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