drivers/cpufreq/cpufreq_ondemand.c

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