git.oblomov.eu Git - linux-2.6/blob - 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/sched.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 with CPUFREQ_ETERNAL)
  47  * 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                  (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
  54 #define MIN_SAMPLING_RATE                       (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
  55 #define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
  56 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (1000)
  57 #define DEF_SAMPLING_DOWN_FACTOR                (1)
  58 #define MAX_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 DEFINE_MUTEX     (dbs_mutex);
  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 static inline unsigned int get_cpu_idle_time(unsigned int cpu)
  92 {
  93         return  kstat_cpu(cpu).cpustat.idle +
  94                 kstat_cpu(cpu).cpustat.iowait +
  95                 ( dbs_tuners_ins.ignore_nice ?
  96                   kstat_cpu(cpu).cpustat.nice :
  97                   0);
  98 }
  99
 100 /************************** sysfs interface ************************/
 101 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 102 {
 103         return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
 104 }
 105
 106 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 107 {
 108         return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 109 }
 110
 111 #define define_one_ro(_name)                                    \
 112 static struct freq_attr _name =                                 \
 113 __ATTR(_name, 0444, show_##_name, NULL)
 114
 115 define_one_ro(sampling_rate_max);
 116 define_one_ro(sampling_rate_min);
 117
 118 /* cpufreq_conservative Governor Tunables */
 119 #define show_one(file_name, object)                                     \
 120 static ssize_t show_##file_name                                         \
 121 (struct cpufreq_policy *unused, char *buf)                              \
 122 {                                                                       \
 123         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 124 }
 125 show_one(sampling_rate, sampling_rate);
 126 show_one(sampling_down_factor, sampling_down_factor);
 127 show_one(up_threshold, up_threshold);
 128 show_one(down_threshold, down_threshold);
 129 show_one(ignore_nice_load, ignore_nice);
 130 show_one(freq_step, freq_step);
 131
 132 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
 133                 const char *buf, size_t count)
 134 {
 135         unsigned int input;
 136         int ret;
 137         ret = sscanf (buf, "%u", &input);
 138         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 139                 return -EINVAL;
 140
 141         mutex_lock(&dbs_mutex);
 142         dbs_tuners_ins.sampling_down_factor = input;
 143         mutex_unlock(&dbs_mutex);
 144
 145         return count;
 146 }
 147
 148 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 149                 const char *buf, size_t count)
 150 {
 151         unsigned int input;
 152         int ret;
 153         ret = sscanf (buf, "%u", &input);
 154
 155         mutex_lock(&dbs_mutex);
 156         if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
 157                 mutex_unlock(&dbs_mutex);
 158                 return -EINVAL;
 159         }
 160
 161         dbs_tuners_ins.sampling_rate = input;
 162         mutex_unlock(&dbs_mutex);
 163
 164         return count;
 165 }
 166
 167 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 168                 const char *buf, size_t count)
 169 {
 170         unsigned int input;
 171         int ret;
 172         ret = sscanf (buf, "%u", &input);
 173
 174         mutex_lock(&dbs_mutex);
 175         if (ret != 1 || input > 100 || input < 0 ||
 176                         input <= dbs_tuners_ins.down_threshold) {
 177                 mutex_unlock(&dbs_mutex);
 178                 return -EINVAL;
 179         }
 180
 181         dbs_tuners_ins.up_threshold = input;
 182         mutex_unlock(&dbs_mutex);
 183
 184         return count;
 185 }
 186
 187 static ssize_t store_down_threshold(struct cpufreq_policy *unused,
 188                 const char *buf, size_t count)
 189 {
 190         unsigned int input;
 191         int ret;
 192         ret = sscanf (buf, "%u", &input);
 193
 194         mutex_lock(&dbs_mutex);
 195         if (ret != 1 || input > 100 || input < 0 ||
 196                         input >= dbs_tuners_ins.up_threshold) {
