linux/drivers/cpufreq/cpufreq_ondemand.c
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   1/*
   2 *  drivers/cpufreq/cpufreq_ondemand.c
   3 *
   4 *  Copyright (C)  2001 Russell King
   5 *            (C)  2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
   6 *                      Jun Nakajima <jun.nakajima@intel.com>
   7 *
   8 * This program is free software; you can redistribute it and/or modify
   9 * it under the terms of the GNU General Public License version 2 as
  10 * published by the Free Software Foundation.
  11 */
  12
  13#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  14
  15#include <linux/cpufreq.h>
  16#include <linux/init.h>
  17#include <linux/kernel.h>
  18#include <linux/kernel_stat.h>
  19#include <linux/kobject.h>
  20#include <linux/module.h>
  21#include <linux/mutex.h>
  22#include <linux/percpu-defs.h>
  23#include <linux/sysfs.h>
  24#include <linux/tick.h>
  25#include <linux/types.h>
  26
  27#include "cpufreq_governor.h"
  28
  29/* On-demand governor macors */
  30#define DEF_FREQUENCY_DOWN_DIFFERENTIAL         (10)
  31#define DEF_FREQUENCY_UP_THRESHOLD              (80)
  32#define DEF_SAMPLING_DOWN_FACTOR                (1)
  33#define MAX_SAMPLING_DOWN_FACTOR                (100000)
  34#define MICRO_FREQUENCY_DOWN_DIFFERENTIAL       (3)
  35#define MICRO_FREQUENCY_UP_THRESHOLD            (95)
  36#define MICRO_FREQUENCY_MIN_SAMPLE_RATE         (10000)
  37#define MIN_FREQUENCY_UP_THRESHOLD              (11)
  38#define MAX_FREQUENCY_UP_THRESHOLD              (100)
  39
  40static struct dbs_data od_dbs_data;
  41static DEFINE_PER_CPU(struct od_cpu_dbs_info_s, od_cpu_dbs_info);
  42
  43#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
  44static struct cpufreq_governor cpufreq_gov_ondemand;
  45#endif
  46
  47static struct od_dbs_tuners od_tuners = {
  48        .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
  49        .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
  50        .down_differential = DEF_FREQUENCY_DOWN_DIFFERENTIAL,
  51        .ignore_nice = 0,
  52        .powersave_bias = 0,
  53};
  54
  55static void ondemand_powersave_bias_init_cpu(int cpu)
  56{
  57        struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
  58
  59        dbs_info->freq_table = cpufreq_frequency_get_table(cpu);
  60        dbs_info->freq_lo = 0;
  61}
  62
  63/*
  64 * Not all CPUs want IO time to be accounted as busy; this depends on how
  65 * efficient idling at a higher frequency/voltage is.
  66 * Pavel Machek says this is not so for various generations of AMD and old
  67 * Intel systems.
  68 * Mike Chan (androidlcom) calis this is also not true for ARM.
  69 * Because of this, whitelist specific known (series) of CPUs by default, and
  70 * leave all others up to the user.
  71 */
  72static int should_io_be_busy(void)
  73{
  74#if defined(CONFIG_X86)
  75        /*
  76         * For Intel, Core 2 (model 15) andl later have an efficient idle.
  77         */
  78        if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
  79                        boot_cpu_data.x86 == 6 &&
  80                        boot_cpu_data.x86_model >= 15)
  81                return 1;
  82#endif
  83        return 0;
  84}
  85
  86/*
  87 * Find right freq to be set now with powersave_bias on.
  88 * Returns the freq_hi to be used right now and will set freq_hi_jiffies,
  89 * freq_lo, and freq_lo_jiffies in percpu area for averaging freqs.
