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 static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)
  99 {
 100         u64 idle_time;
 101         u64 cur_wall_time;
 102         u64 busy_time;
 103
 104         cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
 105
 106         busy_time  = kcpustat_cpu(cpu).cpustat[CPUTIME_USER];
 107         busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SYSTEM];
 108         busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_IRQ];
 109         busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SOFTIRQ];
 110         busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_STEAL];
 111         busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_NICE];
 112
 113         idle_time = cur_wall_time - busy_time;
 114         if (wall)
 115                 *wall = jiffies_to_usecs(cur_wall_time);
 116
 117         return jiffies_to_usecs(idle_time);
 118 }
 119
 120 static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
 121 {
 122         u64 idle_time = get_cpu_idle_time_us(cpu, NULL);
 123
 124         if (idle_time == -1ULL)
 125                 return get_cpu_idle_time_jiffy(cpu, wall);
 126         else
 127                 idle_time += get_cpu_iowait_time_us(cpu, wall);
 128
 129         return idle_time;
 130 }
 131
 132 /* keep track of frequency transitions */
 133 static int
 134 dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
 135                      void *data)
 136 {
 137         struct cpufreq_freqs *freq = data;
 138         struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cs_cpu_dbs_info,
 139                                                         freq->cpu);
 140
 141         struct cpufreq_policy *policy;
 142
 143         if (!this_dbs_info->enable)
 144                 return 0;
 145
 146         policy = this_dbs_info->cur_policy;
 147
 148         /*
 149          * we only care if our internally tracked freq moves outside
 150          * the 'valid' ranges of freqency available to us otherwise
 151          * we do not change it
 152         */
 153         if (this_dbs_info->requested_freq > policy->max
 154                         || this_dbs_info->requested_freq < policy->min)
 155                 this_dbs_info->requested_freq = freq->new;
 156
 157         return 0;
 158 }
 159
 160 static struct notifier_block dbs_cpufreq_notifier_block = {
 161         .notifier_call = dbs_cpufreq_notifier
 162 };
 163
 164 /************************** sysfs interface ************************/
 165 static ssize_t show_sampling_rate_min(struct kobject *kobj,
 166                                       struct attribute *attr, char *buf)
 167 {
 168         return sprintf(buf, "%u\n", min_sampling_rate);
 169 }
 170
 171 define_one_global_ro(sampling_rate_min);
 172
 173 /* cpufreq_conservative Governor Tunables */
 174 #define show_one(file_name, object)                                     \
 175 static ssize_t show_##file_name                                         \
 176 (struct kobject *kobj, struct attribute *attr, char *buf)               \
 177 {                                                                       \
 178         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 179 }
 180 show_one(sampling_rate, sampling_rate);
 181 show_one(sampling_down_factor, sampling_down_factor);
 182 show_one(up_threshold, up_threshold);
 183 show_one(down_threshold, down_threshold);
 184 show_one(ignore_nice_load, ignore_nice);
 185 show_one(freq_step, freq_step);
 186
 187 static ssize_t store_sampling_down_factor(struct kobject *a,
 188                                           struct attribute *b,
 189                                           const char *buf, size_t count)
 190 {
 191         unsigned int input;
 192         int ret;
 193         ret = sscanf(buf, "%u", &input);
 194
 195         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 196                 return -EINVAL;
 197
 198         dbs_tuners_ins.sampling_down_factor = input;
 199         return count;
 200 }
 201
 202 static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
 203                                    const char *buf, size_t count)
 204 {
 205         unsigned int input;
 206         int ret;
 207         ret = sscanf(buf, "%u", &input);
 208
 209         if (ret != 1)
 210                 return -EINVAL;
 211
 212         dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);
