cpufreq_conservative.c revision cd354f1ae75e6466a7e31b727faede57a1f89ca5 
1/*
2 *  drivers/cpufreq/cpufreq_conservative.c
3 *
4 *  Copyright (C)  2001 Russell King
5 *            (C)  2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
6 *                      Jun Nakajima <jun.nakajima@intel.com>
7 *            (C)  2004 Alexander Clouter <alex-kernel@digriz.org.uk>
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
12 */
13
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/smp.h>
17#include <linux/init.h>
18#include <linux/interrupt.h>
19#include <linux/ctype.h>
20#include <linux/cpufreq.h>
21#include <linux/sysctl.h>
22#include <linux/types.h>
23#include <linux/fs.h>
24#include <linux/sysfs.h>
25#include <linux/cpu.h>
26#include <linux/kmod.h>
27#include <linux/workqueue.h>
28#include <linux/jiffies.h>
29#include <linux/kernel_stat.h>
30#include <linux/percpu.h>
31#include <linux/mutex.h>
32/*
33 * dbs is used in this file as a shortform for demandbased switching
34 * It helps to keep variable names smaller, simpler
35 */
36
37#define DEF_FREQUENCY_UP_THRESHOLD		(80)
38#define DEF_FREQUENCY_DOWN_THRESHOLD		(20)
39
40/*
41 * The polling frequency of this governor depends on the capability of
42 * the processor. Default polling frequency is 1000 times the transition
43 * latency of the processor. The governor will work on any processor with
44 * transition latency <= 10mS, using appropriate sampling
45 * rate.
46 * For CPUs with transition latency > 10mS (mostly drivers
47 * with CPUFREQ_ETERNAL), this governor will not work.
48 * All times here are in uS.
49 */
50static unsigned int 				def_sampling_rate;
51#define MIN_SAMPLING_RATE_RATIO			(2)
52/* for correct statistics, we need at least 10 ticks between each measure */
53#define MIN_STAT_SAMPLING_RATE			\
54			(MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
55#define MIN_SAMPLING_RATE			\
56			(def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
57#define MAX_SAMPLING_RATE			(500 * def_sampling_rate)
58#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER	(1000)
59#define DEF_SAMPLING_DOWN_FACTOR		(1)
60#define MAX_SAMPLING_DOWN_FACTOR		(10)
61#define TRANSITION_LATENCY_LIMIT		(10 * 1000)
62
63static void do_dbs_timer(struct work_struct *work);
64
65struct cpu_dbs_info_s {
66	struct cpufreq_policy 	*cur_policy;
67	unsigned int 		prev_cpu_idle_up;
68	unsigned int 		prev_cpu_idle_down;
69	unsigned int 		enable;
70	unsigned int		down_skip;
71	unsigned int		requested_freq;
72};
73static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
74
75static unsigned int dbs_enable;	/* number of CPUs using this policy */
76
77/*
78 * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
79 * lock and dbs_mutex. cpu_hotplug lock should always be held before
80 * dbs_mutex. If any function that can potentially take cpu_hotplug lock
81 * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
82 * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
83 * is recursive for the same process. -Venki
84 */
85static DEFINE_MUTEX 	(dbs_mutex);
86static DECLARE_DELAYED_WORK(dbs_work, do_dbs_timer);
87
88struct dbs_tuners {
89	unsigned int 		sampling_rate;
90	unsigned int		sampling_down_factor;
91	unsigned int		up_threshold;
92	unsigned int		down_threshold;
93	unsigned int		ignore_nice;
94	unsigned int		freq_step;
95};
96
97static struct dbs_tuners dbs_tuners_ins = {
98	.up_threshold 		= DEF_FREQUENCY_UP_THRESHOLD,
99	.down_threshold 	= DEF_FREQUENCY_DOWN_THRESHOLD,
100	.sampling_down_factor 	= DEF_SAMPLING_DOWN_FACTOR,
101	.ignore_nice		= 0,
102	.freq_step		= 5,
103};
104
105static inline unsigned int get_cpu_idle_time(unsigned int cpu)
106{
107	unsigned int add_nice = 0, ret;
108
109	if (dbs_tuners_ins.ignore_nice)
110		add_nice = kstat_cpu(cpu).cpustat.nice;
111
112	ret = 	kstat_cpu(cpu).cpustat.idle +
113		kstat_cpu(cpu).cpustat.iowait +
114		add_nice;
115
116	return ret;
117}
118
119/************************** sysfs interface ************************/
120static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
121{
122	return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
123}
124
125static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
126{
127	return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
128}
129
130#define define_one_ro(_name) 					\
131static struct freq_attr _name =  				\
132__ATTR(_name, 0444, show_##_name, NULL)
133
134define_one_ro(sampling_rate_max);
135define_one_ro(sampling_rate_min);
136
137/* cpufreq_conservative Governor Tunables */
138#define show_one(file_name, object)					\
139static ssize_t show_##file_name						\
140(struct cpufreq_policy *unused, char *buf)				\
141{									\
142	return sprintf(buf, "%u\n", dbs_tuners_ins.object);		\
143}
144show_one(sampling_rate, sampling_rate);
145show_one(sampling_down_factor, sampling_down_factor);
146show_one(up_threshold, up_threshold);
