drivers/cpufreq/cpufreq_conservative.c

   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  */
  50 static 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
  63 static void do_dbs_timer(struct work_struct *work);
  64
  65 struct 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 };
  73 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
  74
  75 static 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  */
  85 static DEFINE_MUTEX(dbs_mutex);
  86 static DECLARE_DELAYED_WORK(dbs_work, do_dbs_timer);
  87
  88 struct 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
  97 static 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
 105 static 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 */
 120 static int
 121 dbs_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
 136 static struct notifier_block dbs_cpufreq_notifier_block = {
 137         .notifier_call = dbs_cpufreq_notifier
 138 };
 139
 140 /************************** sysfs interface ************************/
 141 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 142 {
 143         return sprintf(buf, "%u\n", MAX_SAMPLING_RATE);
 144 }
 145
 146 static 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)                            \
 152 static struct freq_attr _name =                         \
 153 __ATTR(_name, 0444, show_##_name, NULL)
 154
 155 define_one_ro(sampling_rate_max);
 156 define_one_ro(sampling_rate_min);
 157
 158 /* cpufreq_conservative Governor Tunables */
 159 #define show_one(file_name, object)                                     \
 160 static ssize_t show_##file_name                                         \
 161 (struct cpufreq_policy *unused, char *buf)                              \
 162 {                                                                       \
 163         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 164 }
 165 show_one(sampling_rate, sampling_rate);
 166 show_one(sampling_down_factor, sampling_down_factor);
 167 show_one(up_threshold, up_threshold);
 168 show_one(down_threshold, down_threshold);
 169 show_one(ignore_nice_load, ignore_nice);
 170 show_one(freq_step, freq_step);
 171
 172 static 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
 188 static 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 ||
 197             input < MIN_SAMPLING_RATE) {
 198                 mutex_unlock(&dbs_mutex);
 199                 return -EINVAL;
 200         }
 201
 202         dbs_tuners_ins.sampling_rate = input;
 203         mutex_unlock(&dbs_mutex);
 204
 205         return count;
 206 }
 207
 208 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 209                 const char *buf, size_t count)
 210 {
 211         unsigned int input;
 212         int ret;
 213         ret = sscanf(buf, "%u", &input);
 214
 215         mutex_lock(&dbs_mutex);
 216         if (ret != 1 || input > 100 ||
 217             input <= dbs_tuners_ins.down_threshold) {
 218                 mutex_unlock(&dbs_mutex);
 219                 return -EINVAL;
 220         }
 221
 222         dbs_tuners_ins.up_threshold = input;
 223         mutex_unlock(&dbs_mutex);
 224
 225         return count;
 226 }
 227
 228 static ssize_t store_down_threshold(struct cpufreq_policy *unused,
 229                 const char *buf, size_t count)
 230 {
 231         unsigned int input;
 232         int ret;
 233         ret = sscanf(buf, "%u", &input);
 234
 235         mutex_lock(&dbs_mutex);
 236         if (ret != 1 || input > 100 || input >= dbs_tuners_ins.up_threshold) {
 237                 mutex_unlock(&dbs_mutex);
 238                 return -EINVAL;
 239         }
 240
 241         dbs_tuners_ins.down_threshold = input;
 242         mutex_unlock(&dbs_mutex);
 243
 244         return count;
 245 }
 246
