1 /*
2  * drivers/cpufreq/cpufreq_governor.c
3  *
4  * CPUFREQ governors common code
5  *
6  * Copyright	(C) 2001 Russell King
7  *		(C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
8  *		(C) 2003 Jun Nakajima <jun.nakajima@intel.com>
9  *		(C) 2009 Alexander Clouter <alex@digriz.org.uk>
10  *		(c) 2012 Viresh Kumar <viresh.kumar@linaro.org>
11  *
12  * This program is free software; you can redistribute it and/or modify
13  * it under the terms of the GNU General Public License version 2 as
14  * published by the Free Software Foundation.
15  */
16 
17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18 
19 #include <linux/export.h>
20 #include <linux/kernel_stat.h>
21 #include <linux/slab.h>
22 
23 #include "cpufreq_governor.h"
24 
25 #define CPUFREQ_DBS_MIN_SAMPLING_INTERVAL	(2 * TICK_NSEC / NSEC_PER_USEC)
26 
27 static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs);
28 
29 static DEFINE_MUTEX(gov_dbs_data_mutex);
30 
31 /* Common sysfs tunables */
32 /**
33  * store_sampling_rate - update sampling rate effective immediately if needed.
34  *
35  * If new rate is smaller than the old, simply updating
36  * dbs.sampling_rate might not be appropriate. For example, if the
37  * original sampling_rate was 1 second and the requested new sampling rate is 10
38  * ms because the user needs immediate reaction from ondemand governor, but not
39  * sure if higher frequency will be required or not, then, the governor may
40  * change the sampling rate too late; up to 1 second later. Thus, if we are
41  * reducing the sampling rate, we need to make the new value effective
42  * immediately.
43  *
44  * This must be called with dbs_data->mutex held, otherwise traversing
45  * policy_dbs_list isn't safe.
46  */
store_sampling_rate(struct gov_attr_set * attr_set,const char * buf,size_t count)47 ssize_t store_sampling_rate(struct gov_attr_set *attr_set, const char *buf,
48 			    size_t count)
49 {
50 	struct dbs_data *dbs_data = to_dbs_data(attr_set);
51 	struct policy_dbs_info *policy_dbs;
52 	unsigned int sampling_interval;
53 	int ret;
54 
55 	ret = sscanf(buf, "%u", &sampling_interval);
56 	if (ret != 1 || sampling_interval < CPUFREQ_DBS_MIN_SAMPLING_INTERVAL)
57 		return -EINVAL;
58 
59 	dbs_data->sampling_rate = sampling_interval;
60 
61 	/*
62 	 * We are operating under dbs_data->mutex and so the list and its
63 	 * entries can't be freed concurrently.
64 	 */
65 	list_for_each_entry(policy_dbs, &attr_set->policy_list, list) {
66 		mutex_lock(&policy_dbs->update_mutex);
67 		/*
68 		 * On 32-bit architectures this may race with the
69 		 * sample_delay_ns read in dbs_update_util_handler(), but that
70 		 * really doesn't matter.  If the read returns a value that's
71 		 * too big, the sample will be skipped, but the next invocation
72 		 * of dbs_update_util_handler() (when the update has been
73 		 * completed) will take a sample.
74 		 *
75 		 * If this runs in parallel with dbs_work_handler(), we may end
76 		 * up overwriting the sample_delay_ns value that it has just
77 		 * written, but it will be corrected next time a sample is
78 		 * taken, so it shouldn't be significant.
79 		 */
80 		gov_update_sample_delay(policy_dbs, 0);
81 		mutex_unlock(&policy_dbs->update_mutex);
82 	}
83 
84 	return count;
85 }
86 EXPORT_SYMBOL_GPL(store_sampling_rate);
87 
88 /**
89  * gov_update_cpu_data - Update CPU load data.
90  * @dbs_data: Top-level governor data pointer.
91  *
92  * Update CPU load data for all CPUs in the domain governed by @dbs_data
93  * (that may be a single policy or a bunch of them if governor tunables are
94  * system-wide).
