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              (11)
  38 #define MAX_FREQUENCY_UP_THRESHOLD              (100)
  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 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            ignore_nice;
  81 };
  82
  83 static struct dbs_tuners dbs_tuners_ins = {
  84         .up_threshold           = DEF_FREQUENCY_UP_THRESHOLD,
  85         .sampling_down_factor   = DEF_SAMPLING_DOWN_FACTOR,
  86 };
  87
  88 static inline unsigned int get_cpu_idle_time(unsigned int cpu)
  89 {
  90         return  kstat_cpu(cpu).cpustat.idle +
  91                 kstat_cpu(cpu).cpustat.iowait +
  92                 ( !dbs_tuners_ins.ignore_nice ?
  93                   kstat_cpu(cpu).cpustat.nice :
  94                   0);
  95 }
  96
  97 /************************** sysfs interface ************************/
  98 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
  99 {
 100         return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
 101 }
 102
 103 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 104 {
 105         return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 106 }
 107
 108 #define define_one_ro(_name)                                    \
 109 static struct freq_attr _name =                                 \
 110 __ATTR(_name, 0444, show_##_name, NULL)
 111
 112 define_one_ro(sampling_rate_max);
 113 define_one_ro(sampling_rate_min);
 114
 115 /* cpufreq_ondemand Governor Tunables */
 116 #define show_one(file_name, object)                                     \
 117 static ssize_t show_##file_name                                         \
 118 (struct cpufreq_policy *unused, char *buf)                              \
 119 {                                                                       \
 120         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 121 }
 122 show_one(sampling_rate, sampling_rate);
 123 show_one(sampling_down_factor, sampling_down_factor);
 124 show_one(up_threshold, up_threshold);
 125 show_one(ignore_nice, ignore_nice);
 126
 127 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
 128                 const char *buf, size_t count)
 129 {
 130         unsigned int input;
 131         int ret;
 132         ret = sscanf (buf, "%u", &input);
 133         if (ret != 1 )
 134                 return -EINVAL;
 135
 136         if (input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 137                 return -EINVAL;
 138
 139         down(&dbs_sem);
 140         dbs_tuners_ins.sampling_down_factor = input;
 141         up(&dbs_sem);
 142
 143         return count;
 144 }
 145
 146 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 147                 const char *buf, size_t count)
 148 {
 149         unsigned int input;
 150         int ret;
 151         ret = sscanf (buf, "%u", &input);
 152
 153         down(&dbs_sem);
 154         if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
 155                 up(&dbs_sem);
 156                 return -EINVAL;
 157         }
 158
 159         dbs_tuners_ins.sampling_rate = input;
 160         up(&dbs_sem);
 161
 162         return count;
 163 }
 164
 165 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 166                 const char *buf, size_t count)
 167 {
 168         unsigned int input;
 169         int ret;
 170         ret = sscanf (buf, "%u", &input);
 171
 172         down(&dbs_sem);
 173         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 174                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 175                 up(&dbs_sem);
 176                 return -EINVAL;
 177         }
 178
 179         dbs_tuners_ins.up_threshold = input;
 180         up(&dbs_sem);
 181
 182         return count;
 183 }
 184
 185 static ssize_t store_ignore_nice(struct cpufreq_policy *policy,
 186                 const char *buf, size_t count)
 187 {
 188         unsigned int input;
 189         int ret;
 190
 191         unsigned int j;
 192
 193         ret = sscanf (buf, "%u", &input);
 194         if ( ret != 1 )
 195                 return -EINVAL;
 196
 197         if ( input > 1 )
 198                 input = 1;
 199
 200         down(&dbs_sem);
 201         if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
 202                 up(&dbs_sem);
 203                 return count;
 204         }
 205         dbs_tuners_ins.ignore_nice = input;
 206
 207         /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
 208         for_each_online_cpu(j) {
 209                 struct cpu_dbs_info_s *j_dbs_info;
 210                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 211                 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 212                 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
 213         }
 214         up(&dbs_sem);
 215
 216         return count;
 217 }
 218
 219 #define define_one_rw(_name) \
 220 static struct freq_attr _name = \
 221 __ATTR(_name, 0644, show_##_name, store_##_name)
 222
 223 define_one_rw(sampling_rate);
 224 define_one_rw(sampling_down_factor);
 225 define_one_rw(up_threshold);
 226 define_one_rw(ignore_nice);
 227
 228 static struct attribute * dbs_attributes[] = {
 229         &sampling_rate_max.attr,
 230         &sampling_rate_min.attr,
 231         &sampling_rate.attr,
 232         &sampling_down_factor.attr,
 233         &up_threshold.attr,
 234         &ignore_nice.attr,
 235         NULL
 236 };
 237
 238 static struct attribute_group dbs_attr_group = {
 239         .attrs = dbs_attributes,
 240         .name = "ondemand",
 241 };
 242
 243 /************************** sysfs end ************************/
 244
 245 static void dbs_check_cpu(int cpu)
 246 {
 247         unsigned int idle_ticks, up_idle_ticks, total_ticks;
 248         unsigned int freq_next;
 249         unsigned int freq_down_sampling_rate;
 250         static int down_skip[NR_CPUS];
 251         struct cpu_dbs_info_s *this_dbs_info;
 252
 253         struct cpufreq_policy *policy;
 254         unsigned int j;
 255
 256         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 257         if (!this_dbs_info->enable)
 258                 return;
 259
 260         policy = this_dbs_info->cur_policy;
 261         /*
 262          * Every sampling_rate, we check, if current idle time is less
 263          * than 20% (default), then we try to increase frequency
 264          * Every sampling_rate*sampling_down_factor, we look for a the lowest
 265          * frequency which can sustain the load while keeping idle time over
 266          * 30%. If such a frequency exist, we try to decrease to this frequency.
