kernel/sched/cpufreq_schedutil.c

   1 /*
   2  * CPUFreq governor based on scheduler-provided CPU utilization data.
   3  *
   4  * Copyright (C) 2016, Intel Corporation
   5  * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13
  14 #include <linux/cpufreq.h>
  15 #include <linux/module.h>
  16 #include <linux/slab.h>
  17 #include <trace/events/power.h>
  18
  19 #include "sched.h"
  20
  21 struct sugov_tunables {
  22         struct gov_attr_set attr_set;
  23         unsigned int rate_limit_us;
  24 };
  25
  26 struct sugov_policy {
  27         struct cpufreq_policy *policy;
  28
  29         struct sugov_tunables *tunables;
  30         struct list_head tunables_hook;
  31
  32         raw_spinlock_t update_lock;  /* For shared policies */
  33         u64 last_freq_update_time;
  34         s64 freq_update_delay_ns;
  35         unsigned int next_freq;
  36
  37         /* The next fields are only needed if fast switch cannot be used. */
  38         struct irq_work irq_work;
  39         struct work_struct work;
  40         struct mutex work_lock;
  41         bool work_in_progress;
  42
  43         bool need_freq_update;
  44 };
  45
  46 struct sugov_cpu {
  47         struct update_util_data update_util;
  48         struct sugov_policy *sg_policy;
  49
  50         unsigned int cached_raw_freq;
  51
  52         /* The fields below are only needed when sharing a policy. */
  53         unsigned long util;
  54         unsigned long max;
  55         u64 last_update;
  56 };
  57
  58 static DEFINE_PER_CPU(struct sugov_cpu, sugov_cpu);
  59
  60 /************************ Governor internals ***********************/
  61
  62 static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
  63 {
  64         s64 delta_ns;
  65
  66         if (sg_policy->work_in_progress)
  67                 return false;
  68
  69         if (unlikely(sg_policy->need_freq_update)) {
  70                 sg_policy->need_freq_update = false;
  71                 /*
  72                  * This happens when limits change, so forget the previous
  73                  * next_freq value and force an update.
  74                  */
  75                 sg_policy->next_freq = UINT_MAX;
  76                 return true;
  77         }
  78
  79         delta_ns = time - sg_policy->last_freq_update_time;
  80         return delta_ns >= sg_policy->freq_update_delay_ns;
  81 }
  82
  83 static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
  84                                 unsigned int next_freq)
  85 {
  86         struct cpufreq_policy *policy = sg_policy->policy;
  87
  88         sg_policy->last_freq_update_time = time;
  89
  90         if (policy->fast_switch_enabled) {
  91                 if (sg_policy->next_freq == next_freq) {
  92                         trace_cpu_frequency(policy->cur, smp_processor_id());
  93                         return;
  94                 }
  95                 sg_policy->next_freq = next_freq;
  96                 next_freq = cpufreq_driver_fast_switch(policy, next_freq);
  97                 if (next_freq == CPUFREQ_ENTRY_INVALID)
  98                         return;
  99
 100                 policy->cur = next_freq;
 101                 trace_cpu_frequency(next_freq, smp_processor_id());
 102         } else if (sg_policy->next_freq != next_freq) {
 103                 sg_policy->next_freq = next_freq;
 104                 sg_policy->work_in_progress = true;
 105                 irq_work_queue(&sg_policy->irq_work);
 106         }
 107 }
 108
 109 /**
 110  * get_next_freq - Compute a new frequency for a given cpufreq policy.
 111  * @sg_cpu: schedutil cpu object to compute the new frequency for.
 112  * @util: Current CPU utilization.
 113  * @max: CPU capacity.
 114  *
 115  * If the utilization is frequency-invariant, choose the new frequency to be
 116  * proportional to it, that is
 117  *
 118  * next_freq = C * max_freq * util / max
 119  *
 120  * Otherwise, approximate the would-be frequency-invariant utilization by
 121  * util_raw * (curr_freq / max_freq) which leads to
 122  *
 123  * next_freq = C * curr_freq * util_raw / max
 124  *
 125  * Take C = 1.25 for the frequency tipping point at (util / max) = 0.8.
 126  *
 127  * The lowest driver-supported frequency which is equal or greater than the raw
 128  * next_freq (as calculated above) is returned, subject to policy min/max and
 129  * cpufreq driver limitations.
 130  */
 131 static unsigned int get_next_freq(struct sugov_cpu *sg_cpu, unsigned long util,
 132                                   unsigned long max)
 133 {
 134         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
 135         struct cpufreq_policy *policy = sg_policy->policy;
 136         unsigned int freq = arch_scale_freq_invariant() ?
