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/kthread.h>
  16 #include <linux/slab.h>
  17 #include <trace/events/power.h>
  18
  19 #include "sched.h"
  20
  21 #define SUGOV_KTHREAD_PRIORITY  50
  22
  23 struct sugov_tunables {
  24         struct gov_attr_set attr_set;
  25         unsigned int rate_limit_us;
  26 };
  27
  28 struct sugov_policy {
  29         struct cpufreq_policy *policy;
  30
  31         struct sugov_tunables *tunables;
  32         struct list_head tunables_hook;
  33
  34         raw_spinlock_t update_lock;  /* For shared policies */
  35         u64 last_freq_update_time;
  36         s64 freq_update_delay_ns;
  37         unsigned int next_freq;
  38
  39         /* The next fields are only needed if fast switch cannot be used. */
  40         struct irq_work irq_work;
  41         struct kthread_work work;
  42         struct mutex work_lock;
  43         struct kthread_worker worker;
  44         struct task_struct *thread;
  45         bool work_in_progress;
  46
  47         bool need_freq_update;
  48 };
  49
  50 struct sugov_cpu {
  51         struct update_util_data update_util;
  52         struct sugov_policy *sg_policy;
  53
  54         unsigned int cached_raw_freq;
  55         unsigned long iowait_boost;
  56         unsigned long iowait_boost_max;
  57         u64 last_update;
  58
  59         /* The fields below are only needed when sharing a policy. */
  60         unsigned long util;
  61         unsigned long max;
  62         unsigned int flags;
  63 };
  64
  65 static DEFINE_PER_CPU(struct sugov_cpu, sugov_cpu);
  66
  67 /************************ Governor internals ***********************/
  68
  69 static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
  70 {
  71         s64 delta_ns;
  72
  73         if (sg_policy->work_in_progress)
  74                 return false;
  75
  76         if (unlikely(sg_policy->need_freq_update)) {
  77                 sg_policy->need_freq_update = false;
  78                 /*
  79                  * This happens when limits change, so forget the previous
  80                  * next_freq value and force an update.
  81                  */
  82                 sg_policy->next_freq = UINT_MAX;
  83                 return true;
  84         }
  85
  86         delta_ns = time - sg_policy->last_freq_update_time;
  87         return delta_ns >= sg_policy->freq_update_delay_ns;
  88 }
  89
  90 static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
  91                                 unsigned int next_freq)
  92 {
  93         struct cpufreq_policy *policy = sg_policy->policy;
  94
  95         sg_policy->last_freq_update_time = time;
  96
  97         if (policy->fast_switch_enabled) {
  98                 if (sg_policy->next_freq == next_freq) {
  99                         trace_cpu_frequency(policy->cur, smp_processor_id());
 100                         return;
 101                 }
 102                 sg_policy->next_freq = next_freq;
 103                 next_freq = cpufreq_driver_fast_switch(policy, next_freq);
 104                 if (next_freq == CPUFREQ_ENTRY_INVALID)
 105                         return;
 106
 107                 policy->cur = next_freq;
 108                 trace_cpu_frequency(next_freq, smp_processor_id());
 109         } else if (sg_policy->next_freq != next_freq) {
 110                 sg_policy->next_freq = next_freq;
 111                 sg_policy->work_in_progress = true;
 112                 irq_work_queue(&sg_policy->irq_work);
 113         }
 114 }
 115
 116 /**
 117  * get_next_freq - Compute a new frequency for a given cpufreq policy.
 118  * @sg_cpu: schedutil cpu object to compute the new frequency for.
 119  * @util: Current CPU utilization.
 120  * @max: CPU capacity.
 121  *
 122  * If the utilization is frequency-invariant, choose the new frequency to be
 123  * proportional to it, that is
 124  *
 125  * next_freq = C * max_freq * util / max
 126  *
 127  * Otherwise, approximate the would-be frequency-invariant utilization by
 128  * util_raw * (curr_freq / max_freq) which leads to
 129  *
 130  * next_freq = C * curr_freq * util_raw / max
 131  *
 132  * Take C = 1.25 for the frequency tipping point at (util / max) = 0.8.
