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
48 * with CPUFREQ_ETERNAL), 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 \
55 (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
56 #define MIN_SAMPLING_RATE \
57 (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
58 #define MAX_SAMPLING_RATE (500 * def_sampling_rate)
59 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000)
60 #define DEF_SAMPLING_DOWN_FACTOR (1)
61 #define MAX_SAMPLING_DOWN_FACTOR (10)
62 #define TRANSITION_LATENCY_LIMIT (10 * 1000)
64 static void do_dbs_timer(struct work_struct
*work
);
66 struct cpu_dbs_info_s
{
67 struct cpufreq_policy
*cur_policy
;
68 unsigned int prev_cpu_idle_up
;
69 unsigned int prev_cpu_idle_down
;
71 unsigned int down_skip
;
72 unsigned int requested_freq
;
74 static DEFINE_PER_CPU(struct cpu_dbs_info_s
, cpu_dbs_info
);
76 static unsigned int dbs_enable
; /* number of CPUs using this policy */
79 * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
80 * lock and dbs_mutex. cpu_hotplug lock should always be held before
81 * dbs_mutex. If any function that can potentially take cpu_hotplug lock
82 * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
83 * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
84 * is recursive for the same process. -Venki
86 static DEFINE_MUTEX (dbs_mutex
);
87 static DECLARE_DELAYED_WORK(dbs_work
, do_dbs_timer
);
90 unsigned int sampling_rate
;
91 unsigned int sampling_down_factor
;
92 unsigned int up_threshold
;
93 unsigned int down_threshold
;
94 unsigned int ignore_nice
;
95 unsigned int freq_step
;
98 static struct dbs_tuners dbs_tuners_ins
= {
99 .up_threshold
= DEF_FREQUENCY_UP_THRESHOLD
,
100 .down_threshold
= DEF_FREQUENCY_DOWN_THRESHOLD
,
101 .sampling_down_factor
= DEF_SAMPLING_DOWN_FACTOR
,
106 static inline unsigned int get_cpu_idle_time(unsigned int cpu
)
108 unsigned int add_nice
= 0, ret
;
110 if (dbs_tuners_ins
.ignore_nice
)
111 add_nice
= kstat_cpu(cpu
).cpustat
.nice
;
113 ret
= kstat_cpu(cpu
).cpustat
.idle
+
114 kstat_cpu(cpu
).cpustat
.iowait
+
120 /************************** sysfs interface ************************/
121 static ssize_t
show_sampling_rate_max(struct cpufreq_policy
*policy
, char *buf
)
123 return sprintf (buf
, "%u\n", MAX_SAMPLING_RATE
);
126 static ssize_t
show_sampling_rate_min(struct cpufreq_policy
*policy
, char *buf
)
128 return sprintf (buf
, "%u\n", MIN_SAMPLING_RATE
);
131 #define define_one_ro(_name) \
132 static struct freq_attr _name = \
133 __ATTR(_name, 0444, show_##_name, NULL)
135 define_one_ro(sampling_rate_max
);
136 define_one_ro(sampling_rate_min
);
138 /* cpufreq_conservative Governor Tunables */
139 #define show_one(file_name, object) \
140 static ssize_t show_##file_name \
141 (struct cpufreq_policy *unused, char *buf) \
143 return sprintf(buf, "%u\n", dbs_tuners_ins.object); \
145 show_one(sampling_rate
, sampling_rate
);
146 show_one(sampling_down_factor
, sampling_down_factor
);
147 show_one(up_threshold
, up_threshold
);
148 show_one(down_threshold
, down_threshold
);
149 show_one(ignore_nice_load
, ignore_nice
);
150 show_one(freq_step
, freq_step
);
152 static ssize_t
store_sampling_down_factor(struct cpufreq_policy
*unused
,
153 const char *buf
, size_t count
)
157 ret
= sscanf (buf
, "%u", &input
);
158 if (ret
!= 1 || input
> MAX_SAMPLING_DOWN_FACTOR
|| input
< 1)
161 mutex_lock(&dbs_mutex
);
162 dbs_tuners_ins
.sampling_down_factor
= input
;
163 mutex_unlock(&dbs_mutex
);
168 static ssize_t
store_sampling_rate(struct cpufreq_policy
