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/init.h>
  16 #include <linux/cpufreq.h>
  17 #include <linux/cpu.h>
  18 #include <linux/jiffies.h>
  19 #include <linux/kernel_stat.h>
  20 #include <linux/mutex.h>
  21
  22 /*
  23  * dbs is used in this file as a shortform for demandbased switching
  24  * It helps to keep variable names smaller, simpler
  25  */
  26
  27 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
  28 #define MIN_FREQUENCY_UP_THRESHOLD              (11)
  29 #define MAX_FREQUENCY_UP_THRESHOLD              (100)
  30
  31 /*
  32  * The polling frequency of this governor depends on the capability of
  33  * the processor. Default polling frequency is 1000 times the transition
  34  * latency of the processor. The governor will work on any processor with
  35  * transition latency <= 10mS, using appropriate sampling
  36  * rate.
  37  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
  38  * this governor will not work.
  39  * All times here are in uS.
  40  */
  41 static unsigned int def_sampling_rate;
  42 #define MIN_SAMPLING_RATE_RATIO                 (2)
  43 /* for correct statistics, we need at least 10 ticks between each measure */
  44 #define MIN_STAT_SAMPLING_RATE                  (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
  45 #define MIN_SAMPLING_RATE                       (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
  46 #define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
  47 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (1000)
  48 #define TRANSITION_LATENCY_LIMIT                (10 * 1000)
  49
  50 static void do_dbs_timer(void *data);
  51
  52 struct cpu_dbs_info_s {
  53         cputime64_t prev_cpu_idle;
  54         cputime64_t prev_cpu_wall;
  55         struct cpufreq_policy *cur_policy;
  56         struct work_struct work;
  57         unsigned int enable;
  58         struct cpufreq_frequency_table *freq_table;
  59         unsigned int freq_lo;
  60         unsigned int freq_lo_jiffies;
  61         unsigned int freq_hi_jiffies;
  62 };
  63 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
  64
  65 static unsigned int dbs_enable; /* number of CPUs using this policy */
  66
  67 /*
  68  * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
  69  * lock and dbs_mutex. cpu_hotplug lock should always be held before
  70  * dbs_mutex. If any function that can potentially take cpu_hotplug lock
  71  * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
  72  * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
  73  * is recursive for the same process. -Venki
  74  */
  75 static DEFINE_MUTEX(dbs_mutex);
  76
  77 static struct workqueue_struct  *kondemand_wq;
  78
  79 static struct dbs_tuners {
  80         unsigned int sampling_rate;
  81         unsigned int up_threshold;
  82         unsigned int ignore_nice;
  83         unsigned int powersave_bias;
  84 } dbs_tuners_ins = {
  85         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
  86         .ignore_nice = 0,
  87         .powersave_bias = 0,
  88 };
  89
  90 static inline cputime64_t get_cpu_idle_time(unsigned int cpu)
  91 {
  92         cputime64_t retval;
  93
  94         retval = cputime64_add(kstat_cpu(cpu).cpustat.idle,
  95                         kstat_cpu(cpu).cpustat.iowait);
  96
  97         if (dbs_tuners_ins.ignore_nice)
  98                 retval = cputime64_add(retval, kstat_cpu(cpu).cpustat.nice);
  99
 100         return retval;
 101 }
 102
 103 /*
 104  * Find right freq to be set now with powersave_bias on.
 105  * Returns the freq_hi to be used right now and will set freq_hi_jiffies,
 106  * freq_lo, and freq_lo_jiffies in percpu area for averaging freqs.