 213         return count;
 214 }
 215
 216 static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
 217                                   const char *buf, size_t count)
 218 {
 219         unsigned int input;
 220         int ret;
 221         ret = sscanf(buf, "%u", &input);
 222
 223         if (ret != 1 || input > 100 ||
 224                         input <= dbs_tuners_ins.down_threshold)
 225                 return -EINVAL;
 226
 227         dbs_tuners_ins.up_threshold = input;
 228         return count;
 229 }
 230
 231 static ssize_t store_down_threshold(struct kobject *a, struct attribute *b,
 232                                     const char *buf, size_t count)
 233 {
 234         unsigned int input;
 235         int ret;
 236         ret = sscanf(buf, "%u", &input);
 237
 238         /* cannot be lower than 11 otherwise freq will not fall */
 239         if (ret != 1 || input < 11 || input > 100 ||
 240                         input >= dbs_tuners_ins.up_threshold)
 241                 return -EINVAL;
 242
 243         dbs_tuners_ins.down_threshold = input;
 244         return count;
 245 }
 246
 247 static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
 248                                       const char *buf, size_t count)
 249 {
 250         unsigned int input;
 251         int ret;
 252
 253         unsigned int j;
 254
 255         ret = sscanf(buf, "%u", &input);
 256         if (ret != 1)
 257                 return -EINVAL;
 258
 259         if (input > 1)
 260                 input = 1;
 261
 262         if (input == dbs_tuners_ins.ignore_nice) /* nothing to do */
 263                 return count;
 264
 265         dbs_tuners_ins.ignore_nice = input;
 266
 267         /* we need to re-evaluate prev_cpu_idle */
 268         for_each_online_cpu(j) {
 269                 struct cpu_dbs_info_s *dbs_info;
 270                 dbs_info = &per_cpu(cs_cpu_dbs_info, j);
 271                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 272                                                 &dbs_info->prev_cpu_wall);
 273                 if (dbs_tuners_ins.ignore_nice)
 274                         dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 275         }
 276         return count;
 277 }
 278
 279 static ssize_t store_freq_step(struct kobject *a, struct attribute *b,
 280                                const char *buf, size_t count)
 281 {
 282         unsigned int input;
 283         int ret;
 284         ret = sscanf(buf, "%u", &input);
 285
 286         if (ret != 1)
 287                 return -EINVAL;
 288
 289         if (input > 100)
 290                 input = 100;
 291
 292         /* no need to test here if freq_step is zero as the user might actually
 293          * want this, they would be crazy though :) */
 294         dbs_tuners_ins.freq_step = input;
 295         return count;
 296 }
 297
 298 define_one_global_rw(sampling_rate);
 299 define_one_global_rw(sampling_down_factor);
 300 define_one_global_rw(up_threshold);
 301 define_one_global_rw(down_threshold);
 302 define_one_global_rw(ignore_nice_load);
 303 define_one_global_rw(freq_step);
 304
 305 static struct attribute *dbs_attributes[] = {
 306         &sampling_rate_min.attr,
 307         &sampling_rate.attr,
 308         &sampling_down_factor.attr,
 309         &up_threshold.attr,
 310         &down_threshold.attr,
 311         &ignore_nice_load.attr,
 312         &freq_step.attr,
 313         NULL
 314 };
 315
 316 static struct attribute_group dbs_attr_group = {
 317         .attrs = dbs_attributes,
 318         .name = "conservative",
 319 };
 320
 321 /************************** sysfs end ************************/
 322
 323 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 324 {
 325         unsigned int load = 0;
 326         unsigned int max_load = 0;
 327         unsigned int freq_target;
 328
 329         struct cpufreq_policy *policy;
 330         unsigned int j;
 331
 332         policy = this_dbs_info->cur_policy;
 333
 334         /*
 335          * Every sampling_rate, we check, if current idle time is less
 336          * than 20% (default), then we try to increase frequency
 337          * Every sampling_rate*sampling_down_factor, we check, if current
 338          * idle time is more than 80%, then we try to decrease frequency
 339          *
 340          * Any frequency increase takes it to the maximum frequency.