  90 */
  91static unsigned int powersave_bias_target(struct cpufreq_policy *policy,
  92                unsigned int freq_next, unsigned int relation)
  93{
  94        unsigned int freq_req, freq_reduc, freq_avg;
  95        unsigned int freq_hi, freq_lo;
  96        unsigned int index = 0;
  97        unsigned int jiffies_total, jiffies_hi, jiffies_lo;
  98        struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
  99                                                   policy->cpu);
 100
 101        if (!dbs_info->freq_table) {
 102                dbs_info->freq_lo = 0;
 103                dbs_info->freq_lo_jiffies = 0;
 104                return freq_next;
 105        }
 106
 107        cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_next,
 108                        relation, &index);
 109        freq_req = dbs_info->freq_table[index].frequency;
 110        freq_reduc = freq_req * od_tuners.powersave_bias / 1000;
 111        freq_avg = freq_req - freq_reduc;
 112
 113        /* Find freq bounds for freq_avg in freq_table */
 114        index = 0;
 115        cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 116                        CPUFREQ_RELATION_H, &index);
 117        freq_lo = dbs_info->freq_table[index].frequency;
 118        index = 0;
 119        cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 120                        CPUFREQ_RELATION_L, &index);
 121        freq_hi = dbs_info->freq_table[index].frequency;
 122
 123        /* Find out how long we have to be in hi and lo freqs */
 124        if (freq_hi == freq_lo) {
 125                dbs_info->freq_lo = 0;
 126                dbs_info->freq_lo_jiffies = 0;
 127                return freq_lo;
 128        }
 129        jiffies_total = usecs_to_jiffies(od_tuners.sampling_rate);
 130        jiffies_hi = (freq_avg - freq_lo) * jiffies_total;
 131        jiffies_hi += ((freq_hi - freq_lo) / 2);
 132        jiffies_hi /= (freq_hi - freq_lo);
 133        jiffies_lo = jiffies_total - jiffies_hi;
 134        dbs_info->freq_lo = freq_lo;
 135        dbs_info->freq_lo_jiffies = jiffies_lo;
 136        dbs_info->freq_hi_jiffies = jiffies_hi;
 137        return freq_hi;
 138}
 139
 140static void ondemand_powersave_bias_init(void)
 141{
 142        int i;
 143        for_each_online_cpu(i) {
 144                ondemand_powersave_bias_init_cpu(i);
 145        }
 146}
 147
 148static void dbs_freq_increase(struct cpufreq_policy *p, unsigned int freq)
 149{
 150        if (od_tuners.powersave_bias)
 151                freq = powersave_bias_target(p, freq, CPUFREQ_RELATION_H);
 152        else if (p->cur == p->max)
 153                return;
 154
 155        __cpufreq_driver_target(p, freq, od_tuners.powersave_bias ?
 156                        CPUFREQ_RELATION_L : CPUFREQ_RELATION_H);
 157}
 158
 159/*
 160 * Every sampling_rate, we check, if current idle time is less than 20%
 161 * (default), then we try to increase frequency Every sampling_rate, we look for
 162 * a the lowest frequency which can sustain the load while keeping idle time
 163 * over 30%. If such a frequency exist, we try to decrease to this frequency.
 164 *
 165 * Any frequency increase takes it to the maximum frequency. Frequency reduction
 166 * happens at minimum steps of 5% (default) of current frequency
 167 */
 168static void od_check_cpu(int cpu, unsigned int load_freq)
 169{
 170        struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
 171        struct cpufreq_policy *policy = dbs_info->cdbs.cur_policy;
 172
 173        dbs_info->freq_lo = 0;
 174
 175        /* Check for frequency increase */
 176        if (load_freq > od_tuners.up_threshold * policy->cur) {
 177                /* If switching to max speed, apply sampling_down_factor */
 178                if (policy->cur < policy->max)
 179                        dbs_info->rate_mult =
 180                                od_tuners.sampling_down_factor;
 181                dbs_freq_increase(policy, policy->max);
 182                return;
 183        }
 184
 185        /* Check for frequency decrease */
 186        /* if we cannot reduce the frequency anymore, break out early */
 187        if (policy->cur == policy->min)
 188                return;
 189
 190        /*
 191         * The optimal frequency is the frequency that is the lowest that can
 192         * support the current CPU usage without triggering the up policy. To be
 193         * safe, we focus 10 points under the threshold.
