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)
 246 {
 247         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
 248         struct cpufreq_policy *policy = sg_policy->policy;
 249         u64 last_freq_update_time = sg_policy->last_freq_update_time;
 250         unsigned long util = 0, max = 1;
 251         unsigned int j;
 252
 253         for_each_cpu(j, policy->cpus) {
 254                 struct sugov_cpu *j_sg_cpu = &per_cpu(sugov_cpu, j);
 255                 unsigned long j_util, j_max;
 256                 s64 delta_ns;
 257
 258                 /*
 259                  * If the CPU utilization was last updated before the previous
 260                  * frequency update and the time elapsed between the last update
 261                  * of the CPU utilization and the last frequency update is long
 262                  * enough, don't take the CPU into account as it probably is
 263                  * idle now (and clear iowait_boost for it).
 264                  */
 265                 delta_ns = last_freq_update_time - j_sg_cpu->last_update;
 266                 if (delta_ns > TICK_NSEC) {
 267                         j_sg_cpu->iowait_boost = 0;
 268                         continue;
 269                 }
 270                 if (j_sg_cpu->flags & SCHED_CPUFREQ_RT_DL)
 271                         return policy->cpuinfo.max_freq;
 272
 273                 j_util = j_sg_cpu->util;
 274                 j_max = j_sg_cpu->max;
 275                 if (j_util * max > j_max * util) {
 276                         util = j_util;
 277                         max = j_max;
 278                 }
 279
 280                 sugov_iowait_boost(j_sg_cpu, &util, &max);
 281         }
 282
 283         return get_next_freq(sg_policy, util, max);
 284 }
 285
 286 static void sugov_update_shared(struct update_util_data *hook, u64 time,
 287                                 unsigned int flags)
 288 {
 289         struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
 290         struct sugov_policy *sg_policy = sg_cpu->sg_policy;
 291         unsigned long util, max;
 292         unsigned int next_f;
 293
 294         sugov_get_util(&util, &max);
 295
 296         raw_spin_lock(&sg_policy->update_lock);
 297
 298         sg_cpu->util = util;
 299         sg_cpu->max = max;
 300         sg_cpu->flags = flags;
 301
 302         sugov_set_iowait_boost(sg_cpu, time, flags);
 303         sg_cpu->last_update = time;
 304
 305         if (sugov_should_update_freq(sg_policy, time)) {
 306                 if (flags & SCHED_CPUFREQ_RT_DL)
 307                         next_f = sg_policy->policy->cpuinfo.max_freq;
 308                 else
 309                         next_f = sugov_next_freq_shared(sg_cpu);
 310
 311                 sugov_update_commit(sg_policy, time, next_f);
 312         }
 313
 314         raw_spin_unlock(&sg_policy->update_lock);
 315 }
 316
 317 static void sugov_work(struct kthread_work *work)
 318 {
 319         struct sugov_policy *sg_policy = container_of(work, struct sugov_policy, work);
 320
 321         mutex_lock(&sg_policy->work_lock);
 322         __cpufreq_driver_target(sg_policy->policy, sg_policy->next_freq,
 323                                 CPUFREQ_RELATION_L);
 324         mutex_unlock(&sg_policy->work_lock);
 325
 326         sg_policy->work_in_progress = false;
 327 }
 328
 329 static void sugov_irq_work(struct irq_work *irq_work)
 330 {
 331         struct sugov_policy *sg_policy;
 332
 333         sg_policy = container_of(irq_work, struct sugov_policy, irq_work);
 334
 335         /*
 336          * For RT and deadline tasks, the schedutil governor shoots the
 337          * frequency to maximum. Special care must be taken to ensure that this
 338          * kthread doesn't result in the same behavior.
 339          *
 340          * This is (mostly) guaranteed by the work_in_progress flag. The flag is
 341          * updated only at the end of the sugov_work() function and before that
 342          * the schedutil governor rejects all other frequency scaling requests.