 247 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 248                 const char *buf, size_t count)
 249 {
 250         unsigned int input;
 251         int ret;
 252
 253         unsigned int j;
 254
 255         ret = sscanf(buf, "%u", &input);
 256         if (ret != 1)
 257                 return -EINVAL;
 258
 259         if (input > 1)
 260                 input = 1;
 261
 262         mutex_lock(&dbs_mutex);
 263         if (input == dbs_tuners_ins.ignore_nice) { /* nothing to do */
 264                 mutex_unlock(&dbs_mutex);
 265                 return count;
 266         }
 267         dbs_tuners_ins.ignore_nice = input;
 268
 269         /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
 270         for_each_online_cpu(j) {
 271                 struct cpu_dbs_info_s *j_dbs_info;
 272                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 273                 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 274                 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
 275         }
 276         mutex_unlock(&dbs_mutex);
 277
 278         return count;
 279 }
 280
 281 static ssize_t store_freq_step(struct cpufreq_policy *policy,
 282                 const char *buf, size_t count)
 283 {
 284         unsigned int input;
 285         int ret;
 286
 287         ret = sscanf(buf, "%u", &input);
 288
 289         if (ret != 1)
 290                 return -EINVAL;
 291
 292         if (input > 100)
 293                 input = 100;
 294
 295         /* no need to test here if freq_step is zero as the user might actually
 296          * want this, they would be crazy though :) */
 297         mutex_lock(&dbs_mutex);
 298         dbs_tuners_ins.freq_step = input;
 299         mutex_unlock(&dbs_mutex);
 300
 301         return count;
 302 }
 303
 304 #define define_one_rw(_name) \
 305 static struct freq_attr _name = \
 306 __ATTR(_name, 0644, show_##_name, store_##_name)
 307
 308 define_one_rw(sampling_rate);
 309 define_one_rw(sampling_down_factor);
 310 define_one_rw(up_threshold);
 311 define_one_rw(down_threshold);
 312 define_one_rw(ignore_nice_load);
 313 define_one_rw(freq_step);
 314
 315 static struct attribute *dbs_attributes[] = {
 316         &sampling_rate_max.attr,
 317         &sampling_rate_min.attr,
 318         &sampling_rate.attr,
 319         &sampling_down_factor.attr,
 320         &up_threshold.attr,
 321         &down_threshold.attr,
 322         &ignore_nice_load.attr,
 323         &freq_step.attr,
 324         NULL
 325 };
 326
 327 static struct attribute_group dbs_attr_group = {
 328         .attrs = dbs_attributes,
 329         .name = "conservative",
 330 };
 331
 332 /************************** sysfs end ************************/
 333
 334 static void dbs_check_cpu(int cpu)
 335 {
 336         unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;
 337         unsigned int tmp_idle_ticks, total_idle_ticks;
 338         unsigned int freq_target;
 339         unsigned int freq_down_sampling_rate;
 340         struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 341         struct cpufreq_policy *policy;
 342
 343         if (!this_dbs_info->enable)
 344                 return;
 345
 346         policy = this_dbs_info->cur_policy;
 347
 348         /*
 349          * The default safe range is 20% to 80%
 350          * Every sampling_rate, we check
 351          *      - If current idle time is less than 20%, then we try to
 352          *        increase frequency
 353          * Every sampling_rate*sampling_down_factor, we check
 354          *      - If current idle time is more than 80%, then we try to
 355          *        decrease frequency
 356          *
 357          * Any frequency increase takes it to the maximum frequency.
