[CPUFREQ] ondemand governor automatic downscaling

[linux-2.6/cjktty.git] / drivers / cpufreq / cpufreq_ondemand.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/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                       (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)

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;

        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;
                        if (latency < 1000)
                                latency = 1000;

                        def_sampling_rate = (latency / 1000) *
                                        DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
                        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);