drivers/cpufreq/cpufreq_conservative.c

   1 /*
   2  *  drivers/cpufreq/cpufreq_conservative.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  *            (C)  2009 Alexander Clouter <alex@digriz.org.uk>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  */
  13
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/init.h>
  17 #include <linux/cpufreq.h>
  18 #include <linux/cpu.h>
  19 #include <linux/jiffies.h>
  20 #include <linux/kernel_stat.h>
  21 #include <linux/mutex.h>
  22 #include <linux/hrtimer.h>
  23 #include <linux/tick.h>
  24 #include <linux/ktime.h>
  25 #include <linux/sched.h>
  26
  27 /*
  28  * dbs is used in this file as a shortform for demandbased switching
  29  * It helps to keep variable names smaller, simpler
  30  */
  31
  32 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
  33 #define DEF_FREQUENCY_DOWN_THRESHOLD            (20)
  34
  35 /*
  36  * The polling frequency of this governor depends on the capability of
  37  * the processor. Default polling frequency is 1000 times the transition
  38  * latency of the processor. The governor will work on any processor with
  39  * transition latency <= 10mS, using appropriate sampling
  40  * rate.
  41  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
  42  * this governor will not work.
  43  * All times here are in uS.
  44  */
  45 #define MIN_SAMPLING_RATE_RATIO                 (2)
  46
  47 static unsigned int min_sampling_rate;
  48
  49 #define LATENCY_MULTIPLIER                      (1000)
  50 #define MIN_LATENCY_MULTIPLIER                  (100)
  51 #define DEF_SAMPLING_DOWN_FACTOR                (1)
  52 #define MAX_SAMPLING_DOWN_FACTOR                (10)
  53 #define TRANSITION_LATENCY_LIMIT                (10 * 1000 * 1000)
  54
  55 static void do_dbs_timer(struct work_struct *work);
  56
  57 struct cpu_dbs_info_s {
  58         cputime64_t prev_cpu_idle;
  59         cputime64_t prev_cpu_wall;
  60         cputime64_t prev_cpu_nice;
  61         struct cpufreq_policy *cur_policy;
  62         struct delayed_work work;
  63         unsigned int down_skip;
  64         unsigned int requested_freq;
  65         int cpu;
  66         unsigned int enable:1;
  67         /*
  68          * percpu mutex that serializes governor limit change with
  69          * do_dbs_timer invocation. We do not want do_dbs_timer to run
  70          * when user is changing the governor or limits.
  71          */
  72         struct mutex timer_mutex;
  73 };
  74 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cs_cpu_dbs_info);
  75
  76 static unsigned int dbs_enable; /* number of CPUs using this policy */
  77
  78 /*
  79  * dbs_mutex protects dbs_enable in governor start/stop.
  80  */
  81 static DEFINE_MUTEX(dbs_mutex);
  82
  83 static struct dbs_tuners {
  84         unsigned int sampling_rate;
  85         unsigned int sampling_down_factor;
  86         unsigned int up_threshold;
  87         unsigned int down_threshold;
  88         unsigned int ignore_nice;
  89         unsigned int freq_step;
  90 } dbs_tuners_ins = {
  91         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
  92         .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
  93         .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
  94         .ignore_nice = 0,
  95         .freq_step = 5,
  96 };
  97
  98 /* keep track of frequency transitions */
  99 static int
 100 dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
 101                      void *data)
 102 {
 103         struct cpufreq_freqs *freq = data;
 104         struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cs_cpu_dbs_info,
 105                                                         freq->cpu);
 106
 107         struct cpufreq_policy *policy;
 108
 109         if (!this_dbs_info->enable)
 110                 return 0;
 111
 112         policy = this_dbs_info->cur_policy;
 113
 114         /*
 115          * we only care if our internally tracked freq moves outside
 116          * the 'valid' ranges of freqency available to us otherwise
 117          * we do not change it
 118         */
 119         if (this_dbs_info->requested_freq > policy->max
 120                         || this_dbs_info->requested_freq < policy->min)
 121                 this_dbs_info->requested_freq = freq->new;
 122
 123         return 0;
 124 }
 125
 126 static struct notifier_block dbs_cpufreq_notifier_block = {
 127         .notifier_call = dbs_cpufreq_notifier
 128 };
 129
 130 /************************** sysfs interface ************************/
 131 static ssize_t show_sampling_rate_min(struct kobject *kobj,
 132                                       struct attribute *attr, char *buf)
 133 {
 134         return sprintf(buf, "%u\n", min_sampling_rate);
 135 }
 136
 137 define_one_global_ro(sampling_rate_min);