 133  *
 134  * The lowest driver-supported frequency which is equal or greater than the raw
 135  * next_freq (as calculated above) is returned, subject to policy min/max and
 136  * cpufreq driver limitations.
 137  */
 138 static unsigned int get_next_freq(struct sugov_cpu *sg_cpu, unsigned long util,
 139                                   unsigned long max)
 140 {
 141         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
 142         struct cpufreq_policy *policy = sg_policy->policy;
 143         unsigned int freq = arch_scale_freq_invariant() ?
 144                                 policy->cpuinfo.max_freq : policy->cur;
 145
 146         freq = (freq + (freq >> 2)) * util / max;
 147
 148         if (freq == sg_cpu->cached_raw_freq && sg_policy->next_freq != UINT_MAX)
 149                 return sg_policy->next_freq;
 150         sg_cpu->cached_raw_freq = freq;
 151         return cpufreq_driver_resolve_freq(policy, freq);
 152 }
 153
 154 static void sugov_get_util(unsigned long *util, unsigned long *max)
 155 {
 156         struct rq *rq = this_rq();
 157         unsigned long cfs_max;
 158
 159         cfs_max = arch_scale_cpu_capacity(NULL, smp_processor_id());
 160
 161         *util = min(rq->cfs.avg.util_avg, cfs_max);
 162         *max = cfs_max;
 163 }
 164
 165 static void sugov_set_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
 166                                    unsigned int flags)
 167 {
 168         if (flags & SCHED_CPUFREQ_IOWAIT) {
 169                 sg_cpu->iowait_boost = sg_cpu->iowait_boost_max;
 170         } else if (sg_cpu->iowait_boost) {
 171                 s64 delta_ns = time - sg_cpu->last_update;
 172
 173                 /* Clear iowait_boost if the CPU apprears to have been idle. */
 174                 if (delta_ns > TICK_NSEC)
 175                         sg_cpu->iowait_boost = 0;
 176         }
 177 }
 178
 179 static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, unsigned long *util,
 180                                unsigned long *max)
 181 {
 182         unsigned long boost_util = sg_cpu->iowait_boost;
 183         unsigned long boost_max = sg_cpu->iowait_boost_max;
 184
 185         if (!boost_util)
 186                 return;
 187
 188         if (*util * boost_max < *max * boost_util) {
 189                 *util = boost_util;
 190                 *max = boost_max;
 191         }
 192         sg_cpu->iowait_boost >>= 1;
 193 }
 194
 195 static void sugov_update_single(struct update_util_data *hook, u64 time,
 196                                 unsigned int flags)
 197 {
 198         struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
 199         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
 200         struct cpufreq_policy *policy = sg_policy->policy;
 201         unsigned long util, max;
 202         unsigned int next_f;
 203
 204         sugov_set_iowait_boost(sg_cpu, time, flags);
 205         sg_cpu->last_update = time;
 206
 207         if (!sugov_should_update_freq(sg_policy, time))
 208                 return;
 209
 210         if (flags & SCHED_CPUFREQ_RT_DL) {
 211                 next_f = policy->cpuinfo.max_freq;
 212         } else {
 213                 sugov_get_util(&util, &max);
 214                 sugov_iowait_boost(sg_cpu, &util, &max);
 215                 next_f = get_next_freq(sg_cpu, util, max);
 216         }
 217         sugov_update_commit(sg_policy, time, next_f);
 218 }
 219
 220 static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu,
 221                                            unsigned long util, unsigned long max,
 222                                            unsigned int flags)
 223 {
 224         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
 225         struct cpufreq_policy *policy = sg_policy->policy;
 226         unsigned int max_f = policy->cpuinfo.max_freq;
 227         u64 last_freq_update_time = sg_policy->last_freq_update_time;
 228         unsigned int j;
 229
 230         if (flags & SCHED_CPUFREQ_RT_DL)
 231                 return max_f;
 232
 233         sugov_iowait_boost(sg_cpu, &util, &max);
 234
 235         for_each_cpu(j, policy->cpus) {
 236                 struct sugov_cpu *j_sg_cpu;
 237                 unsigned long j_util, j_max;
 238                 s64 delta_ns;
 239
 240                 if (j == smp_processor_id())
 241                         continue;
 242
 243                 j_sg_cpu = &per_cpu(sugov_cpu, j);
 244                 /*
 245                  * If the CPU utilization was last updated before the previous
 246                  * frequency update and the time elapsed between the last update
 247                  * of the CPU utilization and the last frequency update is long
 248                  * enough, don't take the CPU into account as it probably is
 249                  * idle now (and clear iowait_boost for it).