147show_one(down_threshold, down_threshold);
148show_one(ignore_nice_load, ignore_nice);
149show_one(freq_step, freq_step);
150
151static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
152		const char *buf, size_t count)
153{
154	unsigned int input;
155	int ret;
156	ret = sscanf (buf, "%u", &input);
157	if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
158		return -EINVAL;
159
160	mutex_lock(&dbs_mutex);
161	dbs_tuners_ins.sampling_down_factor = input;
162	mutex_unlock(&dbs_mutex);
163
164	return count;
165}
166
167static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
168		const char *buf, size_t count)
169{
170	unsigned int input;
171	int ret;
172	ret = sscanf (buf, "%u", &input);
173
174	mutex_lock(&dbs_mutex);
175	if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
176		mutex_unlock(&dbs_mutex);
177		return -EINVAL;
178	}
179
180	dbs_tuners_ins.sampling_rate = input;
181	mutex_unlock(&dbs_mutex);
182
183	return count;
184}
185
186static ssize_t store_up_threshold(struct cpufreq_policy *unused,
187		const char *buf, size_t count)
188{
189	unsigned int input;
190	int ret;
191	ret = sscanf (buf, "%u", &input);
192
193	mutex_lock(&dbs_mutex);
194	if (ret != 1 || input > 100 || input <= dbs_tuners_ins.down_threshold) {
195		mutex_unlock(&dbs_mutex);
196		return -EINVAL;
197	}
198
199	dbs_tuners_ins.up_threshold = input;
200	mutex_unlock(&dbs_mutex);
201
202	return count;
203}
204
205static ssize_t store_down_threshold(struct cpufreq_policy *unused,
206		const char *buf, size_t count)
207{
208	unsigned int input;
209	int ret;
210	ret = sscanf (buf, "%u", &input);
211
212	mutex_lock(&dbs_mutex);
213	if (ret != 1 || input > 100 || input >= dbs_tuners_ins.up_threshold) {
214		mutex_unlock(&dbs_mutex);
215		return -EINVAL;
216	}
217
218	dbs_tuners_ins.down_threshold = input;
219	mutex_unlock(&dbs_mutex);
220
221	return count;
222}
223
224static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
225		const char *buf, size_t count)
226{
227	unsigned int input;
228	int ret;
229
230	unsigned int j;
231
232	ret = sscanf (buf, "%u", &input);
233	if ( ret != 1 )
234		return -EINVAL;
235
236	if ( input > 1 )
237		input = 1;
238
239	mutex_lock(&dbs_mutex);
240	if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
241		mutex_unlock(&dbs_mutex);
242		return count;
243	}
244	dbs_tuners_ins.ignore_nice = input;
245
246	/* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
247	for_each_online_cpu(j) {
248		struct cpu_dbs_info_s *j_dbs_info;
249		j_dbs_info = &per_cpu(cpu_dbs_info, j);
250		j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
251		j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
252	}
253	mutex_unlock(&dbs_mutex);
254
255	return count;
256}
257
258static ssize_t store_freq_step(struct cpufreq_policy *policy,
259		const char *buf, size_t count)
260{
261	unsigned int input;
262	int ret;
263
264	ret = sscanf (buf, "%u", &input);
265
266	if ( ret != 1 )
267		return -EINVAL;
268
269	if ( input > 100 )
270		input = 100;
271
272	/* no need to test here if freq_step is zero as the user might actually
273	 * want this, they would be crazy though :) */
274	mutex_lock(&dbs_mutex);
275	dbs_tuners_ins.freq_step = input;
276	mutex_unlock(&dbs_mutex);
277
278	return count;
279}
280
281#define define_one_rw(_name) \
282static struct freq_attr _name = \
283__ATTR(_name, 0644, show_##_name, store_##_name)
284
285define_one_rw(sampling_rate);
286define_one_rw(sampling_down_factor);
287define_one_rw(up_threshold);
288define_one_rw(down_threshold);
289define_one_rw(ignore_nice_load);
290define_one_rw(freq_step);
291
292static struct attribute * dbs_attributes[] = {
293	&sampling_rate_max.attr,
294	&sampling_rate_min.attr,
295	&sampling_rate.attr,
296	&sampling_down_factor.attr,
297	&up_threshold.attr,
298	&down_threshold.attr,
299	&ignore_nice_load.attr,
300	&freq_step.attr,
301	NULL
302};
303
304static struct attribute_group dbs_attr_group = {
305	.attrs = dbs_attributes,
306	.name = "conservative",
307};
308
309/************************** sysfs end ************************/
310
311static void dbs_check_cpu(int cpu)
312{
313	unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;
314	unsigned int tmp_idle_ticks, total_idle_ticks;
315	unsigned int freq_step;
316	unsigned int freq_down_sampling_rate;
317	struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
318	struct cpufreq_policy *policy;
319
320	if (!this_dbs_info->enable)
321		return;
322
323	policy = this_dbs_info->cur_policy;
324
325	/*
326	 * The default safe range is 20% to 80%
327	 * Every sampling_rate, we check
328	 * 	- If current idle time is less than 20%, then we try to
329	 * 	  increase frequency
330	 * Every sampling_rate*sampling_down_factor, we check
331	 * 	- If current idle time is more than 80%, then we try to
332	 * 	  decrease frequency
333	 *
334	 * Any frequency increase takes it to the maximum frequency.