 358          * Frequency reduction happens at minimum steps of
 359          * 5% (default) of max_frequency
 360          */
 361
 362         /* Check for frequency increase */
 363         idle_ticks = UINT_MAX;
 364
 365         /* Check for frequency increase */
 366         total_idle_ticks = get_cpu_idle_time(cpu);
 367         tmp_idle_ticks = total_idle_ticks -
 368                 this_dbs_info->prev_cpu_idle_up;
 369         this_dbs_info->prev_cpu_idle_up = total_idle_ticks;
 370
 371         if (tmp_idle_ticks < idle_ticks)
 372                 idle_ticks = tmp_idle_ticks;
 373
 374         /* Scale idle ticks by 100 and compare with up and down ticks */
 375         idle_ticks *= 100;
 376         up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
 377                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 378
 379         if (idle_ticks < up_idle_ticks) {
 380                 this_dbs_info->down_skip = 0;
 381                 this_dbs_info->prev_cpu_idle_down =
 382                         this_dbs_info->prev_cpu_idle_up;
 383
 384                 /* if we are already at full speed then break out early */
 385                 if (this_dbs_info->requested_freq == policy->max)
 386                         return;
 387
 388                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 389
 390                 /* max freq cannot be less than 100. But who knows.... */
 391                 if (unlikely(freq_target == 0))
 392                         freq_target = 5;
 393
 394                 this_dbs_info->requested_freq += freq_target;
 395                 if (this_dbs_info->requested_freq > policy->max)
 396                         this_dbs_info->requested_freq = policy->max;
 397
 398                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 399                         CPUFREQ_RELATION_H);
 400                 return;
 401         }
 402
 403         /* Check for frequency decrease */
 404         this_dbs_info->down_skip++;
 405         if (this_dbs_info->down_skip < dbs_tuners_ins.sampling_down_factor)
 406                 return;
 407
 408         /* Check for frequency decrease */
 409         total_idle_ticks = this_dbs_info->prev_cpu_idle_up;
 410         tmp_idle_ticks = total_idle_ticks -
 411                 this_dbs_info->prev_cpu_idle_down;
 412         this_dbs_info->prev_cpu_idle_down = total_idle_ticks;
 413
 414         if (tmp_idle_ticks < idle_ticks)
 415                 idle_ticks = tmp_idle_ticks;
 416
 417         /* Scale idle ticks by 100 and compare with up and down ticks */
 418         idle_ticks *= 100;
 419         this_dbs_info->down_skip = 0;
 420
 421         freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
 422                 dbs_tuners_ins.sampling_down_factor;
 423         down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) *
 424                 usecs_to_jiffies(freq_down_sampling_rate);
 425
 426         if (idle_ticks > down_idle_ticks) {
 427                 /*
 428                  * if we are already at the lowest speed then break out early
 429                  * or if we 'cannot' reduce the speed as the user might want
 430                  * freq_target to be zero
 431                  */
 432                 if (this_dbs_info->requested_freq == policy->min
 433                                 || dbs_tuners_ins.freq_step == 0)
 434                         return;
 435
 436                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 437
 438                 /* max freq cannot be less than 100. But who knows.... */
 439                 if (unlikely(freq_target == 0))
 440                         freq_target = 5;
 441
 442                 this_dbs_info->requested_freq -= freq_target;
 443                 if (this_dbs_info->requested_freq < policy->min)
 444                         this_dbs_info->requested_freq = policy->min;
 445
 446                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 447                                 CPUFREQ_RELATION_H);
 448                 return;
 449         }
 450 }
 451
 452 static void do_dbs_timer(struct work_struct *work)
 453 {
 454         int i;
 455         mutex_lock(&dbs_mutex);
 456         for_each_online_cpu(i)
 457                 dbs_check_cpu(i);
 458         schedule_delayed_work(&dbs_work,
 459                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 460         mutex_unlock(&dbs_mutex);
 461 }
 462
 463 static inline void dbs_timer_init(void)
 464 {
 465         init_timer_deferrable(&dbs_work.timer);
 466         schedule_delayed_work(&dbs_work,
 467                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 468         return;
 469 }
 470
 471 static inline void dbs_timer_exit(void)
 472 {
 473         cancel_delayed_work(&dbs_work);
 474         return;
 475 }
 476
 477 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 478                                    unsigned int event)
 479 {
 480         unsigned int cpu = policy->cpu;
 481         struct cpu_dbs_info_s *this_dbs_info;
 482         unsigned int j;
 483         int rc;
 484
 485         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 486
 487         switch (event) {
 488         case CPUFREQ_GOV_START:
 489                 if ((!cpu_online(cpu)) || (!policy->cur))
