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) 2009 Alexander Clouter <alex@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/init.h>
17 #include <linux/cpufreq.h>
18 #include <linux/cpu.h>
19 #include <linux/jiffies.h>
20 #include <linux/kernel_stat.h>
21 #include <linux/mutex.h>
22 #include <linux/hrtimer.h>
23 #include <linux/tick.h>
24 #include <linux/ktime.h>
25 #include <linux/sched.h>
28 * dbs is used in this file as a shortform for demandbased switching
29 * It helps to keep variable names smaller, simpler
32 #define DEF_FREQUENCY_UP_THRESHOLD (80)
33 #define DEF_FREQUENCY_DOWN_THRESHOLD (20)
36 * The polling frequency of this governor depends on the capability of
37 * the processor. Default polling frequency is 1000 times the transition
38 * latency of the processor. The governor will work on any processor with
39 * transition latency <= 10mS, using appropriate sampling
41 * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
42 * this governor will not work.
43 * All times here are in uS.
45 static unsigned int def_sampling_rate
;
46 #define MIN_SAMPLING_RATE_RATIO (2)
47 /* for correct statistics, we need at least 10 ticks between each measure */
48 #define MIN_STAT_SAMPLING_RATE \
49 (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
50 #define MIN_SAMPLING_RATE \
51 (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
52 /* Above MIN_SAMPLING_RATE will vanish with its sysfs file soon
53 * Define the minimal settable sampling rate to the greater of:
54 * - "HW transition latency" * 100 (same as default sampling / 10)
55 * - MIN_STAT_SAMPLING_RATE
56 * To avoid that userspace shoots itself.
58 static unsigned int minimum_sampling_rate(void)
60 return max(def_sampling_rate
/ 10, MIN_STAT_SAMPLING_RATE
);
63 /* This will also vanish soon with removing sampling_rate_max */
64 #define MAX_SAMPLING_RATE (500 * def_sampling_rate)
65 #define LATENCY_MULTIPLIER (1000)
66 #define DEF_SAMPLING_DOWN_FACTOR (1)
67 #define MAX_SAMPLING_DOWN_FACTOR (10)
68 #define TRANSITION_LATENCY_LIMIT (10 * 1000 * 1000)
70 static void do_dbs_timer(struct work_struct
*work
);
72 struct cpu_dbs_info_s
{
73 cputime64_t prev_cpu_idle
;
74 cputime64_t prev_cpu_wall
;
75 cputime64_t prev_cpu_nice
;
76 struct cpufreq_policy
*cur_policy
;
77 struct delayed_work work
;
78 unsigned int down_skip
;
79 unsigned int requested_freq
;
81 unsigned int enable
:1;
83 static DEFINE_PER_CPU(struct cpu_dbs_info_s
, cpu_dbs_info
);
85 static unsigned int dbs_enable
; /* number of CPUs using this policy */
88 * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
89 * lock and dbs_mutex. cpu_hotplug lock should always be held before
90 * dbs_mutex. If any function that can potentially take cpu_hotplug lock
91 * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
92 * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
93 * is recursive for the same process. -Venki
94 * DEADLOCK ALERT! (2) : do_dbs_timer() must not take the dbs_mutex, because it
95 * would deadlock with cancel_delayed_work_sync(), which is needed for proper
96 * raceless workqueue teardown.