 194         */
 195        if (load_freq < (od_tuners.up_threshold - od_tuners.down_differential) *
 196                        policy->cur) {
 197                unsigned int freq_next;
 198                freq_next = load_freq / (od_tuners.up_threshold -
 199                                od_tuners.down_differential);
 200
 201                /* No longer fully busy, reset rate_mult */
 202                dbs_info->rate_mult = 1;
 203
 204                if (freq_next < policy->min)
 205                        freq_next = policy->min;
 206
 207                if (!od_tuners.powersave_bias) {
 208                        __cpufreq_driver_target(policy, freq_next,
 209                                        CPUFREQ_RELATION_L);
 210                } else {
 211                        int freq = powersave_bias_target(policy, freq_next,
 212                                        CPUFREQ_RELATION_L);
 213                        __cpufreq_driver_target(policy, freq,
 214                                        CPUFREQ_RELATION_L);
 215                }
 216        }
 217}
 218
 219static void od_dbs_timer(struct work_struct *work)
 220{
 221        struct od_cpu_dbs_info_s *dbs_info =
 222                container_of(work, struct od_cpu_dbs_info_s, cdbs.work.work);
 223        unsigned int cpu = dbs_info->cdbs.cpu;
 224        int delay, sample_type = dbs_info->sample_type;
 225
 226        mutex_lock(&dbs_info->cdbs.timer_mutex);
 227
 228        /* Common NORMAL_SAMPLE setup */
 229        dbs_info->sample_type = OD_NORMAL_SAMPLE;
 230        if (sample_type == OD_SUB_SAMPLE) {
 231                delay = dbs_info->freq_lo_jiffies;
 232                __cpufreq_driver_target(dbs_info->cdbs.cur_policy,
 233                        dbs_info->freq_lo, CPUFREQ_RELATION_H);
 234        } else {
 235                dbs_check_cpu(&od_dbs_data, cpu);
 236                if (dbs_info->freq_lo) {
 237                        /* Setup timer for SUB_SAMPLE */
 238                        dbs_info->sample_type = OD_SUB_SAMPLE;
 239                        delay = dbs_info->freq_hi_jiffies;
 240                } else {
 241                        delay = delay_for_sampling_rate(od_tuners.sampling_rate
 242                                                * dbs_info->rate_mult);
 243                }
 244        }
 245
 246        schedule_delayed_work_on(cpu, &dbs_info->cdbs.work, delay);
 247        mutex_unlock(&dbs_info->cdbs.timer_mutex);
 248}
 249
 250/************************** sysfs interface ************************/
 251
 252static ssize_t show_sampling_rate_min(struct kobject *kobj,
 253                                      struct attribute *attr, char *buf)
 254{
 255        return sprintf(buf, "%u\n", od_dbs_data.min_sampling_rate);
 256}
 257
 258/**
 259 * update_sampling_rate - update sampling rate effective immediately if needed.
 260 * @new_rate: new sampling rate
 261 *
 262 * If new rate is smaller than the old, simply updaing
 263 * dbs_tuners_int.sampling_rate might not be appropriate. For example, if the
 264 * original sampling_rate was 1 second and the requested new sampling rate is 10
 265 * ms because the user needs immediate reaction from ondemand governor, but not
 266 * sure if higher frequency will be required or not, then, the governor may
 267 * change the sampling rate too late; up to 1 second later. Thus, if we are
 268 * reducing the sampling rate, we need to make the new value effective
 269 * immediately.
