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 <uapi/linux/sched/types.h>
  17 #include <linux/slab.h>
  18 #include <trace/events/power.h>
  19
  20 #include "sched.h"
  21
  22 #define SUGOV_KTHREAD_PRIORITY  50
  23
  24 struct sugov_tunables {
  25         struct gov_attr_set attr_set;
  26         unsigned int rate_limit_us;
  27 };
  28
  29 struct sugov_policy {
  30         struct cpufreq_policy *policy;
  31
  32         struct sugov_tunables *tunables;
  33         struct list_head tunables_hook;
  34
  35         raw_spinlock_t update_lock;  /* For shared policies */
  36         u64 last_freq_update_time;
  37         s64 freq_update_delay_ns;
  38         unsigned int next_freq;
  39         unsigned int cached_raw_freq;
  40
  41         /* The next fields are only needed if fast switch cannot be used. */
  42         struct irq_work irq_work;
  43         struct kthread_work work;
  44         struct mutex work_lock;
  45         struct kthread_worker worker;
  46         struct task_struct *thread;
  47         bool work_in_progress;
  48
  49         bool need_freq_update;
  50 };
  51
  52 struct sugov_cpu {
  53         struct update_util_data update_util;
  54         struct sugov_policy *sg_policy;
  55
  56         unsigned long iowait_boost;
  57         unsigned long iowait_boost_max;
  58         u64 last_update;
  59
  60         /* The fields below are only needed when sharing a policy. */
  61         unsigned long util;
  62         unsigned long max;
  63         unsigned int flags;
  64
  65         /* The field below is for single-CPU policies only. */
  66 #ifdef CONFIG_NO_HZ_COMMON
  67         unsigned long saved_idle_calls;
  68 #endif
  69 };
  70
  71 static DEFINE_PER_CPU(struct sugov_cpu, sugov_cpu);
  72
  73 /************************ Governor internals ***********************/
  74
  75 static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
  76 {
  77         s64 delta_ns;
  78
  79         if (sg_policy->work_in_progress)
  80                 return false;
  81
  82         if (unlikely(sg_policy->need_freq_update)) {
  83                 sg_policy->need_freq_update = false;
  84                 /*
  85                  * This happens when limits change, so forget the previous
  86                  * next_freq value and force an update.
  87                  */
  88                 sg_policy->next_freq = UINT_MAX;
  89                 return true;
  90         }
  91
  92         delta_ns = time - sg_policy->last_freq_update_time;
  93         return delta_ns >= sg_policy->freq_update_delay_ns;
  94 }
  95
  96 static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
  97                                 unsigned int next_freq)
  98 {
  99         struct cpufreq_policy *policy = sg_policy->policy;
 100
 101         if (sg_policy->next_freq == next_freq)
 102                 return;
 103
 104         sg_policy->next_freq = next_freq;
 105         sg_policy->last_freq_update_time = time;
 106
 107         if (policy->fast_switch_enabled) {
 108                 next_freq = cpufreq_driver_fast_switch(policy, next_freq);
 109                 if (next_freq == CPUFREQ_ENTRY_INVALID)
 110                         return;
 111
 112                 policy->cur = next_freq;
 113                 trace_cpu_frequency(next_freq, smp_processor_id());
 114         } else {
 115                 sg_policy->work_in_progress = true;
 116                 irq_work_queue(&sg_policy->irq_work);
 117         }
 118 }
 119
 120 /**
 121  * get_next_freq - Compute a new frequency for a given cpufreq policy.
 122  * @sg_policy: schedutil policy object to compute the new frequency for.
 123  * @util: Current CPU utilization.
 124  * @max: CPU capacity.
 125  *
 126  * If the utilization is frequency-invariant, choose the new frequency to be
 127  * proportional to it, that is
 128  *
 129  * next_freq = C * max_freq * util / max
 130  *
 131  * Otherwise, approximate the would-be frequency-invariant utilization by
 132  * util_raw * (curr_freq / max_freq) which leads to
 133  *
 134  * next_freq = C * curr_freq * util_raw / max
 135  *
 136  * Take C = 1.25 for the frequency tipping point at (util / max) = 0.8.