98 static DEFINE_MUTEX(dbs_mutex
);
100 static struct workqueue_struct
*kconservative_wq
;
102 static struct dbs_tuners
{
103 unsigned int sampling_rate
;
104 unsigned int sampling_down_factor
;
105 unsigned int up_threshold
;
106 unsigned int down_threshold
;
107 unsigned int ignore_nice
;
108 unsigned int freq_step
;
110 .up_threshold
= DEF_FREQUENCY_UP_THRESHOLD
,
111 .down_threshold
= DEF_FREQUENCY_DOWN_THRESHOLD
,
112 .sampling_down_factor
= DEF_SAMPLING_DOWN_FACTOR
,
117 static inline cputime64_t
get_cpu_idle_time_jiffy(unsigned int cpu
,
120 cputime64_t idle_time
;
121 cputime64_t cur_wall_time
;
122 cputime64_t busy_time
;
124 cur_wall_time
= jiffies64_to_cputime64(get_jiffies_64());
125 busy_time
= cputime64_add(kstat_cpu(cpu
).cpustat
.user
,
126 kstat_cpu(cpu
).cpustat
.system
);
128 busy_time
= cputime64_add(busy_time
, kstat_cpu(cpu
).cpustat
.irq
);
129 busy_time
= cputime64_add(busy_time
, kstat_cpu(cpu
).cpustat
.softirq
);
130 busy_time
= cputime64_add(busy_time
, kstat_cpu(cpu
).cpustat
.steal
);
131 busy_time
= cputime64_add(busy_time
, kstat_cpu(cpu
).cpustat
.nice
);
133 idle_time
= cputime64_sub(cur_wall_time
, busy_time
);
135 *wall
= cur_wall_time
;
140 static inline cputime64_t
get_cpu_idle_time(unsigned int cpu
, cputime64_t
*wall
)
142 u64 idle_time
= get_cpu_idle_time_us(cpu
, wall
);
144 if (idle_time
== -1ULL)
145 return get_cpu_idle_time_jiffy(cpu
, wall
);
150 /* keep track of frequency transitions */
152 dbs_cpufreq_notifier(struct notifier_block
*nb
, unsigned long val
,
155 struct cpufreq_freqs
*freq
= data
;
156 struct cpu_dbs_info_s
*this_dbs_info
= &per_cpu(cpu_dbs_info
,
159 struct cpufreq_policy
*policy
;
161 if (!this_dbs_info
->enable
)
164 policy
= this_dbs_info
->cur_policy
;
167 * we only care if our internally tracked freq moves outside
168 * the 'valid' ranges of freqency available to us otherwise
169 * we do not change it
171 if (this_dbs_info
->requested_freq
> policy
->max
172 || this_dbs_info
->requested_freq
< policy
->min
)
173 this_dbs_info
->requested_freq
= freq
->new;
178 static struct notifier_block dbs_cpufreq_notifier_block
= {
179 .notifier_call
= dbs_cpufreq_notifier
182 /************************** sysfs interface ************************/
183 static ssize_t
show_sampling_rate_max(struct cpufreq_policy
*policy
, char *buf
)
185 static int print_once
;
188 printk(KERN_INFO
"CPUFREQ: conservative sampling_rate_max "
189 "sysfs file is deprecated - used by: %s\n",
193 return sprintf(buf
, "%u\n", MAX_SAMPLING_RATE
);
196 static ssize_t
show_sampling_rate_min(struct cpufreq_policy
*policy
, char *buf
)
198 static int print_once
;
201 printk(KERN_INFO
"CPUFREQ: conservative sampling_rate_max "
202 "sysfs file is deprecated - used by: %s\n", current
->comm
);
205 return sprintf(buf
, "%u\n", MIN_SAMPLING_RATE
);
208 #define define_one_ro(_name) \
209 static struct freq_attr _name = \
210 __ATTR(_name, 0444, show_##_name, NULL)
212 define_one_ro(sampling_rate_max
);
213 define_one_ro(sampling_rate_min
);
215 /* cpufreq_conservative Governor Tunables */
216 #define show_one(file_name, object) \
217 static ssize_t show_##file_name \
218 (struct cpufreq_policy *unused, char *buf) \
220 return sprintf(buf, "%u\n", dbs_tuners_ins.object); \
222 show_one(sampling_rate
, sampling_rate
);
223 show_one(sampling_down_factor
, sampling_down_factor
);
224 show_one(up_threshold
, up_threshold
);
225 show_one(down_threshold
, down_threshold
);
226 show_one(ignore_nice_load
, ignore_nice
);
227 show_one(freq_step
, freq_step
);
229 static ssize_t
store_sampling_down_factor(struct cpufreq_policy
*unused
,
230 const char *buf