 270 */
 271static void update_sampling_rate(unsigned int new_rate)
 272{
 273        int cpu;
 274
 275        od_tuners.sampling_rate = new_rate = max(new_rate,
 276                        od_dbs_data.min_sampling_rate);
 277
 278        for_each_online_cpu(cpu) {
 279                struct cpufreq_policy *policy;
 280                struct od_cpu_dbs_info_s *dbs_info;
 281                unsigned long next_sampling, appointed_at;
 282
 283                policy = cpufreq_cpu_get(cpu);
 284                if (!policy)
 285                        continue;
 286                if (policy->governor != &cpufreq_gov_ondemand) {
 287                        cpufreq_cpu_put(policy);
 288                        continue;
 289                }
 290                dbs_info = &per_cpu(od_cpu_dbs_info, policy->cpu);
 291                cpufreq_cpu_put(policy);
 292
 293                mutex_lock(&dbs_info->cdbs.timer_mutex);
 294
 295                if (!delayed_work_pending(&dbs_info->cdbs.work)) {
 296                        mutex_unlock(&dbs_info->cdbs.timer_mutex);
 297                        continue;
 298                }
 299
 300                next_sampling = jiffies + usecs_to_jiffies(new_rate);
 301                appointed_at = dbs_info->cdbs.work.timer.expires;
 302
 303                if (time_before(next_sampling, appointed_at)) {
 304
 305                        mutex_unlock(&dbs_info->cdbs.timer_mutex);
 306                        cancel_delayed_work_sync(&dbs_info->cdbs.work);
 307                        mutex_lock(&dbs_info->cdbs.timer_mutex);
 308
 309                        schedule_delayed_work_on(dbs_info->cdbs.cpu,
 310                                        &dbs_info->cdbs.work,
 311                                        usecs_to_jiffies(new_rate));
 312
 313                }
 314                mutex_unlock(&dbs_info->cdbs.timer_mutex);
 315        }
 316}
 317
 318static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
 319                                   const char *buf, size_t count)
 320{
 321        unsigned int input;
 322        int ret;
 323        ret = sscanf(buf, "%u", &input);
 324        if (ret != 1)
 325                return -EINVAL;
 326        update_sampling_rate(input);
 327        return count;
 328}
 329
 330static ssize_t store_io_is_busy(struct kobject *a, struct attribute *b,
 331                                   const char *buf, size_t count)
 332{
 333        unsigned int input;
 334        int ret;
 335
 336        ret = sscanf(buf, "%u", &input);
 337        if (ret != 1)
 338                return -EINVAL;
 339        od_tuners.io_is_busy = !!input;
 340        return count;
 341}
 342
 343static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
 344                                  const char *buf, size_t count)
 345{
 346        unsigned int input;
 347        int ret;
 348        ret = sscanf(buf, "%u", &input);
 349
 350        if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 351                        input < MIN_FREQUENCY_UP_THRESHOLD) {
 352                return -EINVAL;
 353        }
 354        od_tuners.up_threshold = input;
 355        return count;
 356}
 357
 358static ssize_t store_sampling_down_factor(struct kobject *a,
 359                        struct attribute *b, const char *buf, size_t count)
 360{
 361        unsigned int input, j;
 362        int ret;
 363        ret = sscanf(buf, "%u", &input);
 364
 365        if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 366                return -EINVAL;
 367        od_tuners.sampling_down_factor = input;
 368
 369        /* Reset down sampling multiplier in case it was active */
 370        for_each_online_cpu(j) {
 371                struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
 372                                j);
 373                dbs_info->rate_mult = 1;
 374        }
 375        return count;
 376}
 377
 378static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
 379                                      const char *buf, size_t count)
 380{
 381        unsigned int input;
 382        int ret;
 383
 384        unsigned int j;
 385
 386        ret = sscanf(buf, "%u", &input);
 387        if (ret != 1)
 388                return -EINVAL;
 389
 390        if (input > 1)
 391                input = 1;
 392
 393        if (input == od_tuners.ignore_nice) { /* nothing to do */
 394                return count;
 395        }
 396        od_tuners.ignore_nice = input;
 397
 398        /* we need to re-evaluate prev_cpu_idle */
 399        for_each_online_cpu(j) {
 400                struct od_cpu_dbs_info_s *dbs_info;
 401                dbs_info = &per_cpu(od_cpu_dbs_info, j);
 402                dbs_info->cdbs.prev_cpu_idle = get_cpu_idle_time(j,
 403                                                &dbs_info->cdbs.prev_cpu_wall);
 404                if (od_tuners.ignore_nice)
 405                        dbs_info->cdbs.prev_cpu_nice =
