2 * drivers/cpufreq/cpufreq_conservative.c
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>
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.
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>
24 #include <linux/sysfs.h>
25 #include <linux/cpu.h>
26 #include <linux/sched.h>
27 #include <linux/kmod.h>
28 #include <linux/workqueue.h>
29 #include <linux/jiffies.h>
30 #include <linux/kernel_stat.h>
31 #include <linux/percpu.h>
32 #include <linux/mutex.h>
34 * dbs is used in this file as a shortform for demandbased switching
35 * It helps to keep variable names smaller, simpler
38 #define DEF_FREQUENCY_UP_THRESHOLD (80)
39 #define DEF_FREQUENCY_DOWN_THRESHOLD (20)
42 * The polling frequency of this governor depends on the capability of
43 * the processor. Default polling frequency is 1000 times the transition
44 * latency of the processor. The governor will work on any processor with
45 * transition latency <= 10mS, using appropriate sampling
47 * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
48 * this governor will not work.
49 * All times here are in uS.
51 static unsigned int def_sampling_rate;
52 #define MIN_SAMPLING_RATE_RATIO (2)
53 /* for correct statistics, we need at least 10 ticks between each measure */
54 #define MIN_STAT_SAMPLING_RATE (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
55 #define MIN_SAMPLING_RATE (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
56 #define MAX_SAMPLING_RATE (500 * def_sampling_rate)
57 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000)
58 #define DEF_SAMPLING_DOWN_FACTOR (1)
59 #define MAX_SAMPLING_DOWN_FACTOR (10)
60 #define TRANSITION_LATENCY_LIMIT (10 * 1000)
62 static void do_dbs_timer(struct work_struct *work);
64 struct cpu_dbs_info_s {
65 struct cpufreq_policy *cur_policy;
66 unsigned int prev_cpu_idle_up;
67 unsigned int prev_cpu_idle_down;
69 unsigned int down_skip;
70 unsigned int requested_freq;
72 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
74 static unsigned int dbs_enable; /* number of CPUs using this policy */
77 * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
78 * lock and dbs_mutex. cpu_hotplug lock should always be held before
79 * dbs_mutex. If any function that can potentially take cpu_hotplug lock
80 * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
81 * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
82 * is recursive for the same process. -Venki
84 static DEFINE_MUTEX (dbs_mutex);
85 static DECLARE_DELAYED_WORK(dbs_work, do_dbs_timer);
88 unsigned int sampling_rate;
89 unsigned int sampling_down_factor;
90 unsigned int up_threshold;
91 unsigned int down_threshold;
92 unsigned int ignore_nice;
93 unsigned int freq_step;
96 static struct dbs_tuners dbs_tuners_ins = {
97 .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
98 .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
99 .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
104 static inline unsigned int get_cpu_idle_time(unsigned int cpu)
106 return kstat_cpu(cpu).cpustat.idle +
107 kstat_cpu(cpu).cpustat.iowait +
108 ( dbs_tuners_ins.ignore_nice ?
109 kstat_cpu(cpu).cpustat.nice :
113 /************************** sysfs interface ************************/
114 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
116 return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
119 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
121 return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
124 #define define_one_ro(_name) \
125 static struct freq_attr _name = \
126 __ATTR(_name, 0444, show_##_name, NULL)
128 define_one_ro(sampling_rate_max);
129 define_one_ro(sampling_rate_min);
131 /* cpufreq_conservative Governor Tunables */
132 #define show_one(file_name, object) \
133 static ssize_t show_##file_name \
134 (struct cpufreq_policy *unused, char *buf) \
136 return sprintf(buf, "%u\n", dbs_tuners_ins.object); \
138 show_one(sampling_rate, sampling_rate);
139 show_one(sampling_down_factor, sampling_down_factor);
140 show_one(up_threshold, up_threshold);
141 show_one(down_threshold, down_threshold);
142 show_one(ignore_nice_load, ignore_nice);
143 show_one(freq_step, freq_step);
145 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
146 const char *buf, size_t count)
150 ret = sscanf (buf, "%u", &input);
151 if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
154 mutex_lock(&dbs_mutex);
155 dbs_tuners_ins.sampling_down_factor = input;
156 mutex_unlock(&dbs_mutex);
161 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
162 const char *buf, size_t count)
166 ret = sscanf (buf, "%u", &input);
168 mutex_lock(&dbs_mutex);
169 if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
