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 #include <linux/mutex.h>
  31
  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              (11)
  39 #define MAX_FREQUENCY_UP_THRESHOLD              (100)
  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 };
  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            ignore_nice;
  82 };
  83
  84 static struct dbs_tuners dbs_tuners_ins = {
  85         .up_threshold           = DEF_FREQUENCY_UP_THRESHOLD,
  86         .sampling_down_factor   = DEF_SAMPLING_DOWN_FACTOR,
  87 };
  88
  89 static inline unsigned int get_cpu_idle_time(unsigned int cpu)
  90 {
  91         return  kstat_cpu(cpu).cpustat.idle +
  92                 kstat_cpu(cpu).cpustat.iowait +
  93                 ( dbs_tuners_ins.ignore_nice ?
  94                   kstat_cpu(cpu).cpustat.nice :
  95                   0);
  96 }
  97
  98 /************************** sysfs interface ************************/
  99 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 100 {
 101         return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
 102 }
 103
 104 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 105 {
 106         return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 107 }
 108
 109 #define define_one_ro(_name)                                    \
 110 static struct freq_attr _name =                                 \
 111 __ATTR(_name, 0444, show_##_name, NULL)
 112
 113 define_one_ro(sampling_rate_max);
 114 define_one_ro(sampling_rate_min);
 115
 116 /* cpufreq_ondemand Governor Tunables */
 117 #define show_one(file_name, object)                                     \
 118 static ssize_t show_##file_name                                         \
 119 (struct cpufreq_policy *unused, char *buf)                              \
 120 {                                                                       \
 121         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 122 }
 123 show_one(sampling_rate, sampling_rate);
 124 show_one(sampling_down_factor, sampling_down_factor);
 125 show_one(up_threshold, up_threshold);
 126 show_one(ignore_nice_load, ignore_nice);
 127
 128 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
 129                 const char *buf, size_t count)
 130 {
 131         unsigned int input;
 132         int ret;
 133         ret = sscanf (buf, "%u", &input);
 134         if (ret != 1 )
 135                 return -EINVAL;
 136
 137         if (input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 138                 return -EINVAL;
 139
 140         mutex_lock(&dbs_mutex);
 141         dbs_tuners_ins.sampling_down_factor = input;
 142         mutex_unlock(&dbs_mutex);
 143
 144         return count;
 145 }
 146
 147 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 148                 const char *buf, size_t count)
 149 {
 150         unsigned int input;
 151         int ret;
 152         ret = sscanf (buf, "%u", &input);
 153
 154         mutex_lock(&dbs_mutex);
 155         if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
 156                 mutex_unlock(&dbs_mutex);
 157                 return -EINVAL;
 158         }
 159
 160         dbs_tuners_ins.sampling_rate = input;
 161         mutex_unlock(&dbs_mutex);
 162
 163         return count;
 164 }
 165
 166 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 167                 const char *buf, size_t count)
 168 {
 169         unsigned int input;
 170         int ret;
 171         ret = sscanf (buf, "%u", &input);
 172
 173         mutex_lock(&dbs_mutex);
 174         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 175                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 176                 mutex_unlock(&dbs_mutex);
 177                 return -EINVAL;
 178         }
 179
 180         dbs_tuners_ins.up_threshold = input;
 181         mutex_unlock(&dbs_mutex);
 182
 183         return count;
 184 }
 185
 186 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 187                 const char *buf, size_t count)
 188 {
 189         unsigned int input;
 190         int ret;
 191
 192         unsigned int j;
 193
 194         ret = sscanf (buf, "%u", &input);
 195         if ( ret != 1 )
 196                 return -EINVAL;
 197
 198         if ( input > 1 )
 199                 input = 1;
 200
 201         mutex_lock(&dbs_mutex);
 202         if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
 203                 mutex_unlock(&dbs_mutex);
 204                 return count;
 205         }
 206         dbs_tuners_ins.ignore_nice = input;
 207
 208         /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
 209         for_each_online_cpu(j) {
 210                 struct cpu_dbs_info_s *j_dbs_info;
 211                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 212                 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 213                 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
 214         }
 215         mutex_unlock(&dbs_mutex);
 216
 217         return count;
 218 }
 219
 220 #define define_one_rw(_name) \
 221 static struct freq_attr _name = \
 222 __ATTR(_name, 0644, show_##_name, store_##_name)
 223
 224 define_one_rw(sampling_rate);
 225 define_one_rw(sampling_down_factor);
 226 define_one_rw(up_threshold);
 227 define_one_rw(ignore_nice_load);
 228
 229 static struct attribute * dbs_attributes[] = {
 230         &sampling_rate_max.attr,
 231         &sampling_rate_min.attr,
 232         &sampling_rate.attr,
 233         &sampling_down_factor.attr,
 234         &up_threshold.attr,
 235         &ignore_nice_load.attr,
 236         NULL
 237 };
 238
 239 static struct attribute_group dbs_attr_group = {
 240         .attrs = dbs_attributes,
 241         .name = "ondemand",
 242 };
 243
 244 /************************** sysfs end ************************/
 245
 246 static void dbs_check_cpu(int cpu)
 247 {
 248         unsigned int idle_ticks, up_idle_ticks, total_ticks;
 249         unsigned int freq_next;
 250         unsigned int freq_down_sampling_rate;
 251         static int down_skip[NR_CPUS];
 252         struct cpu_dbs_info_s *this_dbs_info;
 253
 254         struct cpufreq_policy *policy;
 255         unsigned int j;
 256
 257         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 258         if (!this_dbs_info->enable)
 259                 return;
 260
 261         policy = this_dbs_info->cur_policy;
 262         /*
 263          * Every sampling_rate, we check, if current idle time is less
 264          * than 20% (default), then we try to increase frequency
 265          * Every sampling_rate*sampling_down_factor, we look for a the lowest
 266          * frequency which can sustain the load while keeping idle time over
 267          * 30%. If such a frequency exist, we try to decrease to this frequency.