 250                  */
 251                 delta_ns = last_freq_update_time - j_sg_cpu->last_update;
 252                 if (delta_ns > TICK_NSEC) {
 253                         j_sg_cpu->iowait_boost = 0;
 254                         continue;
 255                 }
 256                 if (j_sg_cpu->flags & SCHED_CPUFREQ_RT_DL)
 257                         return max_f;
 258
 259                 j_util = j_sg_cpu->util;
 260                 j_max = j_sg_cpu->max;
 261                 if (j_util * max > j_max * util) {
 262                         util = j_util;
 263                         max = j_max;
 264                 }
 265
 266                 sugov_iowait_boost(j_sg_cpu, &util, &max);
 267         }
 268
 269         return get_next_freq(sg_cpu, util, max);
 270 }
 271
 272 static void sugov_update_shared(struct update_util_data *hook, u64 time,
 273                                 unsigned int flags)
 274 {
 275         struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
 276         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
 277         unsigned long util, max;
 278         unsigned int next_f;
 279
 280         sugov_get_util(&util, &max);
 281
 282         raw_spin_lock(&sg_policy->update_lock);
 283
 284         sg_cpu->util = util;
 285         sg_cpu->max = max;
 286         sg_cpu->flags = flags;
 287
 288         sugov_set_iowait_boost(sg_cpu, time, flags);
 289         sg_cpu->last_update = time;
 290
 291         if (sugov_should_update_freq(sg_policy, time)) {
 292                 next_f = sugov_next_freq_shared(sg_cpu, util, max, flags);
 293                 sugov_update_commit(sg_policy, time, next_f);
 294         }
 295
 296         raw_spin_unlock(&sg_policy->update_lock);
 297 }
 298
 299 static void sugov_work(struct kthread_work *work)
 300 {
 301         struct sugov_policy *sg_policy = container_of(work, struct sugov_policy, work);
 302
 303         mutex_lock(&sg_policy->work_lock);
 304         __cpufreq_driver_target(sg_policy->policy, sg_policy->next_freq,
 305                                 CPUFREQ_RELATION_L);
 306         mutex_unlock(&sg_policy->work_lock);
 307
 308         sg_policy->work_in_progress = false;
 309 }
 310
 311 static void sugov_irq_work(struct irq_work *irq_work)
 312 {
 313         struct sugov_policy *sg_policy;
 314
 315         sg_policy = container_of(irq_work, struct sugov_policy, irq_work);
 316
 317         /*
 318          * For RT and deadline tasks, the schedutil governor shoots the
 319          * frequency to maximum. Special care must be taken to ensure that this
 320          * kthread doesn't result in the same behavior.
 321          *
 322          * This is (mostly) guaranteed by the work_in_progress flag. The flag is
 323          * updated only at the end of the sugov_work() function and before that
 324          * the schedutil governor rejects all other frequency scaling requests.
 325          *
 326          * There is a very rare case though, where the RT thread yields right
 327          * after the work_in_progress flag is cleared. The effects of that are
 328          * neglected for now.