 138
 139 /* cpufreq_conservative Governor Tunables */
 140 #define show_one(file_name, object)                                     \
 141 static ssize_t show_##file_name                                         \
 142 (struct kobject *kobj, struct attribute *attr, char *buf)               \
 143 {                                                                       \
 144         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 145 }
 146 show_one(sampling_rate, sampling_rate);
 147 show_one(sampling_down_factor, sampling_down_factor);
 148 show_one(up_threshold, up_threshold);
 149 show_one(down_threshold, down_threshold);
 150 show_one(ignore_nice_load, ignore_nice);
 151 show_one(freq_step, freq_step);
 152
 153 static ssize_t store_sampling_down_factor(struct kobject *a,
 154                                           struct attribute *b,
 155                                           const char *buf, size_t count)
 156 {
 157         unsigned int input;
 158         int ret;
 159         ret = sscanf(buf, "%u", &input);
 160
 161         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 162                 return -EINVAL;
 163
 164         dbs_tuners_ins.sampling_down_factor = input;
 165         return count;
 166 }
 167
 168 static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
 169                                    const char *buf, size_t count)
 170 {
 171         unsigned int input;
 172         int ret;
 173         ret = sscanf(buf, "%u", &input);
 174
 175         if (ret != 1)
 176                 return -EINVAL;
 177
 178         dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);
 179         return count;
 180 }
 181
 182 static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
 183                                   const char *buf, size_t count)
 184 {
 185         unsigned int input;
 186         int ret;
 187         ret = sscanf(buf, "%u", &input);
 188
 189         if (ret != 1 || input > 100 ||
 190                         input <= dbs_tuners_ins.down_threshold)
 191                 return -EINVAL;
 192
 193         dbs_tuners_ins.up_threshold = input;
 194         return count;
 195 }
 196
 197 static ssize_t store_down_threshold(struct kobject *a, struct attribute *b,
 198                                     const char *buf, size_t count)
 199 {
 200         unsigned int input;
 201         int ret;
 202         ret = sscanf(buf, "%u", &input);
 203
 204         /* cannot be lower than 11 otherwise freq will not fall */
 205         if (ret != 1 || input < 11 || input > 100 ||
 206                         input >= dbs_tuners_ins.up_threshold)
 207                 return -EINVAL;
 208
 209         dbs_tuners_ins.down_threshold = input;
 210         return count;
 211 }
 212
 213 static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
 214                                       const char *buf, size_t count)
 215 {
 216         unsigned int input;
 217         int ret;
 218
 219         unsigned int j;
 220
 221         ret = sscanf(buf, "%u", &input);
 222         if (ret != 1)
 223                 return -EINVAL;
 224
 225         if (input > 1)
 226                 input = 1;
 227
 228         if (input == dbs_tuners_ins.ignore_nice) /* nothing to do */
 229                 return count;
 230
 231         dbs_tuners_ins.ignore_nice = input;
 232
 233         /* we need to re-evaluate prev_cpu_idle */
 234         for_each_online_cpu(j) {
 235                 struct cpu_dbs_info_s *dbs_info;
 236                 dbs_info = &per_cpu(cs_cpu_dbs_info, j);
 237                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 238                                                 &dbs_info->prev_cpu_wall);
 239                 if (dbs_tuners_ins.ignore_nice)
 240                         dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 241         }
 242         return count;
 243 }
 244
 245 static ssize_t store_freq_step(struct kobject *a, struct attribute *b,
 246                                const char *buf, size_t count)
 247 {
 248         unsigned int input;
 249         int ret;
 250         ret = sscanf(buf, "%u", &input);
 251
 252         if (ret != 1)
 253                 return -EINVAL;
 254
 255         if (input > 100)
 256                 input = 100;
 257
 258         /* no need to test here if freq_step is zero as the user might actually
 259          * want this, they would be crazy though :) */
 260         dbs_tuners_ins.freq_step = input;
 261         return count;
 262 }
 263
 264 define_one_global_rw(sampling_rate);
 265 define_one_global_rw(sampling_down_factor);
 266 define_one_global_rw(up_threshold);
 267 define_one_global_rw(down_threshold);
 268 define_one_global_rw(ignore_nice_load);
 269 define_one_global_rw(freq_step);
 270
 271 static struct attribute *dbs_attributes[] = {
