cpufreq_conservative.c

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/*
 *  drivers/cpufreq/cpufreq_conservative.c
 *
 *  Copyright (C)  2001 Russell King
 *            (C)  2003 Venkatesh Pallipadi <[email protected]>.
 *                      Jun Nakajima <[email protected]>
 *            (C)  2009 Alexander Clouter <[email protected]>
 *
 * 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      (80)
#define DEF_FREQUENCY_DOWN_THRESHOLD        (20)

/*
 * 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 <[email protected]>");
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);