linux/drivers/cpufreq/cpufreq_ondemand.c

590 lines
16 KiB
C

/*
* 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/init.h>
#include <linux/cpufreq.h>
#include <linux/cpu.h>
#include <linux/jiffies.h>
#include <linux/kernel_stat.h>
#include <linux/mutex.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 TRANSITION_LATENCY_LIMIT (10 * 1000)
static void do_dbs_timer(struct work_struct *work);
/* Sampling types */
enum dbs_sample {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE};
struct cpu_dbs_info_s {
cputime64_t prev_cpu_idle;
cputime64_t prev_cpu_wall;
struct cpufreq_policy *cur_policy;
struct delayed_work work;
enum dbs_sample sample_type;
unsigned int enable;
struct cpufreq_frequency_table *freq_table;
unsigned int freq_lo;
unsigned int freq_lo_jiffies;
unsigned int freq_hi_jiffies;
};
static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
static unsigned int dbs_enable; /* number of CPUs using this policy */
/*
* DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
* lock and dbs_mutex. cpu_hotplug lock should always be held before
* dbs_mutex. If any function that can potentially take cpu_hotplug lock
* (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
* cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
* is recursive for the same process. -Venki
*/
static DEFINE_MUTEX(dbs_mutex);
static struct workqueue_struct *kondemand_wq;
static struct dbs_tuners {
unsigned int sampling_rate;
unsigned int up_threshold;
unsigned int ignore_nice;
unsigned int powersave_bias;
} dbs_tuners_ins = {
.up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
.ignore_nice = 0,
.powersave_bias = 0,
};
static inline cputime64_t get_cpu_idle_time(unsigned int cpu)
{
cputime64_t retval;
retval = cputime64_add(kstat_cpu(cpu).cpustat.idle,
kstat_cpu(cpu).cpustat.iowait);
if (dbs_tuners_ins.ignore_nice)
retval = cputime64_add(retval, kstat_cpu(cpu).cpustat.nice);
return retval;
}
/*
* Find right freq to be set now with powersave_bias on.
* Returns the freq_hi to be used right now and will set freq_hi_jiffies,
* freq_lo, and freq_lo_jiffies in percpu area for averaging freqs.
*/
static unsigned int powersave_bias_target(struct cpufreq_policy *policy,
unsigned int freq_next,
unsigned int relation)
{
unsigned int freq_req, freq_reduc, freq_avg;
unsigned int freq_hi, freq_lo;
unsigned int index = 0;
unsigned int jiffies_total, jiffies_hi, jiffies_lo;
struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, policy->cpu);
if (!dbs_info->freq_table) {
dbs_info->freq_lo = 0;
dbs_info->freq_lo_jiffies = 0;
return freq_next;
}
cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_next,
relation, &index);
freq_req = dbs_info->freq_table[index].frequency;
freq_reduc = freq_req * dbs_tuners_ins.powersave_bias / 1000;
freq_avg = freq_req - freq_reduc;
/* Find freq bounds for freq_avg in freq_table */
index = 0;
cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
CPUFREQ_RELATION_H, &index);
freq_lo = dbs_info->freq_table[index].frequency;
index = 0;
cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
CPUFREQ_RELATION_L, &index);
freq_hi = dbs_info->freq_table[index].frequency;
/* Find out how long we have to be in hi and lo freqs */
if (freq_hi == freq_lo) {
dbs_info->freq_lo = 0;
dbs_info->freq_lo_jiffies = 0;
return freq_lo;
}
jiffies_total = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
jiffies_hi = (freq_avg - freq_lo) * jiffies_total;
jiffies_hi += ((freq_hi - freq_lo) / 2);
jiffies_hi /= (freq_hi - freq_lo);
jiffies_lo = jiffies_total - jiffies_hi;
dbs_info->freq_lo = freq_lo;
dbs_info->freq_lo_jiffies = jiffies_lo;
dbs_info->freq_hi_jiffies = jiffies_hi;
return freq_hi;
}
static void ondemand_powersave_bias_init(void)
{
int i;
for_each_online_cpu(i) {
struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, i);
dbs_info->freq_table = cpufreq_frequency_get_table(i);
dbs_info->freq_lo = 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(up_threshold, up_threshold);
show_one(ignore_nice_load, ignore_nice);
show_one(powersave_bias, powersave_bias);
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);
mutex_lock(&dbs_mutex);
if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
mutex_unlock(&dbs_mutex);
return -EINVAL;
}
dbs_tuners_ins.sampling_rate = input;
mutex_unlock(&dbs_mutex);
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);
mutex_lock(&dbs_mutex);
if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
input < MIN_FREQUENCY_UP_THRESHOLD) {
mutex_unlock(&dbs_mutex);
return -EINVAL;
}
dbs_tuners_ins.up_threshold = input;
mutex_unlock(&dbs_mutex);
return count;
}
static ssize_t store_ignore_nice_load(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;
mutex_lock(&dbs_mutex);
if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
mutex_unlock(&dbs_mutex);
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(cpu_dbs_info, j);
dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
dbs_info->prev_cpu_wall = get_jiffies_64();
}
mutex_unlock(&dbs_mutex);
return count;
}
static ssize_t store_powersave_bias(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 > 1000)
input = 1000;
mutex_lock(&dbs_mutex);
dbs_tuners_ins.powersave_bias = input;
ondemand_powersave_bias_init();
mutex_unlock(&dbs_mutex);
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(up_threshold);
define_one_rw(ignore_nice_load);