 329          */
 330         kthread_queue_work(&sg_policy->worker, &sg_policy->work);
 331 }
 332
 333 /************************** sysfs interface ************************/
 334
 335 static struct sugov_tunables *global_tunables;
 336 static DEFINE_MUTEX(global_tunables_lock);
 337
 338 static inline struct sugov_tunables *to_sugov_tunables(struct gov_attr_set *attr_set)
 339 {
 340         return container_of(attr_set, struct sugov_tunables, attr_set);
 341 }
 342
 343 static ssize_t rate_limit_us_show(struct gov_attr_set *attr_set, char *buf)
 344 {
 345         struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
 346
 347         return sprintf(buf, "%u\n", tunables->rate_limit_us);
 348 }
 349
 350 static ssize_t rate_limit_us_store(struct gov_attr_set *attr_set, const char *buf,
 351                                    size_t count)
 352 {
 353         struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
 354         struct sugov_policy *sg_policy;
 355         unsigned int rate_limit_us;
 356
 357         if (kstrtouint(buf, 10, &rate_limit_us))
 358                 return -EINVAL;
 359
 360         tunables->rate_limit_us = rate_limit_us;
 361
 362         list_for_each_entry(sg_policy, &attr_set->policy_list, tunables_hook)
 363                 sg_policy->freq_update_delay_ns = rate_limit_us * NSEC_PER_USEC;
 364
 365         return count;
 366 }
 367
 368 static struct governor_attr rate_limit_us = __ATTR_RW(rate_limit_us);
 369
 370 static struct attribute *sugov_attributes[] = {
 371         &rate_limit_us.attr,
 372         NULL
 373 };
 374
 375 static struct kobj_type sugov_tunables_ktype = {
 376         .default_attrs = sugov_attributes,
 377         .sysfs_ops = &governor_sysfs_ops,
 378 };
 379
 380 /********************** cpufreq governor interface *********************/
 381
 382 static struct cpufreq_governor schedutil_gov;
 383
 384 static struct sugov_policy *sugov_policy_alloc(struct cpufreq_policy *policy)
 385 {
 386         struct sugov_policy *sg_policy;
 387
 388         sg_policy = kzalloc(sizeof(*sg_policy), GFP_KERNEL);
 389         if (!sg_policy)
 390                 return NULL;
 391
 392         sg_policy->policy = policy;
 393         raw_spin_lock_init(&sg_policy->update_lock);
 394         return sg_policy;
 395 }
 396
 397 static void sugov_policy_free(struct sugov_policy *sg_policy)
 398 {
 399         kfree(sg_policy);
 400 }
 401
 402 static int sugov_kthread_create(struct sugov_policy *sg_policy)
 403 {
 404         struct task_struct *thread;
 405         struct sched_param param = { .sched_priority = MAX_USER_RT_PRIO / 2 };
 406         struct cpufreq_policy *policy = sg_policy->policy;
 407         int ret;
 408
 409         /* kthread only required for slow path */
 410         if (policy->fast_switch_enabled)
 411                 return 0;
 412
 413         kthread_init_work(&sg_policy->work, sugov_work);
 414         kthread_init_worker(&sg_policy->worker);
 415         thread = kthread_create(kthread_worker_fn, &sg_policy->worker,
 416                                 "sugov:%d",
 417                                 cpumask_first(policy->related_cpus));
 418         if (IS_ERR(thread)) {
 419                 pr_err("failed to create sugov thread: %ld\n", PTR_ERR(thread));
 420                 return PTR_ERR(thread);
 421         }
 422
 423         ret = sched_setscheduler_nocheck(thread, SCHED_FIFO, &param);
 424         if (ret) {
 425                 kthread_stop(thread);
 426                 pr_warn("%s: failed to set SCHED_FIFO\n", __func__);
 427                 return ret;
 428         }
 429
 430         sg_policy->thread = thread;
 431         kthread_bind_mask(thread, policy->related_cpus);
 432         init_irq_work(&sg_policy->irq_work, sugov_irq_work);
 433         mutex_init(&sg_policy->work_lock);