335	 * Frequency reduction happens at minimum steps of
336	 * 5% (default) of max_frequency
337	 */
338
339	/* Check for frequency increase */
340	idle_ticks = UINT_MAX;
341
342	/* Check for frequency increase */
343	total_idle_ticks = get_cpu_idle_time(cpu);
344	tmp_idle_ticks = total_idle_ticks -
345		this_dbs_info->prev_cpu_idle_up;
346	this_dbs_info->prev_cpu_idle_up = total_idle_ticks;
347
348	if (tmp_idle_ticks < idle_ticks)
349		idle_ticks = tmp_idle_ticks;
350
351	/* Scale idle ticks by 100 and compare with up and down ticks */
352	idle_ticks *= 100;
353	up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
354			usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
355
356	if (idle_ticks < up_idle_ticks) {
357		this_dbs_info->down_skip = 0;
358		this_dbs_info->prev_cpu_idle_down =
359			this_dbs_info->prev_cpu_idle_up;
360
361		/* if we are already at full speed then break out early */
362		if (this_dbs_info->requested_freq == policy->max)
363			return;
364
365		freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
366
367		/* max freq cannot be less than 100. But who knows.... */
368		if (unlikely(freq_step == 0))
369			freq_step = 5;
370
371		this_dbs_info->requested_freq += freq_step;
372		if (this_dbs_info->requested_freq > policy->max)
373			this_dbs_info->requested_freq = policy->max;
374
375		__cpufreq_driver_target(policy, this_dbs_info->requested_freq,
376			CPUFREQ_RELATION_H);
377		return;
378	}
379
380	/* Check for frequency decrease */
381	this_dbs_info->down_skip++;
382	if (this_dbs_info->down_skip < dbs_tuners_ins.sampling_down_factor)
383		return;
384
385	/* Check for frequency decrease */
386	total_idle_ticks = this_dbs_info->prev_cpu_idle_up;
387	tmp_idle_ticks = total_idle_ticks -
388		this_dbs_info->prev_cpu_idle_down;
389	this_dbs_info->prev_cpu_idle_down = total_idle_ticks;
390
391	if (tmp_idle_ticks < idle_ticks)
392		idle_ticks = tmp_idle_ticks;
393
394	/* Scale idle ticks by 100 and compare with up and down ticks */
395	idle_ticks *= 100;
396	this_dbs_info->down_skip = 0;
397
398	freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
399		dbs_tuners_ins.sampling_down_factor;
400	down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) *
401		usecs_to_jiffies(freq_down_sampling_rate);
402
403	if (idle_ticks > down_idle_ticks) {
404		/*
405		 * if we are already at the lowest speed then break out early
406		 * or if we 'cannot' reduce the speed as the user might want
407		 * freq_step to be zero
408		 */
409		if (this_dbs_info->requested_freq == policy->min
410				|| dbs_tuners_ins.freq_step == 0)
411			return;
412
413		freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
414
415		/* max freq cannot be less than 100. But who knows.... */
416		if (unlikely(freq_step == 0))
417			freq_step = 5;
418
419		this_dbs_info->requested_freq -= freq_step;
420		if (this_dbs_info->requested_freq < policy->min)
421			this_dbs_info->requested_freq = policy->min;
422
423		__cpufreq_driver_target(policy, this_dbs_info->requested_freq,
424				CPUFREQ_RELATION_H);
425		return;
426	}
427}
428
429static void do_dbs_timer(struct work_struct *work)
430{
431	int i;
432	lock_cpu_hotplug();
433	mutex_lock(&dbs_mutex);
434	for_each_online_cpu(i)
435		dbs_check_cpu(i);
436	schedule_delayed_work(&dbs_work,
437			usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
438	mutex_unlock(&dbs_mutex);
439	unlock_cpu_hotplug();
440}
441
442static inline void dbs_timer_init(void)
443{
444	schedule_delayed_work(&dbs_work,
445			usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
446	return;
447}
448
449static inline void dbs_timer_exit(void)
450{
451	cancel_delayed_work(&dbs_work);