*unused
,
169 const char *buf
, size_t count
)
173 ret
= sscanf (buf
, "%u", &input
);
175 mutex_lock(&dbs_mutex
);
176 if (ret
!= 1 || input
> MAX_SAMPLING_RATE
|| input
< MIN_SAMPLING_RATE
) {
177 mutex_unlock(&dbs_mutex
);
181 dbs_tuners_ins
.sampling_rate
= input
;
182 mutex_unlock(&dbs_mutex
);
187 static ssize_t
store_up_threshold(struct cpufreq_policy
*unused
,
188 const char *buf
, size_t count
)
192 ret
= sscanf (buf
, "%u", &input
);
194 mutex_lock(&dbs_mutex
);
195 if (ret
!= 1 || input
> 100 || input
<= dbs_tuners_ins
.down_threshold
) {
196 mutex_unlock(&dbs_mutex
);
200 dbs_tuners_ins
.up_threshold
= input
;
201 mutex_unlock(&dbs_mutex
);
206 static ssize_t
store_down_threshold(struct cpufreq_policy
*unused
,
207 const char *buf
, size_t count
)
211 ret
= sscanf (buf
, "%u", &input
);
213 mutex_lock(&dbs_mutex
);
214 if (ret
!= 1 || input
> 100 || input
>= dbs_tuners_ins
.up_threshold
) {
215 mutex_unlock(&dbs_mutex
);
219 dbs_tuners_ins
.down_threshold
= input
;
220 mutex_unlock(&dbs_mutex
);
225 static ssize_t
store_ignore_nice_load(struct cpufreq_policy
*policy
,
226 const char *buf
, size_t count
)
233 ret
= sscanf (buf
, "%u", &input
);
240 mutex_lock(&dbs_mutex
);
241 if ( input
== dbs_tuners_ins
.ignore_nice
) { /* nothing to do */
242 mutex_unlock(&dbs_mutex
);
245 dbs_tuners_ins
.ignore_nice
= input
;
247 /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
248 for_each_online_cpu(j
) {
249 struct cpu_dbs_info_s
*j_dbs_info
;
250 j_dbs_info
= &per_cpu(cpu_dbs_info
, j
);
251 j_dbs_info
->prev_cpu_idle_up
= get_cpu_idle_time(j
);
252 j_dbs_info
->prev_cpu_idle_down
= j_dbs_info
->prev_cpu_idle_up
;
254 mutex_unlock(&dbs_mutex
);
259 static ssize_t
store_freq_step(struct cpufreq_policy
*policy
,
260 const char *buf
, size_t count
)
265 ret
= sscanf (buf
, "%u", &input
);
273 /* no need to test here if freq_step is zero as the user might actually
274 * want this, they would be crazy though :) */
275 mutex_lock(&dbs_mutex
);
276 dbs_tuners_ins
.freq_step
= input
;
277 mutex_unlock(&dbs_mutex
);
282 #define define_one_rw(_name) \
283 static struct freq_attr _name = \
284 __ATTR(_name, 0644, show_##_name, store_##_name)
286 define_one_rw(sampling_rate
);
287 define_one_rw(sampling_down_factor
);
288 define_one_rw(up_threshold
);
289 define_one_rw(down_threshold
);
290 define_one_rw(ignore_nice_load
);
291 define_one_rw(freq_step
);
293 static struct attribute
* dbs_attributes
[] = {
294 &sampling_rate_max
.attr
,
295 &sampling_rate_min
.attr
,
297 &sampling_down_factor
.attr
,
299 &down_threshold
.attr
,
300 &ignore_nice_load
.attr
,
305 static struct attribute_group dbs_attr_group
= {
306 .attrs
= dbs_attributes
,
307 .name
= "conservative",
310 /************************** sysfs end ************************/
312 static void dbs_check_cpu(int cpu
)
314 unsigned int idle_ticks
, up_idle_ticks
, down_idle_ticks
;
315 unsigned int tmp_idle_ticks
, total_idle_ticks
;
316 unsigned int freq_step
;
317 unsigned int freq_down_sampling_rate
;
318 struct cpu_dbs_info_s
*this_dbs_info
= &per_cpu(cpu_dbs_info
, cpu
);
319 struct cpufreq_policy
*policy
;
321 if (!this_dbs_info
->enable
)
324 policy
= this_dbs_info
->cur_policy
;
327 * The default safe range is 20% to 80%
328 * Every sampling_rate, we check
329 * - If current idle time is less than 20%, then we try to
331 * Every sampling_rate*sampling_down_factor, we check
332 * - If current idle time is more than 80%, then we try to
335 * Any frequency increase takes it to the maximum frequency.