 268          *
 269          * Any frequency increase takes it to the maximum frequency.
 270          * Frequency reduction happens at minimum steps of
 271          * 5% (default) of current frequency
 272          */
 273
 274         /* Check for frequency increase */
 275         idle_ticks = UINT_MAX;
 276         for_each_cpu_mask(j, policy->cpus) {
 277                 unsigned int tmp_idle_ticks, total_idle_ticks;
 278                 struct cpu_dbs_info_s *j_dbs_info;
 279
 280                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 281                 total_idle_ticks = get_cpu_idle_time(j);
 282                 tmp_idle_ticks = total_idle_ticks -
 283                         j_dbs_info->prev_cpu_idle_up;
 284                 j_dbs_info->prev_cpu_idle_up = total_idle_ticks;
 285
 286                 if (tmp_idle_ticks < idle_ticks)
 287                         idle_ticks = tmp_idle_ticks;
 288         }
 289
 290         /* Scale idle ticks by 100 and compare with up and down ticks */
 291         idle_ticks *= 100;
 292         up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
 293                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 294
 295         if (idle_ticks < up_idle_ticks) {
 296                 down_skip[cpu] = 0;
 297                 for_each_cpu_mask(j, policy->cpus) {
 298                         struct cpu_dbs_info_s *j_dbs_info;
 299
 300                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 301                         j_dbs_info->prev_cpu_idle_down =
 302                                         j_dbs_info->prev_cpu_idle_up;
 303                 }
 304                 /* if we are already at full speed then break out early */
 305                 if (policy->cur == policy->max)
 306                         return;
 307
 308                 __cpufreq_driver_target(policy, policy->max,
 309                         CPUFREQ_RELATION_H);
 310                 return;
 311         }
 312
 313         /* Check for frequency decrease */
 314         down_skip[cpu]++;
 315         if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
 316                 return;
 317
 318         idle_ticks = UINT_MAX;
 319         for_each_cpu_mask(j, policy->cpus) {
 320                 unsigned int tmp_idle_ticks, total_idle_ticks;
 321                 struct cpu_dbs_info_s *j_dbs_info;
 322
 323                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 324                 /* Check for frequency decrease */
 325                 total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
 326                 tmp_idle_ticks = total_idle_ticks -
 327                         j_dbs_info->prev_cpu_idle_down;
 328                 j_dbs_info->prev_cpu_idle_down = total_idle_ticks;
 329
 330                 if (tmp_idle_ticks < idle_ticks)
 331                         idle_ticks = tmp_idle_ticks;
 332         }
 333
 334         down_skip[cpu] = 0;
 335         /* if we cannot reduce the frequency anymore, break out early */
 336         if (policy->cur == policy->min)
 337                 return;
 338
 339         /* Compute how many ticks there are between two measurements */
 340         freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
 341                 dbs_tuners_ins.sampling_down_factor;
 342         total_ticks = usecs_to_jiffies(freq_down_sampling_rate);
 343
 344         /*
 345          * The optimal frequency is the frequency that is the lowest that
 346          * can support the current CPU usage without triggering the up
 347          * policy. To be safe, we focus 10 points under the threshold.
