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 MIN_FREQUENCY_UP_THRESHOLD              (0)
  39 #define MAX_FREQUENCY_UP_THRESHOLD              (100)
  40
  41 #define DEF_FREQUENCY_DOWN_THRESHOLD            (20)
  42 #define MIN_FREQUENCY_DOWN_THRESHOLD            (0)
  43 #define MAX_FREQUENCY_DOWN_THRESHOLD            (100)
  44
  45 /*
  46  * The polling frequency of this governor depends on the capability of
  47  * the processor. Default polling frequency is 1000 times the transition
  48  * latency of the processor. The governor will work on any processor with
  49  * transition latency <= 10mS, using appropriate sampling
  50  * rate.
  51  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
  52  * this governor will not work.
  53  * All times here are in uS.
  54  */
  55 static unsigned int                             def_sampling_rate;
  56 #define MIN_SAMPLING_RATE                       (def_sampling_rate / 2)
  57 #define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
  58 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (100000)
  59 #define DEF_SAMPLING_DOWN_FACTOR                (5)
  60 #define TRANSITION_LATENCY_LIMIT                (10 * 1000)
  61
  62 static void do_dbs_timer(void *data);
  63
  64 struct cpu_dbs_info_s {
  65         struct cpufreq_policy   *cur_policy;
  66         unsigned int            prev_cpu_idle_up;
  67         unsigned int            prev_cpu_idle_down;
  68         unsigned int            enable;
  69 };
  70 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
  71
  72 static unsigned int dbs_enable; /* number of CPUs using this policy */
  73
  74 static DEFINE_MUTEX     (dbs_mutex);
  75 static DECLARE_WORK     (dbs_work, do_dbs_timer, NULL);
  76
  77 struct dbs_tuners {
  78         unsigned int            sampling_rate;
  79         unsigned int            sampling_down_factor;
  80         unsigned int            up_threshold;
  81         unsigned int            down_threshold;
  82         unsigned int            ignore_nice;
  83         unsigned int            freq_step;
  84 };
  85
  86 static struct dbs_tuners dbs_tuners_ins = {
  87         .up_threshold           = DEF_FREQUENCY_UP_THRESHOLD,
  88         .down_threshold         = DEF_FREQUENCY_DOWN_THRESHOLD,
  89         .sampling_down_factor   = DEF_SAMPLING_DOWN_FACTOR,
  90 };
  91
  92 static inline unsigned int get_cpu_idle_time(unsigned int cpu)
  93 {
  94         return  kstat_cpu(cpu).cpustat.idle +
  95                 kstat_cpu(cpu).cpustat.iowait +
  96                 ( dbs_tuners_ins.ignore_nice ?
  97                   kstat_cpu(cpu).cpustat.nice :
  98                   0);
  99 }
 100
 101 /************************** sysfs interface ************************/
 102 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 103 {
 104         return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
 105 }
 106
 107 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 108 {
 109         return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 110 }
 111
 112 #define define_one_ro(_name)                                    \
 113 static struct freq_attr _name =                                 \
 114 __ATTR(_name, 0444, show_##_name, NULL)
 115
 116 define_one_ro(sampling_rate_max);
 117 define_one_ro(sampling_rate_min);
 118
 119 /* cpufreq_conservative Governor Tunables */
 120 #define show_one(file_name, object)                                     \
 121 static ssize_t show_##file_name                                         \
 122 (struct cpufreq_policy *unused, char *buf)                              \
 123 {                                                                       \
 124         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 125 }
 126 show_one(sampling_rate, sampling_rate);
 127 show_one(sampling_down_factor, sampling_down_factor);
 128 show_one(up_threshold, up_threshold);
 129 show_one(down_threshold, down_threshold);
 130 show_one(ignore_nice_load, ignore_nice);
 131 show_one(freq_step, freq_step);
 132
 133 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
 134                 const char *buf, size_t count)
 135 {
 136         unsigned int input;
 137         int ret;
 138         ret = sscanf (buf, "%u", &input);
 139         if (ret != 1 )
 140                 return -EINVAL;
 141
 142         mutex_lock(&dbs_mutex);
 143         dbs_tuners_ins.sampling_down_factor = input;
 144         mutex_unlock(&dbs_mutex);
 145
 146         return count;
 147 }
 148
 149 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 150                 const char *buf, size_t count)
 151 {
 152         unsigned int input;
 153         int ret;
 154         ret = sscanf (buf, "%u", &input);
 155
 156         mutex_lock(&dbs_mutex);
 157         if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
 158                 mutex_unlock(&dbs_mutex);
 159                 return -EINVAL;
 160         }
 161
 162         dbs_tuners_ins.sampling_rate = input;
 163         mutex_unlock(&dbs_mutex);
 164
 165         return count;
 166 }
 167
 168 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 169                 const char *buf, size_t count)
 170 {
 171         unsigned int input;
 172         int ret;
 173         ret = sscanf (buf, "%u", &input);
 174
 175         mutex_lock(&dbs_mutex);
