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 cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu,
  99                                                         cputime64_t *wall)
 100 {
 101         cputime64_t idle_time;
 102         cputime64_t cur_wall_time;
 103         cputime64_t busy_time;
 104
 105         cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
 106         busy_time = cputime64_add(kstat_cpu(cpu).cpustat.user,
 107                         kstat_cpu(cpu).cpustat.system);
 108
 109         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.irq);
 110         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.softirq);
 111         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.steal);
 112         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.nice);
 113
 114         idle_time = cputime64_sub(cur_wall_time, busy_time);
 115         if (wall)
 116                 *wall = (cputime64_t)jiffies_to_usecs(cur_wall_time);
 117
 118         return (cputime64_t)jiffies_to_usecs(idle_time);
 119 }
 120
 121 static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
 122 {
 123         u64 idle_time = get_cpu_idle_time_us(cpu, NULL);
 124
 125         if (idle_time == -1ULL)
 126                 return get_cpu_idle_time_jiffy(cpu, wall);
 127         else
 128                 idle_time += get_cpu_iowait_time_us(cpu, wall);
 129
 130         return idle_time;
 131 }
 132
 133 /* keep track of frequency transitions */
 134 static int
 135 dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
 136                      void *data)
 137 {
 138         struct cpufreq_freqs *freq = data;
 139         struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cs_cpu_dbs_info,
 140                                                         freq->cpu);
 141
 142         struct cpufreq_policy *policy;
 143
 144         if (!this_dbs_info->enable)
 145                 return 0;
 146
 147         policy = this_dbs_info->cur_policy;
 148
 149         /*
 150          * we only care if our internally tracked freq moves outside
 151          * the 'valid' ranges of freqency available to us otherwise
 152          * we do not change it
 153         */
 154         if (this_dbs_info->requested_freq > policy->max
 155                         || this_dbs_info->requested_freq < policy->min)
 156                 this_dbs_info->requested_freq = freq->new;
 157
 158         return 0;
 159 }
 160
 161 static struct notifier_block dbs_cpufreq_notifier_block = {
 162         .notifier_call = dbs_cpufreq_notifier
 163 };
 164
 165 /************************** sysfs interface ************************/
 166 static ssize_t show_sampling_rate_min(struct kobject *kobj,
 167                                       struct attribute *attr, char *buf)
 168 {
 169         return sprintf(buf, "%u\n", min_sampling_rate);
 170 }
 171
 172 define_one_global_ro(sampling_rate_min);
 173
 174 /* cpufreq_conservative Governor Tunables */
 175 #define show_one(file_name, object)                                     \
 176 static ssize_t show_##file_name                                         \
 177 (struct kobject *kobj, struct attribute *attr, char *buf)               \
 178 {                                                                       \
 179         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 180 }
 181 show_one(sampling_rate, sampling_rate);
 182 show_one(sampling_down_factor, sampling_down_factor);
 183 show_one(up_threshold, up_threshold);
 184 show_one(down_threshold, down_threshold);
 185 show_one(ignore_nice_load, ignore_nice);
 186 show_one(freq_step, freq_step);
 187
 188 static ssize_t store_sampling_down_factor(struct kobject *a,
 189                                           struct attribute *b,
 190                                           const char *buf, size_t count)
 191 {
 192         unsigned int input;
 193         int ret;
 194         ret = sscanf(buf, "%u", &input);
 195
 196         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 197                 return -EINVAL;
 198
 199         dbs_tuners_ins.sampling_down_factor = input;
 200         return count;
 201 }
 202
 203 static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
 204                                    const char *buf, size_t count)
 205 {
 206         unsigned int input;
 207         int ret;
 208         ret = sscanf(buf, "%u", &input);
 209
 210         if (ret != 1)
 211                 return -EINVAL;
