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/*
* drivers/cpufreq/cpufreq_conservative.c
*
* Copyright (C) 2001 Russell King
* (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
* Jun Nakajima <jun.nakajima@intel.com>
* (C) 2009 Alexander Clouter <alex@digriz.org.uk>
*
* 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/init.h>
#include <linux/cpufreq.h>
#include <linux/cpu.h>
#include <linux/jiffies.h>
#include <linux/kernel_stat.h>
#include <linux/mutex.h>
#include <linux/hrtimer.h>
#include <linux/tick.h>
#include <linux/ktime.h>
#include <linux/sched.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 (63)
#define DEF_FREQUENCY_DOWN_THRESHOLD (26)
/*
* 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.
*/
#define MIN_SAMPLING_RATE_RATIO (2)
static unsigned int min_sampling_rate;
#define LATENCY_MULTIPLIER (1000)
#define MIN_LATENCY_MULTIPLIER (100)
#define DEF_SAMPLING_DOWN_FACTOR (1)
#define MAX_SAMPLING_DOWN_FACTOR (10)
#define TRANSITION_LATENCY_LIMIT (10 * 1000 * 1000)
static void do_dbs_timer(struct work_struct *work);
struct cpu_dbs_info_s {
cputime64_t prev_cpu_idle;
cputime64_t prev_cpu_wall;
cputime64_t prev_cpu_nice;
struct cpufreq_policy *cur_policy;
struct delayed_work work;
unsigned int down_skip;
unsigned int requested_freq;
int cpu;
unsigned int enable:1;
/*
* percpu mutex that serializes governor limit change with
* do_dbs_timer invocation. We do not want do_dbs_timer to run
* when user is changing the governor or limits.
*/
struct mutex timer_mutex;
};
static DEFINE_PER_CPU(struct cpu_dbs_info_s, cs_cpu_dbs_info);
static unsigned int dbs_enable; /* number of CPUs using this policy */
/*
* dbs_mutex protects dbs_enable in governor start/stop.
*/
static DEFINE_MUTEX(dbs_mutex);
static struct dbs_tuners {
unsigned int sampling_rate;
unsigned int sampling_down_factor;
unsigned int up_threshold;
unsigned int down_threshold;
unsigned int ignore_nice;
unsigned int freq_step;
} dbs_tuners_ins = {
.up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
.down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
.sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
.ignore_nice = 0,
.freq_step = 5,
};
static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)
{
u64 idle_time;
u64 cur_wall_time;
u64 busy_time;
cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
busy_time = kcpustat_cpu(cpu).cpustat[CPUTIME_USER];
busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SYSTEM];
busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_IRQ];
busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SOFTIRQ];
busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_STEAL];
busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_NICE];
idle_time = cur_wall_time - busy_time;
if (wall)
*wall = jiffies_to_usecs(cur_wall_time);
return jiffies_to_usecs(idle_time);
}
static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
{
u64 idle_time = get_cpu_idle_time_us(cpu, NULL);
if (idle_time == -1ULL)
return get_cpu_idle_time_jiffy(cpu, wall);
else
idle_time += get_cpu_iowait_time_us(cpu, wall);
return idle_time;
}
/* keep track of frequency transitions */
static int
dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
void *data)
{
struct cpufreq_freqs *freq = data;
struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cs_cpu_dbs_info,
freq->cpu);
struct cpufreq_policy *policy;
if (!this_dbs_info->enable)
return 0;
policy = this_dbs_info->cur_policy;
/*
* we only care if our internally tracked freq moves outside
* the 'valid' ranges of freqency available to us otherwise
* we do not change it
*/
if (this_dbs_info->requested_freq > policy->max
|| this_dbs_info->requested_freq < policy->min)
this_dbs_info->requested_freq = freq->new;
return 0;
}
static struct notifier_block dbs_cpufreq_notifier_block = {
.notifier_call = dbs_cpufreq_notifier
};
/************************** sysfs interface ************************/
static ssize_t show_sampling_rate_min(struct kobject *kobj,
struct attribute *attr, char *buf)
{
return sprintf(buf, "%u\n", min_sampling_rate);
}
define_one_global_ro(sampling_rate_min);
/* cpufreq_conservative Governor Tunables */
#define show_one(file_name, object) \
static ssize_t show_##file_name \
(struct kobject *kobj, struct attribute *attr, 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(down_threshold, down_threshold);
show_one(ignore_nice_load, ignore_nice);
show_one(freq_step, freq_step);
static ssize_t store_sampling_down_factor(struct kobject *a,
struct attribute *b,
const char *buf, size_t count)
{
unsigned int input;
int ret;
ret = sscanf(buf, "%u", &input);
if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
return -EINVAL;
dbs_tuners_ins.sampling_down_factor = input;
return count;
}
static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