170 mutex_unlock(&dbs_mutex);
174 dbs_tuners_ins.sampling_rate = input;
175 mutex_unlock(&dbs_mutex);
180 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
181 const char *buf, size_t count)
185 ret = sscanf (buf, "%u", &input);
187 mutex_lock(&dbs_mutex);
188 if (ret != 1 || input > 100 || input <= dbs_tuners_ins.down_threshold) {
189 mutex_unlock(&dbs_mutex);
193 dbs_tuners_ins.up_threshold = input;
194 mutex_unlock(&dbs_mutex);
199 static ssize_t store_down_threshold(struct cpufreq_policy *unused,
200 const char *buf, size_t count)
204 ret = sscanf (buf, "%u", &input);
206 mutex_lock(&dbs_mutex);
207 if (ret != 1 || input > 100 || input >= dbs_tuners_ins.up_threshold) {
208 mutex_unlock(&dbs_mutex);
212 dbs_tuners_ins.down_threshold = input;
213 mutex_unlock(&dbs_mutex);
218 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
219 const char *buf, size_t count)
226 ret = sscanf (buf, "%u", &input);
233 mutex_lock(&dbs_mutex);
234 if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
235 mutex_unlock(&dbs_mutex);
238 dbs_tuners_ins.ignore_nice = input;
240 /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
241 for_each_online_cpu(j) {
242 struct cpu_dbs_info_s *j_dbs_info;
243 j_dbs_info = &per_cpu(cpu_dbs_info, j);
244 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
245 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
247 mutex_unlock(&dbs_mutex);
252 static ssize_t store_freq_step(struct cpufreq_policy *policy,
253 const char *buf, size_t count)
258 ret = sscanf (buf, "%u", &input);
266 /* no need to test here if freq_step is zero as the user might actually
267 * want this, they would be crazy though :) */
268 mutex_lock(&dbs_mutex);
269 dbs_tuners_ins.freq_step = input;
270 mutex_unlock(&dbs_mutex);
275 #define define_one_rw(_name) \
276 static struct freq_attr _name = \
277 __ATTR(_name, 0644, show_##_name, store_##_name)
279 define_one_rw(sampling_rate);
280 define_one_rw(sampling_down_factor);
281 define_one_rw(up_threshold);
282 define_one_rw(down_threshold);
283 define_one_rw(ignore_nice_load);
284 define_one_rw(freq_step);
286 static struct attribute * dbs_attributes[] = {
287 &sampling_rate_max.attr,
288 &sampling_rate_min.attr,
290 &sampling_down_factor.attr,
292 &down_threshold.attr,
293 &ignore_nice_load.attr,
298 static struct attribute_group dbs_attr_group = {
299 .attrs = dbs_attributes,
300 .name = "conservative",
303 /************************** sysfs end ************************/
305 static void dbs_check_cpu(int cpu)
307 unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;
308 unsigned int tmp_idle_ticks, total_idle_ticks;
309 unsigned int freq_step;
310 unsigned int freq_down_sampling_rate;
311 struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
312 struct cpufreq_policy *policy;
314 if (!this_dbs_info->enable)
317 policy = this_dbs_info->cur_policy;
320 * The default safe range is 20% to 80%
321 * Every sampling_rate, we check
322 * - If current idle time is less than 20%, then we try to
324 * Every sampling_rate*sampling_down_factor, we check
325 * - If current idle time is more than 80%, then we try to
328 * Any frequency increase takes it to the maximum frequency.
329 * Frequency reduction happens at minimum steps of
330 * 5% (default) of max_frequency
333 /* Check for frequency increase */
334 idle_ticks = UINT_MAX;
336 /* Check for frequency increase */
337 total_idle_ticks = get_cpu_idle_time(cpu);
338 tmp_idle_ticks = total_idle_ticks -
339 this_dbs_info->prev_cpu_idle_up;
340 this_dbs_info->prev_cpu_idle_up = total_idle_ticks;
342 if (tmp_idle_ticks < idle_ticks)
343 idle_ticks = tmp_idle_ticks;
345 /* Scale idle ticks by 100 and compare with up and down ticks */
347 up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
348 usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
350 if (idle_ticks < up_idle_ticks) {
351 this_dbs_info->down_skip = 0;
352 this_dbs_info->prev_cpu_idle_down =
353 this_dbs_info->prev_cpu_idle_up;
355 /* if we are already at full speed then break out early */
356 if (this_dbs_info->requested_freq == policy->max)
359 freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
361 /* max freq cannot be less than 100. But who knows.... */
362 if (unlikely(freq_step == 0))
365 this_dbs_info->requested_freq += freq_step;
366 if (this_dbs_info->requested_freq > policy->max)
367 this_dbs_info->requested_freq = policy->max;
369 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
374 /* Check for frequency decrease */
375 this_dbs_info->down_skip++;
376 if (this_dbs_info->down_skip < dbs_tuners_ins.sampling_down_factor)
379 /* Check for frequency decrease */