 137  *
 138  * The lowest driver-supported frequency which is equal or greater than the raw
 139  * next_freq (as calculated above) is returned, subject to policy min/max and
 140  * cpufreq driver limitations.
 141  */
 142 static unsigned int get_next_freq(struct sugov_policy *sg_policy,
 143                                   unsigned long util, unsigned long max)
 144 {
 145         struct cpufreq_policy *policy = sg_policy->policy;
 146         unsigned int freq = arch_scale_freq_invariant() ?
 147                                 policy->cpuinfo.max_freq : policy->cur;
 148
 149         freq = (freq + (freq >> 2)) * util / max;
 150
 151         if (freq == sg_policy->cached_raw_freq && sg_policy->next_freq != UINT_MAX)
 152                 return sg_policy->next_freq;
 153         sg_policy->cached_raw_freq = freq;
 154         return cpufreq_driver_resolve_freq(policy, freq);
 155 }
 156
 157 static void sugov_get_util(unsigned long *util, unsigned long *max)
 158 {
 159         struct rq *rq = this_rq();
 160         unsigned long cfs_max;
 161
 162         cfs_max = arch_scale_cpu_capacity(NULL, smp_processor_id());
 163
 164         *util = min(rq->cfs.avg.util_avg, cfs_max);
 165         *max = cfs_max;
 166 }
 167
 168 static void sugov_set_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
 169                                    unsigned int flags)
 170 {
 171         if (flags & SCHED_CPUFREQ_IOWAIT) {
 172                 sg_cpu->iowait_boost = sg_cpu->iowait_boost_max;
 173         } else if (sg_cpu->iowait_boost) {
 174                 s64 delta_ns = time - sg_cpu->last_update;
 175
 176                 /* Clear iowait_boost if the CPU apprears to have been idle. */
 177                 if (delta_ns > TICK_NSEC)
 178                         sg_cpu->iowait_boost = 0;
 179         }
 180 }
 181
 182 static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, unsigned long *util,
 183                                unsigned long *max)
 184 {
 185         unsigned long boost_util = sg_cpu->iowait_boost;
 186         unsigned long boost_max = sg_cpu->iowait_boost_max;
 187
 188         if (!boost_util)
 189                 return;
 190
 191         if (*util * boost_max < *max * boost_util) {
 192                 *util = boost_util;
 193                 *max = boost_max;
 194         }
 195         sg_cpu->iowait_boost >>= 1;
 196 }
 197
 198 #ifdef CONFIG_NO_HZ_COMMON
 199 static bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu)
 200 {
 201         unsigned long idle_calls = tick_nohz_get_idle_calls();
 202         bool ret = idle_calls == sg_cpu->saved_idle_calls;
 203
 204         sg_cpu->saved_idle_calls = idle_calls;
 205         return ret;
 206 }
 207 #else
 208 static inline bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu) { return false; }
 209 #endif /* CONFIG_NO_HZ_COMMON */
 210
 211 static void sugov_update_single(struct update_util_data *hook, u64 time,
 212                                 unsigned int flags)
 213 {
 214         struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
 215         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
 216         struct cpufreq_policy *policy = sg_policy->policy;
 217         unsigned long util, max;
 218         unsigned int next_f;
 219         bool busy;
 220
 221         sugov_set_iowait_boost(sg_cpu, time, flags);
 222         sg_cpu->last_update = time;
 223
 224         if (!sugov_should_update_freq(sg_policy, time))
 225                 return;
 226
 227         busy = sugov_cpu_is_busy(sg_cpu);
 228
 229         if (flags & SCHED_CPUFREQ_RT_DL) {
 230                 next_f = policy->cpuinfo.max_freq;
 231         } else {
 232                 sugov_get_util(&util, &max);
 233                 sugov_iowait_boost(sg_cpu, &util, &max);
 234                 next_f = get_next_freq(sg_policy, util, max);
 235                 /*
 236                  * Do not reduce the frequency if the CPU has not been idle
 237                  * recently, as the reduction is likely to be premature then.