 212
 213         dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);
 214         return count;
 215 }
 216
 217 static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
 218                                   const char *buf, size_t count)
 219 {
 220         unsigned int input;
 221         int ret;
 222         ret = sscanf(buf, "%u", &input);
 223
 224         if (ret != 1 || input > 100 ||
 225                         input <= dbs_tuners_ins.down_threshold)
 226                 return -EINVAL;
 227
 228         dbs_tuners_ins.up_threshold = input;
 229         return count;
 230 }
 231
 232 static ssize_t store_down_threshold(struct kobject *a, struct attribute *b,
 233                                     const char *buf, size_t count)
 234 {
 235         unsigned int input;
 236         int ret;
 237         ret = sscanf(buf, "%u", &input);
 238
 239         /* cannot be lower than 11 otherwise freq will not fall */
 240         if (ret != 1 || input < 11 || input > 100 ||
 241                         input >= dbs_tuners_ins.up_threshold)
 242                 return -EINVAL;
 243
 244         dbs_tuners_ins.down_threshold = input;
 245         return count;
 246 }
 247
 248 static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
 249                                       const char *buf, size_t count)
 250 {
 251         unsigned int input;
 252         int ret;
 253
 254         unsigned int j;
 255
 256         ret = sscanf(buf, "%u", &input);
 257         if (ret != 1)
 258                 return -EINVAL;
 259
 260         if (input > 1)
 261                 input = 1;
 262
 263         if (input == dbs_tuners_ins.ignore_nice) /* nothing to do */
 264                 return count;
 265
 266         dbs_tuners_ins.ignore_nice = input;
 267
 268         /* we need to re-evaluate prev_cpu_idle */
 269         for_each_online_cpu(j) {
 270                 struct cpu_dbs_info_s *dbs_info;
 271                 dbs_info = &per_cpu(cs_cpu_dbs_info, j);
 272                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 273                                                 &dbs_info->prev_cpu_wall);
 274                 if (dbs_tuners_ins.ignore_nice)
 275                         dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
 276         }
 277         return count;
 278 }
 279
 280 static ssize_t store_freq_step(struct kobject *a, struct attribute *b,
 281                                const char *buf, size_t count)
 282 {
 283         unsigned int input;
 284         int ret;
 285         ret = sscanf(buf, "%u", &input);
 286
 287         if (ret != 1)
 288                 return -EINVAL;
 289
 290         if (input > 100)
 291                 input = 100;
 292
 293         /* no need to test here if freq_step is zero as the user might actually
 294          * want this, they would be crazy though :) */
 295         dbs_tuners_ins.freq_step = input;
 296         return count;
 297 }
 298
 299 define_one_global_rw(sampling_rate);
 300 define_one_global_rw(sampling_down_factor);
 301 define_one_global_rw(up_threshold);
 302 define_one_global_rw(down_threshold);
 303 define_one_global_rw(ignore_nice_load);
 304 define_one_global_rw(freq_step);
 305
 306 static struct attribute *dbs_attributes[] = {
 307         &sampling_rate_min.attr,
 308         &sampling_rate.attr,
 309         &sampling_down_factor.attr,
 310         &up_threshold.attr,
 311         &down_threshold.attr,
 312         &ignore_nice_load.attr,
 313         &freq_step.attr,
 314         NULL
 315 };
 316
 317 static struct attribute_group dbs_attr_group = {
 318         .attrs = dbs_attributes,
 319         .name = "conservative",
 320 };
 321
 322 /************************** sysfs end ************************/
 323
 324 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 325 {
 326         unsigned int load = 0;
 327         unsigned int max_load = 0;
 328         unsigned int freq_target;
 329
 330         struct cpufreq_policy *policy;
 331         unsigned int j;
 332
 333         policy = this_dbs_info->cur_policy;
 334
 335         /*
 336          * Every sampling_rate, we check, if current idle time is less
 337          * than 20% (default), then we try to increase frequency
 338          * Every sampling_rate*sampling_down_factor, we check, if current
 339          * idle time is more than 80%, then we try to decrease frequency
 340          *
 341          * Any frequency increase takes it to the maximum frequency.