 197                 mutex_unlock(&dbs_mutex);
 198                 return -EINVAL;
 199         }
 200
 201         dbs_tuners_ins.down_threshold = input;
 202         mutex_unlock(&dbs_mutex);
 203
 204         return count;
 205 }
 206
 207 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 208                 const char *buf, size_t count)
 209 {
 210         unsigned int input;
 211         int ret;
 212
 213         unsigned int j;
 214
 215         ret = sscanf (buf, "%u", &input);
 216         if ( ret != 1 )
 217                 return -EINVAL;
 218
 219         if ( input > 1 )
 220                 input = 1;
 221
 222         mutex_lock(&dbs_mutex);
 223         if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
 224                 mutex_unlock(&dbs_mutex);
 225                 return count;
 226         }
 227         dbs_tuners_ins.ignore_nice = input;
 228
 229         /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
 230         for_each_online_cpu(j) {
 231                 struct cpu_dbs_info_s *j_dbs_info;
 232                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 233                 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 234                 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
 235         }
 236         mutex_unlock(&dbs_mutex);
 237
 238         return count;
 239 }
 240
 241 static ssize_t store_freq_step(struct cpufreq_policy *policy,
 242                 const char *buf, size_t count)
 243 {
 244         unsigned int input;
 245         int ret;
 246
 247         ret = sscanf (buf, "%u", &input);
 248
 249         if ( ret != 1 )
 250                 return -EINVAL;
 251
 252         if ( input > 100 )
 253                 input = 100;
 254
 255         /* no need to test here if freq_step is zero as the user might actually
 256          * want this, they would be crazy though :) */
 257         mutex_lock(&dbs_mutex);
 258         dbs_tuners_ins.freq_step = input;
 259         mutex_unlock(&dbs_mutex);
 260
 261         return count;
 262 }
 263
 264 #define define_one_rw(_name) \
 265 static struct freq_attr _name = \
 266 __ATTR(_name, 0644, show_##_name, store_##_name)
 267
 268 define_one_rw(sampling_rate);
 269 define_one_rw(sampling_down_factor);
 270 define_one_rw(up_threshold);
 271 define_one_rw(down_threshold);
 272 define_one_rw(ignore_nice_load);
 273 define_one_rw(freq_step);
 274
 275 static struct attribute * dbs_attributes[] = {
 276         &sampling_rate_max.attr,
 277         &sampling_rate_min.attr,
 278         &sampling_rate.attr,
 279         &sampling_down_factor.attr,
 280         &up_threshold.attr,
 281         &down_threshold.attr,
 282         &ignore_nice_load.attr,
 283         &freq_step.attr,
 284         NULL
 285 };
 286
 287 static struct attribute_group dbs_attr_group = {
 288         .attrs = dbs_attributes,
 289         .name = "conservative",
 290 };
 291
 292 /************************** sysfs end ************************/
 293
 294 static void dbs_check_cpu(int cpu)
 295 {
 296         unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;
 297         unsigned int freq_step;
 298         unsigned int freq_down_sampling_rate;
 299         static int down_skip[NR_CPUS];
 300         static int requested_freq[NR_CPUS];
 301         static unsigned short init_flag = 0;
 302         struct cpu_dbs_info_s *this_dbs_info;
 303         struct cpu_dbs_info_s *dbs_info;
 304
 305         struct cpufreq_policy *policy;
 306         unsigned int j;
 307
 308         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 309         if (!this_dbs_info->enable)
 310                 return;
 311
 312         policy = this_dbs_info->cur_policy;
 313
 314         if ( init_flag == 0 ) {
 315                 for_each_online_cpu(j) {
 316                         dbs_info = &per_cpu(cpu_dbs_info, j);
 317                         requested_freq[j] = dbs_info->cur_policy->cur;
 318                 }
 319                 init_flag = 1;
 320         }
 321
 322         /*
 323          * The default safe range is 20% to 80%
 324          * Every sampling_rate, we check
 325          *      - If current idle time is less than 20%, then we try to
 326          *        increase frequency
 327          * Every sampling_rate*sampling_down_factor, we check
 328          *      - If current idle time is more than 80%, then we try to
 329          *        decrease frequency
 330          *
 331          * Any frequency increase takes it to the maximum frequency.