 137                                 policy->cpuinfo.max_freq : policy->cur;
 138
 139         freq = (freq + (freq >> 2)) * util / max;
 140
 141         if (freq == sg_cpu->cached_raw_freq && sg_policy->next_freq != UINT_MAX)
 142                 return sg_policy->next_freq;
 143         sg_cpu->cached_raw_freq = freq;
 144         return cpufreq_driver_resolve_freq(policy, freq);
 145 }
 146
 147 static void sugov_update_single(struct update_util_data *hook, u64 time,
 148                                 unsigned long util, unsigned long max)
 149 {
 150         struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
 151         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
 152         struct cpufreq_policy *policy = sg_policy->policy;
 153         unsigned int next_f;
 154
 155         if (!sugov_should_update_freq(sg_policy, time))
 156                 return;
 157
 158         next_f = util == ULONG_MAX ? policy->cpuinfo.max_freq :
 159                         get_next_freq(sg_cpu, util, max);
 160         sugov_update_commit(sg_policy, time, next_f);
 161 }
 162
 163 static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu,
 164                                            unsigned long util, unsigned long max)
 165 {
 166         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
 167         struct cpufreq_policy *policy = sg_policy->policy;
 168         unsigned int max_f = policy->cpuinfo.max_freq;
 169         u64 last_freq_update_time = sg_policy->last_freq_update_time;
 170         unsigned int j;
 171
 172         if (util == ULONG_MAX)
 173                 return max_f;
 174
 175         for_each_cpu(j, policy->cpus) {
 176                 struct sugov_cpu *j_sg_cpu;
 177                 unsigned long j_util, j_max;
 178                 s64 delta_ns;
 179
 180                 if (j == smp_processor_id())
 181                         continue;
 182
 183                 j_sg_cpu = &per_cpu(sugov_cpu, j);
 184                 /*
 185                  * If the CPU utilization was last updated before the previous
 186                  * frequency update and the time elapsed between the last update
 187                  * of the CPU utilization and the last frequency update is long
 188                  * enough, don't take the CPU into account as it probably is
 189                  * idle now.
 190                  */
 191                 delta_ns = last_freq_update_time - j_sg_cpu->last_update;
 192                 if (delta_ns > TICK_NSEC)
 193                         continue;
 194
 195                 j_util = j_sg_cpu->util;
 196                 if (j_util == ULONG_MAX)
 197                         return max_f;
 198
 199                 j_max = j_sg_cpu->max;
 200                 if (j_util * max > j_max * util) {
 201                         util = j_util;
 202                         max = j_max;
 203                 }
 204         }
 205
 206         return get_next_freq(sg_cpu, util, max);
 207 }
 208
 209 static void sugov_update_shared(struct update_util_data *hook, u64 time,
 210                                 unsigned long util, unsigned long max)
 211 {
 212         struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
 213         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
 214         unsigned int next_f;
 215
 216         raw_spin_lock(&sg_policy->update_lock);
 217
 218         sg_cpu->util = util;
 219         sg_cpu->max = max;
 220         sg_cpu->last_update = time;
 221
 222         if (sugov_should_update_freq(sg_policy, time)) {
 223                 next_f = sugov_next_freq_shared(sg_cpu, util, max);
 224                 sugov_update_commit(sg_policy, time, next_f);
 225         }
 226
 227         raw_spin_unlock(&sg_policy->update_lock);
 228 }
 229
 230 static void sugov_work(struct work_struct *work)
 231 {
 232         struct sugov_policy *sg_policy = container_of(work, struct sugov_policy, work);
 233
 234         mutex_lock(&sg_policy->work_lock);
 235         __cpufreq_driver_target(sg_policy->policy, sg_policy->next_freq,
 236                                 CPUFREQ_RELATION_L);
 237         mutex_unlock(&sg_policy->work_lock);
 238
 239         sg_policy->work_in_progress = false;
 240 }
 241
 242 static void sugov_irq_work(struct irq_work *irq_work)
 243 {
 244         struct sugov_policy *sg_policy;
 245
 246         sg_policy = container_of(irq_work, struct sugov_policy, irq_work);
 247         schedule_work_on(smp_processor_id(), &sg_policy->work);
 248 }
 249
 250 /************************** sysfs interface ************************/
 251
 252 static struct sugov_tunables *global_tunables;