380 total_idle_ticks = this_dbs_info->prev_cpu_idle_up;
381 tmp_idle_ticks = total_idle_ticks -
382 this_dbs_info->prev_cpu_idle_down;
383 this_dbs_info->prev_cpu_idle_down = total_idle_ticks;
385 if (tmp_idle_ticks < idle_ticks)
386 idle_ticks = tmp_idle_ticks;
388 /* Scale idle ticks by 100 and compare with up and down ticks */
390 this_dbs_info->down_skip = 0;
392 freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
393 dbs_tuners_ins.sampling_down_factor;
394 down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) *
395 usecs_to_jiffies(freq_down_sampling_rate);
397 if (idle_ticks > down_idle_ticks) {
399 * if we are already at the lowest speed then break out early
400 * or if we 'cannot' reduce the speed as the user might want
401 * freq_step to be zero
403 if (this_dbs_info->requested_freq == policy->min
404 || dbs_tuners_ins.freq_step == 0)
407 freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
409 /* max freq cannot be less than 100. But who knows.... */
410 if (unlikely(freq_step == 0))
413 this_dbs_info->requested_freq -= freq_step;
414 if (this_dbs_info->requested_freq < policy->min)
415 this_dbs_info->requested_freq = policy->min;
417 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
423 static void do_dbs_timer(struct work_struct *work)
427 mutex_lock(&dbs_mutex);
428 for_each_online_cpu(i)
430 schedule_delayed_work(&dbs_work,
431 usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
432 mutex_unlock(&dbs_mutex);
433 unlock_cpu_hotplug();
436 static inline void dbs_timer_init(void)
438 schedule_delayed_work(&dbs_work,
439 usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
443 static inline void dbs_timer_exit(void)
445 cancel_delayed_work(&dbs_work);
449 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
452 unsigned int cpu = policy->cpu;
453 struct cpu_dbs_info_s *this_dbs_info;
456 this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
459 case CPUFREQ_GOV_START:
460 if ((!cpu_online(cpu)) ||
464 if (policy->cpuinfo.transition_latency >
465 (TRANSITION_LATENCY_LIMIT * 1000))
467 if (this_dbs_info->enable) /* Already enabled */
470 mutex_lock(&dbs_mutex);
471 for_each_cpu_mask(j, policy->cpus) {
472 struct cpu_dbs_info_s *j_dbs_info;
473 j_dbs_info = &per_cpu(cpu_dbs_info, j);
474 j_dbs_info->cur_policy = policy;
476 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(cpu);
477 j_dbs_info->prev_cpu_idle_down
478 = j_dbs_info->prev_cpu_idle_up;
480 this_dbs_info->enable = 1;
481 this_dbs_info->down_skip = 0;
482 this_dbs_info->requested_freq = policy->cur;
483 sysfs_create_group(&policy->kobj, &dbs_attr_group);
486 * Start the timerschedule work, when this governor
487 * is used for first time
489 if (dbs_enable == 1) {
490 unsigned int latency;
491 /* policy latency is in nS. Convert it to uS first */
492 latency = policy->cpuinfo.transition_latency / 1000;
496 def_sampling_rate = 10 * latency *
497 DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
499 if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
500 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
502 dbs_tuners_ins.sampling_rate = def_sampling_rate;
507 mutex_unlock(&dbs_mutex);
510 case CPUFREQ_GOV_STOP:
511 mutex_lock(&dbs_mutex);
512 this_dbs_info->enable = 0;
513 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
516 * Stop the timerschedule work, when this governor
517 * is used for first time
522 mutex_unlock(&dbs_mutex);
526 case CPUFREQ_GOV_LIMITS:
527 mutex_lock(&dbs_mutex);
528 if (policy->max < this_dbs_info->cur_policy->cur)
529 __cpufreq_driver_target(
530 this_dbs_info->cur_policy,
531 policy->max, CPUFREQ_RELATION_H);
532 else if (policy->min > this_dbs_info->cur_policy->cur)
533 __cpufreq_driver_target(
534 this_dbs_info->cur_policy,
535 policy->min, CPUFREQ_RELATION_L);
536 mutex_unlock(&dbs_mutex);
542 static struct cpufreq_governor cpufreq_gov_dbs = {
543 .name = "conservative",
544 .governor = cpufreq_governor_dbs,
545 .owner = THIS_MODULE,
548 static int __init cpufreq_gov_dbs_init(void)
550 return cpufreq_register_governor(&cpufreq_gov_dbs);
553 static void __exit cpufreq_gov_dbs_exit(void)
555 /* Make sure that the scheduled work is indeed not running */
556 flush_scheduled_work();
558 cpufreq_unregister_governor(&cpufreq_gov_dbs);
562 MODULE_AUTHOR ("Alexander Clouter <alex-kernel@digriz.org.uk>");
563 MODULE_DESCRIPTION ("'cpufreq_conservative' - A dynamic cpufreq governor for "
564 "Low Latency Frequency Transition capable processors "
565 "optimised for use in a battery environment");
566 MODULE_LICENSE ("GPL");
568 module_init(cpufreq_gov_dbs_init);
569 module_exit(cpufreq_gov_dbs_exit);