 332          * Frequency reduction happens at minimum steps of
 333          * 5% (default) of max_frequency
 334          */
 335
 336         /* Check for frequency increase */
 337         idle_ticks = UINT_MAX;
 338         for_each_cpu_mask(j, policy->cpus) {
 339                 unsigned int tmp_idle_ticks, total_idle_ticks;
 340                 struct cpu_dbs_info_s *j_dbs_info;
 341
 342                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 343                 /* Check for frequency increase */
 344                 total_idle_ticks = get_cpu_idle_time(j);
 345                 tmp_idle_ticks = total_idle_ticks -
 346                         j_dbs_info->prev_cpu_idle_up;
 347                 j_dbs_info->prev_cpu_idle_up = total_idle_ticks;
 348
 349                 if (tmp_idle_ticks < idle_ticks)
 350                         idle_ticks = tmp_idle_ticks;
 351         }
 352
 353         /* Scale idle ticks by 100 and compare with up and down ticks */
 354         idle_ticks *= 100;
 355         up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
 356                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 357
 358         if (idle_ticks < up_idle_ticks) {
 359                 down_skip[cpu] = 0;
 360                 for_each_cpu_mask(j, policy->cpus) {
 361                         struct cpu_dbs_info_s *j_dbs_info;
 362
 363                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 364                         j_dbs_info->prev_cpu_idle_down =
 365                                         j_dbs_info->prev_cpu_idle_up;
 366                 }
 367                 /* if we are already at full speed then break out early */
 368                 if (requested_freq[cpu] == policy->max)
 369                         return;
 370
 371                 freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
 372
 373                 /* max freq cannot be less than 100. But who knows.... */
 374                 if (unlikely(freq_step == 0))
 375                         freq_step = 5;
 376
 377                 requested_freq[cpu] += freq_step;
 378                 if (requested_freq[cpu] > policy->max)
 379                         requested_freq[cpu] = policy->max;
 380
 381                 __cpufreq_driver_target(policy, requested_freq[cpu],
 382                         CPUFREQ_RELATION_H);
 383                 return;
 384         }
 385
 386         /* Check for frequency decrease */
 387         down_skip[cpu]++;
 388         if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
 389                 return;
 390
 391         idle_ticks = UINT_MAX;
 392         for_each_cpu_mask(j, policy->cpus) {
 393                 unsigned int tmp_idle_ticks, total_idle_ticks;
 394                 struct cpu_dbs_info_s *j_dbs_info;
 395
 396                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 397                 /* Check for frequency decrease */
 398                 total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
 399                 tmp_idle_ticks = total_idle_ticks -
 400                         j_dbs_info->prev_cpu_idle_down;
 401                 j_dbs_info->prev_cpu_idle_down = total_idle_ticks;
 402
 403                 if (tmp_idle_ticks < idle_ticks)
 404                         idle_ticks = tmp_idle_ticks;
 405         }
 406
 407         /* Scale idle ticks by 100 and compare with up and down ticks */
 408         idle_ticks *= 100;
 409         down_skip[cpu] = 0;
 410
 411         freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
 412                 dbs_tuners_ins.sampling_down_factor;
 413         down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) *
 414                 usecs_to_jiffies(freq_down_sampling_rate);
 415
 416         if (idle_ticks > down_idle_ticks) {
 417                 /*
 418                  * if we are already at the lowest speed then break out early
 419                  * or if we 'cannot' reduce the speed as the user might want
 420                  * freq_step to be zero
 421                  */
 422                 if (requested_freq[cpu] == policy->min
 423                                 || dbs_tuners_ins.freq_step == 0)
 424                         return;
 425
 426                 freq_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_step == 0))
 430                         freq_step = 5;
 431
 432                 requested_freq[cpu] -= freq_step;
 433                 if (requested_freq[cpu] < policy->min)
 434                         requested_freq[cpu] = policy->min;
 435
 436                 __cpufreq_driver_target(policy, requested_freq[cpu],
 437                                 CPUFREQ_RELATION_H);
 438                 return;
 439         }
 440 }
 441
 442 static void do_dbs_timer(void *data)
 443 {
 444         int i;
 445         mutex_lock(&dbs_mutex);
 446         for_each_online_cpu(i)
 447                 dbs_check_cpu(i);
 448         schedule_delayed_work(&dbs_work,
 449                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 450         mutex_unlock(&dbs_mutex);
 451 }
 452
 453 static inline void dbs_timer_init(void)
 454 {
 455         INIT_WORK(&dbs_work, do_dbs_timer, NULL);
 456         schedule_delayed_work(&dbs_work,
