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                       (def_sampling_rate / 2)
  52 #define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
  53 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (1000)
  54 #define DEF_SAMPLING_DOWN_FACTOR                (1)
  55 #define MAX_SAMPLING_DOWN_FACTOR                (10)
  56 #define TRANSITION_LATENCY_LIMIT                (10 * 1000)
  57
  58 static void do_dbs_timer(void *data);
  59
  60 struct cpu_dbs_info_s {
  61         struct cpufreq_policy   *cur_policy;
  62         unsigned int            prev_cpu_idle_up;
  63         unsigned int            prev_cpu_idle_down;
  64         unsigned int            enable;
  65 };
  66 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
  67
  68 static unsigned int dbs_enable; /* number of CPUs using this policy */
  69
  70 static DECLARE_MUTEX    (dbs_sem);
  71 static DECLARE_WORK     (dbs_work, do_dbs_timer, NULL);
  72
  73 struct dbs_tuners {
  74         unsigned int            sampling_rate;
  75         unsigned int            sampling_down_factor;
  76         unsigned int            up_threshold;
  77         unsigned int            ignore_nice;
  78 };
  79
  80 static struct dbs_tuners dbs_tuners_ins = {
  81         .up_threshold           = DEF_FREQUENCY_UP_THRESHOLD,
  82         .sampling_down_factor   = DEF_SAMPLING_DOWN_FACTOR,
  83 };
  84
  85 static inline unsigned int get_cpu_idle_time(unsigned int cpu)
  86 {
  87         return  kstat_cpu(cpu).cpustat.idle +
  88                 kstat_cpu(cpu).cpustat.iowait +
  89                 ( !dbs_tuners_ins.ignore_nice ?
  90                   kstat_cpu(cpu).cpustat.nice :
  91                   0);
  92 }
  93
  94 /************************** sysfs interface ************************/
  95 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
  96 {
  97         return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
  98 }
  99
 100 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 101 {
 102         return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 103 }
 104
 105 #define define_one_ro(_name)                                    \
 106 static struct freq_attr _name =                                 \
 107 __ATTR(_name, 0444, show_##_name, NULL)
 108
 109 define_one_ro(sampling_rate_max);
 110 define_one_ro(sampling_rate_min);
 111
 112 /* cpufreq_ondemand Governor Tunables */
 113 #define show_one(file_name, object)                                     \
 114 static ssize_t show_##file_name                                         \
 115 (struct cpufreq_policy *unused, char *buf)                              \
 116 {                                                                       \
 117         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 118 }
 119 show_one(sampling_rate, sampling_rate);
 120 show_one(sampling_down_factor, sampling_down_factor);
 121 show_one(up_threshold, up_threshold);
 122 show_one(ignore_nice, ignore_nice);
 123
 124 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
 125                 const char *buf, size_t count)
 126 {
 127         unsigned int input;
 128         int ret;
 129         ret = sscanf (buf, "%u", &input);
 130         if (ret != 1 )
 131                 return -EINVAL;
 132
 133         if (input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 134                 return -EINVAL;
 135
 136         down(&dbs_sem);
 137         dbs_tuners_ins.sampling_down_factor = input;
 138         up(&dbs_sem);
 139
 140         return count;
 141 }
 142
 143 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 144                 const char *buf, size_t count)
 145 {
 146         unsigned int input;
 147         int ret;
 148         ret = sscanf (buf, "%u", &input);
 149
 150         down(&dbs_sem);
 151         if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
 152                 up(&dbs_sem);
 153                 return -EINVAL;
 154         }
 155
 156         dbs_tuners_ins.sampling_rate = input;
 157         up(&dbs_sem);
 158
 159         return count;
 160 }
 161
 162 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 163                 const char *buf, size_t count)
 164 {
 165         unsigned int input;
 166         int ret;
 167         ret = sscanf (buf, "%u", &input);
 168
 169         down(&dbs_sem);
 170         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 171                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 172                 up(&dbs_sem);
 173                 return -EINVAL;
 174         }
 175
 176         dbs_tuners_ins.up_threshold = input;
 177         up(&dbs_sem);
 178
 179         return count;
 180 }
 181
 182 static ssize_t store_ignore_nice(struct cpufreq_policy *policy,
 183                 const char *buf, size_t count)
 184 {
 185         unsigned int input;
 186         int ret;
 187
 188         unsigned int j;
 189
 190         ret = sscanf (buf, "%u", &input);
 191         if ( ret != 1 )
 192                 return -EINVAL;
 193
 194         if ( input > 1 )
 195                 input = 1;
 196
 197         down(&dbs_sem);
 198         if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
 199                 up(&dbs_sem);
 200                 return count;
 201         }
 202         dbs_tuners_ins.ignore_nice = input;
 203
 204         /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
 205         for_each_online_cpu(j) {
 206                 struct cpu_dbs_info_s *j_dbs_info;