 434
 435         wake_up_process(thread);
 436
 437         return 0;
 438 }
 439
 440 static void sugov_kthread_stop(struct sugov_policy *sg_policy)
 441 {
 442         /* kthread only required for slow path */
 443         if (sg_policy->policy->fast_switch_enabled)
 444                 return;
 445
 446         kthread_flush_worker(&sg_policy->worker);
 447         kthread_stop(sg_policy->thread);
 448         mutex_destroy(&sg_policy->work_lock);
 449 }
 450
 451 static struct sugov_tunables *sugov_tunables_alloc(struct sugov_policy *sg_policy)
 452 {
 453         struct sugov_tunables *tunables;
 454
 455         tunables = kzalloc(sizeof(*tunables), GFP_KERNEL);
 456         if (tunables) {
 457                 gov_attr_set_init(&tunables->attr_set, &sg_policy->tunables_hook);
 458                 if (!have_governor_per_policy())
 459                         global_tunables = tunables;
 460         }
 461         return tunables;
 462 }
 463
 464 static void sugov_tunables_free(struct sugov_tunables *tunables)
 465 {
 466         if (!have_governor_per_policy())
 467                 global_tunables = NULL;
 468
 469         kfree(tunables);
 470 }
 471
 472 static int sugov_init(struct cpufreq_policy *policy)
 473 {
 474         struct sugov_policy *sg_policy;
 475         struct sugov_tunables *tunables;
 476         unsigned int lat;
 477         int ret = 0;
 478
 479         /* State should be equivalent to EXIT */
 480         if (policy->governor_data)
 481                 return -EBUSY;
 482
 483         cpufreq_enable_fast_switch(policy);
 484
 485         sg_policy = sugov_policy_alloc(policy);
 486         if (!sg_policy) {
 487                 ret = -ENOMEM;
 488                 goto disable_fast_switch;
 489         }
 490
 491         ret = sugov_kthread_create(sg_policy);
 492         if (ret)
 493                 goto free_sg_policy;
 494
 495         mutex_lock(&global_tunables_lock);
 496
 497         if (global_tunables) {
 498                 if (WARN_ON(have_governor_per_policy())) {
 499                         ret = -EINVAL;
 500                         goto stop_kthread;
 501                 }
 502                 policy->governor_data = sg_policy;
 503                 sg_policy->tunables = global_tunables;
 504
 505                 gov_attr_set_get(&global_tunables->attr_set, &sg_policy->tunables_hook);
 506                 goto out;
 507         }
 508
 509         tunables = sugov_tunables_alloc(sg_policy);
 510         if (!tunables) {
 511                 ret = -ENOMEM;
 512                 goto stop_kthread;
 513         }
 514
 515         tunables->rate_limit_us = LATENCY_MULTIPLIER;
 516         lat = policy->cpuinfo.transition_latency / NSEC_PER_USEC;
 517         if (lat)
 518                 tunables->rate_limit_us *= lat;
 519
 520         policy->governor_data = sg_policy;
 521         sg_policy->tunables = tunables;
 522
 523         ret = kobject_init_and_add(&tunables->attr_set.kobj, &sugov_tunables_ktype,
 524                                    get_governor_parent_kobj(policy), "%s",
 525                                    schedutil_gov.name);
 526         if (ret)
 527                 goto fail;
 528
 529 out:
 530         mutex_unlock(&global_tunables_lock);
 531         return 0;
 532
 533 fail:
 534         policy->governor_data = NULL;
 535         sugov_tunables_free(tunables);
 536
 537 stop_kthread:
 538         sugov_kthread_stop(sg_policy);
 539
 540 free_sg_policy:
 541         mutex_unlock(&global_tunables_lock);
 542
 543         sugov_policy_free(sg_policy);
 544
 545 disable_fast_switch:
 546         cpufreq_disable_fast_switch(policy);
 547
 548         pr_err("initialization failed (error %d)\n", ret);
 549         return ret;
 550 }
 551
 552 static void sugov_exit(struct cpufreq_policy *policy)