 342          * Frequency reduction happens at minimum steps of
 343          * 5% (default) of maximum frequency
 344          */
 345
 346         /* Get Absolute Load */
 347         for_each_cpu(j, policy->cpus) {
 348                 struct cpu_dbs_info_s *j_dbs_info;
 349                 cputime64_t cur_wall_time, cur_idle_time;
 350                 unsigned int idle_time, wall_time;
 351
 352                 j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
 353
 354                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
 355
 356                 wall_time = (unsigned int) cputime64_sub(cur_wall_time,
 357                                 j_dbs_info->prev_cpu_wall);
 358                 j_dbs_info->prev_cpu_wall = cur_wall_time;
 359
 360                 idle_time = (unsigned int) cputime64_sub(cur_idle_time,
 361                                 j_dbs_info->prev_cpu_idle);
 362                 j_dbs_info->prev_cpu_idle = cur_idle_time;
 363
 364                 if (dbs_tuners_ins.ignore_nice) {
 365                         cputime64_t cur_nice;
 366                         unsigned long cur_nice_jiffies;
 367
 368                         cur_nice = cputime64_sub(kstat_cpu(j).cpustat.nice,
 369                                          j_dbs_info->prev_cpu_nice);
 370                         /*
 371                          * Assumption: nice time between sampling periods will
 372                          * be less than 2^32 jiffies for 32 bit sys
 373                          */
 374                         cur_nice_jiffies = (unsigned long)
 375                                         cputime64_to_jiffies64(cur_nice);
 376
 377                         j_dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
 378                         idle_time += jiffies_to_usecs(cur_nice_jiffies);
 379                 }
 380
 381                 if (unlikely(!wall_time || wall_time < idle_time))
 382                         continue;
 383
 384                 load = 100 * (wall_time - idle_time) / wall_time;
 385
 386                 if (load > max_load)
 387                         max_load = load;
 388         }
 389
 390         /*
 391          * break out if we 'cannot' reduce the speed as the user might
 392          * want freq_step to be zero
 393          */
 394         if (dbs_tuners_ins.freq_step == 0)
 395                 return;
 396
 397         /* Check for frequency increase */
 398         if (max_load > dbs_tuners_ins.up_threshold) {
 399                 this_dbs_info->down_skip = 0;
 400
 401                 /* if we are already at full speed then break out early */
 402                 if (this_dbs_info->requested_freq == policy->max)
 403                         return;
 404
 405                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 406
 407                 /* max freq cannot be less than 100. But who knows.... */
 408                 if (unlikely(freq_target == 0))
 409                         freq_target = 5;
 410
 411                 this_dbs_info->requested_freq += freq_target;
 412                 if (this_dbs_info->requested_freq > policy->max)
 413                         this_dbs_info->requested_freq = policy->max;
 414
 415                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 416                         CPUFREQ_RELATION_H);
 417                 return;
 418         }
 419
 420         /*
 421          * The optimal frequency is the frequency that is the lowest that
 422          * can support the current CPU usage without triggering the up
 423          * policy. To be safe, we focus 10 points under the threshold.
 424          */
 425         if (max_load < (dbs_tuners_ins.down_threshold - 10)) {
 426                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 427
 428                 this_dbs_info->requested_freq -= freq_target;
 429                 if (this_dbs_info->requested_freq < policy->min)
 430                         this_dbs_info->requested_freq = policy->min;
 431
 432                 /*
 433                  * if we cannot reduce the frequency anymore, break out early
 434                  */
 435                 if (policy->cur == policy->min)
 436                         return;
 437
 438                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 439                                 CPUFREQ_RELATION_H);
 440                 return;
 441         }
 442 }
 443
 444 static void do_dbs_timer(struct work_struct *work)
 445 {
 446         struct cpu_dbs_info_s *dbs_info =
 447                 container_of(work, struct cpu_dbs_info_s, work.work);
 448         unsigned int cpu = dbs_info->cpu;
 449
 450         /* We want all CPUs to do sampling nearly on same jiffy */
 451         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 452
 453         delay -= jiffies % delay;
 454
 455         mutex_lock(&dbs_info->timer_mutex);
 456
 457         dbs_check_cpu(dbs_info);
 458
 459         schedule_delayed_work_on(cpu, &dbs_info->work, delay);
 460         mutex_unlock(&dbs_info->timer_mutex);
 461 }
 462
 463 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 464 {
 465         /* We want all CPUs to do sampling nearly on same jiffy */
 466         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 467         delay -= jiffies % delay;
 468
 469         dbs_info->enable = 1;
 470         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
 471         schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work, delay);
 472 }
 473
 474 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 475 {
 476         dbs_info->enable = 0;
 477         cancel_delayed_work_sync(&dbs_info->work);
 478 }
 479
 480 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 481                                    unsigned int event)
 482 {
 483         unsigned int cpu = policy->cpu;
 484         struct cpu_dbs_info_s *this_dbs_info;
 485         unsigned int j;