 176         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 177                         input < MIN_FREQUENCY_UP_THRESHOLD ||
 178                         input <= dbs_tuners_ins.down_threshold) {
 179                 mutex_unlock(&dbs_mutex);
 180                 return -EINVAL;
 181         }
 182
 183         dbs_tuners_ins.up_threshold = input;
 184         mutex_unlock(&dbs_mutex);
 185
 186         return count;
 187 }
 188
 189 static ssize_t store_down_threshold(struct cpufreq_policy *unused,
 190                 const char *buf, size_t count)
 191 {
 192         unsigned int input;
 193         int ret;
 194         ret = sscanf (buf, "%u", &input);
 195
 196         mutex_lock(&dbs_mutex);
 197         if (ret != 1 || input > MAX_FREQUENCY_DOWN_THRESHOLD ||
 198                         input < MIN_FREQUENCY_DOWN_THRESHOLD ||
 199                         input >= dbs_tuners_ins.up_threshold) {
 200                 mutex_unlock(&dbs_mutex);
 201                 return -EINVAL;
 202         }
 203
 204         dbs_tuners_ins.down_threshold = input;
 205         mutex_unlock(&dbs_mutex);
 206
 207         return count;
 208 }
 209
 210 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 211                 const char *buf, size_t count)
 212 {
 213         unsigned int input;
 214         int ret;
 215
 216         unsigned int j;
 217
 218         ret = sscanf (buf, "%u", &input);
 219         if ( ret != 1 )
 220                 return -EINVAL;
 221
 222         if ( input > 1 )
 223                 input = 1;
 224
 225         mutex_lock(&dbs_mutex);
 226         if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
 227                 mutex_unlock(&dbs_mutex);
 228                 return count;
 229         }
 230         dbs_tuners_ins.ignore_nice = input;
 231
 232         /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
 233         for_each_online_cpu(j) {
 234                 struct cpu_dbs_info_s *j_dbs_info;
 235                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 236                 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 237                 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
 238         }
 239         mutex_unlock(&dbs_mutex);
 240
 241         return count;
 242 }
 243
 244 static ssize_t store_freq_step(struct cpufreq_policy *policy,
 245                 const char *buf, size_t count)
 246 {
 247         unsigned int input;
 248         int ret;
 249
 250         ret = sscanf (buf, "%u", &input);
 251
 252         if ( ret != 1 )
 253                 return -EINVAL;
 254
 255         if ( input > 100 )
 256                 input = 100;
 257
 258         /* no need to test here if freq_step is zero as the user might actually
 259          * want this, they would be crazy though :) */
 260         mutex_lock(&dbs_mutex);
 261         dbs_tuners_ins.freq_step = input;
 262         mutex_unlock(&dbs_mutex);
 263
 264         return count;
 265 }
 266
 267 #define define_one_rw(_name) \
 268 static struct freq_attr _name = \
 269 __ATTR(_name, 0644, show_##_name, store_##_name)
 270
 271 define_one_rw(sampling_rate);
 272 define_one_rw(sampling_down_factor);
 273 define_one_rw(up_threshold);
 274 define_one_rw(down_threshold);
 275 define_one_rw(ignore_nice_load);
 276 define_one_rw(freq_step);
 277
 278 static struct attribute * dbs_attributes[] = {
 279         &sampling_rate_max.attr,
 280         &sampling_rate_min.attr,
 281         &sampling_rate.attr,
 282         &sampling_down_factor.attr,
 283         &up_threshold.attr,
 284         &down_threshold.attr,
 285         &ignore_nice_load.attr,
 286         &freq_step.attr,
 287         NULL
 288 };
 289
 290 static struct attribute_group dbs_attr_group = {
 291         .attrs = dbs_attributes,
 292         .name = "conservative",
 293 };
 294
 295 /************************** sysfs end ************************/
 296
 297 static void dbs_check_cpu(int cpu)
 298 {
 299         unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;
 300         unsigned int freq_step;
 301         unsigned int freq_down_sampling_rate;
 302         static int down_skip[NR_CPUS];
 303         static int requested_freq[NR_CPUS];
 304         static unsigned short init_flag = 0;
 305         struct cpu_dbs_info_s *this_dbs_info;
 306         struct cpu_dbs_info_s *dbs_info;
 307
 308         struct cpufreq_policy *policy;
 309         unsigned int j;
 310
 311         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 312         if (!this_dbs_info->enable)
 313                 return;
 314
 315         policy = this_dbs_info->cur_policy;
 316
 317         if ( init_flag == 0 ) {
 318                 for_each_online_cpu(j) {
 319                         dbs_info = &per_cpu(cpu_dbs_info, j);
 320                         requested_freq[j] = dbs_info->cur_policy->cur;
 321                 }
 322                 init_flag = 1;
 323         }
 324
 325         /*
 326          * The default safe range is 20% to 80%
 327          * Every sampling_rate, we check
 328          *      - If current idle time is less than 20%, then we try to
 329          *        increase frequency
 330          * Every sampling_rate*sampling_down_factor, we check
 331          *      - If current idle time is more than 80%, then we try to
 332          *        decrease frequency
 333          *
 334          * Any frequency increase takes it to the maximum frequency.