 238                  */
 239                 if (busy && next_f < sg_policy->next_freq)
 240                         next_f = sg_policy->next_freq;
 241         }
 242         sugov_update_commit(sg_policy, time, next_f);
 243 }
 244
 245 static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
 246 {
 247         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
 248         struct cpufreq_policy *policy = sg_policy->policy;
 249         unsigned long util = 0, max = 1;
 250         unsigned int j;
 251
 252         for_each_cpu(j, policy->cpus) {
 253                 struct sugov_cpu *j_sg_cpu = &per_cpu(sugov_cpu, j);
 254                 unsigned long j_util, j_max;
 255                 s64 delta_ns;
 256
 257                 /*
 258                  * If the CPU utilization was last updated before the previous
 259                  * frequency update and the time elapsed between the last update
 260                  * of the CPU utilization and the last frequency update is long
 261                  * enough, don't take the CPU into account as it probably is
 262                  * idle now (and clear iowait_boost for it).
 263                  */
 264                 delta_ns = time - j_sg_cpu->last_update;
 265                 if (delta_ns > TICK_NSEC) {
 266                         j_sg_cpu->iowait_boost = 0;
 267                         continue;
 268                 }
 269                 if (j_sg_cpu->flags & SCHED_CPUFREQ_RT_DL)
 270                         return policy->cpuinfo.max_freq;
 271
 272                 j_util = j_sg_cpu->util;
 273                 j_max = j_sg_cpu->max;
 274                 if (j_util * max > j_max * util) {
 275                         util = j_util;
 276                         max = j_max;
 277                 }
 278
 279                 sugov_iowait_boost(j_sg_cpu, &util, &max);
 280         }
 281
 282         return get_next_freq(sg_policy, util, max);
 283 }
 284
 285 static void sugov_update_shared(struct update_util_data *hook, u64 time,
 286                                 unsigned int flags)
 287 {
 288         struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
 289         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
 290         unsigned long util, max;
 291         unsigned int next_f;
 292
 293         sugov_get_util(&util, &max);
 294
 295         raw_spin_lock(&sg_policy->update_lock);
 296
 297         sg_cpu->util = util;
 298         sg_cpu->max = max;
 299         sg_cpu->flags = flags;
 300
 301         sugov_set_iowait_boost(sg_cpu, time, flags);
 302         sg_cpu->last_update = time;
 303
 304         if (sugov_should_update_freq(sg_policy, time)) {
 305                 if (flags & SCHED_CPUFREQ_RT_DL)
 306                         next_f = sg_policy->policy->cpuinfo.max_freq;
 307                 else
 308                         next_f = sugov_next_freq_shared(sg_cpu, time);
 309
 310                 sugov_update_commit(sg_policy, time, next_f);
 311         }
 312
 313         raw_spin_unlock(&sg_policy->update_lock);
 314 }
 315
 316 static void sugov_work(struct kthread_work *work)
 317 {
 318         struct sugov_policy *sg_policy = container_of(work, struct sugov_policy, work);
 319
 320         mutex_lock(&sg_policy->work_lock);
 321         __cpufreq_driver_target(sg_policy->policy, sg_policy->next_freq,
 322                                 CPUFREQ_RELATION_L);
 323         mutex_unlock(&sg_policy->work_lock);
 324
 325         sg_policy->work_in_progress = false;
 326 }
 327
 328 static void sugov_irq_work(struct irq_work *irq_work)
 329 {
 330         struct sugov_policy *sg_policy;
 331
 332         sg_policy = container_of(irq_work, struct sugov_policy, irq_work);
 333
 334         /*
 335          * For RT and deadline tasks, the schedutil governor shoots the
 336          * frequency to maximum. Special care must be taken to ensure that this
 337          * kthread doesn't result in the same behavior.
 338          *
 339          * This is (mostly) guaranteed by the work_in_progress flag. The flag is
 340          * updated only at the end of the sugov_work() function and before that
 341          * the schedutil governor rejects all other frequency scaling requests.
