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

drivers/cpufreq/cpufreq_ondemand.c

+46 −1
Original line number Diff line number Diff line
@@ -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);