 335          * Frequency reduction happens at minimum steps of
 336          * 5% (default) of max_frequency
 337          */
 338
 339         /* Check for frequency increase */
 340
 341         idle_ticks = UINT_MAX;
 342         for_each_cpu_mask(j, policy->cpus) {
 343                 unsigned int tmp_idle_ticks, total_idle_ticks;
 344                 struct cpu_dbs_info_s *j_dbs_info;
 345
 346                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 347                 /* Check for frequency increase */
 348                 total_idle_ticks = get_cpu_idle_time(j);
 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                 down_skip[cpu] = 0;
 364                 for_each_cpu_mask(j, policy->cpus) {
 365                         struct cpu_dbs_info_s *j_dbs_info;
 366
 367                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 368                         j_dbs_info->prev_cpu_idle_down =
 369                                         j_dbs_info->prev_cpu_idle_up;
 370                 }
 371                 /* if we are already at full speed then break out early */
 372                 if (requested_freq[cpu] == policy->max)
 373                         return;
 374
 375                 freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
 376
 377                 /* max freq cannot be less than 100. But who knows.... */
 378                 if (unlikely(freq_step == 0))
 379                         freq_step = 5;
 380
 381                 requested_freq[cpu] += freq_step;
 382                 if (requested_freq[cpu] > policy->max)
 383                         requested_freq[cpu] = policy->max;
 384
 385                 __cpufreq_driver_target(policy, requested_freq[cpu],
 386                         CPUFREQ_RELATION_H);
 387                 return;
 388         }
 389
 390         /* Check for frequency decrease */
 391         down_skip[cpu]++;
 392         if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
 393                 return;
 394
 395         idle_ticks = UINT_MAX;
 396         for_each_cpu_mask(j, policy->cpus) {
 397                 unsigned int tmp_idle_ticks, total_idle_ticks;
 398                 struct cpu_dbs_info_s *j_dbs_info;
 399
 400                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 401                 total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
 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 (requested_freq[cpu] == policy->min
 424                                 || dbs_tuners_ins.freq_step == 0)
 425                         return;
 426
 427                 freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
 428
 429                 /* max freq cannot be less than 100. But who knows.... */
 430                 if (unlikely(freq_step == 0))
 431                         freq_step = 5;
 432
 433                 requested_freq[cpu] -= freq_step;
 434                 if (requested_freq[cpu] < policy->min)
 435                         requested_freq[cpu] = policy->min;
 436
 437                 __cpufreq_driver_target(policy,
 438                         requested_freq[cpu],
 439                         CPUFREQ_RELATION_H);
 440                 return;
 441         }
 442 }
 443
 444 static void do_dbs_timer(void *data)
 445 {
 446         int i;
 447         mutex_lock(&dbs_mutex);
 448         for_each_online_cpu(i)
 449                 dbs_check_cpu(i);
 450         schedule_delayed_work(&dbs_work,
 451                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 452         mutex_unlock(&dbs_mutex);
 453 }
 454
 455 static inline void dbs_timer_init(void)
 456 {
 457         INIT_WORK(&dbs_work, do_dbs_timer, NULL);
 458         schedule_delayed_work(&dbs_work,
 459                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 460         return;
 461 }
 462
 463 static inline void dbs_timer_exit(void)
 464 {
 465         cancel_delayed_work(&dbs_work);
 466         return;
 467 }
 468
 469 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 470                                    unsigned int event)
 471 {
 472         unsigned int cpu = policy->cpu;
 473         struct cpu_dbs_info_s *this_dbs_info;
 474         unsigned int j;
 475
 476         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 477
 478         switch (event) {
 479         case CPUFREQ_GOV_START:
 480                 if ((!cpu_online(cpu)) ||
