summaryrefslogtreecommitdiffstats
path: root/kernel/sched/cpufreq_schedutil.c
blob: a84641b222c1b4769fbceec1bf16236cd5abc010 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
/*
 * CPUFreq governor based on scheduler-provided CPU utilization data.
 *
 * Copyright (C) 2016, Intel Corporation
 * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/cpufreq.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <trace/events/power.h>

#include "sched.h"

struct sugov_tunables {
	struct gov_attr_set attr_set;
	unsigned int rate_limit_us;
};

struct sugov_policy {
	struct cpufreq_policy *policy;

	struct sugov_tunables *tunables;
	struct list_head tunables_hook;

	raw_spinlock_t update_lock;  /* For shared policies */
	u64 last_freq_update_time;
	s64 freq_update_delay_ns;
	unsigned int next_freq;

	/* The next fields are only needed if fast switch cannot be used. */
	struct irq_work irq_work;
	struct work_struct work;
	struct mutex work_lock;
	bool work_in_progress;

	bool need_freq_update;
};

struct sugov_cpu {
	struct update_util_data update_util;
	struct sugov_policy *sg_policy;

	unsigned int cached_raw_freq;

	/* The fields below are only needed when sharing a policy. */
	unsigned long util;
	unsigned long max;
	u64 last_update;
};

static DEFINE_PER_CPU(struct sugov_cpu, sugov_cpu);

/************************ Governor internals ***********************/

static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
{
	s64 delta_ns;

	if (sg_policy->work_in_progress)
		return false;

	if (unlikely(sg_policy->need_freq_update)) {
		sg_policy->need_freq_update = false;
		/*
		 * This happens when limits change, so forget the previous
		 * next_freq value and force an update.
		 */
		sg_policy->next_freq = UINT_MAX;
		return true;
	}

	delta_ns = time - sg_policy->last_freq_update_time;
	return delta_ns >= sg_policy->freq_update_delay_ns;
}

static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
				unsigned int next_freq)
{
	struct cpufreq_policy *policy = sg_policy->policy;

	sg_policy->last_freq_update_time = time;

	if (policy->fast_switch_enabled) {
		if (sg_policy->next_freq == next_freq) {
			trace_cpu_frequency(policy->cur, smp_processor_id());
			return;
		}
		sg_policy->next_freq = next_freq;
		next_freq = cpufreq_driver_fast_switch(policy, next_freq);
		if (next_freq == CPUFREQ_ENTRY_INVALID)
			return;

		policy->cur = next_freq;
		trace_cpu_frequency(next_freq, smp_processor_id());
	} else if (sg_policy->next_freq != next_freq) {
		sg_policy->next_freq = next_freq;
		sg_policy->work_in_progress = true;
		irq_work_queue(&sg_policy->irq_work);
	}
}

/**
 * get_next_freq - Compute a new frequency for a given cpufreq policy.
 * @sg_cpu: schedutil cpu object to compute the new frequency for.
 * @util: Current CPU utilization.
 * @max: CPU capacity.
 *
 * If the utilization is frequency-invariant, choose the new frequency to be
 * proportional to it, that is
 *
 * next_freq = C * max_freq * util / max
 *
 * Otherwise, approximate the would-be frequency-invariant utilization by
 * util_raw * (curr_freq / max_freq) which leads to
 *
 * next_freq = C * curr_freq * util_raw / max
 *
 * Take C = 1.25 for the frequency tipping point at (util / max) = 0.8.
 *
 * The lowest driver-supported frequency which is equal or greater than the raw
 * next_freq (as calculated above) is returned, subject to policy min/max and
 * cpufreq driver limitations.
 */
static unsigned int get_next_freq(struct sugov_cpu *sg_cpu, unsigned long util,
				  unsigned long max)
{
	struct sugov_policy *sg_policy = sg_cpu->sg_policy;
	struct cpufreq_policy *policy = sg_policy->policy;
	unsigned int freq = arch_scale_freq_invariant() ?
				policy->cpuinfo.max_freq : policy->cur;