 272         &sampling_rate_min.attr,
 273         &sampling_rate.attr,
 274         &sampling_down_factor.attr,
 275         &up_threshold.attr,
 276         &down_threshold.attr,
 277         &ignore_nice_load.attr,
 278         &freq_step.attr,
 279         NULL
 280 };
 281
 282 static struct attribute_group dbs_attr_group = {
 283         .attrs = dbs_attributes,
 284         .name = "conservative",
 285 };
 286
 287 /************************** sysfs end ************************/
 288
 289 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 290 {
 291         unsigned int load = 0;
 292         unsigned int max_load = 0;
 293         unsigned int freq_target;
 294
 295         struct cpufreq_policy *policy;
 296         unsigned int j;
 297
 298         policy = this_dbs_info->cur_policy;
 299
 300         /*
 301          * Every sampling_rate, we check, if current idle time is less
 302          * than 20% (default), then we try to increase frequency
 303          * Every sampling_rate*sampling_down_factor, we check, if current
 304          * idle time is more than 80%, then we try to decrease frequency
 305          *
 306          * Any frequency increase takes it to the maximum frequency.
 307          * Frequency reduction happens at minimum steps of
 308          * 5% (default) of maximum frequency
 309          */
 310
 311         /* Get Absolute Load */
 312         for_each_cpu(j, policy->cpus) {
 313                 struct cpu_dbs_info_s *j_dbs_info;
 314                 cputime64_t cur_wall_time, cur_idle_time;
 315                 unsigned int idle_time, wall_time;
 316
 317                 j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
 318
 319                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
 320
 321                 wall_time = (unsigned int)
 322                         (cur_wall_time - j_dbs_info->prev_cpu_wall);
 323                 j_dbs_info->prev_cpu_wall = cur_wall_time;
 324
 325                 idle_time = (unsigned int)
 326                         (cur_idle_time - j_dbs_info->prev_cpu_idle);
 327                 j_dbs_info->prev_cpu_idle = cur_idle_time;
 328
 329                 if (dbs_tuners_ins.ignore_nice) {
 330                         u64 cur_nice;
 331                         unsigned long cur_nice_jiffies;
 332
 333                         cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE] -
 334                                          j_dbs_info->prev_cpu_nice;
 335                         /*
 336                          * Assumption: nice time between sampling periods will
 337                          * be less than 2^32 jiffies for 32 bit sys
 338                          */
 339                         cur_nice_jiffies = (unsigned long)
 340                                         cputime64_to_jiffies64(cur_nice);
 341
 342                         j_dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 343                         idle_time += jiffies_to_usecs(cur_nice_jiffies);
 344                 }
 345
 346                 if (unlikely(!wall_time || wall_time < idle_time))
 347                         continue;
 348
 349                 load = 100 * (wall_time - idle_time) / wall_time;
 350
 351                 if (load > max_load)
 352                         max_load = load;
 353         }
 354
 355         /*
 356          * break out if we 'cannot' reduce the speed as the user might
 357          * want freq_step to be zero
 358          */
 359         if (dbs_tuners_ins.freq_step == 0)
 360                 return;
 361
 362         /* Check for frequency increase */
 363         if (max_load > dbs_tuners_ins.up_threshold) {
 364                 this_dbs_info->down_skip = 0;
 365
 366                 /* if we are already at full speed then break out early */
 367                 if (this_dbs_info->requested_freq == policy->max)
 368                         return;
 369
 370                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 371
 372                 /* max freq cannot be less than 100. But who knows.... */
 373                 if (unlikely(freq_target == 0))
 374                         freq_target = 5;
 375
 376                 this_dbs_info->requested_freq += freq_target;
 377                 if (this_dbs_info->requested_freq > policy->max)
 378                         this_dbs_info->requested_freq = policy->max;
 379
 380                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 381                         CPUFREQ_RELATION_H);
 382                 return;
 383         }
 384
 385         /*
 386          * The optimal frequency is the frequency that is the lowest that
 387          * can support the current CPU usage without triggering the up
 388          * policy. To be safe, we focus 10 points under the threshold.