 341          * Frequency reduction happens at minimum steps of
 342          * 5% (default) of maximum frequency
 343          */
 344
 345         /* Get Absolute Load */
 346         for_each_cpu(j, policy->cpus) {
 347                 struct cpu_dbs_info_s *j_dbs_info;
 348                 cputime64_t cur_wall_time, cur_idle_time;
 349                 unsigned int idle_time, wall_time;
 350
 351                 j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
 352
 353                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
 354
 355                 wall_time = (unsigned int)
 356                         (cur_wall_time - j_dbs_info->prev_cpu_wall);
 357                 j_dbs_info->prev_cpu_wall = cur_wall_time;
 358
 359                 idle_time = (unsigned int)
 360                         (cur_idle_time - j_dbs_info->prev_cpu_idle);
 361                 j_dbs_info->prev_cpu_idle = cur_idle_time;
 362
 363                 if (dbs_tuners_ins.ignore_nice) {
 364                         u64 cur_nice;
 365                         unsigned long cur_nice_jiffies;
 366
 367                         cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE] -
 368                                          j_dbs_info->prev_cpu_nice;
 369                         /*
 370                          * Assumption: nice time between sampling periods will
 371                          * be less than 2^32 jiffies for 32 bit sys
 372                          */
 373                         cur_nice_jiffies = (unsigned long)
 374                                         cputime64_to_jiffies64(cur_nice);
 375
 376                         j_dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 377                         idle_time += jiffies_to_usecs(cur_nice_jiffies);
 378                 }
 379
 380                 if (unlikely(!wall_time || wall_time < idle_time))
 381                         continue;
 382
 383                 load = 100 * (wall_time - idle_time) / wall_time;
 384
 385                 if (load > max_load)
 386                         max_load = load;
 387         }
 388
 389         /*
 390          * break out if we 'cannot' reduce the speed as the user might
 391          * want freq_step to be zero
 392          */
 393         if (dbs_tuners_ins.freq_step == 0)
 394                 return;
 395
 396         /* Check for frequency increase */
 397         if (max_load > dbs_tuners_ins.up_threshold) {
 398                 this_dbs_info->down_skip = 0;
 399
 400                 /* if we are already at full speed then break out early */
 401                 if (this_dbs_info->requested_freq == policy->max)
 402                         return;
 403
 404                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 405
 406                 /* max freq cannot be less than 100. But who knows.... */
 407                 if (unlikely(freq_target == 0))
 408                         freq_target = 5;
 409
 410                 this_dbs_info->requested_freq += freq_target;
 411                 if (this_dbs_info->requested_freq > policy->max)
 412                         this_dbs_info->requested_freq = policy->max;
 413
 414                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 415                         CPUFREQ_RELATION_H);
 416                 return;
 417         }
 418
 419         /*
 420          * The optimal frequency is the frequency that is the lowest that
 421          * can support the current CPU usage without triggering the up
 422          * policy. To be safe, we focus 10 points under the threshold.
 423          */
 424         if (max_load < (dbs_tuners_ins.down_threshold - 10)) {
 425                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 426
 427                 this_dbs_info->requested_freq -= freq_target;
 428                 if (this_dbs_info->requested_freq < policy->min)
 429                         this_dbs_info->requested_freq = policy->min;
 430
 431                 /*
 432                  * if we cannot reduce the frequency anymore, break out early
 433                  */
 434                 if (policy->cur == policy->min)
 435                         return;
 436
 437                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 438                                 CPUFREQ_RELATION_H);
 439                 return;
 440         }
 441 }
 442
 443 static void do_dbs_timer(struct work_struct *work)
 444 {
 445         struct cpu_dbs_info_s *dbs_info =
 446                 container_of(work, struct cpu_dbs_info_s, work.work);
 447         unsigned int cpu = dbs_info->cpu;
 448
 449         /* We want all CPUs to do sampling nearly on same jiffy */
 450         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 451
 452         delay -= jiffies % delay;
 453
 454         mutex_lock(&dbs_info->timer_mutex);
 455
 456         dbs_check_cpu(dbs_info);
 457
 458         schedule_delayed_work_on(cpu, &dbs_info->work, delay);
 459         mutex_unlock(&dbs_info->timer_mutex);
 460 }
 461
 462 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 463 {
 464         /* We want all CPUs to do sampling nearly on same jiffy */
 465         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 466         delay -= jiffies % delay;
 467
 468         dbs_info->enable = 1;
 469         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
 470         schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work, delay);
 471 }
 472
 473 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 474 {
 475         dbs_info->enable = 0;
 476         cancel_delayed_work_sync(&dbs_info->work);
 477 }
 478
 479 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 480                                    unsigned int event)
 481 {
 482         unsigned int cpu = policy->cpu;
 483         struct cpu_dbs_info_s *this_dbs_info;
 484         unsigned int j;
 485         int rc;
 486
 487         this_dbs_info = &per_cpu(cs_cpu_dbs_info, cpu);
 488
 489         switch (event) {
