linux/drivers/cpufreq/cpufreq_conservative.c
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   1/*
   2 *  drivers/cpufreq/cpufreq_conservative.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 *            (C)  2004 Alexander Clouter <alex-kernel@digriz.org.uk>
   8 *
   9 * This program is free software; you can redistribute it and/or modify
  10 * it under the terms of the GNU General Public License version 2 as
  11 * published by the Free Software Foundation.
  12 */
  13
  14#include <linux/kernel.h>
  15#include <linux/module.h>
  16#include <linux/smp.h>
  17#include <linux/init.h>
  18#include <linux/interrupt.h>
  19#include <linux/ctype.h>
  20#include <linux/cpufreq.h>
  21#include <linux/sysctl.h>
  22#include <linux/types.h>
  23#include <linux/fs.h>
  24#include <linux/sysfs.h>
  25#include <linux/cpu.h>
  26#include <linux/kmod.h>
  27#include <linux/workqueue.h>
  28#include <linux/jiffies.h>
  29#include <linux/kernel_stat.h>
  30#include <linux/percpu.h>
  31#include <linux/mutex.h>
  32/*
  33 * dbs is used in this file as a shortform for demandbased switching
  34 * It helps to keep variable names smaller, simpler
  35 */
  36
  37#define DEF_FREQUENCY_UP_THRESHOLD              (80)
  38#define DEF_FREQUENCY_DOWN_THRESHOLD            (20)
  39
  40/*
  41 * The polling frequency of this governor depends on the capability of
  42 * the processor. Default polling frequency is 1000 times the transition
  43 * latency of the processor. The governor will work on any processor with
  44 * transition latency <= 10mS, using appropriate sampling
  45 * rate.
  46 * For CPUs with transition latency > 10mS (mostly drivers
  47 * with CPUFREQ_ETERNAL), this governor will not work.
  48 * All times here are in uS.
  49 */
  50static unsigned int def_sampling_rate;
  51#define MIN_SAMPLING_RATE_RATIO                 (2)
  52/* for correct statistics, we need at least 10 ticks between each measure */
  53#define MIN_STAT_SAMPLING_RATE                  \
  54                        (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
  55#define MIN_SAMPLING_RATE                       \
  56                        (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
  57#define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
  58#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (1000)
  59#define DEF_SAMPLING_DOWN_FACTOR                (1)
  60#define MAX_SAMPLING_DOWN_FACTOR                (10)
  61#define TRANSITION_LATENCY_LIMIT                (10 * 1000 * 1000)
  62
  63static void do_dbs_timer(struct work_struct *work);
  64
  65struct cpu_dbs_info_s {
  66        struct cpufreq_policy *cur_policy;
  67        unsigned int prev_cpu_idle_up;
  68        unsigned int prev_cpu_idle_down;
  69        unsigned int enable;
  70        unsigned int down_skip;
  71        unsigned int requested_freq;
  72};
  73static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
  74
  75static unsigned int dbs_enable; /* number of CPUs using this policy */
  76
  77/*
  78 * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
  79 * lock and dbs_mutex. cpu_hotplug lock should always be held before
  80 * dbs_mutex. If any function that can potentially take cpu_hotplug lock
  81 * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
  82 * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
  83 * is recursive for the same process. -Venki
  84 */
  85static DEFINE_MUTEX (dbs_mutex);
  86static DECLARE_DELAYED_WORK(dbs_work, do_dbs_timer);
  87
  88struct dbs_tuners {
  89        unsigned int sampling_rate;
  90        unsigned int sampling_down_factor;
  91        unsigned int up_threshold;
  92        unsigned int down_threshold;
  93        unsigned int ignore_nice;
  94        unsigned int freq_step;
  95};
  96
  97static struct dbs_tuners dbs_tuners_ins = {
  98        .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
  99        .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
 100        .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
 101        .ignore_nice = 0,
 102        .freq_step = 5,
 103};
 104