 389          */
 390         if (max_load < (dbs_tuners_ins.down_threshold - 10)) {
 391                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 392
 393                 this_dbs_info->requested_freq -= freq_target;
 394                 if (this_dbs_info->requested_freq < policy->min)
 395                         this_dbs_info->requested_freq = policy->min;
 396
 397                 /*
 398                  * if we cannot reduce the frequency anymore, break out early
 399                  */
 400                 if (policy->cur == policy->min)
 401                         return;
 402
 403                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 404                                 CPUFREQ_RELATION_H);
 405                 return;
 406         }
 407 }
 408
 409 static void do_dbs_timer(struct work_struct *work)
 410 {
 411         struct cpu_dbs_info_s *dbs_info =
 412                 container_of(work, struct cpu_dbs_info_s, work.work);
 413         unsigned int cpu = dbs_info->cpu;
 414
 415         /* We want all CPUs to do sampling nearly on same jiffy */
 416         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 417
 418         delay -= jiffies % delay;
 419
 420         mutex_lock(&dbs_info->timer_mutex);
 421
 422         dbs_check_cpu(dbs_info);
 423
 424         schedule_delayed_work_on(cpu, &dbs_info->work, delay);
 425         mutex_unlock(&dbs_info->timer_mutex);
 426 }
 427
 428 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 429 {
 430         /* We want all CPUs to do sampling nearly on same jiffy */
 431         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 432         delay -= jiffies % delay;
 433
 434         dbs_info->enable = 1;
 435         INIT_DEFERRABLE_WORK(&dbs_info->work, do_dbs_timer);
 436         schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work, delay);
 437 }
 438
 439 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 440 {
 441         dbs_info->enable = 0;
 442         cancel_delayed_work_sync(&dbs_info->work);
 443 }
 444
 445 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 446                                    unsigned int event)
 447 {
 448         unsigned int cpu = policy->cpu;
 449         struct cpu_dbs_info_s *this_dbs_info;
 450         unsigned int j;
 451         int rc;
 452
 453         this_dbs_info = &per_cpu(cs_cpu_dbs_info, cpu);
 454
 455         switch (event) {
 456         case CPUFREQ_GOV_START:
 457                 if ((!cpu_online(cpu)) || (!policy->cur))
 458                         return -EINVAL;
 459
 460                 mutex_lock(&dbs_mutex);
 461
 462                 for_each_cpu(j, policy->cpus) {
 463                         struct cpu_dbs_info_s *j_dbs_info;
 464                         j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
 465                         j_dbs_info->cur_policy = policy;
 466
 467                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 468                                                 &j_dbs_info->prev_cpu_wall);
 469                         if (dbs_tuners_ins.ignore_nice)
 470                                 j_dbs_info->prev_cpu_nice =
 471                                                 kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 472                 }
 473                 this_dbs_info->cpu = cpu;
 474                 this_dbs_info->down_skip = 0;
 475                 this_dbs_info->requested_freq = policy->cur;
 476
 477                 mutex_init(&this_dbs_info->timer_mutex);
 478                 dbs_enable++;
 479                 /*
 480                  * Start the timerschedule work, when this governor
 481                  * is used for first time
 482                  */
 483                 if (dbs_enable == 1) {
 484                         unsigned int latency;
 485                         /* policy latency is in nS. Convert it to uS first */
 486                         latency = policy->cpuinfo.transition_latency / 1000;
 487                         if (latency == 0)
 488                                 latency = 1;
 489
 490                         rc = sysfs_create_group(cpufreq_global_kobject,
 491                                                 &dbs_attr_group);
 492                         if (rc) {