 342          *
 343          * There is a very rare case though, where the RT thread yields right
 344          * after the work_in_progress flag is cleared. The effects of that are
 345          * neglected for now.
 346          */
 347         kthread_queue_work(&sg_policy->worker, &sg_policy->work);
 348 }
 349
 350 /************************** sysfs interface ************************/
 351
 352 static struct sugov_tunables *global_tunables;
 353 static DEFINE_MUTEX(global_tunables_lock);
 354
 355 static inline struct sugov_tunables *to_sugov_tunables(struct gov_attr_set *attr_set)
 356 {
 357         return container_of(attr_set, struct sugov_tunables, attr_set);
 358 }
 359
 360 static ssize_t rate_limit_us_show(struct gov_attr_set *attr_set, char *buf)
 361 {
 362         struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
 363
 364         return sprintf(buf, "%u\n", tunables->rate_limit_us);
 365 }
 366
 367 static ssize_t rate_limit_us_store(struct gov_attr_set *attr_set, const char *buf,
 368                                    size_t count)
 369 {
 370         struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
 371         struct sugov_policy *sg_policy;
 372         unsigned int rate_limit_us;
 373
 374         if (kstrtouint(buf, 10, &rate_limit_us))
 375                 return -EINVAL;
 376
 377         tunables->rate_limit_us = rate_limit_us;
 378
 379         list_for_each_entry(sg_policy, &attr_set->policy_list, tunables_hook)
 380                 sg_policy->freq_update_delay_ns = rate_limit_us * NSEC_PER_USEC;
 381
 382         return count;
 383 }
 384
 385 static struct governor_attr rate_limit_us = __ATTR_RW(rate_limit_us);
 386
 387 static struct attribute *sugov_attributes[] = {
 388         &rate_limit_us.attr,
 389         NULL
 390 };
 391
 392 static struct kobj_type sugov_tunables_ktype = {
 393         .default_attrs = sugov_attributes,
 394         .sysfs_ops = &governor_sysfs_ops,
 395 };
 396
 397 /********************** cpufreq governor interface *********************/
 398
 399 static struct cpufreq_governor schedutil_gov;
 400
 401 static struct sugov_policy *sugov_policy_alloc(struct cpufreq_policy *policy)
 402 {
 403         struct sugov_policy *sg_policy;
 404
 405         sg_policy = kzalloc(sizeof(*sg_policy), GFP_KERNEL);
 406         if (!sg_policy)
 407                 return NULL;
 408
 409         sg_policy->policy = policy;
 410         raw_spin_lock_init(&sg_policy->update_lock);
 411         return sg_policy;
 412 }
 413
 414 static void sugov_policy_free(struct sugov_policy *sg_policy)
 415 {
 416         kfree(sg_policy);
 417 }
 418
 419 static int sugov_kthread_create(struct sugov_policy *sg_policy)
 420 {
 421         struct task_struct *thread;
 422         struct sched_param param = { .sched_priority = MAX_USER_RT_PRIO / 2 };
 423         struct cpufreq_policy *policy = sg_policy->policy;
 424         int ret;
 425
 426         /* kthread only required for slow path */
 427         if (policy->fast_switch_enabled)
 428                 return 0;
 429
 430         kthread_init_work(&sg_policy->work, sugov_work);
 431         kthread_init_worker(&sg_policy->worker);
 432         thread = kthread_create(kthread_worker_fn, &sg_policy->worker,
 433                                 "sugov:%d",
 434                                 cpumask_first(policy->related_cpus));
 435         if (IS_ERR(thread)) {
 436                 pr_err("failed to create sugov thread: %ld\n", PTR_ERR(thread));
 437                 return PTR_ERR(thread);
 438         }
 439
 440         ret = sched_setscheduler_nocheck(thread, SCHED_FIFO, &param);
 441         if (ret) {
 442                 kthread_stop(thread);
 443                 pr_warn("%s: failed to set SCHED_FIFO\n", __func__);
 444                 return ret;
 445         }
 446
 447         sg_policy->thread = thread;
 448         kthread_bind_mask(thread, policy->related_cpus);