336 * Frequency reduction happens at minimum steps of
337 * 5% (default) of max_frequency
340 /* Check for frequency increase */
341 idle_ticks
= UINT_MAX
;
343 /* Check for frequency increase */
344 total_idle_ticks
= get_cpu_idle_time(cpu
);
345 tmp_idle_ticks
= total_idle_ticks
-
346 this_dbs_info
->prev_cpu_idle_up
;
347 this_dbs_info
->prev_cpu_idle_up
= total_idle_ticks
;
349 if (tmp_idle_ticks
< idle_ticks
)
350 idle_ticks
= tmp_idle_ticks
;
352 /* Scale idle ticks by 100 and compare with up and down ticks */
354 up_idle_ticks
= (100 - dbs_tuners_ins
.up_threshold
) *
355 usecs_to_jiffies(dbs_tuners_ins
.sampling_rate
);
357 if (idle_ticks
< up_idle_ticks
) {
358 this_dbs_info
->down_skip
= 0;
359 this_dbs_info
->prev_cpu_idle_down
=
360 this_dbs_info
->prev_cpu_idle_up
;
362 /* if we are already at full speed then break out early */
363 if (this_dbs_info
->requested_freq
== policy
->max
)
366 freq_step
= (dbs_tuners_ins
.freq_step
* policy
->max
) / 100;
368 /* max freq cannot be less than 100. But who knows.... */
369 if (unlikely(freq_step
== 0))
372 this_dbs_info
->requested_freq
+= freq_step
;
373 if (this_dbs_info
->requested_freq
> policy
->max
)
374 this_dbs_info
->requested_freq
= policy
->max
;
376 __cpufreq_driver_target(policy
, this_dbs_info
->requested_freq
,
381 /* Check for frequency decrease */
382 this_dbs_info
->down_skip
++;
383 if (this_dbs_info
->down_skip
< dbs_tuners_ins
.sampling_down_factor
)
386 /* Check for frequency decrease */
387 total_idle_ticks
= this_dbs_info
->prev_cpu_idle_up
;
388 tmp_idle_ticks
= total_idle_ticks
-
389 this_dbs_info
->prev_cpu_idle_down
;
390 this_dbs_info
->prev_cpu_idle_down
= total_idle_ticks
;
392 if (tmp_idle_ticks
< idle_ticks
)
393 idle_ticks
= tmp_idle_ticks
;
395 /* Scale idle ticks by 100 and compare with up and down ticks */
397 this_dbs_info
->down_skip
= 0;
399 freq_down_sampling_rate
= dbs_tuners_ins
.sampling_rate
*
400 dbs_tuners_ins
.sampling_down_factor
;
401 down_idle_ticks
= (100 - dbs_tuners_ins
.down_threshold
) *
402 usecs_to_jiffies(freq_down_sampling_rate
);
404 if (idle_ticks
> down_idle_ticks
) {
406 * if we are already at the lowest speed then break out early
407 * or if we 'cannot' reduce the speed as the user might want
408 * freq_step to be zero
410 if (this_dbs_info
->requested_freq
== policy
->min
411 || dbs_tuners_ins
.freq_step
== 0)
414 freq_step
= (dbs_tuners_ins
.freq_step
* policy
->max
) / 100;
416 /* max freq cannot be less than 100. But who knows.... */
417 if (unlikely(freq_step
== 0))
420 this_dbs_info
->requested_freq
-= freq_step
;
421 if (this_dbs_info
->requested_freq
< policy
->min
)
422 this_dbs_info
->requested_freq
= policy
->min
;
424 __cpufreq_driver_target(policy
, this_dbs_info
->requested_freq
,
430 static void do_dbs_timer(struct work_struct
*work
)
434 mutex_lock(&dbs_mutex
);
435 for_each_online_cpu(i
)
437 schedule_delayed_work(&dbs_work
,
438 usecs_to_jiffies(dbs_tuners_ins
.sampling_rate
));
439 mutex_unlock(&dbs_mutex
);
440 unlock_cpu_hotplug();
443 static inline void dbs_timer_init(void)
445 schedule_delayed_work(&dbs_work
,
