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/cpu.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 /*
  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 MIN_FREQUENCY_UP_THRESHOLD              (11)
  40 #define MAX_FREQUENCY_UP_THRESHOLD              (100)
  41
  42 /*
  43  * The polling frequency of this governor depends on the capability of
  44  * the processor. Default polling frequency is 1000 times the transition
  45  * latency of the processor. The governor will work on any processor with
  46  * transition latency <= 10mS, using appropriate sampling
  47  * rate.
  48  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
  49  * this governor will not work.
  50  * All times here are in uS.
  51  */
  52 static unsigned int def_sampling_rate;
  53 #define MIN_SAMPLING_RATE_RATIO                 (2)
  54 /* for correct statistics, we need at least 10 ticks between each measure */
  55 #define MIN_STAT_SAMPLING_RATE                  (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
  56 #define MIN_SAMPLING_RATE                       (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
  57 #define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
  58 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (1000)
  59 #define DEF_SAMPLING_DOWN_FACTOR                (1)
  60 #define MAX_SAMPLING_DOWN_FACTOR                (10)
  61 #define TRANSITION_LATENCY_LIMIT                (10 * 1000)
  62
  63 static void do_dbs_timer(void *data);
  64
  65 struct cpu_dbs_info_s {
  66         struct cpufreq_policy *cur_policy;
  67         unsigned int prev_cpu_idle_up;
  68         unsigned int prev_cpu_idle_down;
  69         unsigned int enable;
  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 /*
  76  * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
  77  * lock and dbs_mutex. cpu_hotplug lock should always be held before
  78  * dbs_mutex. If any function that can potentially take cpu_hotplug lock
  79  * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
  80  * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
  81  * is recursive for the same process. -Venki
  82  */
  83 static DEFINE_MUTEX (dbs_mutex);
  84 static DECLARE_WORK     (dbs_work, do_dbs_timer, NULL);
  85
  86 static struct workqueue_struct *dbs_workq;
  87
  88 struct dbs_tuners {
  89         unsigned int sampling_rate;
  90         unsigned int sampling_down_factor;
  91         unsigned int up_threshold;
  92         unsigned int ignore_nice;
  93 };
  94
  95 static struct dbs_tuners dbs_tuners_ins = {
  96         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
  97         .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
  98         .ignore_nice = 0,
  99 };
 100
 101 static inline unsigned int get_cpu_idle_time(unsigned int cpu)
 102 {
 103         return  kstat_cpu(cpu).cpustat.idle +
 104                 kstat_cpu(cpu).cpustat.iowait +
 105                 ( dbs_tuners_ins.ignore_nice ?
 106                   kstat_cpu(cpu).cpustat.nice :
 107                   0);
 108 }
 109
 110 /************************** sysfs interface ************************/
 111 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 112 {
 113         return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
 114 }
 115
 116 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 117 {
 118         return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 119 }
 120
 121 #define define_one_ro(_name)            \
 122 static struct freq_attr _name =         \
 123 __ATTR(_name, 0444, show_##_name, NULL)
 124
 125 define_one_ro(sampling_rate_max);
 126 define_one_ro(sampling_rate_min);
 127
 128 /* cpufreq_ondemand Governor Tunables */
 129 #define show_one(file_name, object)                                     \
 130 static ssize_t show_##file_name                                         \
 131 (struct cpufreq_policy *unused, char *buf)                              \
 132 {                                                                       \
 133         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 134 }
 135 show_one(sampling_rate, sampling_rate);
 136 show_one(sampling_down_factor, sampling_down_factor);
 137 show_one(up_threshold, up_threshold);
 138 show_one(ignore_nice_load, ignore_nice);
 139
 140 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
 141                 const char *buf, size_t count)
 142 {
 143         unsigned int input;
 144         int ret;
 145         ret = sscanf (buf, "%u", &input);
 146         if (ret != 1 )