 107  */
 108 static unsigned int powersave_bias_target(struct cpufreq_policy *policy,
 109                                           unsigned int freq_next,
 110                                           unsigned int relation)
 111 {
 112         unsigned int freq_req, freq_reduc, freq_avg;
 113         unsigned int freq_hi, freq_lo;
 114         unsigned int index = 0;
 115         unsigned int jiffies_total, jiffies_hi, jiffies_lo;
 116         struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, policy->cpu);
 117
 118         if (!dbs_info->freq_table) {
 119                 dbs_info->freq_lo = 0;
 120                 dbs_info->freq_lo_jiffies = 0;
 121                 return freq_next;
 122         }
 123
 124         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_next,
 125                         relation, &index);
 126         freq_req = dbs_info->freq_table[index].frequency;
 127         freq_reduc = freq_req * dbs_tuners_ins.powersave_bias / 1000;
 128         freq_avg = freq_req - freq_reduc;
 129
 130         /* Find freq bounds for freq_avg in freq_table */
 131         index = 0;
 132         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 133                         CPUFREQ_RELATION_H, &index);
 134         freq_lo = dbs_info->freq_table[index].frequency;
 135         index = 0;
 136         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 137                         CPUFREQ_RELATION_L, &index);
 138         freq_hi = dbs_info->freq_table[index].frequency;
 139
 140         /* Find out how long we have to be in hi and lo freqs */
 141         if (freq_hi == freq_lo) {
 142                 dbs_info->freq_lo = 0;
 143                 dbs_info->freq_lo_jiffies = 0;
 144                 return freq_lo;
 145         }
 146         jiffies_total = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 147         jiffies_hi = (freq_avg - freq_lo) * jiffies_total;
 148         jiffies_hi += ((freq_hi - freq_lo) / 2);
 149         jiffies_hi /= (freq_hi - freq_lo);
 150         jiffies_lo = jiffies_total - jiffies_hi;
 151         dbs_info->freq_lo = freq_lo;
 152         dbs_info->freq_lo_jiffies = jiffies_lo;
 153         dbs_info->freq_hi_jiffies = jiffies_hi;
 154         return freq_hi;
 155 }
 156
 157 static void ondemand_powersave_bias_init(void)
 158 {
 159         int i;
 160         for_each_online_cpu(i) {
 161                 struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, i);
 162                 dbs_info->freq_table = cpufreq_frequency_get_table(i);
 163                 dbs_info->freq_lo = 0;
 164         }
 165 }
 166
 167 /************************** sysfs interface ************************/
 168 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 169 {
 170         return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
 171 }
 172
 173 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 174 {
 175         return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 176 }
 177
 178 #define define_one_ro(_name)            \
 179 static struct freq_attr _name =         \
 180 __ATTR(_name, 0444, show_##_name, NULL)
 181
 182 define_one_ro(sampling_rate_max);
 183 define_one_ro(sampling_rate_min);
 184
 185 /* cpufreq_ondemand Governor Tunables */
 186 #define show_one(file_name, object)                                     \
 187 static ssize_t show_##file_name                                         \
 188 (struct cpufreq_policy *unused, char *buf)                              \
 189 {                                                                       \
 190         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 191 }
 192 show_one(sampling_rate, sampling_rate);
 193 show_one(up_threshold, up_threshold);
 194 show_one(ignore_nice_load, ignore_nice);
 195 show_one(powersave_bias, powersave_bias);
 196
 197 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 198                 const char *buf, size_t count)
 199 {
 200         unsigned int input;
 201         int ret;
 202         ret = sscanf(buf, "%u", &input);
 203
 204         mutex_lock(&dbs_mutex);
 205         if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
 206                 mutex_unlock(&dbs_mutex);
 207                 return -EINVAL;
 208         }
 209
 210         dbs_tuners_ins.sampling_rate = input;
 211         mutex_unlock(&dbs_mutex);
 212