446 usecs_to_jiffies(dbs_tuners_ins
.sampling_rate
));
450 static inline void dbs_timer_exit(void)
452 cancel_delayed_work(&dbs_work
);
456 static int cpufreq_governor_dbs(struct cpufreq_policy
*policy
,
459 unsigned int cpu
= policy
->cpu
;
460 struct cpu_dbs_info_s
*this_dbs_info
;
464 this_dbs_info
= &per_cpu(cpu_dbs_info
, cpu
);
467 case CPUFREQ_GOV_START
:
468 if ((!cpu_online(cpu
)) ||
472 if (policy
->cpuinfo
.transition_latency
>
473 (TRANSITION_LATENCY_LIMIT
* 1000))
475 if (this_dbs_info
->enable
) /* Already enabled */
478 mutex_lock(&dbs_mutex
);
480 rc
= sysfs_create_group(&policy
->kobj
, &dbs_attr_group
);
482 mutex_unlock(&dbs_mutex
);
486 for_each_cpu_mask(j
, policy
->cpus
) {
487 struct cpu_dbs_info_s
*j_dbs_info
;
488 j_dbs_info
= &per_cpu(cpu_dbs_info
, j
);
489 j_dbs_info
->cur_policy
= policy
;
491 j_dbs_info
->prev_cpu_idle_up
= get_cpu_idle_time(cpu
);
492 j_dbs_info
->prev_cpu_idle_down
493 = j_dbs_info
->prev_cpu_idle_up
;
495 this_dbs_info
->enable
= 1;
496 this_dbs_info
->down_skip
= 0;
497 this_dbs_info
->requested_freq
= policy
->cur
;
501 * Start the timerschedule work, when this governor
502 * is used for first time
504 if (dbs_enable
== 1) {
505 unsigned int latency
;
506 /* policy latency is in nS. Convert it to uS first */
507 latency
= policy
->cpuinfo
.transition_latency
/ 1000;
511 def_sampling_rate
= 10 * latency
*
512 DEF_SAMPLING_RATE_LATENCY_MULTIPLIER
;
514 if (def_sampling_rate
< MIN_STAT_SAMPLING_RATE
)
515 def_sampling_rate
= MIN_STAT_SAMPLING_RATE
;
517 dbs_tuners_ins
.sampling_rate
= def_sampling_rate
;
522 mutex_unlock(&dbs_mutex
);
525 case CPUFREQ_GOV_STOP
:
526 mutex_lock(&dbs_mutex
);
527 this_dbs_info
->enable
= 0;
528 sysfs_remove_group(&policy
->kobj
, &dbs_attr_group
);
531 * Stop the timerschedule work, when this governor
532 * is used for first time
537 mutex_unlock(&dbs_mutex
);
541 case CPUFREQ_GOV_LIMITS
:
542 mutex_lock(&dbs_mutex
);
543 if (policy
->max
< this_dbs_info
->cur_policy
->cur
)
544 __cpufreq_driver_target(
545 this_dbs_info
->cur_policy
,
546 policy
->max
, CPUFREQ_RELATION_H
);
547 else if (policy
->min
> this_dbs_info
->cur_policy
->cur
)
548 __cpufreq_driver_target(
549 this_dbs_info
->cur_policy
,
550 policy
->min
, CPUFREQ_RELATION_L
);
551 mutex_unlock(&dbs_mutex
);
557 static struct cpufreq_governor cpufreq_gov_dbs
= {
558 .name
= "conservative",
559 .governor
= cpufreq_governor_dbs
,
560 .owner
= THIS_MODULE
,
563 static int __init
cpufreq_gov_dbs_init(void)
565 return cpufreq_register_governor(&cpufreq_gov_dbs
);
568 static void __exit
cpufreq_gov_dbs_exit(void)
570 /* Make sure that the scheduled work is indeed not running */
571 flush_scheduled_work();
573 cpufreq_unregister_governor(&cpufreq_gov_dbs
);
577 MODULE_AUTHOR ("Alexander Clouter <alex-kernel@digriz.org.uk>");
578 MODULE_DESCRIPTION ("'cpufreq_conservative' - A dynamic cpufreq governor for "
579 "Low Latency Frequency Transition capable processors "
580 "optimised for use in a battery environment");
581 MODULE_LICENSE ("GPL");
583 module_init(cpufreq_gov_dbs_init
);
584 module_exit(cpufreq_gov_dbs_exit
);