 147                 return -EINVAL;
 148
 149         if (input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 150                 return -EINVAL;
 151
 152         mutex_lock(&dbs_mutex);
 153         dbs_tuners_ins.sampling_down_factor = input;
 154         mutex_unlock(&dbs_mutex);
 155
 156         return count;
 157 }
 158
 159 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 160                 const char *buf, size_t count)
 161 {
 162         unsigned int input;
 163         int ret;
 164         ret = sscanf (buf, "%u", &input);
 165
 166         mutex_lock(&dbs_mutex);
 167         if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
 168                 mutex_unlock(&dbs_mutex);
 169                 return -EINVAL;
 170         }
 171
 172         dbs_tuners_ins.sampling_rate = input;
 173         mutex_unlock(&dbs_mutex);
 174
 175         return count;
 176 }
 177
 178 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 179                 const char *buf, size_t count)
 180 {
 181         unsigned int input;
 182         int ret;
 183         ret = sscanf (buf, "%u", &input);
 184
 185         mutex_lock(&dbs_mutex);
 186         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 187                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 188                 mutex_unlock(&dbs_mutex);
 189                 return -EINVAL;
 190         }
 191
 192         dbs_tuners_ins.up_threshold = input;
 193         mutex_unlock(&dbs_mutex);
 194
 195         return count;
 196 }
 197
 198 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 199                 const char *buf, size_t count)
 200 {
 201         unsigned int input;
 202         int ret;
 203
 204         unsigned int j;
 205
 206         ret = sscanf (buf, "%u", &input);
 207         if ( ret != 1 )
 208                 return -EINVAL;
 209
 210         if ( input > 1 )
 211                 input = 1;
 212
 213         mutex_lock(&dbs_mutex);
 214         if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
 215                 mutex_unlock(&dbs_mutex);
 216                 return count;
 217         }
 218         dbs_tuners_ins.ignore_nice = input;
 219
 220         /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
 221         for_each_online_cpu(j) {
 222                 struct cpu_dbs_info_s *j_dbs_info;
 223                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 224                 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 225                 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
 226         }
 227         mutex_unlock(&dbs_mutex);
 228
 229         return count;
 230 }
 231
 232 #define define_one_rw(_name) \
 233 static struct freq_attr _name = \
 234 __ATTR(_name, 0644, show_##_name, store_##_name)
 235
 236 define_one_rw(sampling_rate);
 237 define_one_rw(sampling_down_factor);
 238 define_one_rw(up_threshold);
 239 define_one_rw(ignore_nice_load);
 240
 241 static struct attribute * dbs_attributes[] = {
 242         &sampling_rate_max.attr,
 243         &sampling_rate_min.attr,
 244         &sampling_rate.attr,
 245         &sampling_down_factor.attr,
 246         &up_threshold.attr,
 247         &ignore_nice_load.attr,
 248         NULL
 249 };
 250
 251 static struct attribute_group dbs_attr_group = {
 252         .attrs = dbs_attributes,
 253         .name = "ondemand",
 254 };
 255
 256 /************************** sysfs end ************************/
 257
 258 static void dbs_check_cpu(int cpu)
 259 {
 260         unsigned int idle_ticks, up_idle_ticks, total_ticks;
 261         unsigned int freq_next;
 262         unsigned int freq_down_sampling_rate;
 263         static int down_skip[NR_CPUS];
 264         struct cpu_dbs_info_s *this_dbs_info;
 265
 266         struct cpufreq_policy *policy;
 267         unsigned int j;
 268
 269         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 270         if (!this_dbs_info->enable)
 271                 return;
 272
 273         policy = this_dbs_info->cur_policy;
 274         /*
 275          * Every sampling_rate, we check, if current idle time is less
 276          * than 20% (default), then we try to increase frequency
 277          * Every sampling_rate*sampling_down_factor, we look for a the lowest
 278          * frequency which can sustain the load while keeping idle time over
 279          * 30%. If such a frequency exist, we try to decrease to this frequency.
 280          *
 281          * Any frequency increase takes it to the maximum frequency.
