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