 105static inline unsigned int get_cpu_idle_time(unsigned int cpu)
 106{
 107        unsigned int add_nice = 0, ret;
 108
 109        if (dbs_tuners_ins.ignore_nice)
 110                add_nice = kstat_cpu(cpu).cpustat.nice;
 111
 112        ret = kstat_cpu(cpu).cpustat.idle +
 113                kstat_cpu(cpu).cpustat.iowait +
 114                add_nice;
 115
 116        return ret;
 117}
 118
 119/* keep track of frequency transitions */
 120static int
 121dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
 122                     void *data)
 123{
 124        struct cpufreq_freqs *freq = data;
 125        struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info,
 126                                                        freq->cpu);
 127
 128        if (!this_dbs_info->enable)
 129                return 0;
 130
 131        this_dbs_info->requested_freq = freq->new;
 132
 133        return 0;
 134}
 135
 136static struct notifier_block dbs_cpufreq_notifier_block = {
 137        .notifier_call = dbs_cpufreq_notifier
 138};
 139
 140/************************** sysfs interface ************************/
 141static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 142{
 143        return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
 144}
 145
 146static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 147{
 148        return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 149}
 150
 151#define define_one_ro(_name)                            \
 152static struct freq_attr _name =                         \
 153__ATTR(_name, 0444, show_##_name, NULL)
 154
 155define_one_ro(sampling_rate_max);
 156define_one_ro(sampling_rate_min);
 157
 158/* cpufreq_conservative Governor Tunables */
 159#define show_one(file_name, object)                                     \
 160static ssize_t show_##file_name                                         \
 161(struct cpufreq_policy *unused, char *buf)                              \
 162{                                                                       \
 163        return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 164}
 165show_one(sampling_rate, sampling_rate);
 166show_one(sampling_down_factor, sampling_down_factor);
 167show_one(up_threshold, up_threshold);
 168show_one(down_threshold, down_threshold);
 169show_one(ignore_nice_load, ignore_nice);
 170show_one(freq_step, freq_step);
 171
 172static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
 173                const char *buf, size_t count)
 174{
 175        unsigned int input;
 176        int ret;
 177        ret = sscanf (buf, "%u", &input);
 178        if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 179                return -EINVAL;
 180
 181        mutex_lock(&dbs_mutex);
 182        dbs_tuners_ins.sampling_down_factor = input;
 183        mutex_unlock(&dbs_mutex);
 184
 185        return count;
 186}
 187
 188static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 189                const char *buf, size_t count)
 190{
 191        unsigned int input;
 192        int ret;
 193        ret = sscanf (buf, "%u", &input);
 194
 195        mutex_lock(&dbs_mutex);
 196        if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
 197                mutex_unlock(&dbs_mutex);
 198                return -EINVAL;
 199        }
 200
 201        dbs_tuners_ins.sampling_rate = input;
 202        mutex_unlock(&dbs_mutex);
 203
 204        return count;
 205}
 206
 207static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 208                const char *buf, size_t count)
 209{
 210        unsigned int input;
 211        int ret;
 212        ret = sscanf (buf, "%u", &input);
 213
 214        mutex_lock(&dbs_mutex);
 215        if (ret != 1 || input > 100 || input <= dbs_tuners_ins.down_threshold) {
 216                mutex_unlock(&dbs_mutex);
 217                return -EINVAL;
 218        }
 219
 220        dbs_tuners_ins.up_threshold = input;
 221        mutex_unlock(&dbs_mutex);
 222
 223        return count;
 224}
 225
 226static ssize_t store_down_threshold(struct cpufreq_policy *unused,
 227                const char *buf, size_t count)
 228{