 207                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 208                 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 209                 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
 210         }
 211         up(&dbs_sem);
 212
 213         return count;
 214 }
 215
 216 #define define_one_rw(_name) \
 217 static struct freq_attr _name = \
 218 __ATTR(_name, 0644, show_##_name, store_##_name)
 219
 220 define_one_rw(sampling_rate);
 221 define_one_rw(sampling_down_factor);
 222 define_one_rw(up_threshold);
 223 define_one_rw(ignore_nice);
 224
 225 static struct attribute * dbs_attributes[] = {
 226         &sampling_rate_max.attr,
 227         &sampling_rate_min.attr,
 228         &sampling_rate.attr,
 229         &sampling_down_factor.attr,
 230         &up_threshold.attr,
 231         &ignore_nice.attr,
 232         NULL
 233 };
 234
 235 static struct attribute_group dbs_attr_group = {
 236         .attrs = dbs_attributes,
 237         .name = "ondemand",
 238 };
 239
 240 /************************** sysfs end ************************/
 241
 242 static void dbs_check_cpu(int cpu)
 243 {
 244         unsigned int idle_ticks, up_idle_ticks, total_ticks;
 245         unsigned int freq_next;
 246         unsigned int freq_down_sampling_rate;
 247         static int down_skip[NR_CPUS];
 248         struct cpu_dbs_info_s *this_dbs_info;
 249
 250         struct cpufreq_policy *policy;
 251         unsigned int j;
 252
 253         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 254         if (!this_dbs_info->enable)
 255                 return;
 256
 257         policy = this_dbs_info->cur_policy;
 258         /*
 259          * Every sampling_rate, we check, if current idle time is less
 260          * than 20% (default), then we try to increase frequency
 261          * Every sampling_rate*sampling_down_factor, we look for a the lowest
 262          * frequency which can sustain the load while keeping idle time over
 263          * 30%. If such a frequency exist, we try to decrease to this frequency.
 264          *
 265          * Any frequency increase takes it to the maximum frequency.
 266          * Frequency reduction happens at minimum steps of
 267          * 5% (default) of current frequency
 268          */
 269
 270         /* Check for frequency increase */
 271         idle_ticks = UINT_MAX;
 272         for_each_cpu_mask(j, policy->cpus) {
 273                 unsigned int tmp_idle_ticks, total_idle_ticks;
 274                 struct cpu_dbs_info_s *j_dbs_info;
 275
 276                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 277                 total_idle_ticks = get_cpu_idle_time(j);
 278                 tmp_idle_ticks = total_idle_ticks -
 279                         j_dbs_info->prev_cpu_idle_up;
 280                 j_dbs_info->prev_cpu_idle_up = total_idle_ticks;
 281
 282                 if (tmp_idle_ticks < idle_ticks)
 283                         idle_ticks = tmp_idle_ticks;
 284         }
 285
 286         /* Scale idle ticks by 100 and compare with up and down ticks */
 287         idle_ticks *= 100;
 288         up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
 289                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 290
 291         if (idle_ticks < up_idle_ticks) {
 292                 down_skip[cpu] = 0;
 293                 for_each_cpu_mask(j, policy->cpus) {
 294                         struct cpu_dbs_info_s *j_dbs_info;
 295
 296                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 297                         j_dbs_info->prev_cpu_idle_down =
 298                                         j_dbs_info->prev_cpu_idle_up;
 299                 }
 300                 /* if we are already at full speed then break out early */
 301                 if (policy->cur == policy->max)
 302                         return;
 303
 304                 __cpufreq_driver_target(policy, policy->max,
 305                         CPUFREQ_RELATION_H);
 306                 return;
 307         }
 308
 309         /* Check for frequency decrease */
 310         down_skip[cpu]++;
 311         if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
 312                 return;
 313
 314         idle_ticks = UINT_MAX;
 315         for_each_cpu_mask(j, policy->cpus) {
 316                 unsigned int tmp_idle_ticks, total_idle_ticks;
 317                 struct cpu_dbs_info_s *j_dbs_info;
 318
 319                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 320                 /* Check for frequency decrease */
 321                 total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
 322                 tmp_idle_ticks = total_idle_ticks -
 323                         j_dbs_info->prev_cpu_idle_down;
 324                 j_dbs_info->prev_cpu_idle_down = total_idle_ticks;
 325
 326                 if (tmp_idle_ticks < idle_ticks)
 327                         idle_ticks = tmp_idle_ticks;
 328         }
 329
 330         down_skip[cpu] = 0;
 331         /* if we cannot reduce the frequency anymore, break out early */
 332         if (policy->cur == policy->min)
 333                 return;
 334
 335         /* Compute how many ticks there are between two measurements */
 336         freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
 337                 dbs_tuners_ins.sampling_down_factor;
 338         total_ticks = usecs_to_jiffies(freq_down_sampling_rate);
 339
 340         /*
 341          * The optimal frequency is the frequency that is the lowest that
 342          * can support the current CPU usage without triggering the up
 343          * policy. To be safe, we focus 10 points under the threshold.