 481                     (!policy->cur))
 482                         return -EINVAL;
 483
 484                 if (policy->cpuinfo.transition_latency >
 485                                 (TRANSITION_LATENCY_LIMIT * 1000))
 486                         return -EINVAL;
 487                 if (this_dbs_info->enable) /* Already enabled */
 488                         break;
 489
 490                 mutex_lock(&dbs_mutex);
 491                 for_each_cpu_mask(j, policy->cpus) {
 492                         struct cpu_dbs_info_s *j_dbs_info;
 493                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 494                         j_dbs_info->cur_policy = policy;
 495
 496                         j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 497                         j_dbs_info->prev_cpu_idle_down
 498                                 = j_dbs_info->prev_cpu_idle_up;
 499                 }
 500                 this_dbs_info->enable = 1;
 501                 sysfs_create_group(&policy->kobj, &dbs_attr_group);
 502                 dbs_enable++;
 503                 /*
 504                  * Start the timerschedule work, when this governor
 505                  * is used for first time
 506                  */
 507                 if (dbs_enable == 1) {
 508                         unsigned int latency;
 509                         /* policy latency is in nS. Convert it to uS first */
 510
 511                         latency = policy->cpuinfo.transition_latency;
 512                         if (latency < 1000)
 513                                 latency = 1000;
 514
 515                         def_sampling_rate = (latency / 1000) *
 516                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 517                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 518                         dbs_tuners_ins.ignore_nice = 0;
 519                         dbs_tuners_ins.freq_step = 5;
 520
 521                         dbs_timer_init();
 522                 }
 523
 524                 mutex_unlock(&dbs_mutex);
 525                 break;
 526
 527         case CPUFREQ_GOV_STOP:
 528                 mutex_lock(&dbs_mutex);
 529                 this_dbs_info->enable = 0;
 530                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 531                 dbs_enable--;
 532                 /*
 533                  * Stop the timerschedule work, when this governor
 534                  * is used for first time
 535                  */
 536                 if (dbs_enable == 0)
 537                         dbs_timer_exit();
 538
 539                 mutex_unlock(&dbs_mutex);
 540
 541                 break;
 542
 543         case CPUFREQ_GOV_LIMITS:
 544                 mutex_lock(&dbs_mutex);
 545                 if (policy->max < this_dbs_info->cur_policy->cur)
 546                         __cpufreq_driver_target(
 547                                         this_dbs_info->cur_policy,
 548                                         policy->max, CPUFREQ_RELATION_H);
 549                 else if (policy->min > this_dbs_info->cur_policy->cur)
 550                         __cpufreq_driver_target(
 551                                         this_dbs_info->cur_policy,
 552                                         policy->min, CPUFREQ_RELATION_L);
 553                 mutex_unlock(&dbs_mutex);
 554                 break;
 555         }
 556         return 0;
 557 }
 558
 559 static struct cpufreq_governor cpufreq_gov_dbs = {
 560         .name           = "conservative",
 561         .governor       = cpufreq_governor_dbs,
 562         .owner          = THIS_MODULE,
 563 };
 564
 565 static int __init cpufreq_gov_dbs_init(void)
 566 {
 567         return cpufreq_register_governor(&cpufreq_gov_dbs);
 568 }
 569
 570 static void __exit cpufreq_gov_dbs_exit(void)
 571 {
 572         /* Make sure that the scheduled work is indeed not running */
 573         flush_scheduled_work();
 574
 575         cpufreq_unregister_governor(&cpufreq_gov_dbs);
 576 }
 577
 578
 579 MODULE_AUTHOR ("Alexander Clouter <alex-kernel@digriz.org.uk>");
 580 MODULE_DESCRIPTION ("'cpufreq_conservative' - A dynamic cpufreq governor for "
 581                 "Low Latency Frequency Transition capable processors "
 582                 "optimised for use in a battery environment");
 583 MODULE_LICENSE ("GPL");
 584
 585 module_init(cpufreq_gov_dbs_init);
 586 module_exit(cpufreq_gov_dbs_exit);