 457                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 458         return;
 459 }
 460
 461 static inline void dbs_timer_exit(void)
 462 {
 463         cancel_delayed_work(&dbs_work);
 464         return;
 465 }
 466
 467 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 468                                    unsigned int event)
 469 {
 470         unsigned int cpu = policy->cpu;
 471         struct cpu_dbs_info_s *this_dbs_info;
 472         unsigned int j;
 473
 474         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 475
 476         switch (event) {
 477         case CPUFREQ_GOV_START:
 478                 if ((!cpu_online(cpu)) ||
 479                     (!policy->cur))
 480                         return -EINVAL;
 481
 482                 if (policy->cpuinfo.transition_latency >
 483                                 (TRANSITION_LATENCY_LIMIT * 1000))
 484                         return -EINVAL;
 485                 if (this_dbs_info->enable) /* Already enabled */
 486                         break;
 487
 488                 mutex_lock(&dbs_mutex);
 489                 for_each_cpu_mask(j, policy->cpus) {
 490                         struct cpu_dbs_info_s *j_dbs_info;
 491                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 492                         j_dbs_info->cur_policy = policy;
 493
 494                         j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 495                         j_dbs_info->prev_cpu_idle_down
 496                                 = j_dbs_info->prev_cpu_idle_up;
 497                 }
 498                 this_dbs_info->enable = 1;
 499                 sysfs_create_group(&policy->kobj, &dbs_attr_group);
 500                 dbs_enable++;
 501                 /*
 502                  * Start the timerschedule work, when this governor
 503                  * is used for first time
 504                  */
 505                 if (dbs_enable == 1) {
 506                         unsigned int latency;
 507                         /* policy latency is in nS. Convert it to uS first */
 508                         latency = policy->cpuinfo.transition_latency / 1000;
 509                         if (latency == 0)
 510                                 latency = 1;
 511
 512                         def_sampling_rate = 10 * latency *
 513                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 514
 515                         if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
 516                                 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 517
 518                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 519                         dbs_tuners_ins.ignore_nice = 0;
 520                         dbs_tuners_ins.freq_step = 5;
 521
 522                         dbs_timer_init();
 523                 }
 524
 525                 mutex_unlock(&dbs_mutex);
 526                 break;
 527
 528         case CPUFREQ_GOV_STOP:
 529                 mutex_lock(&dbs_mutex);
 530                 this_dbs_info->enable = 0;
 531                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 532                 dbs_enable--;
 533                 /*
 534                  * Stop the timerschedule work, when this governor
 535                  * is used for first time
 536                  */
 537                 if (dbs_enable == 0)
 538                         dbs_timer_exit();
 539
 540                 mutex_unlock(&dbs_mutex);
 541
 542                 break;
 543
 544         case CPUFREQ_GOV_LIMITS:
 545                 mutex_lock(&dbs_mutex);
 546                 if (policy->max < this_dbs_info->cur_policy->cur)
 547                         __cpufreq_driver_target(
 548                                         this_dbs_info->cur_policy,
 549                                         policy->max, CPUFREQ_RELATION_H);
 550                 else if (policy->min > this_dbs_info->cur_policy->cur)
 551                         __cpufreq_driver_target(
 552                                         this_dbs_info->cur_policy,
 553                                         policy->min, CPUFREQ_RELATION_L);
 554                 mutex_unlock(&dbs_mutex);
 555                 break;
 556         }
 557         return 0;
 558 }
 559
 560 static struct cpufreq_governor cpufreq_gov_dbs = {
 561         .name           = "conservative",
 562         .governor       = cpufreq_governor_dbs,
 563         .owner          = THIS_MODULE,
 564 };
 565
 566 static int __init cpufreq_gov_dbs_init(void)
 567 {
 568         return cpufreq_register_governor(&cpufreq_gov_dbs);
 569 }
 570
 571 static void __exit cpufreq_gov_dbs_exit(void)
 572 {
 573         /* Make sure that the scheduled work is indeed not running */
 574         flush_scheduled_work();
 575
 576         cpufreq_unregister_governor(&cpufreq_gov_dbs);
 577 }
 578
 579
 580 MODULE_AUTHOR ("Alexander Clouter <alex-kernel@digriz.org.uk>");
 581 MODULE_DESCRIPTION ("'cpufreq_conservative' - A dynamic cpufreq governor for "
 582                 "Low Latency Frequency Transition capable processors "
 583                 "optimised for use in a battery environment");
 584 MODULE_LICENSE ("GPL");
 585
 586 module_init(cpufreq_gov_dbs_init);
 587 module_exit(cpufreq_gov_dbs_exit);