 343          *
 344          * There is a very rare case though, where the RT thread yields right
 345          * after the work_in_progress flag is cleared. The effects of that are
 346          * neglected for now.
 347          */
 348         kthread_queue_work(&sg_policy->worker, &sg_policy->work);
 349 }
 350
 351 /************************** sysfs interface ************************/
 352
 353 static struct sugov_tunables *global_tunables;
 354 static DEFINE_MUTEX(global_tunables_lock);
 355
 356 static inline struct sugov_tunables *to_sugov_tunables(struct gov_attr_set *attr_set)
 357 {
 358         return container_of(attr_set, struct sugov_tunables, attr_set);
 359 }
 360
 361 static ssize_t rate_limit_us_show(struct gov_attr_set *attr_set, char *buf)
 362 {
 363         struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
 364
 365         return sprintf(buf, "%u\n", tunables->rate_limit_us);
 366 }
 367
 368 static ssize_t rate_limit_us_store(struct gov_attr_set *attr_set, const char *buf,
 369                                    size_t count)
 370 {
 371         struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
 372         struct sugov_policy *sg_policy;
 373         unsigned int rate_limit_us;
 374
 375         if (kstrtouint(buf, 10, &rate_limit_us))
 376                 return -EINVAL;
 377
 378         tunables->rate_limit_us = rate_limit_us;
 379
 380         list_for_each_entry(sg_policy, &attr_set->policy_list, tunables_hook)
 381                 sg_policy->freq_update_delay_ns = rate_limit_us * NSEC_PER_USEC;
 382
 383         return count;
 384 }
 385
 386 static struct governor_attr rate_limit_us = __ATTR_RW(rate_limit_us);
 387
 388 static struct attribute *sugov_attributes[] = {
 389         &rate_limit_us.attr,
 390         NULL
 391 };
 392
 393 static struct kobj_type sugov_tunables_ktype = {
 394         .default_attrs = sugov_attributes,
 395         .sysfs_ops = &governor_sysfs_ops,
 396 };
 397
 398 /********************** cpufreq governor interface *********************/
 399
 400 static struct cpufreq_governor schedutil_gov;
 401
 402 static struct sugov_policy *sugov_policy_alloc(struct cpufreq_policy *policy)
 403 {
 404         struct sugov_policy *sg_policy;
 405
 406         sg_policy = kzalloc(sizeof(*sg_policy), GFP_KERNEL);
 407         if (!sg_policy)
 408                 return NULL;
 409
 410         sg_policy->policy = policy;
 411         raw_spin_lock_init(&sg_policy->update_lock);
 412         return sg_policy;
 413 }
 414
 415 static void sugov_policy_free(struct sugov_policy *sg_policy)
 416 {
 417         kfree(sg_policy);
 418 }
 419
 420 static int sugov_kthread_create(struct sugov_policy *sg_policy)
 421 {
 422         struct task_struct *thread;
 423         struct sched_param param = { .sched_priority = MAX_USER_RT_PRIO / 2 };
 424         struct cpufreq_policy *policy = sg_policy->policy;
 425         int ret;
 426
 427         /* kthread only required for slow path */
 428         if (policy->fast_switch_enabled)
 429                 return 0;
 430
 431         kthread_init_work(&sg_policy->work, sugov_work);
 432         kthread_init_worker(&sg_policy->worker);
 433         thread = kthread_create(kthread_worker_fn, &sg_policy->worker,
 434                                 "sugov:%d",
 435                                 cpumask_first(policy->related_cpus));
 436         if (IS_ERR(thread)) {
 437                 pr_err("failed to create sugov thread: %ld\n", PTR_ERR(thread));
 438                 return PTR_ERR(thread);
 439         }
 440
 441         ret = sched_setscheduler_nocheck(thread, SCHED_FIFO, &param);
 442         if (ret) {
 443                 kthread_stop(thread);
 444                 pr_warn("%s: failed to set SCHED_FIFO\n", __func__);
 445                 return ret;
 446         }
 447
 448         sg_policy->thread = thread;