const char *buf, size_t count)
{
unsigned int input;
int ret;
ret = sscanf(buf, "%u", &input);
if (ret != 1)
return -EINVAL;
dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);
return count;
}
static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
const char *buf, size_t count)
{
unsigned int input;
int ret;
ret = sscanf(buf, "%u", &input);
if (ret != 1 || input > 100 ||
input <= dbs_tuners_ins.down_threshold)
return -EINVAL;
dbs_tuners_ins.up_threshold = input;
return count;
}
static ssize_t store_down_threshold(struct kobject *a, struct attribute *b,
const char *buf, size_t count)
{
unsigned int input;
int ret;
ret = sscanf(buf, "%u", &input);
/* cannot be lower than 11 otherwise freq will not fall */
if (ret != 1 || input < 11 || input > 100 ||
input >= dbs_tuners_ins.up_threshold)
return -EINVAL;
dbs_tuners_ins.down_threshold = input;
return count;
}
static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
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;
if (input == dbs_tuners_ins.ignore_nice) /* nothing to do */
return count;
dbs_tuners_ins.ignore_nice = input;
/* we need to re-evaluate prev_cpu_idle */
for_each_online_cpu(j) {
struct cpu_dbs_info_s *dbs_info;
dbs_info = &per_cpu(cs_cpu_dbs_info, j);
dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
&dbs_info->prev_cpu_wall);
if (dbs_tuners_ins.ignore_nice)
dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
}
return count;
}
static ssize_t store_freq_step(struct kobject *a, struct attribute *b,
const char *buf, size_t count)
{
unsigned int input;
int ret;
ret = sscanf(buf, "%u", &input);
if (ret != 1)
return -EINVAL;
if (input > 100)
input = 100;
/* no need to test here if freq_step is zero as the user might actually
* want this, they would be crazy though :) */
dbs_tuners_ins.freq_step = input;
return count;
}
define_one_global_rw(sampling_rate);
define_one_global_rw(sampling_down_factor);
define_one_global_rw(up_threshold);
define_one_global_rw(down_threshold);
define_one_global_rw(ignore_nice_load);
define_one_global_rw(freq_step);
static struct attribute *dbs_attributes[] = {
&sampling_rate_min.attr,
&sampling_rate.attr,
&sampling_down_factor.attr,
&up_threshold.attr,
&down_threshold.attr,
&ignore_nice_load.attr,
&freq_step.attr,
NULL
};
static struct attribute_group dbs_attr_group = {
.attrs = dbs_attributes,
.name = "conservative",
};
/************************** sysfs end ************************/
static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
{
unsigned int load = 0;
unsigned int max_load = 0;
unsigned int freq_target;
struct cpufreq_policy *policy;
unsigned int j;
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 check, if current
* idle time is more than 80%, then we try to decrease frequency
*
* Any frequency increase takes it to the maximum frequency.
* Frequency reduction happens at minimum steps of
* 5% (default) of maximum frequency
*/
/* Get Absolute Load */
for_each_cpu(j, policy->cpus) {
struct cpu_dbs_info_s *j_dbs_info;
cputime64_t cur_wall_time, cur_idle_time;
unsigned int idle_time, wall_time;
j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
wall_time = (unsigned int)
(cur_wall_time - j_dbs_info->prev_cpu_wall);
j_dbs_info->prev_cpu_wall = cur_wall_time;
idle_time = (unsigned int)
(cur_idle_time - j_dbs_info->prev_cpu_idle);
j_dbs_info->prev_cpu_idle = cur_idle_time;
if (dbs_tuners_ins.ignore_nice) {
u64 cur_nice;
unsigned long cur_nice_jiffies;
cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE] -
j_dbs_info->prev_cpu_nice;
/*
* Assumption: nice time between sampling periods will
* be less than 2^32 jiffies for 32 bit sys
*/
cur_nice_jiffies = (unsigned long)
cputime64_to_jiffies64(cur_nice);
j_dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
idle_time += jiffies_to_usecs(cur_nice_jiffies);
}
if (unlikely(!wall_time || wall_time < idle_time))
continue;
load = 100 * (wall_time - idle_time) / wall_time;
if (load > max_load)
max_load = load;
}
/*
* break out if we 'cannot' reduce the speed as the user might
* want freq_step to be zero
*/
if (dbs_tuners_ins.freq_step == 0)
return;
/* Check for frequency increase */
if (max_load > dbs_tuners_ins.up_threshold) {
this_dbs_info->down_skip = 0;
/* if we are already at full speed then break out early */
if (this_dbs_info->requested_freq == policy->max)
return;
freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
/* max freq cannot be less than 100. But who knows.... */
if (unlikely(freq_target == 0))
freq_target = 5;
this_dbs_info->requested_freq += freq_target;
if (this_dbs_info->requested_freq > policy->max)
this_dbs_info->requested_freq = policy->max;
__cpufreq_driver_target(policy, this_dbs_info->requested_freq,
CPUFREQ_RELATION_H);
return;
}
/*
* 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.