	freq = (freq + (freq >> 2)) * util / max;

	if (freq == sg_cpu->cached_raw_freq && sg_policy->next_freq != UINT_MAX)
		return sg_policy->next_freq;
	sg_cpu->cached_raw_freq = freq;
	return cpufreq_driver_resolve_freq(policy, freq);
}

static void sugov_update_single(struct update_util_data *hook, u64 time,
				unsigned long util, unsigned long max)
{
	struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
	struct sugov_policy *sg_policy = sg_cpu->sg_policy;
	struct cpufreq_policy *policy = sg_policy->policy;
	unsigned int next_f;

	if (!sugov_should_update_freq(sg_policy, time))
		return;

	next_f = util == ULONG_MAX ? policy->cpuinfo.max_freq :
			get_next_freq(sg_cpu, util, max);
	sugov_update_commit(sg_policy, time, next_f);
}

static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu,
					   unsigned long util, unsigned long max)
{
	struct sugov_policy *sg_policy = sg_cpu->sg_policy;
	struct cpufreq_policy *policy = sg_policy->policy;
	unsigned int max_f = policy->cpuinfo.max_freq;
	u64 last_freq_update_time = sg_policy->last_freq_update_time;
	unsigned int j;

	if (util == ULONG_MAX)
		return max_f;

	for_each_cpu(j, policy->cpus) {
		struct sugov_cpu *j_sg_cpu;
		unsigned long j_util, j_max;
		s64 delta_ns;

		if (j == smp_processor_id())
			continue;

		j_sg_cpu = &per_cpu(sugov_cpu, j);
		/*
		 * If the CPU utilization was last updated before the previous
		 * frequency update and the time elapsed between the last update
		 * of the CPU utilization and the last frequency update is long
		 * enough, don't take the CPU into account as it probably is
		 * idle now.
		 */
		delta_ns = last_freq_update_time - j_sg_cpu->last_update;
		if (delta_ns > TICK_NSEC)
			continue;

		j_util = j_sg_cpu->util;
		if (j_util == ULONG_MAX)
			return max_f;

		j_max = j_sg_cpu->max;
		if (j_util * max > j_max * util) {
			util = j_util;
			max = j_max;
		}
	}

	return get_next_freq(sg_cpu, util, max);
}

static void sugov_update_shared(struct update_util_data *hook, u64 time,
				unsigned long util, unsigned long max)
{
	struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
	struct sugov_policy *sg_policy = sg_cpu->sg_policy;
	unsigned int next_f;

	raw_spin_lock(&sg_policy->update_lock);

	sg_cpu->util = util;
	sg_cpu->max = max;
	sg_cpu->last_update = time;

	if (sugov_should_update_freq(sg_policy, time)) {
		next_f = sugov_next_freq_shared(sg_cpu, util, max);
		sugov_update_commit(sg_policy, time, next_f);
	}

	raw_spin_unlock(&sg_policy->update_lock);
}

static void sugov_work(struct work_struct *work)
{
	struct sugov_policy *sg_policy = container_of(work, struct sugov_policy, work);

	mutex_lock(&sg_policy->work_lock);
	__cpufreq_driver_target(sg_policy->policy, sg_policy->next_freq,
				CPUFREQ_RELATION_L);
	mutex_unlock(&sg_policy->work_lock);

	sg_policy->work_in_progress = false;
}

static void sugov_irq_work(struct irq_work *irq_work)
{
	struct sugov_policy *sg_policy;

	sg_policy = container_of(irq_work, struct sugov_policy, irq_work);
	schedule_work_on(smp_processor_id(), &sg_policy->work);
}