 449         init_irq_work(&sg_policy->irq_work, sugov_irq_work);
 450         mutex_init(&sg_policy->work_lock);
 451
 452         wake_up_process(thread);
 453
 454         return 0;
 455 }
 456
 457 static void sugov_kthread_stop(struct sugov_policy *sg_policy)
 458 {
 459         /* kthread only required for slow path */
 460         if (sg_policy->policy->fast_switch_enabled)
 461                 return;
 462
 463         kthread_flush_worker(&sg_policy->worker);
 464         kthread_stop(sg_policy->thread);
 465         mutex_destroy(&sg_policy->work_lock);
 466 }
 467
 468 static struct sugov_tunables *sugov_tunables_alloc(struct sugov_policy *sg_policy)
 469 {
 470         struct sugov_tunables *tunables;
 471
 472         tunables = kzalloc(sizeof(*tunables), GFP_KERNEL);
 473         if (tunables) {
 474                 gov_attr_set_init(&tunables->attr_set, &sg_policy->tunables_hook);
 475                 if (!have_governor_per_policy())
 476                         global_tunables = tunables;
 477         }
 478         return tunables;
 479 }
 480
 481 static void sugov_tunables_free(struct sugov_tunables *tunables)
 482 {
 483         if (!have_governor_per_policy())
 484                 global_tunables = NULL;
 485
 486         kfree(tunables);
 487 }
 488
 489 static int sugov_init(struct cpufreq_policy *policy)
 490 {
 491         struct sugov_policy *sg_policy;
 492         struct sugov_tunables *tunables;
 493         int ret = 0;
 494
 495         /* State should be equivalent to EXIT */
 496         if (policy->governor_data)
 497                 return -EBUSY;
 498
 499         cpufreq_enable_fast_switch(policy);
 500
 501         sg_policy = sugov_policy_alloc(policy);
 502         if (!sg_policy) {
 503                 ret = -ENOMEM;
 504                 goto disable_fast_switch;
 505         }
 506
 507         ret = sugov_kthread_create(sg_policy);
 508         if (ret)
 509                 goto free_sg_policy;
 510
 511         mutex_lock(&global_tunables_lock);
 512
 513         if (global_tunables) {
 514                 if (WARN_ON(have_governor_per_policy())) {
 515                         ret = -EINVAL;
 516                         goto stop_kthread;
 517                 }
 518                 policy->governor_data = sg_policy;
 519                 sg_policy->tunables = global_tunables;
 520
 521                 gov_attr_set_get(&global_tunables->attr_set, &sg_policy->tunables_hook);
 522                 goto out;
 523         }
 524
 525         tunables = sugov_tunables_alloc(sg_policy);
 526         if (!tunables) {
 527                 ret = -ENOMEM;
 528                 goto stop_kthread;
 529         }
 530
 531         if (policy->transition_delay_us) {
 532                 tunables->rate_limit_us = policy->transition_delay_us;
 533         } else {
 534                 unsigned int lat;
 535
 536                 tunables->rate_limit_us = LATENCY_MULTIPLIER;
 537                 lat = policy->cpuinfo.transition_latency / NSEC_PER_USEC;
 538                 if (lat)
 539                         tunables->rate_limit_us *= lat;
 540         }
 541
 542         policy->governor_data = sg_policy;
 543         sg_policy->tunables = tunables;
 544
 545         ret = kobject_init_and_add(&tunables->attr_set.kobj, &sugov_tunables_ktype,
 546                                    get_governor_parent_kobj(policy), "%s",
 547                                    schedutil_gov.name);
 548         if (ret)
 549                 goto fail;
 550
 551 out:
 552         mutex_unlock(&global_tunables_lock);
 553         return 0;
 554
 555 fail:
 556         policy->governor_data = NULL;
 557         sugov_tunables_free(tunables);
 558
 559 stop_kthread:
 560         sugov_kthread_stop(sg_policy);
 561
 562 free_sg_policy:
 563         mutex_unlock(&global_tunables_lock);
 564
 565         sugov_policy_free(sg_policy);