 486         int rc;
 487
 488         this_dbs_info = &per_cpu(cs_cpu_dbs_info, cpu);
 489
 490         switch (event) {
 491         case CPUFREQ_GOV_START:
 492                 if ((!cpu_online(cpu)) || (!policy->cur))
 493                         return -EINVAL;
 494
 495                 mutex_lock(&dbs_mutex);
 496
 497                 for_each_cpu(j, policy->cpus) {
 498                         struct cpu_dbs_info_s *j_dbs_info;
 499                         j_dbs_info = &per_cpu(cs_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);
 504                         if (dbs_tuners_ins.ignore_nice) {
 505                                 j_dbs_info->prev_cpu_nice =
 506                                                 kstat_cpu(j).cpustat.nice;
 507                         }
 508                 }
 509                 this_dbs_info->down_skip = 0;
 510                 this_dbs_info->requested_freq = policy->cur;
 511
 512                 mutex_init(&this_dbs_info->timer_mutex);
 513                 dbs_enable++;
 514                 /*
 515                  * Start the timerschedule work, when this governor
 516                  * is used for first time
 517                  */
 518                 if (dbs_enable == 1) {
 519                         unsigned int latency;
 520                         /* policy latency is in nS. Convert it to uS first */
 521                         latency = policy->cpuinfo.transition_latency / 1000;
 522                         if (latency == 0)
 523                                 latency = 1;
 524
 525                         rc = sysfs_create_group(cpufreq_global_kobject,
 526                                                 &dbs_attr_group);
 527                         if (rc) {
 528                                 mutex_unlock(&dbs_mutex);
 529                                 return rc;
 530                         }
 531
 532                         /*
 533                          * conservative does not implement micro like ondemand
 534                          * governor, thus we are bound to jiffes/HZ
 535                          */
 536                         min_sampling_rate =
 537                                 MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
 538                         /* Bring kernel and HW constraints together */
 539                         min_sampling_rate = max(min_sampling_rate,
 540                                         MIN_LATENCY_MULTIPLIER * latency);
 541                         dbs_tuners_ins.sampling_rate =
 542                                 max(min_sampling_rate,
 543                                     latency * LATENCY_MULTIPLIER);
 544
 545                         cpufreq_register_notifier(
 546                                         &dbs_cpufreq_notifier_block,
 547                                         CPUFREQ_TRANSITION_NOTIFIER);
 548                 }
 549                 mutex_unlock(&dbs_mutex);
 550
 551                 dbs_timer_init(this_dbs_info);
 552
 553                 break;
 554
 555         case CPUFREQ_GOV_STOP:
 556                 dbs_timer_exit(this_dbs_info);
 557
 558                 mutex_lock(&dbs_mutex);
 559                 dbs_enable--;
 560                 mutex_destroy(&this_dbs_info->timer_mutex);
 561
 562                 /*
 563                  * Stop the timerschedule work, when this governor
 564                  * is used for first time
 565                  */
 566                 if (dbs_enable == 0)
 567                         cpufreq_unregister_notifier(
 568                                         &dbs_cpufreq_notifier_block,
 569                                         CPUFREQ_TRANSITION_NOTIFIER);
 570
 571                 mutex_unlock(&dbs_mutex);
 572                 if (!dbs_enable)
 573                         sysfs_remove_group(cpufreq_global_kobject,
 574                                            &dbs_attr_group);
 575
 576                 break;
 577
 578         case CPUFREQ_GOV_LIMITS:
 579                 mutex_lock(&this_dbs_info->timer_mutex);
 580                 if (policy->max < this_dbs_info->cur_policy->cur)
 581                         __cpufreq_driver_target(
 582                                         this_dbs_info->cur_policy,
 583                                         policy->max, CPUFREQ_RELATION_H);
 584                 else if (policy->min > this_dbs_info->cur_policy->cur)
 585                         __cpufreq_driver_target(
 586                                         this_dbs_info->cur_policy,
 587                                         policy->min, CPUFREQ_RELATION_L);
 588                 mutex_unlock(&this_dbs_info->timer_mutex);
 589
 590                 break;
 591         }
 592         return 0;
 593 }
 594
 595 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 596 static
 597 #endif
 598 struct cpufreq_governor cpufreq_gov_conservative = {
 599         .name                   = "conservative",
 600         .governor               = cpufreq_governor_dbs,
 601         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 602         .owner                  = THIS_MODULE,
 603 };
 604
 605 static int __init cpufreq_gov_dbs_init(void)
 606 {
 607         return cpufreq_register_governor(&cpufreq_gov_conservative);
 608 }
 609
 610 static void __exit cpufreq_gov_dbs_exit(void)
 611 {
 612         cpufreq_unregister_governor(&cpufreq_gov_conservative);
 613 }
 614
 615
 616 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
 617 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
 618                 "Low Latency Frequency Transition capable processors "
 619                 "optimised for use in a battery environment");
 620 MODULE_LICENSE("GPL");
 621
 622 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 623 fs_initcall(cpufreq_gov_dbs_init);
 624 #else
 625 module_init(cpufreq_gov_dbs_init);
 626 #endif
 627 module_exit(cpufreq_gov_dbs_exit);