 490                         return -EINVAL;
 491
 492                 if (this_dbs_info->enable) /* Already enabled */
 493                         break;
 494
 495                 mutex_lock(&dbs_mutex);
 496
 497                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
 498                 if (rc) {
 499                         mutex_unlock(&dbs_mutex);
 500                         return rc;
 501                 }
 502
 503                 for_each_cpu(j, policy->cpus) {
 504                         struct cpu_dbs_info_s *j_dbs_info;
 505                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 506                         j_dbs_info->cur_policy = policy;
 507
 508                         j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(cpu);
 509                         j_dbs_info->prev_cpu_idle_down
 510                                 = j_dbs_info->prev_cpu_idle_up;
 511                 }
 512                 this_dbs_info->enable = 1;
 513                 this_dbs_info->down_skip = 0;
 514                 this_dbs_info->requested_freq = policy->cur;
 515
 516                 dbs_enable++;
 517                 /*
 518                  * Start the timerschedule work, when this governor
 519                  * is used for first time
 520                  */
 521                 if (dbs_enable == 1) {
 522                         unsigned int latency;
 523                         /* policy latency is in nS. Convert it to uS first */
 524                         latency = policy->cpuinfo.transition_latency / 1000;
 525                         if (latency == 0)
 526                                 latency = 1;
 527
 528                         def_sampling_rate = 10 * latency *
 529                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 530
 531                         if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
 532                                 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 533
 534                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 535
 536                         dbs_timer_init();
 537                         cpufreq_register_notifier(
 538                                         &dbs_cpufreq_notifier_block,
 539                                         CPUFREQ_TRANSITION_NOTIFIER);
 540                 }
 541
 542                 mutex_unlock(&dbs_mutex);
 543                 break;
 544
 545         case CPUFREQ_GOV_STOP:
 546                 mutex_lock(&dbs_mutex);
 547                 this_dbs_info->enable = 0;
 548                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 549                 dbs_enable--;
 550                 /*
 551                  * Stop the timerschedule work, when this governor
 552                  * is used for first time
 553                  */
 554                 if (dbs_enable == 0) {
 555                         dbs_timer_exit();
 556                         cpufreq_unregister_notifier(
 557                                         &dbs_cpufreq_notifier_block,
 558                                         CPUFREQ_TRANSITION_NOTIFIER);
 559                 }
 560
 561                 mutex_unlock(&dbs_mutex);
 562
 563                 break;
 564
 565         case CPUFREQ_GOV_LIMITS:
 566                 mutex_lock(&dbs_mutex);
 567                 if (policy->max < this_dbs_info->cur_policy->cur)
 568                         __cpufreq_driver_target(
 569                                         this_dbs_info->cur_policy,
 570                                         policy->max, CPUFREQ_RELATION_H);
 571                 else if (policy->min > this_dbs_info->cur_policy->cur)
 572                         __cpufreq_driver_target(
 573                                         this_dbs_info->cur_policy,
 574                                         policy->min, CPUFREQ_RELATION_L);
 575                 mutex_unlock(&dbs_mutex);
 576                 break;
 577         }
 578         return 0;
 579 }
 580
 581 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 582 static
 583 #endif
 584 struct cpufreq_governor cpufreq_gov_conservative = {
 585         .name                   = "conservative",
 586         .governor               = cpufreq_governor_dbs,
 587         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 588         .owner                  = THIS_MODULE,
 589 };
 590
 591 static int __init cpufreq_gov_dbs_init(void)
 592 {
 593         return cpufreq_register_governor(&cpufreq_gov_conservative);
 594 }
 595
 596 static void __exit cpufreq_gov_dbs_exit(void)
 597 {
 598         /* Make sure that the scheduled work is indeed not running */
 599         flush_scheduled_work();
 600
 601         cpufreq_unregister_governor(&cpufreq_gov_conservative);
 602 }
 603
 604
 605 MODULE_AUTHOR("Alexander Clouter <alex-kernel@digriz.org.uk>");
 606 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
 607                 "Low Latency Frequency Transition capable processors "
 608                 "optimised for use in a battery environment");
 609 MODULE_LICENSE("GPL");
 610
 611 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 612 fs_initcall(cpufreq_gov_dbs_init);
 613 #else
 614 module_init(cpufreq_gov_dbs_init);
 615 #endif
 616 module_exit(cpufreq_gov_dbs_exit);