 406                                kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 407
 408        }
 409        return count;
 410}
 411
 412static ssize_t store_powersave_bias(struct kobject *a, struct attribute *b,
 413                                    const char *buf, size_t count)
 414{
 415        unsigned int input;
 416        int ret;
 417        ret = sscanf(buf, "%u", &input);
 418
 419        if (ret != 1)
 420                return -EINVAL;
 421
 422        if (input > 1000)
 423                input = 1000;
 424
 425        od_tuners.powersave_bias = input;
 426        ondemand_powersave_bias_init();
 427        return count;
 428}
 429
 430show_one(od, sampling_rate, sampling_rate);
 431show_one(od, io_is_busy, io_is_busy);
 432show_one(od, up_threshold, up_threshold);
 433show_one(od, sampling_down_factor, sampling_down_factor);
 434show_one(od, ignore_nice_load, ignore_nice);
 435show_one(od, powersave_bias, powersave_bias);
 436
 437define_one_global_rw(sampling_rate);
 438define_one_global_rw(io_is_busy);
 439define_one_global_rw(up_threshold);
 440define_one_global_rw(sampling_down_factor);
 441define_one_global_rw(ignore_nice_load);
 442define_one_global_rw(powersave_bias);
 443define_one_global_ro(sampling_rate_min);
 444
 445static struct attribute *dbs_attributes[] = {
 446        &sampling_rate_min.attr,
 447        &sampling_rate.attr,
 448        &up_threshold.attr,
 449        &sampling_down_factor.attr,
 450        &ignore_nice_load.attr,
 451        &powersave_bias.attr,
 452        &io_is_busy.attr,
 453        NULL
 454};
 455
 456static struct attribute_group od_attr_group = {
 457        .attrs = dbs_attributes,
 458        .name = "ondemand",
 459};
 460
 461/************************** sysfs end ************************/
 462
 463define_get_cpu_dbs_routines(od_cpu_dbs_info);
 464
 465static struct od_ops od_ops = {
 466        .io_busy = should_io_be_busy,
 467        .powersave_bias_init_cpu = ondemand_powersave_bias_init_cpu,
 468        .powersave_bias_target = powersave_bias_target,
 469        .freq_increase = dbs_freq_increase,
 470};
 471
 472static struct dbs_data od_dbs_data = {
 473        .governor = GOV_ONDEMAND,
 474        .attr_group = &od_attr_group,
 475        .tuners = &od_tuners,
 476        .get_cpu_cdbs = get_cpu_cdbs,
 477        .get_cpu_dbs_info_s = get_cpu_dbs_info_s,
 478        .gov_dbs_timer = od_dbs_timer,
 479        .gov_check_cpu = od_check_cpu,
 480        .gov_ops = &od_ops,
 481};
 482
 483static int od_cpufreq_governor_dbs(struct cpufreq_policy *policy,
 484                unsigned int event)
 485{
 486        return cpufreq_governor_dbs(&od_dbs_data, policy, event);
 487}
 488
 489#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 490static
 491#endif
 492struct cpufreq_governor cpufreq_gov_ondemand = {
 493        .name                   = "ondemand",
 494        .governor               = od_cpufreq_governor_dbs,
 495        .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 496        .owner                  = THIS_MODULE,
 497};
 498
 499static int __init cpufreq_gov_dbs_init(void)
 500{
 501        u64 idle_time;
 502        int cpu = get_cpu();
 503
 504        mutex_init(&od_dbs_data.mutex);
 505        idle_time = get_cpu_idle_time_us(cpu, NULL);
 506        put_cpu();
 507        if (idle_time != -1ULL) {
 508                /* Idle micro accounting is supported. Use finer thresholds */
 509                od_tuners.up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
 510                od_tuners.down_differential = MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
 511                /*
 512                 * In nohz/micro accounting case we set the minimum frequency
 513                 * not depending on HZ, but fixed (very low). The deferred
 514                 * timer might skip some samples if idle/sleeping as needed.
 515                */
 516                od_dbs_data.min_sampling_rate = MICRO_FREQUENCY_MIN_SAMPLE_RATE;
 517        } else {
 518                /* For correct statistics, we need 10 ticks for each measure */
 519                od_dbs_data.min_sampling_rate = MIN_SAMPLING_RATE_RATIO *
 520                        jiffies_to_usecs(10);
 521        }
 522
 523        return cpufreq_register_governor(&cpufreq_gov_ondemand);
 524}
 525
 526static void __exit cpufreq_gov_dbs_exit(void)
 527{
 528        cpufreq_unregister_governor(&cpufreq_gov_ondemand);
 529}
 530
 531MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 532MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
 533MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 534        "Low Latency Frequency Transition capable processors");
 535MODULE_LICENSE("GPL");
 536
 537#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 538fs_initcall(cpufreq_gov_dbs_init);
 539#else
 540module_init(cpufreq_gov_dbs_init);
 541#endif
 542module_exit(cpufreq_gov_dbs_exit);
 543
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