 282          * Frequency reduction happens at minimum steps of
 283          * 5% (default) of current frequency
 284          */
 285
 286         /* Check for frequency increase */
 287         idle_ticks = UINT_MAX;
 288         for_each_cpu_mask(j, policy->cpus) {
 289                 unsigned int tmp_idle_ticks, total_idle_ticks;
 290                 struct cpu_dbs_info_s *j_dbs_info;
 291
 292                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 293                 total_idle_ticks = get_cpu_idle_time(j);
 294                 tmp_idle_ticks = total_idle_ticks -
 295                         j_dbs_info->prev_cpu_idle_up;
 296                 j_dbs_info->prev_cpu_idle_up = total_idle_ticks;
 297
 298                 if (tmp_idle_ticks < idle_ticks)
 299                         idle_ticks = tmp_idle_ticks;
 300         }
 301
 302         /* Scale idle ticks by 100 and compare with up and down ticks */
 303         idle_ticks *= 100;
 304         up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
 305                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 306
 307         if (idle_ticks < up_idle_ticks) {
 308                 down_skip[cpu] = 0;
 309                 for_each_cpu_mask(j, policy->cpus) {
 310                         struct cpu_dbs_info_s *j_dbs_info;
 311
 312                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 313                         j_dbs_info->prev_cpu_idle_down =
 314                                         j_dbs_info->prev_cpu_idle_up;
 315                 }
 316                 /* if we are already at full speed then break out early */
 317                 if (policy->cur == policy->max)
 318                         return;
 319
 320                 __cpufreq_driver_target(policy, policy->max,
 321                         CPUFREQ_RELATION_H);
 322                 return;
 323         }
 324
 325         /* Check for frequency decrease */
 326         down_skip[cpu]++;
 327         if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
 328                 return;
 329
 330         idle_ticks = UINT_MAX;
 331         for_each_cpu_mask(j, policy->cpus) {
 332                 unsigned int tmp_idle_ticks, total_idle_ticks;
 333                 struct cpu_dbs_info_s *j_dbs_info;
 334
 335                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 336                 /* Check for frequency decrease */
 337                 total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
 338                 tmp_idle_ticks = total_idle_ticks -
 339                         j_dbs_info->prev_cpu_idle_down;
 340                 j_dbs_info->prev_cpu_idle_down = total_idle_ticks;
 341
 342                 if (tmp_idle_ticks < idle_ticks)
 343                         idle_ticks = tmp_idle_ticks;
 344         }
 345
 346         down_skip[cpu] = 0;
 347         /* if we cannot reduce the frequency anymore, break out early */
 348         if (policy->cur == policy->min)
 349                 return;
 350
 351         /* Compute how many ticks there are between two measurements */
 352         freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
 353                 dbs_tuners_ins.sampling_down_factor;
 354         total_ticks = usecs_to_jiffies(freq_down_sampling_rate);
 355
 356         /*
 357          * The optimal frequency is the frequency that is the lowest that
 358          * can support the current CPU usage without triggering the up
 359          * policy. To be safe, we focus 10 points under the threshold.
 360          */
 361         freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks;
 362         freq_next = (freq_next * policy->cur) /
 363                         (dbs_tuners_ins.up_threshold - 10);
 364
 365         if (freq_next < policy->min)
 366                 freq_next = policy->min;
 367
 368         if (freq_next <= ((policy->cur * 95) / 100))
 369                 __cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);
 370 }
 371
 372 static void do_dbs_timer(void *data)
 373 {
 374         int i;
 375         lock_cpu_hotplug();
 376         mutex_lock(&dbs_mutex);
 377         for_each_online_cpu(i)
 378                 dbs_check_cpu(i);
 379         queue_delayed_work(dbs_workq, &dbs_work,
 380                            usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 381         mutex_unlock(&dbs_mutex);
 382         unlock_cpu_hotplug();
 383 }
 384
 385 static inline void dbs_timer_init(void)
 386 {
 387         INIT_WORK(&dbs_work, do_dbs_timer, NULL);
 388         if (!dbs_workq)
 389                 dbs_workq = create_singlethread_workqueue("ondemand");
 390         if (!dbs_workq) {
 391                 printk(KERN_ERR "ondemand: Cannot initialize kernel thread\n");
 392                 return;
 393         }
 394         queue_delayed_work(dbs_workq, &dbs_work,
 395                            usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 396         return;
 397 }
 398
 399 static inline void dbs_timer_exit(void)
 400 {
 401         if (dbs_workq)
 402                 cancel_rearming_delayed_workqueue(dbs_workq, &dbs_work);
 403 }
 404
 405 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 406                                    unsigned int event)