/************************** sysfs interface ************************/

static struct sugov_tunables *global_tunables;
static DEFINE_MUTEX(global_tunables_lock);

static inline struct sugov_tunables *to_sugov_tunables(struct gov_attr_set *attr_set)
{
	return container_of(attr_set, struct sugov_tunables, attr_set);
}

static ssize_t rate_limit_us_show(struct gov_attr_set *attr_set, char *buf)
{
	struct sugov_tunables *tunables = to_sugov_tunables(attr_set);

	return sprintf(buf, "%u\n", tunables->rate_limit_us);
}

static ssize_t rate_limit_us_store(struct gov_attr_set *attr_set, const char *buf,
				   size_t count)
{
	struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
	struct sugov_policy *sg_policy;
	unsigned int rate_limit_us;

	if (kstrtouint(buf, 10, &rate_limit_us))
		return -EINVAL;

	tunables->rate_limit_us = rate_limit_us;

	list_for_each_entry(sg_policy, &attr_set->policy_list, tunables_hook)
		sg_policy->freq_update_delay_ns = rate_limit_us * NSEC_PER_USEC;

	return count;
}

static struct governor_attr rate_limit_us = __ATTR_RW(rate_limit_us);

static struct attribute *sugov_attributes[] = {
	&rate_limit_us.attr,
	NULL
};

static struct kobj_type sugov_tunables_ktype = {
	.default_attrs = sugov_attributes,
	.sysfs_ops = &governor_sysfs_ops,
};

/********************** cpufreq governor interface *********************/

static struct cpufreq_governor schedutil_gov;

static struct sugov_policy *sugov_policy_alloc(struct cpufreq_policy *policy)
{
	struct sugov_policy *sg_policy;

	sg_policy = kzalloc(sizeof(*sg_policy), GFP_KERNEL);
	if (!sg_policy)
		return NULL;

	sg_policy->policy = policy;
	init_irq_work(&sg_policy->irq_work, sugov_irq_work);
	INIT_WORK(&sg_policy->work, sugov_work);
	mutex_init(&sg_policy->work_lock);
	raw_spin_lock_init(&sg_policy->update_lock);
	return sg_policy;
}

static void sugov_policy_free(struct sugov_policy *sg_policy)
{
	mutex_destroy(&sg_policy->work_lock);
	kfree(sg_policy);
}

static struct sugov_tunables *sugov_tunables_alloc(struct sugov_policy *sg_policy)
{
	struct sugov_tunables *tunables;

	tunables = kzalloc(sizeof(*tunables), GFP_KERNEL);
	if (tunables) {
		gov_attr_set_init(&tunables->attr_set, &sg_policy->tunables_hook);
		if (!have_governor_per_policy())
			global_tunables = tunables;
	}
	return tunables;
}

static void sugov_tunables_free(struct sugov_tunables *tunables)
{
	if (!have_governor_per_policy())
		global_tunables = NULL;

	kfree(tunables);
}

static int sugov_init(struct cpufreq_policy *policy)
{
	struct sugov_policy *sg_policy;
	struct sugov_tunables *tunables;
	unsigned int lat;
	int ret = 0;

	/* State should be equivalent to EXIT */
	if (policy->governor_data)
		return -EBUSY;

	sg_policy = sugov_policy_alloc(policy);
	if (!sg_policy)
		return -ENOMEM;

	mutex_lock(&global_tunables_lock);

	if (global_tunables) {
		if (WARN_ON(have_governor_per_policy())) {
			ret = -EINVAL;
			goto free_sg_policy;
		}
		policy->governor_data = sg_policy;
		sg_policy->tunables = global_tunables;

		gov_attr_set_get(&global_tunables->attr_set, &sg_policy->tunables_hook);
		goto out;
	}

	tunables = sugov_tunables_alloc(sg_policy);
	if (!tunables) {
		ret = -ENOMEM;
		goto free_sg_policy;
	}

	tunables->rate_limit_us = LATENCY_MULTIPLIER;
	lat = policy->cpuinfo.transition_latency / NSEC_PER_USEC;
	if (lat)
		tunables->rate_limit_us *= lat;

	policy->governor_data = sg_policy;
	sg_policy->tunables = tunables;

