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[CPUFREQ] ondemand governor automatic downscaling
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[PATCH] [4/5] ondemand governor automatic downscaling

Here is a change of policy for the ondemand governor. The modification
concerns the frequency downscaling. Instead of decreasing to a lower
frequency when the CPU usage is under 20%, this new policy automatically
scales to the optimal frequency. The optimal frequency being the lowest
frequency which provides enough power to not trigger the upscaling policy.

Signed-off-by: Eric Piel <eric.piel@tremplin-utc.net>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Dave Jones <davej@redhat.com>
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Dave Jones committed Jun 1, 2005
1 parent 9c7d269 commit c29f140
Showing 1 changed file with 25 additions and 92 deletions.
117 changes: 25 additions & 92 deletions drivers/cpufreq/cpufreq_ondemand.c
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Original file line number Diff line number Diff line change
Expand Up @@ -34,13 +34,9 @@
*/

#define DEF_FREQUENCY_UP_THRESHOLD (80)
#define MIN_FREQUENCY_UP_THRESHOLD (0)
#define MIN_FREQUENCY_UP_THRESHOLD (11)
#define MAX_FREQUENCY_UP_THRESHOLD (100)

#define DEF_FREQUENCY_DOWN_THRESHOLD (20)
#define MIN_FREQUENCY_DOWN_THRESHOLD (0)
#define MAX_FREQUENCY_DOWN_THRESHOLD (100)

/*
* The polling frequency of this governor depends on the capability of
* the processor. Default polling frequency is 1000 times the transition
Expand Down Expand Up @@ -77,14 +73,11 @@ struct dbs_tuners {
unsigned int sampling_rate;
unsigned int sampling_down_factor;
unsigned int up_threshold;
unsigned int down_threshold;
unsigned int ignore_nice;
unsigned int freq_step;
};

static struct dbs_tuners dbs_tuners_ins = {
.up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
.down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
.sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
};

Expand Down Expand Up @@ -125,9 +118,7 @@ static ssize_t show_##file_name \
show_one(sampling_rate, sampling_rate);
show_one(sampling_down_factor, sampling_down_factor);
show_one(up_threshold, up_threshold);
show_one(down_threshold, down_threshold);
show_one(ignore_nice, ignore_nice);
show_one(freq_step, freq_step);

static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
const char *buf, size_t count)
Expand Down Expand Up @@ -173,8 +164,7 @@ static ssize_t store_up_threshold(struct cpufreq_policy *unused,

down(&dbs_sem);
if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
input < MIN_FREQUENCY_UP_THRESHOLD ||
input <= dbs_tuners_ins.down_threshold) {
input < MIN_FREQUENCY_UP_THRESHOLD) {
up(&dbs_sem);
return -EINVAL;
}
Expand All @@ -185,27 +175,6 @@ static ssize_t store_up_threshold(struct cpufreq_policy *unused,
return count;
}

static ssize_t store_down_threshold(struct cpufreq_policy *unused,
const char *buf, size_t count)
{
unsigned int input;
int ret;
ret = sscanf (buf, "%u", &input);

down(&dbs_sem);
if (ret != 1 || input > MAX_FREQUENCY_DOWN_THRESHOLD ||
input < MIN_FREQUENCY_DOWN_THRESHOLD ||
input >= dbs_tuners_ins.up_threshold) {
up(&dbs_sem);
return -EINVAL;
}

dbs_tuners_ins.down_threshold = input;
up(&dbs_sem);

return count;
}

static ssize_t store_ignore_nice(struct cpufreq_policy *policy,
const char *buf, size_t count)
{
Expand Down Expand Up @@ -240,49 +209,22 @@ static ssize_t store_ignore_nice(struct cpufreq_policy *policy,
return count;
}

static ssize_t store_freq_step(struct cpufreq_policy *policy,
const char *buf, size_t count)
{
unsigned int input;
int ret;

ret = sscanf (buf, "%u", &input);

if ( ret != 1 )
return -EINVAL;

if ( input > 100 )
input = 100;