 229        unsigned int input;
 230        int ret;
 231        ret = sscanf (buf, "%u", &input);
 232
 233        mutex_lock(&dbs_mutex);
 234        if (ret != 1 || input > 100 || input >= dbs_tuners_ins.up_threshold) {
 235                mutex_unlock(&dbs_mutex);
 236                return -EINVAL;
 237        }
 238
 239        dbs_tuners_ins.down_threshold = input;
 240        mutex_unlock(&dbs_mutex);
 241
 242        return count;
 243}
 244
 245static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 246                const char *buf, size_t count)
 247{
 248        unsigned int input;
 249        int ret;
 250
 251        unsigned int j;
 252
 253        ret = sscanf(buf, "%u", &input);
 254        if (ret != 1)
 255                return -EINVAL;
 256
 257        if (input > 1)
 258                input = 1;
 259
 260        mutex_lock(&dbs_mutex);
 261        if (input == dbs_tuners_ins.ignore_nice) { /* nothing to do */
 262                mutex_unlock(&dbs_mutex);
 263                return count;
 264        }
 265        dbs_tuners_ins.ignore_nice = input;
 266
 267        /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
 268        for_each_online_cpu(j) {
 269                struct cpu_dbs_info_s *j_dbs_info;
 270                j_dbs_info = &per_cpu(cpu_dbs_info, j);
 271                j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 272                j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
 273        }
 274        mutex_unlock(&dbs_mutex);
 275
 276        return count;
 277}
 278
 279static ssize_t store_freq_step(struct cpufreq_policy *policy,
 280                const char *buf, size_t count)
 281{
 282        unsigned int input;
 283        int ret;
 284
 285        ret = sscanf(buf, "%u", &input);
 286
 287        if (ret != 1)
 288                return -EINVAL;
 289
 290        if (input > 100)
 291                input = 100;
 292
 293        /* no need to test here if freq_step is zero as the user might actually
 294         * want this, they would be crazy though :) */
 295        mutex_lock(&dbs_mutex);
 296        dbs_tuners_ins.freq_step = input;
 297        mutex_unlock(&dbs_mutex);
 298
 299        return count;
 300}
 301
 302#define define_one_rw(_name) \
 303static struct freq_attr _name = \
 304__ATTR(_name, 0644, show_##_name, store_##_name)
 305
 306define_one_rw(sampling_rate);
 307define_one_rw(sampling_down_factor);
 308define_one_rw(up_threshold);
 309define_one_rw(down_threshold);
 310define_one_rw(ignore_nice_load);
 311define_one_rw(freq_step);
 312
 313static struct attribute * dbs_attributes[] = {
 314        &sampling_rate_max.attr,
 315        &sampling_rate_min.attr,
 316        &sampling_rate.attr,
 317        &sampling_down_factor.attr,
 318        &up_threshold.attr,
 319        &down_threshold.attr,
 320        &ignore_nice_load.attr,
 321        &freq_step.attr,
 322        NULL
 323};
 324
 325static struct attribute_group dbs_attr_group = {
 326        .attrs = dbs_attributes,
 327        .name = "conservative",
 328};
 329
 330/************************** sysfs end ************************/
 331
 332static void dbs_check_cpu(int cpu)
 333{
 334        unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;
 335        unsigned int tmp_idle_ticks, total_idle_ticks;
 336        unsigned int freq_target;
 337        unsigned int freq_down_sampling_rate;
 338        struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 339        struct cpufreq_policy *policy;
 340
 341        if (!this_dbs_info->enable)
 342                return;
 343
 344        policy = this_dbs_info->cur_policy;
 345
 346        /*
 347         * The default safe range is 20% to 80%
 348         * Every sampling_rate, we check
 349         *      - If current idle time is less than 20%, then we try to
 350         *        increase frequency
 351         * Every sampling_rate*sampling_down_factor, we check
 352         *      - If current idle time is more than 80%, then we try to
 353         *        decrease frequency
 354         *
 355         * Any frequency increase takes it to the maximum frequency.