95  *
96  * Call under the @dbs_data mutex.
97  */
gov_update_cpu_data(struct dbs_data * dbs_data)98 void gov_update_cpu_data(struct dbs_data *dbs_data)
99 {
100 	struct policy_dbs_info *policy_dbs;
101 
102 	list_for_each_entry(policy_dbs, &dbs_data->attr_set.policy_list, list) {
103 		unsigned int j;
104 
105 		for_each_cpu(j, policy_dbs->policy->cpus) {
106 			struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
107 
108 			j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_update_time,
109 								  dbs_data->io_is_busy);
110 			if (dbs_data->ignore_nice_load)
111 				j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
112 		}
113 	}
114 }
115 EXPORT_SYMBOL_GPL(gov_update_cpu_data);
116 
dbs_update(struct cpufreq_policy * policy)117 unsigned int dbs_update(struct cpufreq_policy *policy)
118 {
119 	struct policy_dbs_info *policy_dbs = policy->governor_data;
120 	struct dbs_data *dbs_data = policy_dbs->dbs_data;
121 	unsigned int ignore_nice = dbs_data->ignore_nice_load;
122 	unsigned int max_load = 0, idle_periods = UINT_MAX;
123 	unsigned int sampling_rate, io_busy, j;
124 
125 	/*
126 	 * Sometimes governors may use an additional multiplier to increase
127 	 * sample delays temporarily.  Apply that multiplier to sampling_rate
128 	 * so as to keep the wake-up-from-idle detection logic a bit
129 	 * conservative.
130 	 */
131 	sampling_rate = dbs_data->sampling_rate * policy_dbs->rate_mult;
132 	/*
133 	 * For the purpose of ondemand, waiting for disk IO is an indication
134 	 * that you're performance critical, and not that the system is actually
135 	 * idle, so do not add the iowait time to the CPU idle time then.
136 	 */
137 	io_busy = dbs_data->io_is_busy;
138 
139 	/* Get Absolute Load */
140 	for_each_cpu(j, policy->cpus) {
141 		struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
142 		u64 update_time, cur_idle_time;
143 		unsigned int idle_time, time_elapsed;
144 		unsigned int load;
145 
146 		cur_idle_time = get_cpu_idle_time(j, &update_time, io_busy);
147 
148 		time_elapsed = update_time - j_cdbs->prev_update_time;
149 		j_cdbs->prev_update_time = update_time;
150 
151 		idle_time = cur_idle_time - j_cdbs->prev_cpu_idle;
152 		j_cdbs->prev_cpu_idle = cur_idle_time;
153 
154 		if (ignore_nice) {
155 			u64 cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
156 
157 			idle_time += div_u64(cur_nice - j_cdbs->prev_cpu_nice, NSEC_PER_USEC);
158 			j_cdbs->prev_cpu_nice = cur_nice;
159 		}
160 
161 		if (unlikely(!time_elapsed)) {
162 			/*
163 			 * That can only happen when this function is called
164 			 * twice in a row with a very short interval between the
165 			 * calls, so the previous load value can be used then.
166 			 */
167 			load = j_cdbs->prev_load;
168 		} else if (unlikely((int)idle_time > 2 * sampling_rate &&
169 				    j_cdbs->prev_load)) {
170 			/*
171 			 * If the CPU had gone completely idle and a task has
172 			 * just woken up on this CPU now, it would be unfair to
173 			 * calculate 'load' the usual way for this elapsed
174 			 * time-window, because it would show near-zero load,
175 			 * irrespective of how CPU intensive that task actually
176 			 * was. This is undesirable for latency-sensitive bursty
177 			 * workloads.
178 			 *
179 			 * To avoid this, reuse the 'load' from the previous
180 			 * time-window and give this task a chance to start with
181 			 * a reasonably high CPU frequency. However, that
182 			 * shouldn't be over-done, lest we get stuck at a high
183 			 * load (high frequency) for too long, even when the
184 			 * current system load has actually dropped down, so
185 			 * clear prev_load to guarantee that the load will be
186 			 * computed again next time.
