2 * drivers/cpufreq/cpufreq_ondemand.c
4 * Copyright (C) 2001 Russell King
5 * (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
6 * Jun Nakajima <jun.nakajima@intel.com>
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/smp.h>
16 #include <linux/init.h>
17 #include <linux/interrupt.h>
18 #include <linux/ctype.h>
19 #include <linux/cpufreq.h>
20 #include <linux/sysctl.h>
21 #include <linux/types.h>
23 #include <linux/sysfs.h>
24 #include <linux/sched.h>
25 #include <linux/kmod.h>
26 #include <linux/workqueue.h>
27 #include <linux/jiffies.h>
28 #include <linux/kernel_stat.h>
29 #include <linux/percpu.h>
30 #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 MIN_FREQUENCY_UP_THRESHOLD (11)
39 #define MAX_FREQUENCY_UP_THRESHOLD (100)
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(void *data
);
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
;
70 static DEFINE_PER_CPU(struct cpu_dbs_info_s
, cpu_dbs_info
);
72 static unsigned int dbs_enable
; /* number of CPUs using this policy */
74 static DEFINE_MUTEX (dbs_mutex
);
75 static DECLARE_WORK (dbs_work
, do_dbs_timer
, NULL
);
78 unsigned int sampling_rate
;
79 unsigned int sampling_down_factor
;
80 unsigned int up_threshold
;
81 unsigned int ignore_nice
;
84 static struct dbs_tuners dbs_tuners_ins
= {
85 .up_threshold
= DEF_FREQUENCY_UP_THRESHOLD
,
86 .sampling_down_factor
= DEF_SAMPLING_DOWN_FACTOR
,
90 static inline unsigned int get_cpu_idle_time(unsigned int cpu
)
92 return kstat_cpu(cpu
).cpustat
.idle
+
93 kstat_cpu(cpu
).cpustat
.iowait
+
94 ( dbs_tuners_ins
.ignore_nice
?
95 kstat_cpu(cpu
).cpustat
.nice
:
99 /************************** sysfs interface ************************/
100 static ssize_t
show_sampling_rate_max(struct cpufreq_policy
*policy
, char *buf
)
102 return sprintf (buf
, "%u\n", MAX_SAMPLING_RATE
);
105 static ssize_t
show_sampling_rate_min(struct cpufreq_policy
*policy
, char *buf
)
107 return sprintf (buf
, "%u\n", MIN_SAMPLING_RATE
);
110 #define define_one_ro(_name) \
111 static struct freq_attr _name = \
112 __ATTR(_name, 0444, show_##_name, NULL)
114 define_one_ro(sampling_rate_max
);
115 define_one_ro(sampling_rate_min
);
117 /* cpufreq_ondemand Governor Tunables */
118 #define show_one(file_name, object) \
119 static ssize_t show_##file_name \
120 (struct cpufreq_policy *unused, char *buf) \
122 return sprintf(buf, "%u\n", dbs_tuners_ins.object); \
124 show_one(sampling_rate
, sampling_rate
);
125 show_one(sampling_down_factor
, sampling_down_factor
);
126 show_one(up_threshold
, up_threshold
);
127 show_one(ignore_nice_load
, ignore_nice
);
129 static ssize_t
store_sampling_down_factor(struct cpufreq_policy
*unused
,
130 const char *buf
, size_t count
)
134 ret
= sscanf (buf
, "%u", &input
);
138 if (input
> MAX_SAMPLING_DOWN_FACTOR
|| input
< 1)
141 mutex_lock(&dbs_mutex
);
142 dbs_tuners_ins
.sampling_down_factor