 449         kthread_bind_mask(thread, policy->related_cpus);
 450         init_irq_work(&sg_policy->irq_work, sugov_irq_work);
 451         mutex_init(&sg_policy->work_lock);
 452
 453         wake_up_process(thread);
 454
 455         return 0;
 456 }
 457
 458 static void sugov_kthread_stop(struct sugov_policy *sg_policy)
 459 {
 460         /* kthread only required for slow path */
 461         if (sg_policy->policy->fast_switch_enabled)
 462                 return;
 463
 464         kthread_flush_worker(&sg_policy->worker);
 465         kthread_stop(sg_policy->thread);
 466         mutex_destroy(&sg_policy->work_lock);
 467 }
 468
 469 static struct sugov_tunables *sugov_tunables_alloc(struct sugov_policy *sg_policy)
 470 {
 471         struct sugov_tunables *tunables;
 472
 473         tunables = kzalloc(sizeof(*tunables), GFP_KERNEL);
 474         if (tunables) {
 475                 gov_attr_set_init(&tunables->attr_set, &sg_policy->tunables_hook);
 476                 if (!have_governor_per_policy())
 477                         global_tunables = tunables;
 478         }
 479         return tunables;
 480 }
 481
 482 static void sugov_tunables_free(struct sugov_tunables *tunables)
 483 {
 484         if (!have_governor_per_policy())
 485                 global_tunables = NULL;
 486
 487         kfree(tunables);
 488 }
 489
 490 static int sugov_init(struct cpufreq_policy *policy)
 491 {
 492         struct sugov_policy *sg_policy;
 493         struct sugov_tunables *tunables;
 494         int ret = 0;
 495
 496         /* State should be equivalent to EXIT */
 497         if (policy->governor_data)
 498                 return -EBUSY;
 499
 500         cpufreq_enable_fast_switch(policy);
 501
 502         sg_policy = sugov_policy_alloc(policy);
 503         if (!sg_policy) {
 504                 ret = -ENOMEM;
 505                 goto disable_fast_switch;
 506         }
 507
 508         ret = sugov_kthread_create(sg_policy);
 509         if (ret)
 510                 goto free_sg_policy;
 511
 512         mutex_lock(&global_tunables_lock);
 513
 514         if (global_tunables) {
 515                 if (WARN_ON(have_governor_per_policy())) {
 516                         ret = -EINVAL;
 517                         goto stop_kthread;
 518                 }
 519                 policy->governor_data = sg_policy;
 520                 sg_policy->tunables = global_tunables;
 521
 522                 gov_attr_set_get(&global_tunables->attr_set, &sg_policy->tunables_hook);
 523                 goto out;
 524         }
 525
 526         tunables = sugov_tunables_alloc(sg_policy);
 527         if (!tunables) {
 528                 ret = -ENOMEM;
 529                 goto stop_kthread;
 530         }
 531
 532         if (policy->transition_delay_us) {
 533                 tunables->rate_limit_us = policy->transition_delay_us;
 534         } else {
 535                 unsigned int lat;
 536
 537                 tunables->rate_limit_us = LATENCY_MULTIPLIER;
 538                 lat = policy->cpuinfo.transition_latency / NSEC_PER_USEC;
 539                 if (lat)
 540                         tunables->rate_limit_us *= lat;
 541         }
 542
 543         policy->governor_data = sg_policy;
 544         sg_policy->tunables = tunables;
 545
 546         ret = kobject_init_and_add(&tunables->attr_set.kobj, &sugov_tunables_ktype,
 547                                    get_governor_parent_kobj(policy), "%s",
 548                                    schedutil_gov.name);
 549         if (ret)
 550                 goto fail;
 551
 552 out:
 553         mutex_unlock(&global_tunables_lock);
 554         return 0;
 555
 556 fail:
 557         policy->governor_data = NULL;
 558         sugov_tunables_free(tunables);
 559
 560 stop_kthread:
 561         sugov_kthread_stop(sg_policy);
 562
 563 free_sg_policy:
