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/sched.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>
33 * dbs is used in this file as a shortform for demandbased switching
34 * It helps to keep variable names smaller, simpler
37 #define DEF_FREQUENCY_UP_THRESHOLD (80)
38 #define DEF_FREQUENCY_DOWN_THRESHOLD (20)
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
46 * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
47 * this governor will not work.
48 * All times here are in uS.
50 static 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 (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
54 #define MIN_SAMPLING_RATE (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
55 #define MAX_SAMPLING_RATE (500 * def_sampling_rate)
56 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000)
57 #define DEF_SAMPLING_DOWN_FACTOR (1)
58 #define MAX_SAMPLING_DOWN_FACTOR (10)
59 #define TRANSITION_LATENCY_LIMIT (10 * 1000)
61 static void do_dbs_timer(void *data
);
63 struct cpu_dbs_info_s
{
64 struct cpufreq_policy
*cur_policy
;
65 unsigned int prev_cpu_idle_up
;
66 unsigned int prev_cpu_idle_down
;
68 unsigned int down_skip
;
69 unsigned int requested_freq
;
71 static DEFINE_PER_CPU(struct cpu_dbs_info_s
, cpu_dbs_info
);
73 static unsigned int dbs_enable
; /* number of CPUs using this policy */
76 * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
77 * lock and dbs_mutex. cpu_hotplug lock should always be held before
78 * dbs_mutex. If any function that can potentially take cpu_hotplug lock
79 * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
80 * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
81 * is recursive for the same process. -Venki
83 static DEFINE_MUTEX (dbs_mutex
);
84 static DECLARE_WORK (dbs_work
, do_dbs_timer
, NULL
);
87 unsigned int sampling_rate
;
88 unsigned int sampling_down_factor
;
89 unsigned int up_threshold
;
90 unsigned int down_threshold
;
91 unsigned int ignore_nice
;
92 unsigned int freq_step
;
95 static struct dbs_tuners dbs_tuners_ins
= {
96 .up_threshold
= DEF_FREQUENCY_UP_THRESHOLD
,
97 .down_threshold
= DEF_FREQUENCY_DOWN_THRESHOLD
,
98 .sampling_down_factor
= DEF_SAMPLING_DOWN_FACTOR
,
103 static inline unsigned int get_cpu_idle_time(unsigned int cpu
)
105 return kstat_cpu(cpu
).cpustat
.idle
+
106 kstat_cpu(cpu
).cpustat
.iowait
+
107 ( dbs_tuners_ins
.ignore_nice
?
108 kstat_cpu(cpu
).cpustat
.nice
:
112 /************************** sysfs interface ************************/
113 static ssize_t
show_sampling_rate_max(struct cpufreq_policy
*policy
, char *buf
)
115 return sprintf (buf
, "%u\n", MAX_SAMPLING_RATE
);
118 static ssize_t
show_sampling_rate_min(struct cpufreq_policy
*policy
, char *buf
)
120 return sprintf (buf
, "%u\n", MIN_SAMPLING_RATE
);
123 #define define_one_ro(_name) \
124 static struct freq_attr _name = \
125 __ATTR(_name, 0444, show_##_name, NULL)
127 define_one_ro(sampling_rate_max
);
128 define_one_ro(sampling_rate_min
);
130 /* cpufreq_conservative Governor Tunables */
131 #define show_one(file_name, object) \
132 static ssize_t show_##file_name \
133 (struct cpufreq_policy *unused, char *buf) \
135 return sprintf(buf, "%u\n", dbs_tuners_ins.object); \
137 show_one(sampling_rate
, sampling_rate
);
138 show_one(sampling_down_factor
, sampling_down_factor
);
139 show_one(up_threshold
, up_threshold
);
140 show_one(down_threshold
, down_threshold
);
141 show_one(ignore_nice_load
, ignore_nice
);
142 show_one(freq_step
, freq_step
);
144 static ssize_t
store_sampling_down_factor(struct cpufreq_policy
*unused
,
145 const char *buf
, size_t count
)
149 ret
= sscanf (buf
, "%u", &input
);
150 if (ret
!= 1 || input
> MAX_SAMPLING_DOWN_FACTOR
|| input