 566
 567 disable_fast_switch:
 568         cpufreq_disable_fast_switch(policy);
 569
 570         pr_err("initialization failed (error %d)\n", ret);
 571         return ret;
 572 }
 573
 574 static void sugov_exit(struct cpufreq_policy *policy)
 575 {
 576         struct sugov_policy *sg_policy = policy->governor_data;
 577         struct sugov_tunables *tunables = sg_policy->tunables;
 578         unsigned int count;
 579
 580         mutex_lock(&global_tunables_lock);
 581
 582         count = gov_attr_set_put(&tunables->attr_set, &sg_policy->tunables_hook);
 583         policy->governor_data = NULL;
 584         if (!count)
 585                 sugov_tunables_free(tunables);
 586
 587         mutex_unlock(&global_tunables_lock);
 588
 589         sugov_kthread_stop(sg_policy);
 590         sugov_policy_free(sg_policy);
 591         cpufreq_disable_fast_switch(policy);
 592 }
 593
 594 static int sugov_start(struct cpufreq_policy *policy)
 595 {
 596         struct sugov_policy *sg_policy = policy->governor_data;
 597         unsigned int cpu;
 598
 599         sg_policy->freq_update_delay_ns = sg_policy->tunables->rate_limit_us * NSEC_PER_USEC;
 600         sg_policy->last_freq_update_time = 0;
 601         sg_policy->next_freq = UINT_MAX;
 602         sg_policy->work_in_progress = false;
 603         sg_policy->need_freq_update = false;
 604         sg_policy->cached_raw_freq = 0;
 605
 606         for_each_cpu(cpu, policy->cpus) {
 607                 struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu);
 608
 609                 memset(sg_cpu, 0, sizeof(*sg_cpu));
 610                 sg_cpu->sg_policy = sg_policy;
 611                 sg_cpu->flags = SCHED_CPUFREQ_RT;
 612                 sg_cpu->iowait_boost_max = policy->cpuinfo.max_freq;
 613         }
 614
 615         for_each_cpu(cpu, policy->cpus) {
 616                 struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu);
 617
 618                 cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util,
 619                                              policy_is_shared(policy) ?
 620                                                         sugov_update_shared :
 621                                                         sugov_update_single);
 622         }
 623         return 0;
 624 }
 625
 626 static void sugov_stop(struct cpufreq_policy *policy)
 627 {
 628         struct sugov_policy *sg_policy = policy->governor_data;
 629         unsigned int cpu;
 630
 631         for_each_cpu(cpu, policy->cpus)
 632                 cpufreq_remove_update_util_hook(cpu);
 633
 634         synchronize_sched();
 635
 636         if (!policy->fast_switch_enabled) {
 637                 irq_work_sync(&sg_policy->irq_work);
 638                 kthread_cancel_work_sync(&sg_policy->work);
 639         }
 640 }
 641
 642 static void sugov_limits(struct cpufreq_policy *policy)
 643 {
 644         struct sugov_policy *sg_policy = policy->governor_data;
 645
 646         if (!policy->fast_switch_enabled) {
 647                 mutex_lock(&sg_policy->work_lock);
 648                 cpufreq_policy_apply_limits(policy);
 649                 mutex_unlock(&sg_policy->work_lock);
 650         }
 651
 652         sg_policy->need_freq_update = true;
 653 }
 654
 655 static struct cpufreq_governor schedutil_gov = {
 656         .name = "schedutil",
 657         .owner = THIS_MODULE,
 658         .init = sugov_init,
 659         .exit = sugov_exit,
 660         .start = sugov_start,
 661         .stop = sugov_stop,
 662         .limits = sugov_limits,
 663 };
 664
 665 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL
 666 struct cpufreq_governor *cpufreq_default_governor(void)
 667 {
 668         return &schedutil_gov;
 669 }
 670 #endif
 671
 672 static int __init sugov_register(void)
 673 {
 674         return cpufreq_register_governor(&schedutil_gov);
 675 }
 676 fs_initcall(sugov_register);