 253 static DEFINE_MUTEX(global_tunables_lock);
 254
 255 static inline struct sugov_tunables *to_sugov_tunables(struct gov_attr_set *attr_set)
 256 {
 257         return container_of(attr_set, struct sugov_tunables, attr_set);
 258 }
 259
 260 static ssize_t rate_limit_us_show(struct gov_attr_set *attr_set, char *buf)
 261 {
 262         struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
 263
 264         return sprintf(buf, "%u\n", tunables->rate_limit_us);
 265 }
 266
 267 static ssize_t rate_limit_us_store(struct gov_attr_set *attr_set, const char *buf,
 268                                    size_t count)
 269 {
 270         struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
 271         struct sugov_policy *sg_policy;
 272         unsigned int rate_limit_us;
 273
 274         if (kstrtouint(buf, 10, &rate_limit_us))
 275                 return -EINVAL;
 276
 277         tunables->rate_limit_us = rate_limit_us;
 278
 279         list_for_each_entry(sg_policy, &attr_set->policy_list, tunables_hook)
 280                 sg_policy->freq_update_delay_ns = rate_limit_us * NSEC_PER_USEC;
 281
 282         return count;
 283 }
 284
 285 static struct governor_attr rate_limit_us = __ATTR_RW(rate_limit_us);
 286
 287 static struct attribute *sugov_attributes[] = {
 288         &rate_limit_us.attr,
 289         NULL
 290 };
 291
 292 static struct kobj_type sugov_tunables_ktype = {
 293         .default_attrs = sugov_attributes,
 294         .sysfs_ops = &governor_sysfs_ops,
 295 };
 296
 297 /********************** cpufreq governor interface *********************/
 298
 299 static struct cpufreq_governor schedutil_gov;
 300
 301 static struct sugov_policy *sugov_policy_alloc(struct cpufreq_policy *policy)
 302 {
 303         struct sugov_policy *sg_policy;
 304
 305         sg_policy = kzalloc(sizeof(*sg_policy), GFP_KERNEL);
 306         if (!sg_policy)
 307                 return NULL;
 308
 309         sg_policy->policy = policy;
 310         init_irq_work(&sg_policy->irq_work, sugov_irq_work);
 311         INIT_WORK(&sg_policy->work, sugov_work);
 312         mutex_init(&sg_policy->work_lock);
 313         raw_spin_lock_init(&sg_policy->update_lock);
 314         return sg_policy;
 315 }
 316
 317 static void sugov_policy_free(struct sugov_policy *sg_policy)
 318 {
 319         mutex_destroy(&sg_policy->work_lock);
 320         kfree(sg_policy);
 321 }
 322
 323 static struct sugov_tunables *sugov_tunables_alloc(struct sugov_policy *sg_policy)
 324 {
 325         struct sugov_tunables *tunables;
 326
 327         tunables = kzalloc(sizeof(*tunables), GFP_KERNEL);
 328         if (tunables) {
 329                 gov_attr_set_init(&tunables->attr_set, &sg_policy->tunables_hook);
 330                 if (!have_governor_per_policy())
 331                         global_tunables = tunables;
 332         }
 333         return tunables;
 334 }
 335
 336 static void sugov_tunables_free(struct sugov_tunables *tunables)
 337 {
 338         if (!have_governor_per_policy())
 339                 global_tunables = NULL;
 340
 341         kfree(tunables);
 342 }
 343
 344 static int sugov_init(struct cpufreq_policy *policy)
 345 {
 346         struct sugov_policy *sg_policy;
 347         struct sugov_tunables *tunables;
 348         unsigned int lat;
 349         int ret = 0;
 350
 351         /* State should be equivalent to EXIT */
 352         if (policy->governor_data)
 353                 return -EBUSY;
 354
 355         sg_policy = sugov_policy_alloc(policy);
 356         if (!sg_policy)
 357                 return -ENOMEM;
 358
 359         mutex_lock(&global_tunables_lock);
 360
 361         if (global_tunables) {
 362                 if (WARN_ON(have_governor_per_policy())) {
 363                         ret = -EINVAL;
 364                         goto free_sg_policy;
 365                 }
 366                 policy->governor_data = sg_policy;
 367                 sg_policy->tunables = global_tunables;
 368
 369                 gov_attr_set_get(&global_tunables->attr_set, &sg_policy->tunables_hook);
 370                 goto out;
 371         }
 372
 373         tunables = sugov_tunables_alloc(sg_policy);
 374         if (!tunables) {
 375                 ret = -ENOMEM;
 376                 goto free_sg_policy;
 377         }
 378
 379         tunables->rate_limit_us = LATENCY_MULTIPLIER;
 380         lat = policy->cpuinfo.transition_latency / NSEC_PER_USEC;
 381         if (lat)
 382                 tunables->rate_limit_us *= lat;
 383
 384         policy->governor_data = sg_policy;
 385         sg_policy->tunables = tunables;
 386