 267          *
 268          * Any frequency increase takes it to the maximum frequency.
 269          * Frequency reduction happens at minimum steps of
 270          * 5% (default) of current frequency
 271          */
 272
 273         /* Check for frequency increase */
 274         idle_ticks = UINT_MAX;
 275         for_each_cpu_mask(j, policy->cpus) {
 276                 unsigned int tmp_idle_ticks, total_idle_ticks;
 277                 struct cpu_dbs_info_s *j_dbs_info;
 278
 279                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 280                 total_idle_ticks = get_cpu_idle_time(j);
 281                 tmp_idle_ticks = total_idle_ticks -
 282                         j_dbs_info->prev_cpu_idle_up;
 283                 j_dbs_info->prev_cpu_idle_up = total_idle_ticks;
 284
 285                 if (tmp_idle_ticks < idle_ticks)
 286                         idle_ticks = tmp_idle_ticks;
 287         }
 288
 289         /* Scale idle ticks by 100 and compare with up and down ticks */
 290         idle_ticks *= 100;
 291         up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
 292                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 293
 294         if (idle_ticks < up_idle_ticks) {
 295                 down_skip[cpu] = 0;
 296                 for_each_cpu_mask(j, policy->cpus) {
 297                         struct cpu_dbs_info_s *j_dbs_info;
 298
 299                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 300                         j_dbs_info->prev_cpu_idle_down =
 301                                         j_dbs_info->prev_cpu_idle_up;
 302                 }
 303                 /* if we are already at full speed then break out early */
 304                 if (policy->cur == policy->max)
 305                         return;
 306
 307                 __cpufreq_driver_target(policy, policy->max,
 308                         CPUFREQ_RELATION_H);
 309                 return;
 310         }
 311
 312         /* Check for frequency decrease */
 313         down_skip[cpu]++;
 314         if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
 315                 return;
 316
 317         idle_ticks = UINT_MAX;
 318         for_each_cpu_mask(j, policy->cpus) {
 319                 unsigned int tmp_idle_ticks, total_idle_ticks;
 320                 struct cpu_dbs_info_s *j_dbs_info;
 321
 322                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 323                 /* Check for frequency decrease */
 324                 total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
 325                 tmp_idle_ticks = total_idle_ticks -
 326                         j_dbs_info->prev_cpu_idle_down;
 327                 j_dbs_info->prev_cpu_idle_down = total_idle_ticks;
 328
 329                 if (tmp_idle_ticks < idle_ticks)
 330                         idle_ticks = tmp_idle_ticks;
 331         }
 332
 333         down_skip[cpu] = 0;
 334         /* if we cannot reduce the frequency anymore, break out early */
 335         if (policy->cur == policy->min)
 336                 return;
 337
 338         /* Compute how many ticks there are between two measurements */
 339         freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
 340                 dbs_tuners_ins.sampling_down_factor;
 341         total_ticks = usecs_to_jiffies(freq_down_sampling_rate);
 342
 343         /*
 344          * The optimal frequency is the frequency that is the lowest that
 345          * can support the current CPU usage without triggering the up
 346          * policy. To be safe, we focus 10 points under the threshold.