< 1)
153 mutex_lock(&dbs_mutex
);
154 dbs_tuners_ins
.sampling_down_factor
= input
;
155 mutex_unlock(&dbs_mutex
);
160 static ssize_t
store_sampling_rate(struct cpufreq_policy
*unused
,
161 const char *buf
, size_t count
)
165 ret
= sscanf (buf
, "%u", &input
);
167 mutex_lock(&dbs_mutex
);
168 if (ret
!= 1 || input
> MAX_SAMPLING_RATE
|| input
< MIN_SAMPLING_RATE
) {
169 mutex_unlock(&dbs_mutex
);
173 dbs_tuners_ins
.sampling_rate
= input
;
174 mutex_unlock(&dbs_mutex
);
179 static ssize_t
store_up_threshold(struct cpufreq_policy
*unused
,
180 const char *buf
, size_t count
)
184 ret
= sscanf (buf
, "%u", &input
);
186 mutex_lock(&dbs_mutex
);
187 if (ret
!= 1 || input
> 100 || input
<= dbs_tuners_ins
.down_threshold
) {
188 mutex_unlock(&dbs_mutex
);
192 dbs_tuners_ins
.up_threshold
= input
;
193 mutex_unlock(&dbs_mutex
);
198 static ssize_t
store_down_threshold(struct cpufreq_policy
*unused
,
199 const char *buf
, size_t count
)
203 ret
= sscanf (buf
, "%u", &input
);
205 mutex_lock(&dbs_mutex
);
206 if (ret
!= 1 || input
> 100 || input
>= dbs_tuners_ins
.up_threshold
) {
207 mutex_unlock(&dbs_mutex
);
211 dbs_tuners_ins
.down_threshold
= input
;
212 mutex_unlock(&dbs_mutex
);
217 static ssize_t
store_ignore_nice_load(struct cpufreq_policy
*policy
,
218 const char *buf
, size_t count
)
225 ret
= sscanf (buf
, "%u", &input
);
232 mutex_lock(&dbs_mutex
);
233 if ( input
== dbs_tuners_ins
.ignore_nice
) { /* nothing to do */
234 mutex_unlock(&dbs_mutex
);
237 dbs_tuners_ins
.ignore_nice
= input
;
239 /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
240 for_each_online_cpu(j
) {
241 struct cpu_dbs_info_s
*j_dbs_info
;
242 j_dbs_info
= &per_cpu(cpu_dbs_info
, j
);
243 j_dbs_info
->prev_cpu_idle_up
= get_cpu_idle_time(j
);
244 j_dbs_info
->prev_cpu_idle_down
= j_dbs_info
->prev_cpu_idle_up
;
246 mutex_unlock(&dbs_mutex
);
251 static ssize_t
store_freq_step(struct cpufreq_policy
*policy
,
252 const char *buf
, size_t count
)
257 ret
= sscanf (buf
, "%u", &input
);
265 /* no need to test here if freq_step is zero as the user might actually
266 * want this, they would be crazy though :) */
267 mutex_lock(&dbs_mutex
);
268 dbs_tuners_ins
.freq_step
= input
;
269 mutex_unlock(&dbs_mutex
);
274 #define define_one_rw(_name) \
275 static struct freq_attr _name = \
276 __ATTR(_name, 0644, show_##_name, store_##_name)
278 define_one_rw(sampling_rate
);
279 define_one_rw(sampling_down_factor
);
280 define_one_rw(up_threshold
);
281 define_one_rw(down_threshold
);
282 define_one_rw(ignore_nice_load
);
283 define_one_rw(freq_step
);
285 static struct attribute
* dbs_attributes
[] = {
286 &sampling_rate_max
.attr
,
287 &sampling_rate_min
.attr
,
289 &sampling_down_factor
.attr
,
291 &down_threshold
.attr
,
292 &ignore_nice_load
.attr
,
297 static struct attribute_group dbs_attr_group
= {
298 .attrs
= dbs_attributes
,
299 .name
= "conservative",
302 /************************** sysfs end ************************/
304 static void dbs_check_cpu(int cpu
)
306 unsigned int idle_ticks
, up_idle_ticks
, down_idle_ticks
;
307 unsigned int tmp_idle_ticks
, total_idle_ticks
;
308 unsigned int freq_step
;
309 unsigned int freq_down_sampling_rate
;
310 struct cpu_dbs_info_s
*this_dbs_info
= &per_cpu(cpu_dbs_info
, cpu
);
311 struct cpufreq_policy
*policy
;
313 if (!this_dbs_info
->enable
)
316 policy
= this_dbs_info
->cur_policy
;
319 * The default safe range is 20% to 80%
320 * Every sampling_rate, we check
321 * - If current idle time is less than 20%, then we try to
323 * Every sampling_rate*sampling_down_factor, we check
324 * - If current idle time is more than 80%, then we try to
327 * Any frequency increase takes it to the maximum frequency.