define_one_rw(powersave_bias);
static struct attribute * dbs_attributes[] = {
&sampling_rate_max.attr,
&sampling_rate_min.attr,
&sampling_rate.attr,
&up_threshold.attr,
&ignore_nice_load.attr,
&powersave_bias.attr,
NULL
};
static struct attribute_group dbs_attr_group = {
.attrs = dbs_attributes,
.name = "ondemand",
};
/************************** sysfs end ************************/
static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
{
unsigned int idle_ticks, total_ticks;
unsigned int load;
cputime64_t cur_jiffies;
struct cpufreq_policy *policy;
unsigned int j;
if (!this_dbs_info->enable)
return;
this_dbs_info->freq_lo = 0;
policy = this_dbs_info->cur_policy;
cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());
total_ticks = (unsigned int) cputime64_sub(cur_jiffies,
this_dbs_info->prev_cpu_wall);
this_dbs_info->prev_cpu_wall = cur_jiffies;
if (!total_ticks)
return;
/*
* Every sampling_rate, we check, if current idle time is less
* than 20% (default), then we try to increase frequency
* Every sampling_rate, 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
*/
/* Get Idle Time */
idle_ticks = UINT_MAX;
for_each_cpu_mask(j, policy->cpus) {
cputime64_t total_idle_ticks;
unsigned int tmp_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 = (unsigned int) cputime64_sub(total_idle_ticks,
j_dbs_info->prev_cpu_idle);
j_dbs_info->prev_cpu_idle = total_idle_ticks;
if (tmp_idle_ticks < idle_ticks)
idle_ticks = tmp_idle_ticks;
}
load = (100 * (total_ticks - idle_ticks)) / total_ticks;
/* Check for frequency increase */
if (load > dbs_tuners_ins.up_threshold) {
/* if we are already at full speed then break out early */
if (!dbs_tuners_ins.powersave_bias) {
if (policy->cur == policy->max)
return;
__cpufreq_driver_target(policy, policy->max,
CPUFREQ_RELATION_H);
} else {
int freq = powersave_bias_target(policy, policy->max,
CPUFREQ_RELATION_H);
__cpufreq_driver_target(policy, freq,
CPUFREQ_RELATION_L);
}
return;
}
/* Check for frequency decrease */
/* if we cannot reduce the frequency anymore, break out early */
if (policy->cur == policy->min)
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 (load < (dbs_tuners_ins.up_threshold - 10)) {
unsigned int freq_next = (policy->cur * load) /
(dbs_tuners_ins.up_threshold - 10);
if (!dbs_tuners_ins.powersave_bias) {
__cpufreq_driver_target(policy, freq_next,
CPUFREQ_RELATION_L);
} else {
int freq = powersave_bias_target(policy, freq_next,
CPUFREQ_RELATION_L);
__cpufreq_driver_target(policy, freq,
CPUFREQ_RELATION_L);
}
}
}
static void do_dbs_timer(struct work_struct *work)
{
unsigned int cpu = smp_processor_id();
struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
enum dbs_sample sample_type = dbs_info->sample_type;
/* We want all CPUs to do sampling nearly on same jiffy */
int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
/* Permit rescheduling of this work item */
work_release(work);
delay -= jiffies % delay;
if (!dbs_info->enable)
return;
/* Common NORMAL_SAMPLE setup */
dbs_info->sample_type = DBS_NORMAL_SAMPLE;
if (!dbs_tuners_ins.powersave_bias ||
sample_type == DBS_NORMAL_SAMPLE) {
lock_cpu_hotplug();
dbs_check_cpu(dbs_info);
unlock_cpu_hotplug();
if (dbs_info->freq_lo) {
/* Setup timer for SUB_SAMPLE */
dbs_info->sample_type = DBS_SUB_SAMPLE;
delay = dbs_info->freq_hi_jiffies;
}
} else {
__cpufreq_driver_target(dbs_info->cur_policy,
dbs_info->freq_lo,
CPUFREQ_RELATION_H);
}
queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
}
static inline void dbs_timer_init(unsigned int cpu)
{
struct cpu_dbs_info_s *dbs_info = &per_cpu(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;
ondemand_powersave_bias_init();
INIT_DELAYED_WORK_NAR(&dbs_info->work, do_dbs_timer);
dbs_info->sample_type = DBS_NORMAL_SAMPLE;
queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
}
static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
{
dbs_info->enable = 0;
cancel_delayed_work(&dbs_info->work);
flush_workqueue(kondemand_wq);
}
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)) {
printk(KERN_WARNING "ondemand governor failed to load "
"due to too long transition latency\n");
return -EINVAL;
}
if (this_dbs_info->enable) /* Already enabled */
break;
mutex_lock(&dbs_mutex);
dbs_enable++;
if (dbs_enable == 1) {
kondemand_wq = create_workqueue("kondemand");
if (!kondemand_wq) {
printk(KERN_ERR "Creation of kondemand failed\n");
dbs_enable--;
mutex_unlock(&dbs_mutex);
return -ENOSPC;
}
}
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 = get_cpu_idle_time(j);
j_dbs_info->prev_cpu_wall = get_jiffies_64();
}
this_dbs_info->enable = 1;
sysfs_create_group(&policy->kobj, &dbs_attr_group);
/*
* 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_timer_init(policy->cpu);
mutex_unlock(&dbs_mutex);
break;
case CPUFREQ_GOV_STOP:
mutex_lock(&dbs_mutex);
dbs_timer_exit(this_dbs_info);
sysfs_remove_group(&policy->kobj, &dbs_attr_group);
dbs_enable--;
if (dbs_enable == 0)
destroy_workqueue(kondemand_wq);
mutex_unlock(&dbs_mutex);
break;
case CPUFREQ_GOV_LIMITS:
mutex_lock(&dbs_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);
mutex_unlock(&dbs_mutex);
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)
{
cpufreq_unregister_governor(&cpufreq_gov_dbs);
}
MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@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);