, size_t count
)
234 ret
= sscanf(buf
, "%u", &input
);
236 if (ret
!= 1 || input
> MAX_SAMPLING_DOWN_FACTOR
|| input
< 1)
239 mutex_lock(&dbs_mutex
);
240 dbs_tuners_ins
.sampling_down_factor
= input
;
241 mutex_unlock(&dbs_mutex
);
246 static ssize_t
store_sampling_rate(struct cpufreq_policy
*unused
,
247 const char *buf
, size_t count
)
251 ret
= sscanf(buf
, "%u", &input
);
256 mutex_lock(&dbs_mutex
);
257 dbs_tuners_ins
.sampling_rate
= max(input
, minimum_sampling_rate());
258 mutex_unlock(&dbs_mutex
);
263 static ssize_t
store_up_threshold(struct cpufreq_policy
*unused
,
264 const char *buf
, size_t count
)
268 ret
= sscanf(buf
, "%u", &input
);
270 mutex_lock(&dbs_mutex
);
271 if (ret
!= 1 || input
> 100 ||
272 input
<= dbs_tuners_ins
.down_threshold
) {
273 mutex_unlock(&dbs_mutex
);
277 dbs_tuners_ins
.up_threshold
= input
;
278 mutex_unlock(&dbs_mutex
);
283 static ssize_t
store_down_threshold(struct cpufreq_policy
*unused
,
284 const char *buf
, size_t count
)
288 ret
= sscanf(buf
, "%u", &input
);
290 mutex_lock(&dbs_mutex
);
291 /* cannot be lower than 11 otherwise freq will not fall */
292 if (ret
!= 1 || input
< 11 || input
> 100 ||
293 input
>= dbs_tuners_ins
.up_threshold
) {
294 mutex_unlock(&dbs_mutex
);
298 dbs_tuners_ins
.down_threshold
= input
;
299 mutex_unlock(&dbs_mutex
);
304 static ssize_t
store_ignore_nice_load(struct cpufreq_policy
*policy
,
305 const char *buf
, size_t count
)
312 ret
= sscanf(buf
, "%u", &input
);
319 mutex_lock(&dbs_mutex
);
320 if (input
== dbs_tuners_ins
.ignore_nice
) { /* nothing to do */
321 mutex_unlock(&dbs_mutex
);
324 dbs_tuners_ins
.ignore_nice
= input
;
326 /* we need to re-evaluate prev_cpu_idle */
327 for_each_online_cpu(j
) {
328 struct cpu_dbs_info_s
*dbs_info
;
329 dbs_info
= &per_cpu(cpu_dbs_info
, j
);
330 dbs_info
->prev_cpu_idle
= get_cpu_idle_time(j
,
331 &dbs_info
->prev_cpu_wall
);
332 if (dbs_tuners_ins
.ignore_nice
)
333 dbs_info
->prev_cpu_nice
= kstat_cpu(j
).cpustat
.nice
;
335 mutex_unlock(&dbs_mutex
);
340 static ssize_t
store_freq_step(struct cpufreq_policy
*policy
,
341 const char *buf
, size_t count
)
345 ret
= sscanf(buf
, "%u", &input
);
353 /* no need to test here if freq_step is zero as the user might actually
354 * want this, they would be crazy though :) */
355 mutex_lock(&dbs_mutex
);
356 dbs_tuners_ins
.freq_step
= input
;
357 mutex_unlock(&dbs_mutex
);
362 #define define_one_rw(_name) \
363 static struct freq_attr _name = \
364 __ATTR(_name, 0644, show_##_name, store_##_name)
366 define_one_rw(sampling_rate
);
367 define_one_rw(sampling_down_factor
);
368 define_one_rw(up_threshold
);
369 define_one_rw(down_threshold
);
370 define_one_rw(ignore_nice_load
);
371 define_one_rw(freq_step
);
373 static struct attribute
*dbs_attributes
[] = {
374 &sampling_rate_max
.attr
,
375 &sampling_rate_min
.attr
,
377 &sampling_down_factor
.attr
,
379 &down_threshold
.attr
,
380 &ignore_nice_load
.attr
,
385 static struct attribute_group dbs_attr_group
= {
386 .attrs
= dbs_attributes
,
387 .name
= "conservative",
390 /************************** sysfs end ************************/
392 static void dbs_check_cpu(struct cpu_dbs_info_s
*this_dbs_info
)
394 unsigned int load
= 0;
395 unsigned int freq_target
;
397 struct cpufreq_policy
*policy
;
400 policy
= this_dbs_info
->cur_policy
;
403 * Every sampling_rate, we check, if current idle time is less
404 * than 20% (default), then we try to increase frequency
405 * Every sampling_rate*sampling_down_factor, we check, if current
406 * idle time is more than 80%, then we try to decrease frequency
408 * Any frequency increase takes it to the maximum frequency.
