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, ¶m); 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); 677