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