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