187 			 *
188 			 * Detecting this situation is easy: an unusually large
189 			 * 'idle_time' (as compared to the sampling rate)
190 			 * indicates this scenario.
191 			 */
192 			load = j_cdbs->prev_load;
193 			j_cdbs->prev_load = 0;
194 		} else {
195 			if (time_elapsed >= idle_time) {
196 				load = 100 * (time_elapsed - idle_time) / time_elapsed;
197 			} else {
198 				/*
199 				 * That can happen if idle_time is returned by
200 				 * get_cpu_idle_time_jiffy().  In that case
201 				 * idle_time is roughly equal to the difference
202 				 * between time_elapsed and "busy time" obtained
203 				 * from CPU statistics.  Then, the "busy time"
204 				 * can end up being greater than time_elapsed
205 				 * (for example, if jiffies_64 and the CPU
206 				 * statistics are updated by different CPUs),
207 				 * so idle_time may in fact be negative.  That
208 				 * means, though, that the CPU was busy all
209 				 * the time (on the rough average) during the
210 				 * last sampling interval and 100 can be
211 				 * returned as the load.
212 				 */
213 				load = (int)idle_time < 0 ? 100 : 0;
214 			}
215 			j_cdbs->prev_load = load;
216 		}
217 
218 		if (unlikely((int)idle_time > 2 * sampling_rate)) {
219 			unsigned int periods = idle_time / sampling_rate;
220 
221 			if (periods < idle_periods)
222 				idle_periods = periods;
223 		}
224 
225 		if (load > max_load)
226 			max_load = load;
227 	}
228 
229 	policy_dbs->idle_periods = idle_periods;
230 
231 	return max_load;
232 }
233 EXPORT_SYMBOL_GPL(dbs_update);
234 
dbs_work_handler(struct work_struct * work)235 static void dbs_work_handler(struct work_struct *work)
236 {
237 	struct policy_dbs_info *policy_dbs;
238 	struct cpufreq_policy *policy;
239 	struct dbs_governor *gov;
240 
241 	policy_dbs = container_of(work, struct policy_dbs_info, work);
242 	policy = policy_dbs->policy;
243 	gov = dbs_governor_of(policy);
244 
245 	/*
246 	 * Make sure cpufreq_governor_limits() isn't evaluating load or the
247 	 * ondemand governor isn't updating the sampling rate in parallel.
248 	 */
249 	mutex_lock(&policy_dbs->update_mutex);
250 	gov_update_sample_delay(policy_dbs, gov->gov_dbs_update(policy));
251 	mutex_unlock(&policy_dbs->update_mutex);
252 
253 	/* Allow the utilization update handler to queue up more work. */
254 	atomic_set(&policy_dbs->work_count, 0);
255 	/*
256 	 * If the update below is reordered with respect to the sample delay
257 	 * modification, the utilization update handler may end up using a stale
258 	 * sample delay value.
259 	 */
260 	smp_wmb();
261 	policy_dbs->work_in_progress = false;
262 }
263 
dbs_irq_work(struct irq_work * irq_work)264 static void dbs_irq_work(struct irq_work *irq_work)
265 {
266 	struct policy_dbs_info *policy_dbs;
267 
268 	policy_dbs = container_of(irq_work, struct policy_dbs_info, irq_work);
269 	schedule_work_on(smp_processor_id(), &policy_dbs->work);
270 }
271 
dbs_update_util_handler(struct update_util_data * data,u64 time,unsigned int flags)272 static void dbs_update_util_handler(struct update_util_data *data, u64 time,
273 				    unsigned int flags)
274 {
275 	struct cpu_dbs_info *cdbs = container_of(data, struct cpu_dbs_info, update_util);
276 	struct policy_dbs_info *policy_dbs = cdbs->policy_dbs;
277 	u64 delta_ns, lst;
278 
279 	if (!cpufreq_this_cpu_can_update(policy_dbs->policy))
280 		return;
281 
282 	/*
283 	 * The work may not be allowed to be queued up right now.