 213         return count;
 214 }
 215
 216 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 217                 const char *buf, size_t count)
 218 {
 219         unsigned int input;
 220         int ret;
 221         ret = sscanf(buf, "%u", &input);
 222
 223         mutex_lock(&dbs_mutex);
 224         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 225                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 226                 mutex_unlock(&dbs_mutex);
 227                 return -EINVAL;
 228         }
 229
 230         dbs_tuners_ins.up_threshold = input;
 231         mutex_unlock(&dbs_mutex);
 232
 233         return count;
 234 }
 235
 236 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 237                 const char *buf, size_t count)
 238 {
 239         unsigned int input;
 240         int ret;
 241
 242         unsigned int j;
 243
 244         ret = sscanf(buf, "%u", &input);
 245         if ( ret != 1 )
 246                 return -EINVAL;
 247
 248         if ( input > 1 )
 249                 input = 1;
 250
 251         mutex_lock(&dbs_mutex);
 252         if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
 253                 mutex_unlock(&dbs_mutex);
 254                 return count;
 255         }
 256         dbs_tuners_ins.ignore_nice = input;
 257
 258         /* we need to re-evaluate prev_cpu_idle */
 259         for_each_online_cpu(j) {
 260                 struct cpu_dbs_info_s *dbs_info;
 261                 dbs_info = &per_cpu(cpu_dbs_info, j);
 262                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
 263                 dbs_info->prev_cpu_wall = get_jiffies_64();
 264         }
 265         mutex_unlock(&dbs_mutex);
 266
 267         return count;
 268 }
 269
 270 static ssize_t store_powersave_bias(struct cpufreq_policy *unused,
 271                 const char *buf, size_t count)
 272 {
 273         unsigned int input;
 274         int ret;
 275         ret = sscanf(buf, "%u", &input);
 276
 277         if (ret != 1)
 278                 return -EINVAL;
 279
 280         if (input > 1000)
 281                 input = 1000;
 282
 283         mutex_lock(&dbs_mutex);
 284         dbs_tuners_ins.powersave_bias = input;
 285         ondemand_powersave_bias_init();
 286         mutex_unlock(&dbs_mutex);
 287
 288         return count;
 289 }
 290
 291 #define define_one_rw(_name) \
 292 static struct freq_attr _name = \
 293 __ATTR(_name, 0644, show_##_name, store_##_name)
 294
 295 define_one_rw(sampling_rate);
 296 define_one_rw(up_threshold);
 297 define_one_rw(ignore_nice_load);
 298 define_one_rw(powersave_bias);
 299
 300 static struct attribute * dbs_attributes[] = {
 301         &sampling_rate_max.attr,
 302         &sampling_rate_min.attr,
 303         &sampling_rate.attr,
 304         &up_threshold.attr,
 305         &ignore_nice_load.attr,
 306         &powersave_bias.attr,
 307         NULL
 308 };
 309
 310 static struct attribute_group dbs_attr_group = {
 311         .attrs = dbs_attributes,
 312         .name = "ondemand",
 313 };
 314
 315 /************************** sysfs end ************************/
 316
 317 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 318 {
 319         unsigned int idle_ticks, total_ticks;
 320         unsigned int load;
 321         cputime64_t cur_jiffies;
 322
 323         struct cpufreq_policy *policy;
 324         unsigned int j;
 325
 326         if (!this_dbs_info->enable)
 327                 return;
 328
 329         this_dbs_info->freq_lo = 0;
 330         policy = this_dbs_info->cur_policy;
 331         cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());
 332         total_ticks = (unsigned int) cputime64_sub(cur_jiffies,
 333                         this_dbs_info->prev_cpu_wall);
 334         this_dbs_info->prev_cpu_wall = cur_jiffies;
 335         if (!total_ticks)
 336                 return;
 337         /*
 338          * Every sampling_rate, we check, if current idle time is less
 339          * than 20% (default), then we try to increase frequency
 340          * Every sampling_rate, we look for a the lowest
 341          * frequency which can sustain the load while keeping idle time over
 342          * 30%. If such a frequency exist, we try to decrease to this frequency.
 343          *
 344          * Any frequency increase takes it to the maximum frequency.
