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 || 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
 207 static 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
 226 static 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
 245 static 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
 279 static 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) \
 303 static struct freq_attr _name = \
 304 __ATTR(_name, 0644, show_##_name, store_##_name)
 305
 306 define_one_rw(sampling_rate);
 307 define_one_rw(sampling_down_factor);
 308 define_one_rw(up_threshold);
 309 define_one_rw(down_threshold);
 310 define_one_rw(ignore_nice_load);
 311 define_one_rw(freq_step);
 312
 313 static 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
 325 static struct attribute_group dbs_attr_group = {
 326         .attrs = dbs_attributes,
 327         .name = "conservative",
 328 };
 329
 330 /************************** sysfs end ************************/
 331
 332 static 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_step;
 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_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
 387
 388                 /* max freq cannot be less than 100. But who knows.... */
 389                 if (unlikely(freq_step == 0))
 390                         freq_step = 5;
 391
 392                 this_dbs_info->requested_freq += freq_step;
 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_step 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_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
 435
 436                 /* max freq cannot be less than 100. But who knows.... */
 437                 if (unlikely(freq_step == 0))
 438                         freq_step = 5;
 439
 440                 this_dbs_info->requested_freq -= freq_step;
 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
 450 static 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
 461 static inline void dbs_timer_init(void)
 462 {
 463         schedule_delayed_work(&dbs_work,
 464                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 465         return;
 466 }
 467
 468 static inline void dbs_timer_exit(void)
 469 {
 470         cancel_delayed_work(&dbs_work);
 471         return;
 472 }
 473
 474 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 475                                    unsigned int event)
 476 {
 477         unsigned int cpu = policy->cpu;
 478         struct cpu_dbs_info_s *this_dbs_info;
 479         unsigned int j;
 480         int rc;
 481
 482         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 483
 484         switch (event) {
 485         case CPUFREQ_GOV_START:
 486                 if ((!cpu_online(cpu)) || (!policy->cur))
 487                         return -EINVAL;
 488
 489                 if (this_dbs_info->enable) /* Already enabled */
 490                         break;
 491
 492                 mutex_lock(&dbs_mutex);
 493
 494                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
 495                 if (rc) {
 496                         mutex_unlock(&dbs_mutex);
 497                         return rc;
 498                 }
 499
 500                 for_each_cpu_mask_nr(j, policy->cpus) {
 501                         struct cpu_dbs_info_s *j_dbs_info;
 502                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 503                         j_dbs_info->cur_policy = policy;
 504
 505                         j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(cpu);
 506                         j_dbs_info->prev_cpu_idle_down
 507                                 = j_dbs_info->prev_cpu_idle_up;
 508                 }
 509                 this_dbs_info->enable = 1;
 510                 this_dbs_info->down_skip = 0;
 511                 this_dbs_info->requested_freq = policy->cur;
 512
 513                 dbs_enable++;
 514                 /*
 515                  * Start the timerschedule work, when this governor
 516                  * is used for first time
 517                  */
 518                 if (dbs_enable == 1) {
 519                         unsigned int latency;
 520                         /* policy latency is in nS. Convert it to uS first */
 521                         latency = policy->cpuinfo.transition_latency / 1000;
 522                         if (latency == 0)
 523                                 latency = 1;
 524
 525                         def_sampling_rate = 10 * latency *
 526                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 527
 528                         if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
 529                                 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 530
 531                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 532
 533                         dbs_timer_init();
 534                         cpufreq_register_notifier(
 535                                         &dbs_cpufreq_notifier_block,
 536                                         CPUFREQ_TRANSITION_NOTIFIER);
 537                 }
 538
 539                 mutex_unlock(&dbs_mutex);
 540                 break;
 541
 542         case CPUFREQ_GOV_STOP:
 543                 mutex_lock(&dbs_mutex);
 544                 this_dbs_info->enable = 0;
 545                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 546                 dbs_enable--;
 547                 /*
 548                  * Stop the timerschedule work, when this governor
 549                  * is used for first time
 550                  */
 551                 if (dbs_enable == 0) {
 552                         dbs_timer_exit();
 553                         cpufreq_unregister_notifier(
 554                                         &dbs_cpufreq_notifier_block,
 555                                         CPUFREQ_TRANSITION_NOTIFIER);
 556                 }
 557
 558                 mutex_unlock(&dbs_mutex);
 559
 560                 break;
 561
 562         case CPUFREQ_GOV_LIMITS:
 563                 mutex_lock(&dbs_mutex);
 564                 if (policy->max < this_dbs_info->cur_policy->cur)
 565                         __cpufreq_driver_target(
 566                                         this_dbs_info->cur_policy,
 567                                         policy->max, CPUFREQ_RELATION_H);
 568                 else if (policy->min > this_dbs_info->cur_policy->cur)
 569                         __cpufreq_driver_target(
 570                                         this_dbs_info->cur_policy,
 571                                         policy->min, CPUFREQ_RELATION_L);
 572                 mutex_unlock(&dbs_mutex);
 573                 break;
 574         }
 575         return 0;
 576 }
 577
 578 struct cpufreq_governor cpufreq_gov_conservative = {
 579         .name                   = "conservative",
 580         .governor               = cpufreq_governor_dbs,
 581         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 582         .owner                  = THIS_MODULE,
 583 };
 584 EXPORT_SYMBOL(cpufreq_gov_conservative);
 585
 586 static int __init cpufreq_gov_dbs_init(void)
 587 {
 588         return cpufreq_register_governor(&cpufreq_gov_conservative);
 589 }
 590
 591 static void __exit cpufreq_gov_dbs_exit(void)
 592 {
 593         /* Make sure that the scheduled work is indeed not running */
 594         flush_scheduled_work();
 595
 596         cpufreq_unregister_governor(&cpufreq_gov_conservative);
 597 }
 598
 599
 600 MODULE_AUTHOR ("Alexander Clouter <alex-kernel@digriz.org.uk>");
 601 MODULE_DESCRIPTION ("'cpufreq_conservative' - A dynamic cpufreq governor for "
 602                 "Low Latency Frequency Transition capable processors "
 603                 "optimised for use in a battery environment");
 604 MODULE_LICENSE ("GPL");
 605
 606 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 607 fs_initcall(cpufreq_gov_dbs_init);
 608 #else
 609 module_init(cpufreq_gov_dbs_init);
 610 #endif
 611 module_exit(cpufreq_gov_dbs_exit);