 344          */
 345         freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks;
 346         freq_next = (freq_next * policy->cur) /
 347                         (dbs_tuners_ins.up_threshold - 10);
 348
 349         if (freq_next <= ((policy->cur * 95) / 100))
 350                 __cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);
 351 }
 352
 353 static void do_dbs_timer(void *data)
 354 {
 355         int i;
 356         down(&dbs_sem);
 357         for_each_online_cpu(i)
 358                 dbs_check_cpu(i);
 359         schedule_delayed_work(&dbs_work,
 360                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 361         up(&dbs_sem);
 362 }
 363
 364 static inline void dbs_timer_init(void)
 365 {
 366         INIT_WORK(&dbs_work, do_dbs_timer, NULL);
 367         schedule_delayed_work(&dbs_work,
 368                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 369         return;
 370 }
 371
 372 static inline void dbs_timer_exit(void)
 373 {
 374         cancel_delayed_work(&dbs_work);
 375         return;
 376 }
 377
 378 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 379                                    unsigned int event)
 380 {
 381         unsigned int cpu = policy->cpu;
 382         struct cpu_dbs_info_s *this_dbs_info;
 383         unsigned int j;
 384
 385         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 386
 387         switch (event) {
 388         case CPUFREQ_GOV_START:
 389                 if ((!cpu_online(cpu)) ||
 390                     (!policy->cur))
 391                         return -EINVAL;
 392
 393                 if (policy->cpuinfo.transition_latency >
 394                                 (TRANSITION_LATENCY_LIMIT * 1000))
 395                         return -EINVAL;
 396                 if (this_dbs_info->enable) /* Already enabled */
 397                         break;
 398
 399                 down(&dbs_sem);
 400                 for_each_cpu_mask(j, policy->cpus) {
 401                         struct cpu_dbs_info_s *j_dbs_info;
 402                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 403                         j_dbs_info->cur_policy = policy;
 404
 405                         j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 406                         j_dbs_info->prev_cpu_idle_down
 407                                 = j_dbs_info->prev_cpu_idle_up;
 408                 }
 409                 this_dbs_info->enable = 1;
 410                 sysfs_create_group(&policy->kobj, &dbs_attr_group);
 411                 dbs_enable++;
 412                 /*
 413                  * Start the timerschedule work, when this governor
 414                  * is used for first time
 415                  */
 416                 if (dbs_enable == 1) {
 417                         unsigned int latency;
 418                         /* policy latency is in nS. Convert it to uS first */
 419
 420                         latency = policy->cpuinfo.transition_latency;
 421                         if (latency < 1000)
 422                                 latency = 1000;
 423
 424                         def_sampling_rate = (latency / 1000) *
 425                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 426                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 427                         dbs_tuners_ins.ignore_nice = 0;
 428
 429                         dbs_timer_init();
 430                 }
 431
 432                 up(&dbs_sem);
 433                 break;
 434
 435         case CPUFREQ_GOV_STOP:
 436                 down(&dbs_sem);
 437                 this_dbs_info->enable = 0;
 438                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 439                 dbs_enable--;
 440                 /*
 441                  * Stop the timerschedule work, when this governor
 442                  * is used for first time
 443                  */
 444                 if (dbs_enable == 0)
 445                         dbs_timer_exit();
 446
 447                 up(&dbs_sem);
 448
 449                 break;
 450
 451         case CPUFREQ_GOV_LIMITS:
 452                 down(&dbs_sem);
 453                 if (policy->max < this_dbs_info->cur_policy->cur)
 454                         __cpufreq_driver_target(
 455                                         this_dbs_info->cur_policy,
 456                                         policy->max, CPUFREQ_RELATION_H);
 457                 else if (policy->min > this_dbs_info->cur_policy->cur)
 458                         __cpufreq_driver_target(
 459                                         this_dbs_info->cur_policy,
 460                                         policy->min, CPUFREQ_RELATION_L);
 461                 up(&dbs_sem);
 462                 break;
 463         }
 464         return 0;
 465 }
 466
 467 static struct cpufreq_governor cpufreq_gov_dbs = {
 468         .name           = "ondemand",
 469         .governor       = cpufreq_governor_dbs,
 470         .owner          = THIS_MODULE,
 471 };
 472
 473 static int __init cpufreq_gov_dbs_init(void)
 474 {
 475         return cpufreq_register_governor(&cpufreq_gov_dbs);
 476 }
 477
 478 static void __exit cpufreq_gov_dbs_exit(void)
 479 {
 480         /* Make sure that the scheduled work is indeed not running */
 481         flush_scheduled_work();
 482
 483         cpufreq_unregister_governor(&cpufreq_gov_dbs);
 484 }
 485
 486
 487 MODULE_AUTHOR ("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 488 MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 489                 "Low Latency Frequency Transition capable processors");
 490 MODULE_LICENSE ("GPL");
 491
 492 module_init(cpufreq_gov_dbs_init);
 493 module_exit(cpufreq_gov_dbs_exit);