328 * Frequency reduction happens at minimum steps of
329 * 5% (default) of max_frequency
332 /* Check for frequency increase */
333 idle_ticks
= UINT_MAX
;
335 /* Check for frequency increase */
336 total_idle_ticks
= get_cpu_idle_time(cpu
);
337 tmp_idle_ticks
= total_idle_ticks
-
338 this_dbs_info
->prev_cpu_idle_up
;
339 this_dbs_info
->prev_cpu_idle_up
= total_idle_ticks
;
341 if (tmp_idle_ticks
< idle_ticks
)
342 idle_ticks
= tmp_idle_ticks
;
344 /* Scale idle ticks by 100 and compare with up and down ticks */
346 up_idle_ticks
= (100 - dbs_tuners_ins
.up_threshold
) *
347 usecs_to_jiffies(dbs_tuners_ins
.sampling_rate
);
349 if (idle_ticks
< up_idle_ticks
) {
350 this_dbs_info
->down_skip
= 0;
351 this_dbs_info
->prev_cpu_idle_down
=
352 this_dbs_info
->prev_cpu_idle_up
;
354 /* if we are already at full speed then break out early */
355 if (this_dbs_info
->requested_freq
== policy
->max
)
358 freq_step
= (dbs_tuners_ins
.freq_step
* policy
->max
) / 100;
360 /* max freq cannot be less than 100. But who knows.... */
361 if (unlikely(freq_step
== 0))
364 this_dbs_info
->requested_freq
+= freq_step
;
365 if (this_dbs_info
->requested_freq
> policy
->max
)
366 this_dbs_info
->requested_freq
= policy
->max
;
368 __cpufreq_driver_target(policy
, this_dbs_info
->requested_freq
,
373 /* Check for frequency decrease */
374 this_dbs_info
->down_skip
++;
375 if (this_dbs_info
->down_skip
< dbs_tuners_ins
.sampling_down_factor
)
378 /* Check for frequency decrease */
379 total_idle_ticks
= this_dbs_info
->prev_cpu_idle_up
;
380 tmp_idle_ticks
= total_idle_ticks
-
381 this_dbs_info
->prev_cpu_idle_down
;
382 this_dbs_info
->prev_cpu_idle_down
= total_idle_ticks
;
384 if (tmp_idle_ticks
< idle_ticks
)
385 idle_ticks
= tmp_idle_ticks
;
387 /* Scale idle ticks by 100 and compare with up and down ticks */
389 this_dbs_info
->down_skip
= 0;
391 freq_down_sampling_rate
= dbs_tuners_ins
.sampling_rate
*
392 dbs_tuners_ins
.sampling_down_factor
;
393 down_idle_ticks
= (100 - dbs_tuners_ins
.down_threshold
) *
394 usecs_to_jiffies(freq_down_sampling_rate
);
396 if (idle_ticks
> down_idle_ticks
) {
398 * if we are already at the lowest speed then break out early
399 * or if we 'cannot' reduce the speed as the user might want
400 * freq_step to be zero
402 if (this_dbs_info
->requested_freq
== policy
->min
403 || dbs_tuners_ins
.freq_step
== 0)
406 freq_step
= (dbs_tuners_ins
.freq_step
* policy
->max
) / 100;
408 /* max freq cannot be less than 100. But who knows.... */
409 if (unlikely(freq_step
== 0))
412 this_dbs_info
->requested_freq
-= freq_step
;
413 if (this_dbs_info
->requested_freq
< policy
->min
)
414 this_dbs_info
->requested_freq
= policy
->min
;
416 __cpufreq_driver_target(policy
, this_dbs_info
->requested_freq
,
422 static void do_dbs_timer(void *data
)
426 mutex_lock(&dbs_mutex
);
427 for_each_online_cpu(i
)
429 schedule_delayed_work(&dbs_work
,
430 usecs_to_jiffies(dbs_tuners_ins
.sampling_rate
));
431 mutex_unlock(&dbs_mutex
);
432 unlock_cpu_hotplug();
435 static inline void dbs_timer_init(void)
437 INIT_WORK(&dbs_work
, do_dbs_timer
, NULL
);
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
:
528 mutex_lock(&dbs_mutex
);
529 if (policy
->max
< this_dbs_info
->cur_policy
->cur
)
530 __cpufreq_driver_target(
531 this_dbs_info
->cur_policy
,
532 policy
->max
, CPUFREQ_RELATION_H
);
533 else if (policy
->min
> this_dbs_info
->cur_policy
->cur
)
534 __cpufreq_driver_target(
535 this_dbs_info
->cur_policy
,
536 policy
->min
, CPUFREQ_RELATION_L
);
537 mutex_unlock(&dbs_mutex
);
538 unlock_cpu_hotplug();
544 static struct cpufreq_governor cpufreq_gov_dbs
= {
545 .name
= "conservative",
546 .governor
= cpufreq_governor_dbs
,
547 .owner
= THIS_MODULE
,
550 static int __init
cpufreq_gov_dbs_init(void)
552 return cpufreq_register_governor(&cpufreq_gov_dbs
);
555 static void __exit
cpufreq_gov_dbs_exit(void)
557 /* Make sure that the scheduled work is indeed not running */
558 flush_scheduled_work();
560 cpufreq_unregister_governor(&cpufreq_gov_dbs
);
564 MODULE_AUTHOR ("Alexander Clouter <alex-kernel@digriz.org.uk>");
565 MODULE_DESCRIPTION ("'cpufreq_conservative' - A dynamic cpufreq governor for "
566 "Low Latency Frequency Transition capable processors "
567 "optimised for use in a battery environment");
568 MODULE_LICENSE ("GPL");
570 module_init(cpufreq_gov_dbs_init
);
571 module_exit(cpufreq_gov_dbs_exit
);