*/
if (max_load < (dbs_tuners_ins.down_threshold - 10)) {
freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
this_dbs_info->requested_freq -= freq_target;
if (this_dbs_info->requested_freq < policy->min)
this_dbs_info->requested_freq = policy->min;
/*
* if we cannot reduce the frequency anymore, break out early
*/
if (policy->cur == policy->min)
return;
__cpufreq_driver_target(policy, this_dbs_info->requested_freq,
CPUFREQ_RELATION_H);
return;
}
}
static void do_dbs_timer(struct work_struct *work)
{
struct cpu_dbs_info_s *dbs_info =
container_of(work, struct cpu_dbs_info_s, work.work);
unsigned int cpu = dbs_info->cpu;
/* We want all CPUs to do sampling nearly on same jiffy */
int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
delay -= jiffies % delay;
mutex_lock(&dbs_info->timer_mutex);
dbs_check_cpu(dbs_info);
schedule_delayed_work_on(cpu, &dbs_info->work, delay);
mutex_unlock(&dbs_info->timer_mutex);
}
static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
{
/* We want all CPUs to do sampling nearly on same jiffy */
int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
delay -= jiffies % delay;
dbs_info->enable = 1;
INIT_DEFERRABLE_WORK(&dbs_info->work, do_dbs_timer);
schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work, delay);
}
static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
{
dbs_info->enable = 0;
cancel_delayed_work_sync(&dbs_info->work);
}
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;
int rc;
this_dbs_info = &per_cpu(cs_cpu_dbs_info, cpu);
switch (event) {
case CPUFREQ_GOV_START:
if ((!cpu_online(cpu)) || (!policy->cur))
return -EINVAL;
mutex_lock(&dbs_mutex);
for_each_cpu(j, policy->cpus) {
struct cpu_dbs_info_s *j_dbs_info;
j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
j_dbs_info->cur_policy = policy;
j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
&j_dbs_info->prev_cpu_wall);
if (dbs_tuners_ins.ignore_nice)
j_dbs_info->prev_cpu_nice =
kcpustat_cpu(j).cpustat[CPUTIME_NICE];
}
this_dbs_info->cpu = cpu;
this_dbs_info->down_skip = 0;
this_dbs_info->requested_freq = policy->cur;
mutex_init(&this_dbs_info->timer_mutex);
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;
rc = sysfs_create_group(cpufreq_global_kobject,
&dbs_attr_group);
if (rc) {
mutex_unlock(&dbs_mutex);
return rc;
}
/*
* conservative does not implement micro like ondemand
* governor, thus we are bound to jiffes/HZ
*/
min_sampling_rate =
MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
/* Bring kernel and HW constraints together */
min_sampling_rate = max(min_sampling_rate,
MIN_LATENCY_MULTIPLIER * latency);
dbs_tuners_ins.sampling_rate =
max(min_sampling_rate,
latency * LATENCY_MULTIPLIER);
cpufreq_register_notifier(
&dbs_cpufreq_notifier_block,
CPUFREQ_TRANSITION_NOTIFIER);
}
mutex_unlock(&dbs_mutex);
dbs_timer_init(this_dbs_info);
break;
case CPUFREQ_GOV_STOP:
dbs_timer_exit(this_dbs_info);
mutex_lock(&dbs_mutex);
dbs_enable--;
mutex_destroy(&this_dbs_info->timer_mutex);
/*
* Stop the timerschedule work, when this governor
* is used for first time
*/
if (dbs_enable == 0)
cpufreq_unregister_notifier(
&dbs_cpufreq_notifier_block,
CPUFREQ_TRANSITION_NOTIFIER);
mutex_unlock(&dbs_mutex);
if (!dbs_enable)
sysfs_remove_group(cpufreq_global_kobject,
&dbs_attr_group);
break;
case CPUFREQ_GOV_LIMITS:
mutex_lock(&this_dbs_info->timer_mutex);
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);
dbs_check_cpu(this_dbs_info);
mutex_unlock(&this_dbs_info->timer_mutex);
break;
}
return 0;
}
#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
static
#endif
struct cpufreq_governor cpufreq_gov_conservative = {
.name = "conservative",
.governor = cpufreq_governor_dbs,
.max_transition_latency = TRANSITION_LATENCY_LIMIT,
.owner = THIS_MODULE,
};
static int __init cpufreq_gov_dbs_init(void)
{
return cpufreq_register_governor(&cpufreq_gov_conservative);
}
static void __exit cpufreq_gov_dbs_exit(void)
{
cpufreq_unregister_governor(&cpufreq_gov_conservative);
}
MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
"Low Latency Frequency Transition capable processors "
"optimised for use in a battery environment");
MODULE_LICENSE("GPL");
#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
fs_initcall(cpufreq_gov_dbs_init);
#else
module_init(cpufreq_gov_dbs_init);
#endif
module_exit(cpufreq_gov_dbs_exit);
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