= input
;
143 mutex_unlock(&dbs_mutex
);
148 static ssize_t
store_sampling_rate(struct cpufreq_policy
*unused
,
149 const char *buf
, size_t count
)
153 ret
= sscanf (buf
, "%u", &input
);
155 mutex_lock(&dbs_mutex
);
156 if (ret
!= 1 || input
> MAX_SAMPLING_RATE
|| input
< MIN_SAMPLING_RATE
) {
157 mutex_unlock(&dbs_mutex
);
161 dbs_tuners_ins
.sampling_rate
= input
;
162 mutex_unlock(&dbs_mutex
);
167 static ssize_t
store_up_threshold(struct cpufreq_policy
*unused
,
168 const char *buf
, size_t count
)
172 ret
= sscanf (buf
, "%u", &input
);
174 mutex_lock(&dbs_mutex
);
175 if (ret
!= 1 || input
> MAX_FREQUENCY_UP_THRESHOLD
||
176 input
< MIN_FREQUENCY_UP_THRESHOLD
) {
177 mutex_unlock(&dbs_mutex
);
181 dbs_tuners_ins
.up_threshold
= input
;
182 mutex_unlock(&dbs_mutex
);
187 static ssize_t
store_ignore_nice_load(struct cpufreq_policy
*policy
,
188 const char *buf
, size_t count
)
195 ret
= sscanf (buf
, "%u", &input
);
202 mutex_lock(&dbs_mutex
);
203 if ( input
== dbs_tuners_ins
.ignore_nice
) { /* nothing to do */
204 mutex_unlock(&dbs_mutex
);
207 dbs_tuners_ins
.ignore_nice
= input
;
209 /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
210 for_each_online_cpu(j
) {
211 struct cpu_dbs_info_s
*j_dbs_info
;
212 j_dbs_info
= &per_cpu(cpu_dbs_info
, j
);
213 j_dbs_info
->prev_cpu_idle_up
= get_cpu_idle_time(j
);
214 j_dbs_info
->prev_cpu_idle_down
= j_dbs_info
->prev_cpu_idle_up
;
216 mutex_unlock(&dbs_mutex
);
221 #define define_one_rw(_name) \
222 static struct freq_attr _name = \
223 __ATTR(_name, 0644, show_##_name, store_##_name)
225 define_one_rw(sampling_rate
);
226 define_one_rw(sampling_down_factor
);
227 define_one_rw(up_threshold
);
228 define_one_rw(ignore_nice_load
);
230 static struct attribute
* dbs_attributes
[] = {
231 &sampling_rate_max
.attr
,
232 &sampling_rate_min
.attr
,
234 &sampling_down_factor
.attr
,
236 &ignore_nice_load
.attr
,
240 static struct attribute_group dbs_attr_group
= {
241 .attrs
= dbs_attributes
,
245 /************************** sysfs end ************************/
247 static void dbs_check_cpu(int cpu
)
249 unsigned int idle_ticks
, up_idle_ticks
, total_ticks
;
250 unsigned int freq_next
;
251 unsigned int freq_down_sampling_rate
;
252 static int down_skip
[NR_CPUS
];
253 struct cpu_dbs_info_s
*this_dbs_info
;
255 struct cpufreq_policy
*policy
;
258 this_dbs_info
= &per_cpu(cpu_dbs_info
, cpu
);
259 if (!this_dbs_info
->enable
)
262 policy
= this_dbs_info
->cur_policy
;
264 * Every sampling_rate, we check, if current idle time is less
265 * than 20% (default), then we try to increase frequency
266 * Every sampling_rate*sampling_down_factor, we look for a the lowest
267 * frequency which can sustain the load while keeping idle time over
268 * 30%. If such a frequency exist, we try to decrease to this frequency.
270 * Any frequency increase takes it to the maximum frequency.