284 	 * Possible reasons:
285 	 * - Work has already been queued up or is in progress.
286 	 * - It is too early (too little time from the previous sample).
287 	 */
288 	if (policy_dbs->work_in_progress)
289 		return;
290 
291 	/*
292 	 * If the reads below are reordered before the check above, the value
293 	 * of sample_delay_ns used in the computation may be stale.
294 	 */
295 	smp_rmb();
296 	lst = READ_ONCE(policy_dbs->last_sample_time);
297 	delta_ns = time - lst;
298 	if ((s64)delta_ns < policy_dbs->sample_delay_ns)
299 		return;
300 
301 	/*
302 	 * If the policy is not shared, the irq_work may be queued up right away
303 	 * at this point.  Otherwise, we need to ensure that only one of the
304 	 * CPUs sharing the policy will do that.
305 	 */
306 	if (policy_dbs->is_shared) {
307 		if (!atomic_add_unless(&policy_dbs->work_count, 1, 1))
308 			return;
309 
310 		/*
311 		 * If another CPU updated last_sample_time in the meantime, we
312 		 * shouldn't be here, so clear the work counter and bail out.
313 		 */
314 		if (unlikely(lst != READ_ONCE(policy_dbs->last_sample_time))) {
315 			atomic_set(&policy_dbs->work_count, 0);
316 			return;
317 		}
318 	}
319 
320 	policy_dbs->last_sample_time = time;
321 	policy_dbs->work_in_progress = true;
322 	irq_work_queue(&policy_dbs->irq_work);
323 }
324 
gov_set_update_util(struct policy_dbs_info * policy_dbs,unsigned int delay_us)325 static void gov_set_update_util(struct policy_dbs_info *policy_dbs,
326 				unsigned int delay_us)
327 {
328 	struct cpufreq_policy *policy = policy_dbs->policy;
329 	int cpu;
330 
331 	gov_update_sample_delay(policy_dbs, delay_us);
332 	policy_dbs->last_sample_time = 0;
333 
334 	for_each_cpu(cpu, policy->cpus) {
335 		struct cpu_dbs_info *cdbs = &per_cpu(cpu_dbs, cpu);
336 
337 		cpufreq_add_update_util_hook(cpu, &cdbs->update_util,
338 					     dbs_update_util_handler);
339 	}
340 }
341 
gov_clear_update_util(struct cpufreq_policy * policy)342 static inline void gov_clear_update_util(struct cpufreq_policy *policy)
343 {
344 	int i;
345 
346 	for_each_cpu(i, policy->cpus)
347 		cpufreq_remove_update_util_hook(i);
348 
349 	synchronize_sched();
350 }
351 
alloc_policy_dbs_info(struct cpufreq_policy * policy,struct dbs_governor * gov)352 static struct policy_dbs_info *alloc_policy_dbs_info(struct cpufreq_policy *policy,
353 						     struct dbs_governor *gov)
354 {
355 	struct policy_dbs_info *policy_dbs;
356 	int j;
357 
358 	/* Allocate memory for per-policy governor data. */
359 	policy_dbs = gov->alloc();
360 	if (!policy_dbs)
361 		return NULL;
362 
363 	policy_dbs->policy = policy;
364 	mutex_init(&policy_dbs->update_mutex);
365 	atomic_set(&policy_dbs->work_count, 0);
366 	init_irq_work(&policy_dbs->irq_work, dbs_irq_work);
367 	INIT_WORK(&policy_dbs->work, dbs_work_handler);
368 
369 	/* Set policy_dbs for all CPUs, online+offline */
370 	for_each_cpu(j, policy->related_cpus) {
371 		struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
372 
373 		j_cdbs->policy_dbs = policy_dbs;
374 	}
375 	return policy_dbs;
376 }
377 
