Commit 19379b11 authored by Arjan van de Ven's avatar Arjan van de Ven Committed by Ingo Molnar
Browse files

ondemand: Make the iowait-is-busy time a sysfs tunable



Pavel Machek pointed out that not all CPUs have an efficient
idle at high frequency. Specifically, older Intel and various
AMD cpus would get a higher powerusage when copying files from
USB.

Mike Chan pointed out that the same is true for various ARM
chips as well.

Thomas Renninger suggested to make this a sysfs tunable with a
reasonable default.

This patch adds a sysfs tunable for the new behavior, and uses
a very simple function to determine a reasonable default,
depending on the CPU vendor/type.
Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Acked-by: default avatarPavel Machek <pavel@ucw.cz>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: davej@redhat.com
LKML-Reference: <20100509082651.46914d04@infradead.org>
[ minor tidyup ]
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 6b8fcd90
......@@ -109,6 +109,7 @@ static struct dbs_tuners {
unsigned int down_differential;
unsigned int ignore_nice;
unsigned int powersave_bias;
unsigned int io_is_busy;
} dbs_tuners_ins = {
.up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
.down_differential = DEF_FREQUENCY_DOWN_DIFFERENTIAL,
......@@ -260,6 +261,7 @@ static ssize_t show_##file_name \
return sprintf(buf, "%u\n", dbs_tuners_ins.object); \
}
show_one(sampling_rate, sampling_rate);
show_one(io_is_busy, io_is_busy);
show_one(up_threshold, up_threshold);
show_one(ignore_nice_load, ignore_nice);
show_one(powersave_bias, powersave_bias);
......@@ -310,6 +312,23 @@ static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
return count;
}
static ssize_t store_io_is_busy(struct kobject *a, struct attribute *b,
const char *buf, size_t count)
{
unsigned int input;
int ret;
ret = sscanf(buf, "%u", &input);
if (ret != 1)
return -EINVAL;
mutex_lock(&dbs_mutex);
dbs_tuners_ins.io_is_busy = !!input;
mutex_unlock(&dbs_mutex);
return count;
}
static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
const char *buf, size_t count)
{
......@@ -392,6 +411,7 @@ static struct global_attr _name = \
__ATTR(_name, 0644, show_##_name, store_##_name)
define_one_rw(sampling_rate);
define_one_rw(io_is_busy);
define_one_rw(up_threshold);
define_one_rw(ignore_nice_load);
define_one_rw(powersave_bias);
......@@ -403,6 +423,7 @@ static struct attribute *dbs_attributes[] = {
&up_threshold.attr,
&ignore_nice_load.attr,
&powersave_bias.attr,
&io_is_busy.attr,
NULL
};
......@@ -527,7 +548,7 @@ static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
* from the cpu idle time.
*/
if (idle_time >= iowait_time)
if (dbs_tuners_ins.io_is_busy && idle_time >= iowait_time)
idle_time -= iowait_time;
if (unlikely(!wall_time || wall_time < idle_time))
......@@ -643,6 +664,29 @@ static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
cancel_delayed_work_sync(&dbs_info->work);
}
/*
* Not all CPUs want IO time to be accounted as busy; this dependson how
* efficient idling at a higher frequency/voltage is.
* Pavel Machek says this is not so for various generations of AMD and old
* Intel systems.
* Mike Chan (androidlcom) calis this is also not true for ARM.
* Because of this, whitelist specific known (series) of CPUs by default, and
* leave all others up to the user.
*/
static int should_io_be_busy(void)
{
#if defined(CONFIG_X86)
/*
* For Intel, Core 2 (model 15) andl later have an efficient idle.
*/
if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
boot_cpu_data.x86 == 6 &&
boot_cpu_data.x86_model >= 15)
return 1;
#endif
return 0;
}
static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
unsigned int event)
{
......@@ -705,6 +749,7 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
dbs_tuners_ins.sampling_rate =
max(min_sampling_rate,
latency * LATENCY_MULTIPLIER);
dbs_tuners_ins.io_is_busy = should_io_be_busy();
}
mutex_unlock(&dbs_mutex);
......
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