diff options
Diffstat (limited to 'drivers/cpufreq/cpufreq_ondemand.c')
| -rw-r--r-- | drivers/cpufreq/cpufreq_ondemand.c | 491 |
1 files changed, 491 insertions, 0 deletions
diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c new file mode 100644 index 000000000000..8d83a21c6477 --- /dev/null +++ b/drivers/cpufreq/cpufreq_ondemand.c @@ -0,0 +1,491 @@ +/* + * 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 (0) +#define MAX_FREQUENCY_UP_THRESHOLD (100) + +#define DEF_FREQUENCY_DOWN_THRESHOLD (20) +#define MIN_FREQUENCY_DOWN_THRESHOLD (0) +#define MAX_FREQUENCY_DOWN_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 (def_sampling_rate / 2) +#define MAX_SAMPLING_RATE (500 * def_sampling_rate) +#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000) +#define DEF_SAMPLING_DOWN_FACTOR (10) +#define TRANSITION_LATENCY_LIMIT (10 * 1000) +#define sampling_rate_in_HZ(x) (((x * HZ) < (1000 * 1000))?1:((x * HZ) / (1000 * 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 down_threshold; +}; + +static struct dbs_tuners dbs_tuners_ins = { + .up_threshold = DEF_FREQUENCY_UP_THRESHOLD, + .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD, + .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR, +}; + +/************************** 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(down_threshold, down_threshold); + +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; + + 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 || + input <= dbs_tuners_ins.down_threshold) { + up(&dbs_sem); + return -EINVAL; + } + + dbs_tuners_ins.up_threshold = input; + up(&dbs_sem); + + return count; +} + +static ssize_t store_down_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_DOWN_THRESHOLD || + input < MIN_FREQUENCY_DOWN_THRESHOLD || + input >= dbs_tuners_ins.up_threshold) { + up(&dbs_sem); + return -EINVAL; + } + + dbs_tuners_ins.down_threshold = input; + 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(down_threshold); + +static struct attribute * dbs_attributes[] = { + &sampling_rate_max.attr, + &sampling_rate_min.attr, + &sampling_rate.attr, + &sampling_down_factor.attr, + &up_threshold.attr, + &down_threshold.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, down_idle_ticks; + unsigned int total_idle_ticks; + unsigned int freq_down_step; + 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; + /* + * The default safe range is 20% to 80% + * Every sampling_rate, we check + * - If current idle time is less than 20%, 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% of max_frequency + */ + + /* Check for frequency increase */ + total_idle_ticks = kstat_cpu(cpu).cpustat.idle + + kstat_cpu(cpu).cpustat.iowait; + idle_ticks = total_idle_ticks - + this_dbs_info->prev_cpu_idle_up; + this_dbs_info->prev_cpu_idle_up = total_idle_ticks; + + + for_each_cpu_mask(j, policy->cpus) { + unsigned int tmp_idle_ticks; + struct cpu_dbs_info_s *j_dbs_info; + + if (j == cpu) + continue; + + j_dbs_info = &per_cpu(cpu_dbs_info, j); + /* Check for frequency increase */ + total_idle_ticks = kstat_cpu(j).cpustat.idle + + kstat_cpu(j).cpustat.iowait; + 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) * + sampling_rate_in_HZ(dbs_tuners_ins.sampling_rate); + + if (idle_ticks < up_idle_ticks) { + __cpufreq_driver_target(policy, policy->max, + CPUFREQ_RELATION_H); + down_skip[cpu] = 0; + this_dbs_info->prev_cpu_idle_down = total_idle_ticks; + return; + } + + /* Check for frequency decrease */ + down_skip[cpu]++; + if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor) + return; + + total_idle_ticks = kstat_cpu(cpu).cpustat.idle + + kstat_cpu(cpu).cpustat.iowait; + idle_ticks = total_idle_ticks - + this_dbs_info->prev_cpu_idle_down; + this_dbs_info->prev_cpu_idle_down = total_idle_ticks; + + for_each_cpu_mask(j, policy->cpus) { + unsigned int tmp_idle_ticks; + struct cpu_dbs_info_s *j_dbs_info; + + if (j == cpu) + continue; + + j_dbs_info = &per_cpu(cpu_dbs_info, j); + /* Check for frequency increase */ + total_idle_ticks = kstat_cpu(j).cpustat.idle + + kstat_cpu(j).cpustat.iowait; + 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; + } + + /* Scale idle ticks by 100 and compare with up and down ticks */ + idle_ticks *= 100; + down_skip[cpu] = 0; + + freq_down_sampling_rate = dbs_tuners_ins.sampling_rate * + dbs_tuners_ins.sampling_down_factor; + down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) * + sampling_rate_in_HZ(freq_down_sampling_rate); + + if (idle_ticks > down_idle_ticks ) { + freq_down_step = (5 * policy->max) / 100; + + /* max freq cannot be less than 100. But who knows.... */ + if (unlikely(freq_down_step == 0)) + freq_down_step = 5; + + __cpufreq_driver_target(policy, + policy->cur - freq_down_step, + CPUFREQ_RELATION_H); + return; + } +} + +static void do_dbs_timer(void *data) +{ + int i; + down(&dbs_sem); + for (i = 0; i < NR_CPUS; i++) + if (cpu_online(i)) + dbs_check_cpu(i); + schedule_delayed_work(&dbs_work, + sampling_rate_in_HZ(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, + sampling_rate_in_HZ(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 = + kstat_cpu(j).cpustat.idle + + kstat_cpu(j).cpustat.iowait; + j_dbs_info->prev_cpu_idle_down = + kstat_cpu(j).cpustat.idle + + kstat_cpu(j).cpustat.iowait; + } + 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; + if (latency < 1000) + latency = 1000; + + def_sampling_rate = (latency / 1000) * + DEF_SAMPLING_RATE_LATENCY_MULTIPLIER; + dbs_tuners_ins.sampling_rate = def_sampling_rate; + + 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; +} + +struct cpufreq_governor cpufreq_gov_dbs = { + .name = "ondemand", + .governor = cpufreq_governor_dbs, + .owner = THIS_MODULE, +}; +EXPORT_SYMBOL(cpufreq_gov_dbs); + +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); |