 490         case CPUFREQ_GOV_START:
 491                 if ((!cpu_online(cpu)) || (!policy->cur))
 492                         return -EINVAL;
 493
 494                 mutex_lock(&dbs_mutex);
 495
 496                 for_each_cpu(j, policy->cpus) {
 497                         struct cpu_dbs_info_s *j_dbs_info;
 498                         j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
 499                         j_dbs_info->cur_policy = policy;
 500
 501                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 502                                                 &j_dbs_info->prev_cpu_wall);
 503                         if (dbs_tuners_ins.ignore_nice)
 504                                 j_dbs_info->prev_cpu_nice =
 505                                                 kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 506                 }
 507                 this_dbs_info->down_skip = 0;
 508                 this_dbs_info->requested_freq = policy->cur;
 509
 510                 mutex_init(&this_dbs_info->timer_mutex);
 511                 dbs_enable++;
 512                 /*
 513                  * Start the timerschedule work, when this governor
 514                  * is used for first time
 515                  */
 516                 if (dbs_enable == 1) {
 517                         unsigned int latency;
 518                         /* policy latency is in nS. Convert it to uS first */
 519                         latency = policy->cpuinfo.transition_latency / 1000;
 520                         if (latency == 0)
 521                                 latency = 1;
 522
 523                         rc = sysfs_create_group(cpufreq_global_kobject,
 524                                                 &dbs_attr_group);
 525                         if (rc) {
 526                                 mutex_unlock(&dbs_mutex);
 527                                 return rc;
 528                         }
 529
 530                         /*
 531                          * conservative does not implement micro like ondemand
 532                          * governor, thus we are bound to jiffes/HZ
 533                          */
 534                         min_sampling_rate =
 535                                 MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
 536                         /* Bring kernel and HW constraints together */
 537                         min_sampling_rate = max(min_sampling_rate,
 538                                         MIN_LATENCY_MULTIPLIER * latency);
 539                         dbs_tuners_ins.sampling_rate =
 540                                 max(min_sampling_rate,
 541                                     latency * LATENCY_MULTIPLIER);
 542
 543                         cpufreq_register_notifier(
 544                                         &dbs_cpufreq_notifier_block,
 545                                         CPUFREQ_TRANSITION_NOTIFIER);
 546                 }
 547                 mutex_unlock(&dbs_mutex);
 548
 549                 dbs_timer_init(this_dbs_info);
 550
 551                 break;
 552
 553         case CPUFREQ_GOV_STOP:
 554                 dbs_timer_exit(this_dbs_info);
 555
 556                 mutex_lock(&dbs_mutex);
 557                 dbs_enable--;
 558                 mutex_destroy(&this_dbs_info->timer_mutex);
 559
 560                 /*
 561                  * Stop the timerschedule work, when this governor
 562                  * is used for first time
 563                  */
 564                 if (dbs_enable == 0)
 565                         cpufreq_unregister_notifier(
 566                                         &dbs_cpufreq_notifier_block,
 567                                         CPUFREQ_TRANSITION_NOTIFIER);
 568
 569                 mutex_unlock(&dbs_mutex);
 570                 if (!dbs_enable)
 571                         sysfs_remove_group(cpufreq_global_kobject,
 572                                            &dbs_attr_group);
 573
 574                 break;
 575
 576         case CPUFREQ_GOV_LIMITS:
 577                 mutex_lock(&this_dbs_info->timer_mutex);
 578                 if (policy->max < this_dbs_info->cur_policy->cur)
 579                         __cpufreq_driver_target(
 580                                         this_dbs_info->cur_policy,
 581                                         policy->max, CPUFREQ_RELATION_H);
 582                 else if (policy->min > this_dbs_info->cur_policy->cur)
 583                         __cpufreq_driver_target(
 584                                         this_dbs_info->cur_policy,
 585                                         policy->min, CPUFREQ_RELATION_L);
 586                 mutex_unlock(&this_dbs_info->timer_mutex);
 587
 588                 break;
 589         }
 590         return 0;
 591 }
 592
 593 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 594 static
 595 #endif
 596 struct cpufreq_governor cpufreq_gov_conservative = {
 597         .name                   = "conservative",
 598         .governor               = cpufreq_governor_dbs,
 599         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 600         .owner                  = THIS_MODULE,
 601 };
 602
 603 static int __init cpufreq_gov_dbs_init(void)
 604 {
 605         return cpufreq_register_governor(&cpufreq_gov_conservative);
 606 }
 607
 608 static void __exit cpufreq_gov_dbs_exit(void)
 609 {
 610         cpufreq_unregister_governor(&cpufreq_gov_conservative);
 611 }
 612
 613
 614 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
 615 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
 616                 "Low Latency Frequency Transition capable processors "
 617                 "optimised for use in a battery environment");
 618 MODULE_LICENSE("GPL");
 619
 620 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 621 fs_initcall(cpufreq_gov_dbs_init);
 622 #else
 623 module_init(cpufreq_gov_dbs_init);
 624 #endif
 625 module_exit(cpufreq_gov_dbs_exit);