452	return;
453}
454
455static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
456				   unsigned int event)
457{
458	unsigned int cpu = policy->cpu;
459	struct cpu_dbs_info_s *this_dbs_info;
460	unsigned int j;
461	int rc;
462
463	this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
464
465	switch (event) {
466	case CPUFREQ_GOV_START:
467		if ((!cpu_online(cpu)) ||
468		    (!policy->cur))
469			return -EINVAL;
470
471		if (policy->cpuinfo.transition_latency >
472				(TRANSITION_LATENCY_LIMIT * 1000))
473			return -EINVAL;
474		if (this_dbs_info->enable) /* Already enabled */
475			break;
476
477		mutex_lock(&dbs_mutex);
478
479		rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
480		if (rc) {
481			mutex_unlock(&dbs_mutex);
482			return rc;
483		}
484
485		for_each_cpu_mask(j, policy->cpus) {
486			struct cpu_dbs_info_s *j_dbs_info;
487			j_dbs_info = &per_cpu(cpu_dbs_info, j);
488			j_dbs_info->cur_policy = policy;
489
490			j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(cpu);
491			j_dbs_info->prev_cpu_idle_down
492				= j_dbs_info->prev_cpu_idle_up;
493		}
494		this_dbs_info->enable = 1;
495		this_dbs_info->down_skip = 0;
496		this_dbs_info->requested_freq = policy->cur;
497
498		dbs_enable++;
499		/*
500		 * Start the timerschedule work, when this governor
501		 * is used for first time
502		 */
503		if (dbs_enable == 1) {
504			unsigned int latency;
505			/* policy latency is in nS. Convert it to uS first */
506			latency = policy->cpuinfo.transition_latency / 1000;
507			if (latency == 0)
508				latency = 1;
509
510			def_sampling_rate = 10 * latency *
511					DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
512
513			if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
514				def_sampling_rate = MIN_STAT_SAMPLING_RATE;
515
516			dbs_tuners_ins.sampling_rate = def_sampling_rate;
517
518			dbs_timer_init();
519		}
520
521		mutex_unlock(&dbs_mutex);
522		break;
523
524	case CPUFREQ_GOV_STOP:
525		mutex_lock(&dbs_mutex);
526		this_dbs_info->enable = 0;
527		sysfs_remove_group(&policy->kobj, &dbs_attr_group);
528		dbs_enable--;
529		/*
530		 * Stop the timerschedule work, when this governor
531		 * is used for first time
532		 */
533		if (dbs_enable == 0)
534			dbs_timer_exit();
535
536		mutex_unlock(&dbs_mutex);
537
538		break;
539
540	case CPUFREQ_GOV_LIMITS:
541		mutex_lock(&dbs_mutex);
542		if (policy->max < this_dbs_info->cur_policy->cur)
543			__cpufreq_driver_target(
544					this_dbs_info->cur_policy,
545				       	policy->max, CPUFREQ_RELATION_H);
546		else if (policy->min > this_dbs_info->cur_policy->cur)
547			__cpufreq_driver_target(
548					this_dbs_info->cur_policy,
549				       	policy->min, CPUFREQ_RELATION_L);
550		mutex_unlock(&dbs_mutex);
551		break;
552	}
553	return 0;
554}
555
556static struct cpufreq_governor cpufreq_gov_dbs = {
557	.name		= "conservative",
558	.governor	= cpufreq_governor_dbs,
559	.owner		= THIS_MODULE,
560};
561
562static int __init cpufreq_gov_dbs_init(void)
563{
564	return cpufreq_register_governor(&cpufreq_gov_dbs);
565}
566
567static void __exit cpufreq_gov_dbs_exit(void)
568{
569	/* Make sure that the scheduled work is indeed not running */
570	flush_scheduled_work();
571
572	cpufreq_unregister_governor(&cpufreq_gov_dbs);
573}
574
575
576MODULE_AUTHOR ("Alexander Clouter <alex-kernel@digriz.org.uk>");
577MODULE_DESCRIPTION ("'cpufreq_conservative' - A dynamic cpufreq governor for "
578		"Low Latency Frequency Transition capable processors "
579		"optimised for use in a battery environment");
580MODULE_LICENSE ("GPL");
581
582module_init(cpufreq_gov_dbs_init);
583module_exit(cpufreq_gov_dbs_exit);
584