 345          * Frequency reduction happens at minimum steps of
 346          * 5% (default) of current frequency
 347          */
 348
 349         /* Get Idle Time */
 350         idle_ticks = UINT_MAX;
 351         for_each_cpu_mask(j, policy->cpus) {
 352                 cputime64_t total_idle_ticks;
 353                 unsigned int tmp_idle_ticks;
 354                 struct cpu_dbs_info_s *j_dbs_info;
 355
 356                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 357                 total_idle_ticks = get_cpu_idle_time(j);
 358                 tmp_idle_ticks = (unsigned int) cputime64_sub(total_idle_ticks,
 359                                 j_dbs_info->prev_cpu_idle);
 360                 j_dbs_info->prev_cpu_idle = total_idle_ticks;
 361
 362                 if (tmp_idle_ticks < idle_ticks)
 363                         idle_ticks = tmp_idle_ticks;
 364         }
 365         load = (100 * (total_ticks - idle_ticks)) / total_ticks;
 366
 367         /* Check for frequency increase */
 368         if (load > dbs_tuners_ins.up_threshold) {
 369                 /* if we are already at full speed then break out early */
 370                 if (!dbs_tuners_ins.powersave_bias) {
 371                         if (policy->cur == policy->max)
 372                                 return;
 373
 374                         __cpufreq_driver_target(policy, policy->max,
 375                                 CPUFREQ_RELATION_H);
 376                 } else {
 377                         int freq = powersave_bias_target(policy, policy->max,
 378                                         CPUFREQ_RELATION_H);
 379                         __cpufreq_driver_target(policy, freq,
 380                                 CPUFREQ_RELATION_L);
 381                 }
 382                 return;
 383         }
 384
 385         /* Check for frequency decrease */
 386         /* if we cannot reduce the frequency anymore, break out early */
 387         if (policy->cur == policy->min)
 388                 return;
 389
 390         /*
 391          * The optimal frequency is the frequency that is the lowest that
 392          * can support the current CPU usage without triggering the up
 393          * policy. To be safe, we focus 10 points under the threshold.
 394          */
 395         if (load < (dbs_tuners_ins.up_threshold - 10)) {
 396                 unsigned int freq_next = (policy->cur * load) /
 397                         (dbs_tuners_ins.up_threshold - 10);
 398                 if (!dbs_tuners_ins.powersave_bias) {
 399                         __cpufreq_driver_target(policy, freq_next,
 400                                         CPUFREQ_RELATION_L);
 401                 } else {
 402                         int freq = powersave_bias_target(policy, freq_next,
 403                                         CPUFREQ_RELATION_L);
 404                         __cpufreq_driver_target(policy, freq,
 405                                 CPUFREQ_RELATION_L);
 406                 }
 407         }
 408 }
 409
 410 /* Sampling types */
 411 enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE};
 412
 413 static void do_dbs_timer(void *data)
 414 {
 415         unsigned int cpu = smp_processor_id();
 416         struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
 417         /* We want all CPUs to do sampling nearly on same jiffy */
 418         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 419         delay -= jiffies % delay;
 420
 421         if (!dbs_info->enable)
 422                 return;
 423         /* Common NORMAL_SAMPLE setup */
 424         INIT_WORK(&dbs_info->work, do_dbs_timer, (void *)DBS_NORMAL_SAMPLE);
 425         if (!dbs_tuners_ins.powersave_bias ||
 426             (unsigned long) data == DBS_NORMAL_SAMPLE) {
 427                 lock_cpu_hotplug();
 428                 dbs_check_cpu(dbs_info);
 429                 unlock_cpu_hotplug();
 430                 if (dbs_info->freq_lo) {
 431                         /* Setup timer for SUB_SAMPLE */
 432                         INIT_WORK(&dbs_info->work, do_dbs_timer,
 433                                         (void *)DBS_SUB_SAMPLE);
 434                         delay = dbs_info->freq_hi_jiffies;
 435                 }
 436         } else {
 437                 __cpufreq_driver_target(dbs_info->cur_policy,
 438                                         dbs_info->freq_lo,
 439                                         CPUFREQ_RELATION_H);
 440         }
 441         queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
 442 }
 443
 444 static inline void dbs_timer_init(unsigned int cpu)
 445 {
 446         struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
 447         /* We want all CPUs to do sampling nearly on same jiffy */
 448         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 449         delay -= jiffies % delay;
 450
 451         ondemand_powersave_bias_init();
 452         INIT_WORK(&dbs_info->work, do_dbs_timer, NULL);
 453         queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
 454 }
 455
 456 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 457 {
 458         dbs_info->enable = 0;
 459         cancel_delayed_work(&dbs_info->work);