free_policy_dbs_info(struct policy_dbs_info * policy_dbs,struct dbs_governor * gov)378 static void free_policy_dbs_info(struct policy_dbs_info *policy_dbs,
379 				 struct dbs_governor *gov)
380 {
381 	int j;
382 
383 	mutex_destroy(&policy_dbs->update_mutex);
384 
385 	for_each_cpu(j, policy_dbs->policy->related_cpus) {
386 		struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
387 
388 		j_cdbs->policy_dbs = NULL;
389 		j_cdbs->update_util.func = NULL;
390 	}
391 	gov->free(policy_dbs);
392 }
393 
cpufreq_dbs_governor_init(struct cpufreq_policy * policy)394 int cpufreq_dbs_governor_init(struct cpufreq_policy *policy)
395 {
396 	struct dbs_governor *gov = dbs_governor_of(policy);
397 	struct dbs_data *dbs_data;
398 	struct policy_dbs_info *policy_dbs;
399 	int ret = 0;
400 
401 	/* State should be equivalent to EXIT */
402 	if (policy->governor_data)
403 		return -EBUSY;
404 
405 	policy_dbs = alloc_policy_dbs_info(policy, gov);
406 	if (!policy_dbs)
407 		return -ENOMEM;
408 
409 	/* Protect gov->gdbs_data against concurrent updates. */
410 	mutex_lock(&gov_dbs_data_mutex);
411 
412 	dbs_data = gov->gdbs_data;
413 	if (dbs_data) {
414 		if (WARN_ON(have_governor_per_policy())) {
415 			ret = -EINVAL;
416 			goto free_policy_dbs_info;
417 		}
418 		policy_dbs->dbs_data = dbs_data;
419 		policy->governor_data = policy_dbs;
420 
421 		gov_attr_set_get(&dbs_data->attr_set, &policy_dbs->list);
422 		goto out;
423 	}
424 
425 	dbs_data = kzalloc(sizeof(*dbs_data), GFP_KERNEL);
426 	if (!dbs_data) {
427 		ret = -ENOMEM;
428 		goto free_policy_dbs_info;
429 	}
430 
431 	gov_attr_set_init(&dbs_data->attr_set, &policy_dbs->list);
432 
433 	ret = gov->init(dbs_data);
434 	if (ret)
435 		goto free_policy_dbs_info;
436 
437 	/*
438 	 * The sampling interval should not be less than the transition latency
439 	 * of the CPU and it also cannot be too small for dbs_update() to work
440 	 * correctly.
441 	 */
442 	dbs_data->sampling_rate = max_t(unsigned int,
443 					CPUFREQ_DBS_MIN_SAMPLING_INTERVAL,
444 					cpufreq_policy_transition_delay_us(policy));
445 
446 	if (!have_governor_per_policy())
447 		gov->gdbs_data = dbs_data;
448 
449 	policy_dbs->dbs_data = dbs_data;
450 	policy->governor_data = policy_dbs;
451 
452 	gov->kobj_type.sysfs_ops = &governor_sysfs_ops;
453 	ret = kobject_init_and_add(&dbs_data->attr_set.kobj, &gov->kobj_type,
454 				   get_governor_parent_kobj(policy),
455 				   "%s", gov->gov.name);
456 	if (!ret)
457 		goto out;
458 
459 	/* Failure, so roll back. */
460 	pr_err("initialization failed (dbs_data kobject init error %d)\n", ret);
461 
462 	kobject_put(&dbs_data->attr_set.kobj);
463 
464 	policy->governor_data = NULL;
465 
466 	if (!have_governor_per_policy())
467 		gov->gdbs_data = NULL;
468 	gov->exit(dbs_data);
469 	kfree(dbs_data);
470 
471 free_policy_dbs_info:
472 	free_policy_dbs_info(policy_dbs, gov);
473 
474 out:
475 	mutex_unlock(&gov_dbs_data_mutex);
476 	return ret;
477 }
478 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_init);
479 
cpufreq_dbs_governor_exit(struct cpufreq_policy * policy)480 void cpufreq_dbs_governor_exit(struct cpufreq_policy *policy)
481 {
482 	struct dbs_governor *gov = dbs_governor_of(policy);