 493                                 mutex_unlock(&dbs_mutex);
 494                                 return rc;
 495                         }
 496
 497                         /*
 498                          * conservative does not implement micro like ondemand
 499                          * governor, thus we are bound to jiffes/HZ
 500                          */
 501                         min_sampling_rate =
 502                                 MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
 503                         /* Bring kernel and HW constraints together */
 504                         min_sampling_rate = max(min_sampling_rate,
 505                                         MIN_LATENCY_MULTIPLIER * latency);
 506                         dbs_tuners_ins.sampling_rate =
 507                                 max(min_sampling_rate,
 508                                     latency * LATENCY_MULTIPLIER);
 509
 510                         cpufreq_register_notifier(
 511                                         &dbs_cpufreq_notifier_block,
 512                                         CPUFREQ_TRANSITION_NOTIFIER);
 513                 }
 514                 mutex_unlock(&dbs_mutex);
 515
 516                 dbs_timer_init(this_dbs_info);
 517
 518                 break;
 519
 520         case CPUFREQ_GOV_STOP:
 521                 dbs_timer_exit(this_dbs_info);
 522
 523                 mutex_lock(&dbs_mutex);
 524                 dbs_enable--;
 525                 mutex_destroy(&this_dbs_info->timer_mutex);
 526
 527                 /*
 528                  * Stop the timerschedule work, when this governor
 529                  * is used for first time
 530                  */
 531                 if (dbs_enable == 0)
 532                         cpufreq_unregister_notifier(
 533                                         &dbs_cpufreq_notifier_block,
 534                                         CPUFREQ_TRANSITION_NOTIFIER);
 535
 536                 mutex_unlock(&dbs_mutex);
 537                 if (!dbs_enable)
 538                         sysfs_remove_group(cpufreq_global_kobject,
 539                                            &dbs_attr_group);
 540
 541                 break;
 542
 543         case CPUFREQ_GOV_LIMITS:
 544                 mutex_lock(&this_dbs_info->timer_mutex);
 545                 if (policy->max < this_dbs_info->cur_policy->cur)
 546                         __cpufreq_driver_target(
 547                                         this_dbs_info->cur_policy,
 548                                         policy->max, CPUFREQ_RELATION_H);
 549                 else if (policy->min > this_dbs_info->cur_policy->cur)
 550                         __cpufreq_driver_target(
 551                                         this_dbs_info->cur_policy,
 552                                         policy->min, CPUFREQ_RELATION_L);
 553                 dbs_check_cpu(this_dbs_info);
 554                 mutex_unlock(&this_dbs_info->timer_mutex);
 555
 556                 break;
 557         }
 558         return 0;
 559 }
 560
 561 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 562 static
 563 #endif
 564 struct cpufreq_governor cpufreq_gov_conservative = {
 565         .name                   = "conservative",
 566         .governor               = cpufreq_governor_dbs,
 567         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 568         .owner                  = THIS_MODULE,
 569 };
 570
 571 static int __init cpufreq_gov_dbs_init(void)
 572 {
 573         return cpufreq_register_governor(&cpufreq_gov_conservative);
 574 }
 575
 576 static void __exit cpufreq_gov_dbs_exit(void)
 577 {
 578         cpufreq_unregister_governor(&cpufreq_gov_conservative);
 579 }
 580
 581
 582 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
 583 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
 584                 "Low Latency Frequency Transition capable processors "
 585                 "optimised for use in a battery environment");
 586 MODULE_LICENSE("GPL");
 587
 588 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 589 fs_initcall(cpufreq_gov_dbs_init);
 590 #else
 591 module_init(cpufreq_gov_dbs_init);
 592 #endif
 593 module_exit(cpufreq_gov_dbs_exit);