271 * Frequency reduction happens at minimum steps of
272 * 5% (default) of current frequency
275 /* Check for frequency increase */
276 idle_ticks
= UINT_MAX
;
277 for_each_cpu_mask(j
, policy
->cpus
) {
278 unsigned int tmp_idle_ticks
, total_idle_ticks
;
279 struct cpu_dbs_info_s
*j_dbs_info
;
281 j_dbs_info
= &per_cpu(cpu_dbs_info
, j
);
282 total_idle_ticks
= get_cpu_idle_time(j
);
283 tmp_idle_ticks
= total_idle_ticks
-
284 j_dbs_info
->prev_cpu_idle_up
;
285 j_dbs_info
->prev_cpu_idle_up
= total_idle_ticks
;
287 if (tmp_idle_ticks
< idle_ticks
)
288 idle_ticks
= tmp_idle_ticks
;
291 /* Scale idle ticks by 100 and compare with up and down ticks */
293 up_idle_ticks
= (100 - dbs_tuners_ins
.up_threshold
) *
294 usecs_to_jiffies(dbs_tuners_ins
.sampling_rate
);
296 if (idle_ticks
< up_idle_ticks
) {
298 for_each_cpu_mask(j
, policy
->cpus
) {
299 struct cpu_dbs_info_s
*j_dbs_info
;
301 j_dbs_info
= &per_cpu(cpu_dbs_info
, j
);
302 j_dbs_info
->prev_cpu_idle_down
=
303 j_dbs_info
->prev_cpu_idle_up
;
305 /* if we are already at full speed then break out early */
306 if (policy
->cur
== policy
->max
)
309 __cpufreq_driver_target(policy
, policy
->max
,
314 /* Check for frequency decrease */
316 if (down_skip
[cpu
] < dbs_tuners_ins
.sampling_down_factor
)
319 idle_ticks
= UINT_MAX
;
320 for_each_cpu_mask(j
, policy
->cpus
) {
321 unsigned int tmp_idle_ticks
, total_idle_ticks
;
322 struct cpu_dbs_info_s
*j_dbs_info
;
324 j_dbs_info
= &per_cpu(cpu_dbs_info
, j
);
325 /* Check for frequency decrease */
326 total_idle_ticks
= j_dbs_info
->prev_cpu_idle_up
;
327 tmp_idle_ticks
= total_idle_ticks
-
328 j_dbs_info
->prev_cpu_idle_down
;
329 j_dbs_info
->prev_cpu_idle_down
= total_idle_ticks
;
331 if (tmp_idle_ticks
< idle_ticks
)
332 idle_ticks
= tmp_idle_ticks
;
336 /* if we cannot reduce the frequency anymore, break out early */
337 if (policy
->cur
== policy
->min
)
340 /* Compute how many ticks there are between two measurements */
341 freq_down_sampling_rate
= dbs_tuners_ins
.sampling_rate
*
342 dbs_tuners_ins
.sampling_down_factor
;
343 total_ticks
= usecs_to_jiffies(freq_down_sampling_rate
);
346 * The optimal frequency is the frequency that is the lowest that
347 * can support the current CPU usage without triggering the up
348 * policy. To be safe, we focus 10 points under the threshold.