 553 {
 554         struct sugov_policy *sg_policy = policy->governor_data;
 555         struct sugov_tunables *tunables = sg_policy->tunables;
 556         unsigned int count;
 557
 558         mutex_lock(&global_tunables_lock);
 559
 560         count = gov_attr_set_put(&tunables->attr_set, &sg_policy->tunables_hook);
 561         policy->governor_data = NULL;
 562         if (!count)
 563                 sugov_tunables_free(tunables);
 564
 565         mutex_unlock(&global_tunables_lock);
 566
 567         sugov_kthread_stop(sg_policy);
 568         sugov_policy_free(sg_policy);
 569         cpufreq_disable_fast_switch(policy);
 570 }
 571
 572 static int sugov_start(struct cpufreq_policy *policy)
 573 {
 574         struct sugov_policy *sg_policy = policy->governor_data;
 575         unsigned int cpu;
 576
 577         sg_policy->freq_update_delay_ns = sg_policy->tunables->rate_limit_us * NSEC_PER_USEC;
 578         sg_policy->last_freq_update_time = 0;
 579         sg_policy->next_freq = UINT_MAX;
 580         sg_policy->work_in_progress = false;
 581         sg_policy->need_freq_update = false;
 582
 583         for_each_cpu(cpu, policy->cpus) {
 584                 struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu);
 585
 586                 sg_cpu->sg_policy = sg_policy;
 587                 if (policy_is_shared(policy)) {
 588                         sg_cpu->util = 0;
 589                         sg_cpu->max = 0;
 590                         sg_cpu->flags = SCHED_CPUFREQ_RT;
 591                         sg_cpu->last_update = 0;
 592                         sg_cpu->cached_raw_freq = 0;
 593                         sg_cpu->iowait_boost = 0;
 594                         sg_cpu->iowait_boost_max = policy->cpuinfo.max_freq;
 595                         cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util,
 596                                                      sugov_update_shared);
 597                 } else {
 598                         cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util,
 599                                                      sugov_update_single);
 600                 }
 601         }
 602         return 0;
 603 }
 604
 605 static void sugov_stop(struct cpufreq_policy *policy)
 606 {
 607         struct sugov_policy *sg_policy = policy->governor_data;
 608         unsigned int cpu;
 609
 610         for_each_cpu(cpu, policy->cpus)
 611                 cpufreq_remove_update_util_hook(cpu);
 612
 613         synchronize_sched();
 614
 615         if (!policy->fast_switch_enabled) {
 616                 irq_work_sync(&sg_policy->irq_work);
 617                 kthread_cancel_work_sync(&sg_policy->work);
 618         }
 619 }
 620
 621 static void sugov_limits(struct cpufreq_policy *policy)
 622 {
 623         struct sugov_policy *sg_policy = policy->governor_data;
 624
 625         if (!policy->fast_switch_enabled) {
 626                 mutex_lock(&sg_policy->work_lock);
 627                 cpufreq_policy_apply_limits(policy);
 628                 mutex_unlock(&sg_policy->work_lock);
 629         }
 630
 631         sg_policy->need_freq_update = true;
 632 }
 633
 634 static struct cpufreq_governor schedutil_gov = {
 635         .name = "schedutil",
 636         .owner = THIS_MODULE,
 637         .init = sugov_init,
 638         .exit = sugov_exit,
 639         .start = sugov_start,
 640         .stop = sugov_stop,
 641         .limits = sugov_limits,
 642 };
 643
 644 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL
 645 struct cpufreq_governor *cpufreq_default_governor(void)
 646 {
 647         return &schedutil_gov;
 648 }
 649 #endif
 650
 651 static int __init sugov_register(void)
 652 {
 653         return cpufreq_register_governor(&schedutil_gov);
 654 }
 655 fs_initcall(sugov_register);