483 	struct policy_dbs_info *policy_dbs = policy->governor_data;
484 	struct dbs_data *dbs_data = policy_dbs->dbs_data;
485 	unsigned int count;
486 
487 	/* Protect gov->gdbs_data against concurrent updates. */
488 	mutex_lock(&gov_dbs_data_mutex);
489 
490 	count = gov_attr_set_put(&dbs_data->attr_set, &policy_dbs->list);
491 
492 	policy->governor_data = NULL;
493 
494 	if (!count) {
495 		if (!have_governor_per_policy())
496 			gov->gdbs_data = NULL;
497 
498 		gov->exit(dbs_data);
499 		kfree(dbs_data);
500 	}
501 
502 	free_policy_dbs_info(policy_dbs, gov);
503 
504 	mutex_unlock(&gov_dbs_data_mutex);
505 }
506 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_exit);
507 
cpufreq_dbs_governor_start(struct cpufreq_policy * policy)508 int cpufreq_dbs_governor_start(struct cpufreq_policy *policy)
509 {
510 	struct dbs_governor *gov = dbs_governor_of(policy);
511 	struct policy_dbs_info *policy_dbs = policy->governor_data;
512 	struct dbs_data *dbs_data = policy_dbs->dbs_data;
513 	unsigned int sampling_rate, ignore_nice, j;
514 	unsigned int io_busy;
515 
516 	if (!policy->cur)
517 		return -EINVAL;
518 
519 	policy_dbs->is_shared = policy_is_shared(policy);
520 	policy_dbs->rate_mult = 1;
521 
522 	sampling_rate = dbs_data->sampling_rate;
523 	ignore_nice = dbs_data->ignore_nice_load;
524 	io_busy = dbs_data->io_is_busy;
525 
526 	for_each_cpu(j, policy->cpus) {
527 		struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
528 
529 		j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_update_time, io_busy);
530 		/*
531 		 * Make the first invocation of dbs_update() compute the load.
532 		 */
533 		j_cdbs->prev_load = 0;
534 
535 		if (ignore_nice)
536 			j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
537 	}
538 
539 	gov->start(policy);
540 
541 	gov_set_update_util(policy_dbs, sampling_rate);
542 	return 0;
543 }
544 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_start);
545 
cpufreq_dbs_governor_stop(struct cpufreq_policy * policy)546 void cpufreq_dbs_governor_stop(struct cpufreq_policy *policy)
547 {
548 	struct policy_dbs_info *policy_dbs = policy->governor_data;
549 
550 	gov_clear_update_util(policy_dbs->policy);
551 	irq_work_sync(&policy_dbs->irq_work);
552 	cancel_work_sync(&policy_dbs->work);
553 	atomic_set(&policy_dbs->work_count, 0);
554 	policy_dbs->work_in_progress = false;
555 }
556 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_stop);
557 
cpufreq_dbs_governor_limits(struct cpufreq_policy * policy)558 void cpufreq_dbs_governor_limits(struct cpufreq_policy *policy)
559 {
560 	struct policy_dbs_info *policy_dbs;
561 
562 	/* Protect gov->gdbs_data against cpufreq_dbs_governor_exit() */
563 	mutex_lock(&gov_dbs_data_mutex);
564 	policy_dbs = policy->governor_data;
565 	if (!policy_dbs)
566 		goto out;
567 
568 	mutex_lock(&policy_dbs->update_mutex);
569 	cpufreq_policy_apply_limits(policy);
570 	gov_update_sample_delay(policy_dbs, 0);
571 	mutex_unlock(&policy_dbs->update_mutex);
572 
573 out:
574 	mutex_unlock(&gov_dbs_data_mutex);
575 }
576 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_limits);
577