(sampling_rate, sampling_rate);
show_one(sampling_down_factor, sampling_down_factor);
show_one(up_threshold, up_threshold);
show_one(ignore_nice, ignore_nice);
static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
const char *buf, size_t count)
{
unsigned int input;
int ret;
ret = sscanf (buf, "%u", &input);
if (ret != 1 )
return -EINVAL;
if (input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
return -EINVAL;
down(&dbs_sem);
dbs_tuners_ins.sampling_down_factor = input;
up(&dbs_sem);
return count;
}
static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
const char *buf, size_t count)
{
unsigned int input;
int ret;
ret = sscanf (buf, "%u", &input);
down(&dbs_sem);
if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
up(&dbs_sem);
return -EINVAL;
}
dbs_tuners_ins.sampling_rate = input;
up(&dbs_sem);
return count;
}
static ssize_t store_up_threshold(struct cpufreq_policy *unused,
const char *buf, size_t count)
{
unsigned int input;
int ret;
ret = sscanf (buf, "%u", &input);
down(&dbs_sem);
if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
input < MIN_FREQUENCY_UP_THRESHOLD) {
up(&dbs_sem);
return -EINVAL;
}
dbs_tuners_ins.up_threshold = input;
up(&dbs_sem);
return count;
}
static ssize_t store_ignore_nice(struct cpufreq_policy *policy,
const char *buf, size_t count)
{
unsigned int input;
int ret;
unsigned int j;
ret = sscanf (buf, "%u", &input);
if ( ret != 1 )
return -EINVAL;
if ( input > 1 )
input = 1;
down(&dbs_sem);
if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
up(&dbs_sem);
return count;
}
dbs_tuners_ins.ignore_nice = input;
/* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
for_each_online_cpu(j) {
struct cpu_dbs_info_s *j_dbs_info;
j_dbs_info = &per_cpu(cpu_dbs_info, j);
j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
}
up(&dbs_sem);
return count;
}
#define define_one_rw(_name) \
static struct freq_attr _name = \
__ATTR(_name, 0644, show_##_name, store_##_name)
define_one_rw(sampling_rate);
define_one_rw(sampling_down_factor);
define_one_rw(up_threshold);
define_one_rw(ignore_nice);
static struct attribute * dbs_attributes[] = {
&sampling_rate_max.attr,
&sampling_rate_min.attr,
&sampling_rate.attr,
&sampling_down_factor.attr,
&up_threshold.attr,
&ignore_nice.attr,
NULL
};
static struct attribute_group dbs_attr_group = {
.attrs = dbs_attributes,
.name = "ondemand",
};
/************************** sysfs end ************************/
static void dbs_check_cpu(int cpu)
{
unsigned int idle_ticks, up_idle_ticks, total_ticks;
unsigned int freq_next;
unsigned int freq_down_sampling_rate;
static int down_skip[NR_CPUS];
struct cpu_dbs_info_s *this_dbs_info;
struct cpufreq_policy *policy;
unsigned int j;
this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
if (!this_dbs_info->enable)
return;
policy = this_dbs_info->cur_policy;
/*
* Every sampling_rate, we check, if current idle time is less
* than 20% (default), then we try to increase frequency
* Every sampling_rate*sampling_down_factor, we look for a the lowest
* frequency which can sustain the load while keeping idle time over
* 30%. If such a frequency exist, we try to decrease to this frequency.
*
* Any frequency increase takes it to the maximum frequency.
* Frequency reduction happens at minimum steps of
* 5% (default) of current frequency
*/
/* Check for frequency increase */
idle_ticks = UINT_MAX;
for_each_cpu_mask(j, policy->cpus) {
unsigned int tmp_idle_ticks, total_idle_ticks;
struct cpu_dbs_info_s *j_dbs_info;
j_dbs_info = &per_cpu(cpu_dbs_info, j);
total_idle_ticks = get_cpu_idle_time(j);
tmp_idle_ticks = total_idle_ticks -
j_dbs_info->prev_cpu_idle_up;
j_dbs_info->prev_cpu_idle_up = total_idle_ticks;
if (tmp_idle_ticks < idle_ticks)
idle_ticks = tmp_idle_ticks;
}
/* Scale idle ticks by 100 and compare with up and down ticks */
idle_ticks *= 100;
up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
if (idle_ticks < up_idle_ticks) {
down_skip[cpu] = 0;
for_each_cpu_mask(j, policy->cpus) {
struct cpu_dbs_info_s *j_dbs_info;
j_dbs_info = &per_cpu(cpu_dbs_info, j);
j_dbs_info->prev_cpu_idle_down =
j_dbs_info->prev_cpu_idle_up;
}
/* if we are already at full speed then break out early */
if (policy->cur == policy->max)
return;
__cpufreq_driver_target(policy, policy->max,
CPUFREQ_RELATION_H);
return;
}
/* Check for frequency decrease */
down_skip[cpu]++;
if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
return;
idle_ticks = UINT_MAX;
for_each_cpu_mask(j, policy->cpus) {
unsigned int tmp_idle_ticks, total_idle_ticks;
struct cpu_dbs_info_s *j_dbs_info;
j_dbs_info = &per_cpu(cpu_dbs_info, j);
/* Check for frequency decrease */
total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
tmp_idle_ticks = total_idle_ticks -
j_dbs_info->prev_cpu_idle_down;
j_dbs_info->prev_cpu_idle_down = total_idle_ticks;
if (tmp_idle_ticks < idle_ticks)
idle_ticks = tmp_idle_ticks;
}
down_skip[cpu] = 0;
/* if we cannot reduce the frequency anymore, break out early */
if (policy->cur == policy->min)
return;
/* Compute how many ticks there are between two measurements */
freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
dbs_tuners_ins.sampling_down_factor;
total_ticks = usecs_to_jiffies(freq_down_sampling_rate);
/*
* The optimal frequency is the frequency that is the lowest that
* can support the current CPU usage without triggering the up
* policy. To be safe, we focus 10 points under the threshold.