 356         * Frequency reduction happens at minimum steps of
 357         * 5% (default) of max_frequency
 358         */
 359
 360        /* Check for frequency increase */
 361        idle_ticks = UINT_MAX;
 362
 363        /* Check for frequency increase */
 364        total_idle_ticks = get_cpu_idle_time(cpu);
 365        tmp_idle_ticks = total_idle_ticks -
 366                this_dbs_info->prev_cpu_idle_up;
 367        this_dbs_info->prev_cpu_idle_up = total_idle_ticks;
 368
 369        if (tmp_idle_ticks < idle_ticks)
 370                idle_ticks = tmp_idle_ticks;
 371
 372        /* Scale idle ticks by 100 and compare with up and down ticks */
 373        idle_ticks *= 100;
 374        up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
 375                        usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 376
 377        if (idle_ticks < up_idle_ticks) {
 378                this_dbs_info->down_skip = 0;
 379                this_dbs_info->prev_cpu_idle_down =
 380                        this_dbs_info->prev_cpu_idle_up;
 381
 382                /* if we are already at full speed then break out early */
 383                if (this_dbs_info->requested_freq == policy->max)
 384                        return;
 385
 386                freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 387
 388                /* max freq cannot be less than 100. But who knows.... */
 389                if (unlikely(freq_target == 0))
 390                        freq_target = 5;
 391
 392                this_dbs_info->requested_freq += freq_target;
 393                if (this_dbs_info->requested_freq > policy->max)
 394                        this_dbs_info->requested_freq = policy->max;
 395
 396                __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 397                        CPUFREQ_RELATION_H);
 398                return;
 399        }
 400
 401        /* Check for frequency decrease */
 402        this_dbs_info->down_skip++;
 403        if (this_dbs_info->down_skip < dbs_tuners_ins.sampling_down_factor)
 404                return;
 405
 406        /* Check for frequency decrease */
 407        total_idle_ticks = this_dbs_info->prev_cpu_idle_up;
 408        tmp_idle_ticks = total_idle_ticks -
 409                this_dbs_info->prev_cpu_idle_down;
 410        this_dbs_info->prev_cpu_idle_down = total_idle_ticks;
 411
 412        if (tmp_idle_ticks < idle_ticks)
 413                idle_ticks = tmp_idle_ticks;
 414
 415        /* Scale idle ticks by 100 and compare with up and down ticks */
 416        idle_ticks *= 100;
 417        this_dbs_info->down_skip = 0;
 418
 419        freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
 420                dbs_tuners_ins.sampling_down_factor;
 421        down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) *
 422                usecs_to_jiffies(freq_down_sampling_rate);
 423
 424        if (idle_ticks > down_idle_ticks) {
 425                /*
 426                 * if we are already at the lowest speed then break out early
 427                 * or if we 'cannot' reduce the speed as the user might want
 428                 * freq_target to be zero
 429                 */
 430                if (this_dbs_info->requested_freq == policy->min
 431                                || dbs_tuners_ins.freq_step == 0)
 432                        return;
 433
 434                freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 435
 436                /* max freq cannot be less than 100. But who knows.... */
 437                if (unlikely(freq_target == 0))
 438                        freq_target = 5;
 439
 440                this_dbs_info->requested_freq -= freq_target;
 441                if (this_dbs_info->requested_freq < policy->min)
 442                        this_dbs_info->requested_freq = policy->min;
 443
 444                __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 445                                CPUFREQ_RELATION_H);
 446                return;
 447        }
 448}
 449
 450static void do_dbs_timer(struct work_struct *work)
 451{
 452        int i;
 453        mutex_lock(&dbs_mutex);
 454        for_each_online_cpu(i)
 455                dbs_check_cpu(i);
 456        schedule_delayed_work(&dbs_work,
 457                        usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 458        mutex_unlock(&dbs_mutex);
 459}
 460
 461static inline void dbs_timer_init(void)
 462{
 463        init_timer_deferrable(&dbs_work.timer);
 464        schedule_delayed_work(&dbs_work,
 465                        usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 466        return;
 467}
 468
 469static inline void dbs_timer_exit(void)
 470{
 471        cancel_delayed_work(&dbs_work);
 472        return;
 473}
 474
 475static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 476                                   unsigned int event)
 477{
 478        unsigned int cpu = policy->cpu;
 479        struct cpu_dbs_info_s *this_dbs_info;
 480        unsigned int j;
 481        int rc;
 482
 483        this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 484
 485        switch (event) {
 486        case CPUFREQ_GOV_START:
 487                if ((!cpu_online(cpu)) || (!policy->cur))
 488                        return -EINVAL;