 407 {
 408         unsigned int cpu = policy->cpu;
 409         struct cpu_dbs_info_s *this_dbs_info;
 410         unsigned int j;
 411
 412         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 413
 414         switch (event) {
 415         case CPUFREQ_GOV_START:
 416                 if ((!cpu_online(cpu)) ||
 417                     (!policy->cur))
 418                         return -EINVAL;
 419
 420                 if (policy->cpuinfo.transition_latency >
 421                                 (TRANSITION_LATENCY_LIMIT * 1000)) {
 422                         printk(KERN_WARNING "ondemand governor failed to load "
 423                                "due to too long transition latency\n");
 424                         return -EINVAL;
 425                 }
 426                 if (this_dbs_info->enable) /* Already enabled */
 427                         break;
 428
 429                 mutex_lock(&dbs_mutex);
 430                 for_each_cpu_mask(j, policy->cpus) {
 431                         struct cpu_dbs_info_s *j_dbs_info;
 432                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 433                         j_dbs_info->cur_policy = policy;
 434
 435                         j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 436                         j_dbs_info->prev_cpu_idle_down
 437                                 = j_dbs_info->prev_cpu_idle_up;
 438                 }
 439                 this_dbs_info->enable = 1;
 440                 sysfs_create_group(&policy->kobj, &dbs_attr_group);
 441                 dbs_enable++;
 442                 /*
 443                  * Start the timerschedule work, when this governor
 444                  * is used for first time
 445                  */
 446                 if (dbs_enable == 1) {
 447                         unsigned int latency;
 448                         /* policy latency is in nS. Convert it to uS first */
 449                         latency = policy->cpuinfo.transition_latency / 1000;
 450                         if (latency == 0)
 451                                 latency = 1;
 452
 453                         def_sampling_rate = latency *
 454                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 455
 456                         if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
 457                                 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 458
 459                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 460                         dbs_timer_init();
 461                 }
 462
 463                 mutex_unlock(&dbs_mutex);
 464                 break;
 465
 466         case CPUFREQ_GOV_STOP:
 467                 mutex_lock(&dbs_mutex);
 468                 this_dbs_info->enable = 0;
 469                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 470                 dbs_enable--;
 471                 /*
 472                  * Stop the timerschedule work, when this governor
 473                  * is used for first time
 474                  */
 475                 if (dbs_enable == 0)
 476                         dbs_timer_exit();
 477
 478                 mutex_unlock(&dbs_mutex);
 479
 480                 break;
 481
 482         case CPUFREQ_GOV_LIMITS:
 483                 lock_cpu_hotplug();
 484                 mutex_lock(&dbs_mutex);
 485                 if (policy->max < this_dbs_info->cur_policy->cur)
 486                         __cpufreq_driver_target(
 487                                         this_dbs_info->cur_policy,
 488                                         policy->max, CPUFREQ_RELATION_H);
 489                 else if (policy->min > this_dbs_info->cur_policy->cur)
 490                         __cpufreq_driver_target(
 491                                         this_dbs_info->cur_policy,
 492                                         policy->min, CPUFREQ_RELATION_L);
 493                 mutex_unlock(&dbs_mutex);
 494                 unlock_cpu_hotplug();
 495                 break;
 496         }
 497         return 0;
 498 }
 499
 500 static struct cpufreq_governor cpufreq_gov_dbs = {
 501         .name           = "ondemand",
 502         .governor       = cpufreq_governor_dbs,
 503         .owner          = THIS_MODULE,
 504 };
 505
 506 static int __init cpufreq_gov_dbs_init(void)
 507 {
 508         return cpufreq_register_governor(&cpufreq_gov_dbs);
 509 }
 510
 511 static void __exit cpufreq_gov_dbs_exit(void)
 512 {
 513         /* Make sure that the scheduled work is indeed not running.
 514            Assumes the timer has been cancelled first. */
 515         if (dbs_workq) {
 516                 flush_workqueue(dbs_workq);
 517                 destroy_workqueue(dbs_workq);
 518         }
 519
 520         cpufreq_unregister_governor(&cpufreq_gov_dbs);
 521 }
 522
 523
 524 MODULE_AUTHOR ("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 525 MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 526                 "Low Latency Frequency Transition capable processors");
 527 MODULE_LICENSE ("GPL");
 528
 529 module_init(cpufreq_gov_dbs_init);
 530 module_exit(cpufreq_gov_dbs_exit);