 348          */
 349         freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks;
 350         freq_next = (freq_next * policy->cur) /
 351                         (dbs_tuners_ins.up_threshold - 10);
 352
 353         if (freq_next <= ((policy->cur * 95) / 100))
 354                 __cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);
 355 }
 356
 357 static void do_dbs_timer(void *data)
 358 {
 359         int i;
 360         mutex_lock(&dbs_mutex);
 361         for_each_online_cpu(i)
 362                 dbs_check_cpu(i);
 363         schedule_delayed_work(&dbs_work,
 364                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 365         mutex_unlock(&dbs_mutex);
 366 }
 367
 368 static inline void dbs_timer_init(void)
 369 {
 370         INIT_WORK(&dbs_work, do_dbs_timer, NULL);
 371         schedule_delayed_work(&dbs_work,
 372                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 373         return;
 374 }
 375
 376 static inline void dbs_timer_exit(void)
 377 {
 378         cancel_delayed_work(&dbs_work);
 379         return;
 380 }
 381
 382 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 383                                    unsigned int event)
 384 {
 385         unsigned int cpu = policy->cpu;
 386         struct cpu_dbs_info_s *this_dbs_info;
 387         unsigned int j;
 388
 389         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 390
 391         switch (event) {
 392         case CPUFREQ_GOV_START:
 393                 if ((!cpu_online(cpu)) ||
 394                     (!policy->cur))
 395                         return -EINVAL;
 396
 397                 if (policy->cpuinfo.transition_latency >
 398                                 (TRANSITION_LATENCY_LIMIT * 1000))
 399                         return -EINVAL;
 400                 if (this_dbs_info->enable) /* Already enabled */
 401                         break;
 402
 403                 mutex_lock(&dbs_mutex);
 404                 for_each_cpu_mask(j, policy->cpus) {
 405                         struct cpu_dbs_info_s *j_dbs_info;
 406                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 407                         j_dbs_info->cur_policy = policy;
 408
 409                         j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 410                         j_dbs_info->prev_cpu_idle_down
 411                                 = j_dbs_info->prev_cpu_idle_up;
 412                 }
 413                 this_dbs_info->enable = 1;
 414                 sysfs_create_group(&policy->kobj, &dbs_attr_group);
 415                 dbs_enable++;
 416                 /*
 417                  * Start the timerschedule work, when this governor
 418                  * is used for first time
 419                  */
 420                 if (dbs_enable == 1) {
 421                         unsigned int latency;
 422                         /* policy latency is in nS. Convert it to uS first */
 423                         latency = policy->cpuinfo.transition_latency / 1000;
 424                         if (latency == 0)
 425                                 latency = 1;
 426
 427                         def_sampling_rate = latency *
 428                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 429
 430                         if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
 431                                 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 432
 433                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 434                         dbs_tuners_ins.ignore_nice = 0;
 435
 436                         dbs_timer_init();
 437                 }
 438
 439                 mutex_unlock(&dbs_mutex);
 440                 break;
 441
 442         case CPUFREQ_GOV_STOP:
 443                 mutex_lock(&dbs_mutex);
 444                 this_dbs_info->enable = 0;
 445                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 446                 dbs_enable--;
 447                 /*
 448                  * Stop the timerschedule work, when this governor
 449                  * is used for first time
 450                  */
 451                 if (dbs_enable == 0)
 452                         dbs_timer_exit();
 453
 454                 mutex_unlock(&dbs_mutex);
 455
 456                 break;
 457
 458         case CPUFREQ_GOV_LIMITS:
 459                 mutex_lock(&dbs_mutex);
 460                 if (policy->max < this_dbs_info->cur_policy->cur)
 461                         __cpufreq_driver_target(
 462                                         this_dbs_info->cur_policy,
 463                                         policy->max, CPUFREQ_RELATION_H);
 464                 else if (policy->min > this_dbs_info->cur_policy->cur)
 465                         __cpufreq_driver_target(
 466                                         this_dbs_info->cur_policy,
 467                                         policy->min, CPUFREQ_RELATION_L);
 468                 mutex_unlock(&dbs_mutex);
 469                 break;
 470         }
 471         return 0;
 472 }
 473
 474 static struct cpufreq_governor cpufreq_gov_dbs = {
 475         .name           = "ondemand",
 476         .governor       = cpufreq_governor_dbs,
 477         .owner          = THIS_MODULE,
 478 };
 479
 480 static int __init cpufreq_gov_dbs_init(void)
 481 {
 482         return cpufreq_register_governor(&cpufreq_gov_dbs);
 483 }
 484
 485 static void __exit cpufreq_gov_dbs_exit(void)
 486 {
 487         /* Make sure that the scheduled work is indeed not running */
 488         flush_scheduled_work();
 489
 490         cpufreq_unregister_governor(&cpufreq_gov_dbs);
 491 }
 492
 493
 494 MODULE_AUTHOR ("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 495 MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 496                 "Low Latency Frequency Transition capable processors");
 497 MODULE_LICENSE ("GPL");
 498
 499 module_init(cpufreq_gov_dbs_init);
 500 module_exit(cpufreq_gov_dbs_exit);