409 * Frequency reduction happens at minimum steps of
410 * 5% (default) of maximum frequency
413 /* Get Absolute Load */
414 for_each_cpu(j
, policy
->cpus
) {
415 struct cpu_dbs_info_s
*j_dbs_info
;
416 cputime64_t cur_wall_time
, cur_idle_time
;
417 unsigned int idle_time
, wall_time
;
419 j_dbs_info
= &per_cpu(cpu_dbs_info
, j
);
421 cur_idle_time
= get_cpu_idle_time(j
, &cur_wall_time
);
423 wall_time
= (unsigned int) cputime64_sub(cur_wall_time
,
424 j_dbs_info
->prev_cpu_wall
);
425 j_dbs_info
->prev_cpu_wall
= cur_wall_time
;
427 idle_time
= (unsigned int) cputime64_sub(cur_idle_time
,
428 j_dbs_info
->prev_cpu_idle
);
429 j_dbs_info
->prev_cpu_idle
= cur_idle_time
;
431 if (dbs_tuners_ins
.ignore_nice
) {
432 cputime64_t cur_nice
;
433 unsigned long cur_nice_jiffies
;
435 cur_nice
= cputime64_sub(kstat_cpu(j
).cpustat
.nice
,
436 j_dbs_info
->prev_cpu_nice
);
438 * Assumption: nice time between sampling periods will
439 * be less than 2^32 jiffies for 32 bit sys
441 cur_nice_jiffies
= (unsigned long)
442 cputime64_to_jiffies64(cur_nice
);
444 j_dbs_info
->prev_cpu_nice
= kstat_cpu(j
).cpustat
.nice
;
445 idle_time
+= jiffies_to_usecs(cur_nice_jiffies
);
448 if (unlikely(!wall_time
|| wall_time
< idle_time
))
451 load
= 100 * (wall_time
- idle_time
) / wall_time
;
455 * break out if we 'cannot' reduce the speed as the user might
456 * want freq_step to be zero
458 if (dbs_tuners_ins
.freq_step
== 0)
461 /* Check for frequency increase */
462 if (load
> dbs_tuners_ins
.up_threshold
) {
463 this_dbs_info
->down_skip
= 0;
465 /* if we are already at full speed then break out early */
466 if (this_dbs_info
->requested_freq
== policy
->max
)
469 freq_target
= (dbs_tuners_ins
.freq_step
* policy
->max
) / 100;
471 /* max freq cannot be less than 100. But who knows.... */
472 if (unlikely(freq_target
== 0))
475 this_dbs_info
->requested_freq
+= freq_target
;
476 if (this_dbs_info
->requested_freq
> policy
->max
)
477 this_dbs_info
->requested_freq
= policy
->max
;
479 __cpufreq_driver_target(policy
, this_dbs_info
->requested_freq
,
485 * The optimal frequency is the frequency that is the lowest that
486 * can support the current CPU usage without triggering the up
487 * policy. To be safe, we focus 10 points under the threshold.
489 if (load
< (dbs_tuners_ins
.down_threshold
- 10)) {
490 freq_target
= (dbs_tuners_ins
.freq_step
* policy
->max
) / 100;
492 this_dbs_info
->requested_freq
-= freq_target
;
493 if (this_dbs_info
->requested_freq
< policy
->min
)
494 this_dbs_info
->requested_freq
= policy
->min
;
497 * if we cannot reduce the frequency anymore, break out early
499 if (policy
->cur
== policy
->min
)
502 __cpufreq_driver_target(policy
, this_dbs_info
->requested_freq
,
508 static void do_dbs_timer(struct work_struct
*work
)
510 struct cpu_dbs_info_s
*dbs_info
=
511 container_of(work
, struct cpu_dbs_info_s
, work
.work
);
512 unsigned int cpu
= dbs_info
->cpu
;
514 /* We want all CPUs to do sampling nearly on same jiffy */
515 int delay
= usecs_to_jiffies(dbs_tuners_ins
.sampling_rate
);
517 delay
-= jiffies
% delay
;
519 if (lock_policy_rwsem_write(cpu
) < 0)
522 if (!dbs_info
->enable
) {
523 unlock_policy_rwsem_write(cpu
);
527 dbs_check_cpu(dbs_info
);
529 queue_delayed_work_on(cpu
, kconservative_wq
, &dbs_info
->work
, delay
);
530 unlock_policy_rwsem_write(cpu
);
533 static inline void dbs_timer_init(struct cpu_dbs_info_s
*dbs_info
)
535 /* We want all CPUs to do sampling nearly on same jiffy */
536 int delay
= usecs_to_jiffies(dbs_tuners_ins
.sampling_rate
);
537 delay
-= jiffies
% delay
;
539 dbs_info
->enable
= 1;
540 INIT_DELAYED_WORK_DEFERRABLE(&dbs_info