/* no need to test here if freq_step is zero as the user might actually
* want this, they would be crazy though :) */
down(&dbs_sem);
dbs_tuners_ins.freq_step = input;
up(&dbs_sem);

return count;
}

#define define_one_rw(_name) \
static struct freq_attr _name = \
__ATTR(_name, 0644, show_##_name, store_##_name)

define_one_rw(sampling_rate);
define_one_rw(sampling_down_factor);
define_one_rw(up_threshold);
define_one_rw(down_threshold);
define_one_rw(ignore_nice);
define_one_rw(freq_step);

static struct attribute * dbs_attributes[] = {
&sampling_rate_max.attr,
&sampling_rate_min.attr,
&sampling_rate.attr,
&sampling_down_factor.attr,
&up_threshold.attr,
&down_threshold.attr,
&ignore_nice.attr,
&freq_step.attr,
NULL
};

Expand All @@ -295,8 +237,8 @@ static struct attribute_group dbs_attr_group = {

static void dbs_check_cpu(int cpu)
{
unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;
unsigned int freq_down_step;
unsigned int idle_ticks, up_idle_ticks, total_ticks;
unsigned int freq_next;
unsigned int freq_down_sampling_rate;
static int down_skip[NR_CPUS];
struct cpu_dbs_info_s *this_dbs_info;
Expand All @@ -310,17 +252,15 @@ static void dbs_check_cpu(int cpu)

policy = this_dbs_info->cur_policy;
/*
* The default safe range is 20% to 80%
* Every sampling_rate, we check
* - If current idle time is less than 20%, then we try to
* increase frequency
* Every sampling_rate*sampling_down_factor, we check
* - If current idle time is more than 80%, then we try to
* decrease frequency
* Every sampling_rate, we check, if current idle time is less
* than 20% (default), then we try to increase frequency
* Every sampling_rate*sampling_down_factor, we look for a the lowest
* frequency which can sustain the load while keeping idle time over
* 30%. If such a frequency exist, we try to decrease to this frequency.
*
* Any frequency increase takes it to the maximum frequency.
* Frequency reduction happens at minimum steps of
* 5% (default) of max_frequency
* 5% (default) of current frequency
*/

/* Check for frequency increase */
Expand Down Expand Up @@ -383,33 +323,27 @@ static void dbs_check_cpu(int cpu)
idle_ticks = tmp_idle_ticks;
}

/* Scale idle ticks by 100 and compare with up and down ticks */
idle_ticks *= 100;
down_skip[cpu] = 0;
/* if we cannot reduce the frequency anymore, break out early */
if (policy->cur == policy->min)
return;

/* Compute how many ticks there are between two measurements */
freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
dbs_tuners_ins.sampling_down_factor;
down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) *
usecs_to_jiffies(freq_down_sampling_rate);

if (idle_ticks > down_idle_ticks) {
/* if we are already at the lowest speed then break out early
* or if we 'cannot' reduce the speed as the user might want
* freq_step to be zero */
if (policy->cur == policy->min || dbs_tuners_ins.freq_step == 0)
return;
total_ticks = usecs_to_jiffies(freq_down_sampling_rate);

freq_down_step = (dbs_tuners_ins.freq_step * policy->max) / 100;

/* max freq cannot be less than 100. But who knows.... */
if (unlikely(freq_down_step == 0))
freq_down_step = 5;
/*
* The optimal frequency is the frequency that is the lowest that
* can support the current CPU usage without triggering the up
* policy. To be safe, we focus 10 points under the threshold.
*/
freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks;
freq_next = (freq_next * policy->cur) /
(dbs_tuners_ins.up_threshold - 10);

__cpufreq_driver_target(policy,
policy->cur - freq_down_step,
CPUFREQ_RELATION_H);
return;
}
if (freq_next <= ((policy->cur * 95) / 100))
__cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);
}

static void do_dbs_timer(void *data)
Expand Down Expand Up @@ -487,7 +421,6 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
dbs_tuners_ins.sampling_rate = def_sampling_rate;
dbs_tuners_ins.ignore_nice = 0;
dbs_tuners_ins.freq_step = 5;

dbs_timer_init();
}
Expand Down

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