 347          */
 348         freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks;
 349         freq_next = (freq_next * policy->cur) /
 350                         (dbs_tuners_ins.up_threshold - 10);
 351
 352         if (freq_next <= ((policy->cur * 95) / 100))
 353                 __cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);
 354 }
 355
 356 static void do_dbs_timer(void *data)
 357 {
 358         int i;
 359         down(&dbs_sem);
 360         for_each_online_cpu(i)
 361                 dbs_check_cpu(i);
 362         schedule_delayed_work(&dbs_work,
 363                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 364         up(&dbs_sem);
 365 }
 366
 367 static inline void dbs_timer_init(void)
 368 {
 369         INIT_WORK(&dbs_work, do_dbs_timer, NULL);
 370         schedule_delayed_work(&dbs_work,
 371                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 372         return;
 373 }
 374
 375 static inline void dbs_timer_exit(void)
 376 {
 377         cancel_delayed_work(&dbs_work);
 378         return;
 379 }
 380
 381 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 382                                    unsigned int event)
 383 {
 384         unsigned int cpu = policy->cpu;
 385         struct cpu_dbs_info_s *this_dbs_info;
 386         unsigned int j;
 387
 388         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 389
 390         switch (event) {
 391         case CPUFREQ_GOV_START:
 392                 if ((!cpu_online(cpu)) ||
 393                     (!policy->cur))
 394                         return -EINVAL;
 395
 396                 if (policy->cpuinfo.transition_latency >
 397                                 (TRANSITION_LATENCY_LIMIT * 1000))
 398                         return -EINVAL;
 399                 if (this_dbs_info->enable) /* Already enabled */
 400                         break;
 401
 402                 down(&dbs_sem);
 403                 for_each_cpu_mask(j, policy->cpus) {
 404                         struct cpu_dbs_info_s *j_dbs_info;
 405                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 406                         j_dbs_info->cur_policy = policy;
 407
 408                         j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 409                         j_dbs_info->prev_cpu_idle_down
 410                                 = j_dbs_info->prev_cpu_idle_up;
 411                 }
 412                 this_dbs_info->enable = 1;
 413                 sysfs_create_group(&policy->kobj, &dbs_attr_group);
 414                 dbs_enable++;
 415                 /*
 416                  * Start the timerschedule work, when this governor
 417                  * is used for first time
 418                  */
 419                 if (dbs_enable == 1) {
 420                         unsigned int latency;
 421                         /* policy latency is in nS. Convert it to uS first */
 422                         latency = policy->cpuinfo.transition_latency / 1000;
 423                         if (latency == 0)
 424                                 latency = 1;
 425
 426                         def_sampling_rate = latency *
 427                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 428
 429                         if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
 430                                 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 431
 432                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 433                         dbs_tuners_ins.ignore_nice = 0;
 434
 435                         dbs_timer_init();
 436                 }
 437
 438                 up(&dbs_sem);
 439                 break;
 440
 441         case CPUFREQ_GOV_STOP:
 442                 down(&dbs_sem);
 443                 this_dbs_info->enable = 0;
 444                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 445                 dbs_enable--;
 446                 /*
 447                  * Stop the timerschedule work, when this governor
 448                  * is used for first time
 449                  */
 450                 if (dbs_enable == 0)
 451                         dbs_timer_exit();
 452
 453                 up(&dbs_sem);
 454
 455                 break;
 456
 457         case CPUFREQ_GOV_LIMITS:
 458                 down(&dbs_sem);
 459                 if (policy->max < this_dbs_info->cur_policy->cur)
 460                         __cpufreq_driver_target(
 461                                         this_dbs_info->cur_policy,
 462                                         policy->max, CPUFREQ_RELATION_H);
 463                 else if (policy->min > this_dbs_info->cur_policy->cur)
 464                         __cpufreq_driver_target(
 465                                         this_dbs_info->cur_policy,
 466                                         policy->min, CPUFREQ_RELATION_L);
 467                 up(&dbs_sem);
 468                 break;
 469         }
 470         return 0;
 471 }
 472
 473 static struct cpufreq_governor cpufreq_gov_dbs = {
 474         .name           = "ondemand",
 475         .governor       = cpufreq_governor_dbs,
 476         .owner          = THIS_MODULE,
 477 };
 478
 479 static int __init cpufreq_gov_dbs_init(void)
 480 {
 481         return cpufreq_register_governor(&cpufreq_gov_dbs);
 482 }
 483
 484 static void __exit cpufreq_gov_dbs_exit(void)
 485 {
 486         /* Make sure that the scheduled work is indeed not running */
 487         flush_scheduled_work();
 488
 489         cpufreq_unregister_governor(&cpufreq_gov_dbs);
 490 }
 491
 492
 493 MODULE_AUTHOR ("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 494 MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 495                 "Low Latency Frequency Transition capable processors");
 496 MODULE_LICENSE ("GPL");
 497
 498 module_init(cpufreq_gov_dbs_init);
 499 module_exit(cpufreq_gov_dbs_exit);