 460         flush_workqueue(kondemand_wq);
 461 }
 462
 463 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 464                                    unsigned int event)
 465 {
 466         unsigned int cpu = policy->cpu;
 467         struct cpu_dbs_info_s *this_dbs_info;
 468         unsigned int j;
 469
 470         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 471
 472         switch (event) {
 473         case CPUFREQ_GOV_START:
 474                 if ((!cpu_online(cpu)) || (!policy->cur))
 475                         return -EINVAL;
 476
 477                 if (policy->cpuinfo.transition_latency >
 478                                 (TRANSITION_LATENCY_LIMIT * 1000)) {
 479                         printk(KERN_WARNING "ondemand governor failed to load "
 480                                "due to too long transition latency\n");
 481                         return -EINVAL;
 482                 }
 483                 if (this_dbs_info->enable) /* Already enabled */
 484                         break;
 485
 486                 mutex_lock(&dbs_mutex);
 487                 dbs_enable++;
 488                 if (dbs_enable == 1) {
 489                         kondemand_wq = create_workqueue("kondemand");
 490                         if (!kondemand_wq) {
 491                                 printk(KERN_ERR "Creation of kondemand failed\n");
 492                                 dbs_enable--;
 493                                 mutex_unlock(&dbs_mutex);
 494                                 return -ENOSPC;
 495                         }
 496                 }
 497                 for_each_cpu_mask(j, policy->cpus) {
 498                         struct cpu_dbs_info_s *j_dbs_info;
 499                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 500                         j_dbs_info->cur_policy = policy;
 501
 502                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
 503                         j_dbs_info->prev_cpu_wall = get_jiffies_64();
 504                 }
 505                 this_dbs_info->enable = 1;
 506                 sysfs_create_group(&policy->kobj, &dbs_attr_group);
 507                 /*
 508                  * Start the timerschedule work, when this governor
 509                  * is used for first time
 510                  */
 511                 if (dbs_enable == 1) {
 512                         unsigned int latency;
 513                         /* policy latency is in nS. Convert it to uS first */
 514                         latency = policy->cpuinfo.transition_latency / 1000;
 515                         if (latency == 0)
 516                                 latency = 1;
 517
 518                         def_sampling_rate = latency *
 519                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 520
 521                         if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
 522                                 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 523
 524                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 525                 }
 526                 dbs_timer_init(policy->cpu);
 527
 528                 mutex_unlock(&dbs_mutex);
 529                 break;
 530
 531         case CPUFREQ_GOV_STOP:
 532                 mutex_lock(&dbs_mutex);
 533                 dbs_timer_exit(this_dbs_info);
 534                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 535                 dbs_enable--;
 536                 if (dbs_enable == 0)
 537                         destroy_workqueue(kondemand_wq);
 538
 539                 mutex_unlock(&dbs_mutex);
 540
 541                 break;
 542
 543         case CPUFREQ_GOV_LIMITS:
 544                 mutex_lock(&dbs_mutex);
 545                 if (policy->max < this_dbs_info->cur_policy->cur)
 546                         __cpufreq_driver_target(this_dbs_info->cur_policy,
 547                                                 policy->max,
 548                                                 CPUFREQ_RELATION_H);
 549                 else if (policy->min > this_dbs_info->cur_policy->cur)
 550                         __cpufreq_driver_target(this_dbs_info->cur_policy,
 551                                                 policy->min,
 552                                                 CPUFREQ_RELATION_L);
 553                 mutex_unlock(&dbs_mutex);
 554                 break;
 555         }
 556         return 0;
 557 }
 558
 559 static struct cpufreq_governor cpufreq_gov_dbs = {
 560         .name = "ondemand",
 561         .governor = cpufreq_governor_dbs,
 562         .owner = THIS_MODULE,
 563 };
 564
 565 static int __init cpufreq_gov_dbs_init(void)
 566 {
 567         return cpufreq_register_governor(&cpufreq_gov_dbs);
 568 }
 569
 570 static void __exit cpufreq_gov_dbs_exit(void)
 571 {
 572         cpufreq_unregister_governor(&cpufreq_gov_dbs);
 573 }
 574
 575
 576 MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 577 MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
 578 MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 579                    "Low Latency Frequency Transition capable processors");
 580 MODULE_LICENSE("GPL");
 581
 582 module_init(cpufreq_gov_dbs_init);
 583 module_exit(cpufreq_gov_dbs_exit);