 489
 490                if (this_dbs_info->enable) /* Already enabled */
 491                        break;
 492
 493                mutex_lock(&dbs_mutex);
 494
 495                rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
 496                if (rc) {
 497                        mutex_unlock(&dbs_mutex);
 498                        return rc;
 499                }
 500
 501                for_each_cpu_mask_nr(j, policy->cpus) {
 502                        struct cpu_dbs_info_s *j_dbs_info;
 503                        j_dbs_info = &per_cpu(cpu_dbs_info, j);
 504                        j_dbs_info->cur_policy = policy;
 505
 506                        j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(cpu);
 507                        j_dbs_info->prev_cpu_idle_down
 508                                = j_dbs_info->prev_cpu_idle_up;
 509                }
 510                this_dbs_info->enable = 1;
 511                this_dbs_info->down_skip = 0;
 512                this_dbs_info->requested_freq = policy->cur;
 513
 514                dbs_enable++;
 515                /*
 516                 * Start the timerschedule work, when this governor
 517                 * is used for first time
 518                 */
 519                if (dbs_enable == 1) {
 520                        unsigned int latency;
 521                        /* policy latency is in nS. Convert it to uS first */
 522                        latency = policy->cpuinfo.transition_latency / 1000;
 523                        if (latency == 0)
 524                                latency = 1;
 525
 526                        def_sampling_rate = 10 * latency *
 527                                        DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 528
 529                        if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
 530                                def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 531
 532                        dbs_tuners_ins.sampling_rate = def_sampling_rate;
 533
 534                        dbs_timer_init();
 535                        cpufreq_register_notifier(
 536                                        &dbs_cpufreq_notifier_block,
 537                                        CPUFREQ_TRANSITION_NOTIFIER);
 538                }
 539
 540                mutex_unlock(&dbs_mutex);
 541                break;
 542
 543        case CPUFREQ_GOV_STOP:
 544                mutex_lock(&dbs_mutex);
 545                this_dbs_info->enable = 0;
 546                sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 547                dbs_enable--;
 548                /*
 549                 * Stop the timerschedule work, when this governor
 550                 * is used for first time
 551                 */
 552                if (dbs_enable == 0) {
 553                        dbs_timer_exit();
 554                        cpufreq_unregister_notifier(
 555                                        &dbs_cpufreq_notifier_block,
 556                                        CPUFREQ_TRANSITION_NOTIFIER);
 557                }
 558
 559                mutex_unlock(&dbs_mutex);
 560
 561                break;
 562
 563        case CPUFREQ_GOV_LIMITS:
 564                mutex_lock(&dbs_mutex);
 565                if (policy->max < this_dbs_info->cur_policy->cur)
 566                        __cpufreq_driver_target(
 567                                        this_dbs_info->cur_policy,
 568                                        policy->max, CPUFREQ_RELATION_H);
 569                else if (policy->min > this_dbs_info->cur_policy->cur)
 570                        __cpufreq_driver_target(
 571                                        this_dbs_info->cur_policy,
 572                                        policy->min, CPUFREQ_RELATION_L);
 573                mutex_unlock(&dbs_mutex);
 574                break;
 575        }
 576        return 0;
 577}
 578
 579#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 580static
 581#endif
 582struct cpufreq_governor cpufreq_gov_conservative = {
 583        .name                   = "conservative",
 584        .governor               = cpufreq_governor_dbs,
 585        .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 586        .owner                  = THIS_MODULE,
 587};
 588
 589static int __init cpufreq_gov_dbs_init(void)
 590{
 591        return cpufreq_register_governor(&cpufreq_gov_conservative);
 592}
 593
 594static void __exit cpufreq_gov_dbs_exit(void)
 595{
 596        /* Make sure that the scheduled work is indeed not running */
 597        flush_scheduled_work();
 598
 599        cpufreq_unregister_governor(&cpufreq_gov_conservative);
 600}
 601
 602
 603MODULE_AUTHOR ("Alexander Clouter <alex-kernel@digriz.org.uk>");
 604MODULE_DESCRIPTION ("'cpufreq_conservative' - A dynamic cpufreq governor for "
 605                "Low Latency Frequency Transition capable processors "
 606                "optimised for use in a battery environment");
 607MODULE_LICENSE ("GPL");
 608
 609#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 610fs_initcall(cpufreq_gov_dbs_init);
 611#else
 612module_init(cpufreq_gov_dbs_init);
 613#endif
 614module_exit(cpufreq_gov_dbs_exit);
 615
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