*/
freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks;
freq_next = (freq_next * policy->cur) /
(dbs_tuners_ins.up_threshold - 10);
if (freq_next <= ((policy->cur * 95) / 100))
__cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);
}
static void do_dbs_timer(void *data)
{
int i;
down(&dbs_sem);
for_each_online_cpu(i)
dbs_check_cpu(i);
schedule_delayed_work(&dbs_work,
usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
up(&dbs_sem);
}
static inline void dbs_timer_init(void)
{
INIT_WORK(&dbs_work, do_dbs_timer, NULL);
schedule_delayed_work(&dbs_work,
usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
return;
}
static inline void dbs_timer_exit(void)
{
cancel_delayed_work(&dbs_work);
return;
}
static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
unsigned int event)
{
unsigned int cpu = policy->cpu;
struct cpu_dbs_info_s *this_dbs_info;
unsigned int j;
this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
switch (event) {
case CPUFREQ_GOV_START:
if ((!cpu_online(cpu)) ||
(!policy->cur))
return -EINVAL;
if (policy->cpuinfo.transition_latency >
(TRANSITION_LATENCY_LIMIT * 1000))
return -EINVAL;
if (this_dbs_info->enable) /* Already enabled */
break;
down(&dbs_sem);
for_each_cpu_mask(j, policy->cpus) {
struct cpu_dbs_info_s *j_dbs_info;
j_dbs_info = &per_cpu(cpu_dbs_info, j);
j_dbs_info->cur_policy = policy;
j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
j_dbs_info->prev_cpu_idle_down
= j_dbs_info->prev_cpu_idle_up;
}
this_dbs_info->enable = 1;
sysfs_create_group(&policy->kobj, &dbs_attr_group);
dbs_enable++;
/*
* Start the timerschedule work, when this governor
* is used for first time
*/
if (dbs_enable == 1) {
unsigned int latency;
/* policy latency is in nS. Convert it to uS first */
latency = policy->cpuinfo.transition_latency / 1000;
if (latency == 0)
latency = 1;
def_sampling_rate = latency *
DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
def_sampling_rate = MIN_STAT_SAMPLING_RATE;
dbs_tuners_ins.sampling_rate = def_sampling_rate;
dbs_tuners_ins.ignore_nice = 0;
dbs_timer_init();
}
up(&dbs_sem);
break;
case CPUFREQ_GOV_STOP:
down(&dbs_sem);
this_dbs_info->enable = 0;
sysfs_remove_group(&policy->kobj, &dbs_attr_group);
dbs_enable--;
/*
* Stop the timerschedule work, when this governor
* is used for first time
*/
if (dbs_enable == 0)
dbs_timer_exit();
up(&dbs_sem);
break;
case CPUFREQ_GOV_LIMITS:
down(&dbs_sem);
if (policy->max < this_dbs_info->cur_policy->cur)
__cpufreq_driver_target(
this_dbs_info->cur_policy,
policy->max, CPUFREQ_RELATION_H);
else if (policy->min > this_dbs_info->cur_policy->cur)
__cpufreq_driver_target(
this_dbs_info->cur_policy,
policy->min, CPUFREQ_RELATION_L);
up(&dbs_sem);
break;
}
return 0;
}
static struct cpufreq_governor cpufreq_gov_dbs = {
.name = "ondemand",
.governor = cpufreq_governor_dbs,
.owner = THIS_MODULE,
};
static int __init cpufreq_gov_dbs_init(void)
{
return cpufreq_register_governor(&cpufreq_gov_dbs);
}
static void __exit cpufreq_gov_dbs_exit(void)
{
/* Make sure that the scheduled work is indeed not running */
flush_scheduled_work();
cpufreq_unregister_governor(&cpufreq_gov_dbs);
}
MODULE_AUTHOR ("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor for "
"Low Latency Frequency Transition capable processors");
MODULE_LICENSE ("GPL");
module_init(cpufreq_gov_dbs_init);
module_exit(cpufreq_gov_dbs_exit);