 387         ret = kobject_init_and_add(&tunables->attr_set.kobj, &sugov_tunables_ktype,
 388                                    get_governor_parent_kobj(policy), "%s",
 389                                    schedutil_gov.name);
 390         if (ret)
 391                 goto fail;
 392
 393  out:
 394         mutex_unlock(&global_tunables_lock);
 395
 396         cpufreq_enable_fast_switch(policy);
 397         return 0;
 398
 399  fail:
 400         policy->governor_data = NULL;
 401         sugov_tunables_free(tunables);
 402
 403  free_sg_policy:
 404         mutex_unlock(&global_tunables_lock);
 405
 406         sugov_policy_free(sg_policy);
 407         pr_err("initialization failed (error %d)\n", ret);
 408         return ret;
 409 }
 410
 411 static void sugov_exit(struct cpufreq_policy *policy)
 412 {
 413         struct sugov_policy *sg_policy = policy->governor_data;
 414         struct sugov_tunables *tunables = sg_policy->tunables;
 415         unsigned int count;
 416
 417         cpufreq_disable_fast_switch(policy);
 418
 419         mutex_lock(&global_tunables_lock);
 420
 421         count = gov_attr_set_put(&tunables->attr_set, &sg_policy->tunables_hook);
 422         policy->governor_data = NULL;
 423         if (!count)
 424                 sugov_tunables_free(tunables);
 425
 426         mutex_unlock(&global_tunables_lock);
 427
 428         sugov_policy_free(sg_policy);
 429 }
 430
 431 static int sugov_start(struct cpufreq_policy *policy)
 432 {
 433         struct sugov_policy *sg_policy = policy->governor_data;
 434         unsigned int cpu;
 435
 436         sg_policy->freq_update_delay_ns = sg_policy->tunables->rate_limit_us * NSEC_PER_USEC;
 437         sg_policy->last_freq_update_time = 0;
 438         sg_policy->next_freq = UINT_MAX;
 439         sg_policy->work_in_progress = false;
 440         sg_policy->need_freq_update = false;
 441
 442         for_each_cpu(cpu, policy->cpus) {
 443                 struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu);
 444
 445                 sg_cpu->sg_policy = sg_policy;
 446                 if (policy_is_shared(policy)) {
 447                         sg_cpu->util = ULONG_MAX;
 448                         sg_cpu->max = 0;
 449                         sg_cpu->last_update = 0;
 450                         sg_cpu->cached_raw_freq = 0;
 451                         cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util,
 452                                                      sugov_update_shared);
 453                 } else {
 454                         cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util,
 455                                                      sugov_update_single);
 456                 }
 457         }
 458         return 0;
 459 }
 460
 461 static void sugov_stop(struct cpufreq_policy *policy)
 462 {
 463         struct sugov_policy *sg_policy = policy->governor_data;
 464         unsigned int cpu;
 465
 466         for_each_cpu(cpu, policy->cpus)
 467                 cpufreq_remove_update_util_hook(cpu);
 468
 469         synchronize_sched();
 470
 471         irq_work_sync(&sg_policy->irq_work);
 472         cancel_work_sync(&sg_policy->work);
 473 }
 474
 475 static void sugov_limits(struct cpufreq_policy *policy)
 476 {
 477         struct sugov_policy *sg_policy = policy->governor_data;
 478
 479         if (!policy->fast_switch_enabled) {
 480                 mutex_lock(&sg_policy->work_lock);
 481                 cpufreq_policy_apply_limits(policy);
 482                 mutex_unlock(&sg_policy->work_lock);
 483         }
 484
 485         sg_policy->need_freq_update = true;
 486 }
 487
 488 static struct cpufreq_governor schedutil_gov = {
 489         .name = "schedutil",
 490         .owner = THIS_MODULE,
 491         .init = sugov_init,
 492         .exit = sugov_exit,
 493         .start = sugov_start,
 494         .stop = sugov_stop,
 495         .limits = sugov_limits,
 496 };
 497
 498 static int __init sugov_module_init(void)
 499 {
 500         return cpufreq_register_governor(&schedutil_gov);
 501 }
 502
 503 static void __exit sugov_module_exit(void)
 504 {
 505         cpufreq_unregister_governor(&schedutil_gov);
 506 }
 507
 508 MODULE_AUTHOR("Rafael J. Wysocki <rafael.j.wysocki@intel.com>");
 509 MODULE_DESCRIPTION("Utilization-based CPU frequency selection");
 510 MODULE_LICENSE("GPL");
 511
 512 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL
 513 struct cpufreq_governor *cpufreq_default_governor(void)
 514 {
 515         return &schedutil_gov;
 516 }
 517
 518 fs_initcall(sugov_module_init);
 519 #else
 520 module_init(sugov_module_init);
 521 #endif
 522 module_exit(sugov_module_exit);