	ret = kobject_init_and_add(&tunables->attr_set.kobj, &sugov_tunables_ktype,
				   get_governor_parent_kobj(policy), "%s",
				   schedutil_gov.name);
	if (ret)
		goto fail;

 out:
	mutex_unlock(&global_tunables_lock);

	cpufreq_enable_fast_switch(policy);
	return 0;

 fail:
	policy->governor_data = NULL;
	sugov_tunables_free(tunables);

 free_sg_policy:
	mutex_unlock(&global_tunables_lock);

	sugov_policy_free(sg_policy);
	pr_err("initialization failed (error %d)\n", ret);
	return ret;
}

static void sugov_exit(struct cpufreq_policy *policy)
{
	struct sugov_policy *sg_policy = policy->governor_data;
	struct sugov_tunables *tunables = sg_policy->tunables;
	unsigned int count;

	cpufreq_disable_fast_switch(policy);

	mutex_lock(&global_tunables_lock);

	count = gov_attr_set_put(&tunables->attr_set, &sg_policy->tunables_hook);
	policy->governor_data = NULL;
	if (!count)
		sugov_tunables_free(tunables);

	mutex_unlock(&global_tunables_lock);

	sugov_policy_free(sg_policy);
}

static int sugov_start(struct cpufreq_policy *policy)
{
	struct sugov_policy *sg_policy = policy->governor_data;
	unsigned int cpu;

	sg_policy->freq_update_delay_ns = sg_policy->tunables->rate_limit_us * NSEC_PER_USEC;
	sg_policy->last_freq_update_time = 0;
	sg_policy->next_freq = UINT_MAX;
	sg_policy->work_in_progress = false;
	sg_policy->need_freq_update = false;

	for_each_cpu(cpu, policy->cpus) {
		struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu);

		sg_cpu->sg_policy = sg_policy;
		if (policy_is_shared(policy)) {
			sg_cpu->util = ULONG_MAX;
			sg_cpu->max = 0;
			sg_cpu->last_update = 0;
			sg_cpu->cached_raw_freq = 0;
			cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util,
						     sugov_update_shared);
		} else {
			cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util,
						     sugov_update_single);
		}
	}
	return 0;
}

static void sugov_stop(struct cpufreq_policy *policy)
{
	struct sugov_policy *sg_policy = policy->governor_data;
	unsigned int cpu;

	for_each_cpu(cpu, policy->cpus)
		cpufreq_remove_update_util_hook(cpu);

	synchronize_sched();

	irq_work_sync(&sg_policy->irq_work);
	cancel_work_sync(&sg_policy->work);
}

static void sugov_limits(struct cpufreq_policy *policy)
{
	struct sugov_policy *sg_policy = policy->governor_data;

	if (!policy->fast_switch_enabled) {
		mutex_lock(&sg_policy->work_lock);
		cpufreq_policy_apply_limits(policy);
		mutex_unlock(&sg_policy->work_lock);
	}

	sg_policy->need_freq_update = true;
}

static struct cpufreq_governor schedutil_gov = {
	.name = "schedutil",
	.owner = THIS_MODULE,
	.init = sugov_init,
	.exit = sugov_exit,
	.start = sugov_start,
	.stop = sugov_stop,
	.limits = sugov_limits,
};

static int __init sugov_module_init(void)
{
	return cpufreq_register_governor(&schedutil_gov);
}

static void __exit sugov_module_exit(void)
{
	cpufreq_unregister_governor(&schedutil_gov);
}

MODULE_AUTHOR("Rafael J. Wysocki <rafael.j.wysocki@intel.com>");
MODULE_DESCRIPTION("Utilization-based CPU frequency selection");
MODULE_LICENSE("GPL");

#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL
struct cpufreq_governor *cpufreq_default_governor(void)
{
	return &schedutil_gov;
}

fs_initcall(sugov_module_init);
#else
module_init(sugov_module_init);
#endif
module_exit(sugov_module_exit);