350 freq_next
= ((total_ticks
- idle_ticks
) * 100) / total_ticks
;
351 freq_next
= (freq_next
* policy
->cur
) /
352 (dbs_tuners_ins
.up_threshold
- 10);
354 if (freq_next
< policy
->min
)
355 freq_next
= policy
->min
;
357 if (freq_next
<= ((policy
->cur
* 95) / 100))
358 __cpufreq_driver_target(policy
, freq_next
, CPUFREQ_RELATION_L
);
361 static void do_dbs_timer(void *data
)
364 mutex_lock(&dbs_mutex
);
365 for_each_online_cpu(i
)
367 schedule_delayed_work(&dbs_work
,
368 usecs_to_jiffies(dbs_tuners_ins
.sampling_rate
));
369 mutex_unlock(&dbs_mutex
);
372 static inline void dbs_timer_init(void)
374 INIT_WORK(&dbs_work
, do_dbs_timer
, NULL
);
375 schedule_delayed_work(&dbs_work
,
376 usecs_to_jiffies(dbs_tuners_ins
.sampling_rate
));
380 static inline void dbs_timer_exit(void)
382 cancel_delayed_work(&dbs_work
);
386 static int cpufreq_governor_dbs(struct cpufreq_policy
*policy
,
389 unsigned int cpu
= policy
->cpu
;
390 struct cpu_dbs_info_s
*this_dbs_info
;
393 this_dbs_info
= &per_cpu(cpu_dbs_info
, cpu
);
396 case CPUFREQ_GOV_START
:
397 if ((!cpu_online(cpu
)) ||
401 if (policy
->cpuinfo
.transition_latency
>
402 (TRANSITION_LATENCY_LIMIT
* 1000)) {
403 printk(KERN_WARNING
"ondemand governor failed to load "
404 "due to too long transition latency\n");
407 if (this_dbs_info
->enable
) /* Already enabled */
410 mutex_lock(&dbs_mutex
);
411 for_each_cpu_mask(j
, policy
->cpus
) {
412 struct cpu_dbs_info_s
*j_dbs_info
;
413 j_dbs_info
= &per_cpu(cpu_dbs_info
, j
);
414 j_dbs_info
->cur_policy
= policy
;
416 j_dbs_info
->prev_cpu_idle_up
= get_cpu_idle_time(j
);
417 j_dbs_info
->prev_cpu_idle_down
418 = j_dbs_info
->prev_cpu_idle_up
;
420 this_dbs_info
->enable
= 1;
421 sysfs_create_group(&policy
->kobj
, &dbs_attr_group
);
424 * Start the timerschedule work, when this governor
425 * is used for first time
427 if (dbs_enable
== 1) {
428 unsigned int latency
;
429 /* policy latency is in nS. Convert it to uS first */
430 latency
= policy
->cpuinfo
.transition_latency
/ 1000;
434 def_sampling_rate
= latency
*
435 DEF_SAMPLING_RATE_LATENCY_MULTIPLIER
;
437 if (def_sampling_rate
< MIN_STAT_SAMPLING_RATE
)
438 def_sampling_rate
= MIN_STAT_SAMPLING_RATE
;
440 dbs_tuners_ins
.sampling_rate
= def_sampling_rate
;
444 mutex_unlock(&dbs_mutex
);
447 case CPUFREQ_GOV_STOP
:
448 mutex_lock(&dbs_mutex
);
449 this_dbs_info
->enable
= 0;
450 sysfs_remove_group(&policy
->kobj
, &dbs_attr_group
);
453 * Stop the timerschedule work, when this governor
454 * is used for first time
459 mutex_unlock(&dbs_mutex
);
463 case CPUFREQ_GOV_LIMITS
:
464 mutex_lock(&dbs_mutex
);
465 if (policy
->max
< this_dbs_info
->cur_policy
->cur
)
466 __cpufreq_driver_target(
467 this_dbs_info
->cur_policy
,
468 policy
->max
, CPUFREQ_RELATION_H
);
469 else if (policy
->min
> this_dbs_info
->cur_policy
->cur
)
470 __cpufreq_driver_target(
471 this_dbs_info
->cur_policy
,
472 policy
->min
, CPUFREQ_RELATION_L
);
473 mutex_unlock(&dbs_mutex
);
479 static struct cpufreq_governor cpufreq_gov_dbs
= {
481 .governor
= cpufreq_governor_dbs
,
482 .owner
= THIS_MODULE
,
485 static int __init
cpufreq_gov_dbs_init(void)
487 return cpufreq_register_governor(&cpufreq_gov_dbs
);
490 static void __exit
cpufreq_gov_dbs_exit(void)
492 /* Make sure that the scheduled work is indeed not running */
493 flush_scheduled_work();
495 cpufreq_unregister_governor(&cpufreq_gov_dbs
);
499 MODULE_AUTHOR ("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
500 MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor for "
501 "Low Latency Frequency Transition capable processors");
502 MODULE_LICENSE ("GPL");
504 module_init(cpufreq_gov_dbs_init
);
505 module_exit(cpufreq_gov_dbs_exit
);