->work
, do_dbs_timer
);
541 queue_delayed_work_on(dbs_info
->cpu
, kconservative_wq
, &dbs_info
->work
,
545 static inline void dbs_timer_exit(struct cpu_dbs_info_s
*dbs_info
)
547 dbs_info
->enable
= 0;
548 cancel_delayed_work_sync(&dbs_info
->work
);
551 static int cpufreq_governor_dbs(struct cpufreq_policy
*policy
,
554 unsigned int cpu
= policy
->cpu
;
555 struct cpu_dbs_info_s
*this_dbs_info
;
559 this_dbs_info
= &per_cpu(cpu_dbs_info
, cpu
);
562 case CPUFREQ_GOV_START
:
563 if ((!cpu_online(cpu
)) || (!policy
->cur
))
566 if (this_dbs_info
->enable
) /* Already enabled */
569 mutex_lock(&dbs_mutex
);
571 rc
= sysfs_create_group(&policy
->kobj
, &dbs_attr_group
);
573 mutex_unlock(&dbs_mutex
);
577 for_each_cpu(j
, policy
->cpus
) {
578 struct cpu_dbs_info_s
*j_dbs_info
;
579 j_dbs_info
= &per_cpu(cpu_dbs_info
, j
);
580 j_dbs_info
->cur_policy
= policy
;
582 j_dbs_info
->prev_cpu_idle
= get_cpu_idle_time(j
,
583 &j_dbs_info
->prev_cpu_wall
);
584 if (dbs_tuners_ins
.ignore_nice
) {
585 j_dbs_info
->prev_cpu_nice
=
586 kstat_cpu(j
).cpustat
.nice
;
589 this_dbs_info
->down_skip
= 0;
590 this_dbs_info
->requested_freq
= policy
->cur
;
594 * Start the timerschedule work, when this governor
595 * is used for first time
597 if (dbs_enable
== 1) {
598 unsigned int latency
;
599 /* policy latency is in nS. Convert it to uS first */
600 latency
= policy
->cpuinfo
.transition_latency
/ 1000;
605 max(latency
* LATENCY_MULTIPLIER
,
606 MIN_STAT_SAMPLING_RATE
);
608 dbs_tuners_ins
.sampling_rate
= def_sampling_rate
;
610 cpufreq_register_notifier(
611 &dbs_cpufreq_notifier_block
,
612 CPUFREQ_TRANSITION_NOTIFIER
);
614 dbs_timer_init(this_dbs_info
);
616 mutex_unlock(&dbs_mutex
);
620 case CPUFREQ_GOV_STOP
:
621 mutex_lock(&dbs_mutex
);
622 dbs_timer_exit(this_dbs_info
);
623 sysfs_remove_group(&policy
->kobj
, &dbs_attr_group
);
627 * Stop the timerschedule work, when this governor
628 * is used for first time
631 cpufreq_unregister_notifier(
632 &dbs_cpufreq_notifier_block
,
633 CPUFREQ_TRANSITION_NOTIFIER
);
635 mutex_unlock(&dbs_mutex
);
639 case CPUFREQ_GOV_LIMITS
:
640 mutex_lock(&dbs_mutex
);
641 if (policy
->max
< this_dbs_info
->cur_policy
->cur
)
642 __cpufreq_driver_target(
643 this_dbs_info
->cur_policy
,
644 policy
->max
, CPUFREQ_RELATION_H
);
645 else if (policy
->min
> this_dbs_info
->cur_policy
->cur
)
646 __cpufreq_driver_target(
647 this_dbs_info
->cur_policy
,
648 policy
->min
, CPUFREQ_RELATION_L
);
649 mutex_unlock(&dbs_mutex
);
656 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
659 struct cpufreq_governor cpufreq_gov_conservative
= {
660 .name
= "conservative",
661 .governor
= cpufreq_governor_dbs
,
662 .max_transition_latency
= TRANSITION_LATENCY_LIMIT
,
663 .owner
= THIS_MODULE
,
666 static int __init
cpufreq_gov_dbs_init(void)
670 kconservative_wq
= create_workqueue("kconservative");
671 if (!kconservative_wq
) {
672 printk(KERN_ERR
"Creation of kconservative failed\n");
676 err
= cpufreq_register_governor(&cpufreq_gov_conservative
);
678 destroy_workqueue(kconservative_wq
);
683 static void __exit
cpufreq_gov_dbs_exit(void)
685 cpufreq_unregister_governor(&cpufreq_gov_conservative
);
686 destroy_workqueue(kconservative_wq
);
690 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
691 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
692 "Low Latency Frequency Transition capable processors "
693 "optimised for use in a battery environment");
694 MODULE_LICENSE("GPL");
696 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
697 fs_initcall(cpufreq_gov_dbs_init
);
699 module_init(cpufreq_gov_dbs_init
);
701 module_exit(cpufreq_gov_dbs_exit
);