 564         mutex_unlock(&global_tunables_lock);
 565
 566         sugov_policy_free(sg_policy);
 567
 568 disable_fast_switch:
 569         cpufreq_disable_fast_switch(policy);
 570
 571         pr_err("initialization failed (error %d)\n", ret);
 572         return ret;
 573 }
 574
 575 static void sugov_exit(struct cpufreq_policy *policy)
 576 {
 577         struct sugov_policy *sg_policy = policy->governor_data;
 578         struct sugov_tunables *tunables = sg_policy->tunables;
 579         unsigned int count;
 580
 581         mutex_lock(&global_tunables_lock);
 582
 583         count = gov_attr_set_put(&tunables->attr_set, &sg_policy->tunables_hook);
 584         policy->governor_data = NULL;
 585         if (!count)
 586                 sugov_tunables_free(tunables);
 587
 588         mutex_unlock(&global_tunables_lock);
 589
 590         sugov_kthread_stop(sg_policy);
 591         sugov_policy_free(sg_policy);
 592         cpufreq_disable_fast_switch(policy);
 593 }
 594
 595 static int sugov_start(struct cpufreq_policy *policy)
 596 {
 597         struct sugov_policy *sg_policy = policy->governor_data;
 598         unsigned int cpu;
 599
 600         sg_policy->freq_update_delay_ns = sg_policy->tunables->rate_limit_us * NSEC_PER_USEC;
 601         sg_policy->last_freq_update_time = 0;
 602         sg_policy->next_freq = UINT_MAX;
 603         sg_policy->work_in_progress = false;
 604         sg_policy->need_freq_update = false;
 605         sg_policy->cached_raw_freq = 0;
 606
 607         for_each_cpu(cpu, policy->cpus) {
 608                 struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu);
 609
 610                 memset(sg_cpu, 0, sizeof(*sg_cpu));
 611                 sg_cpu->sg_policy = sg_policy;
 612                 sg_cpu->flags = SCHED_CPUFREQ_RT;
 613                 sg_cpu->iowait_boost_max = policy->cpuinfo.max_freq;
 614                 cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util,
 615                                              policy_is_shared(policy) ?
 616                                                         sugov_update_shared :
 617                                                         sugov_update_single);
 618         }
 619         return 0;
 620 }
 621
 622 static void sugov_stop(struct cpufreq_policy *policy)
 623 {
 624         struct sugov_policy *sg_policy = policy->governor_data;
 625         unsigned int cpu;
 626
 627         for_each_cpu(cpu, policy->cpus)
 628                 cpufreq_remove_update_util_hook(cpu);
 629
 630         synchronize_sched();
 631
 632         if (!policy->fast_switch_enabled) {
 633                 irq_work_sync(&sg_policy->irq_work);
 634                 kthread_cancel_work_sync(&sg_policy->work);
 635         }
 636 }
 637
 638 static void sugov_limits(struct cpufreq_policy *policy)
 639 {
 640         struct sugov_policy *sg_policy = policy->governor_data;
 641
 642         if (!policy->fast_switch_enabled) {
 643                 mutex_lock(&sg_policy->work_lock);
 644                 cpufreq_policy_apply_limits(policy);
 645                 mutex_unlock(&sg_policy->work_lock);
 646         }
 647
 648         sg_policy->need_freq_update = true;
 649 }
 650
 651 static struct cpufreq_governor schedutil_gov = {
 652         .name = "schedutil",
 653         .owner = THIS_MODULE,
 654         .init = sugov_init,
 655         .exit = sugov_exit,
 656         .start = sugov_start,
 657         .stop = sugov_stop,
 658         .limits = sugov_limits,
 659 };
 660
 661 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL
 662 struct cpufreq_governor *cpufreq_default_governor(void)
 663 {
 664         return &schedutil_gov;
 665 }
 666 #endif
 667
 668 static int __init sugov_register(void)
 669 {
 670         return cpufreq_register_governor(&schedutil_gov);
 671 }
 672 fs_initcall(sugov_register);