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Commit 1b72e7fd authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

cpufreq: schedutil: Use policy-dependent transition delays 



Make the schedutil governor take the initial (default) value of the
rate_limit_us sysfs attribute from the (new) transition_delay_us
policy parameter (to be set by the scaling driver).

That will allow scaling drivers to make schedutil use smaller default
values of rate_limit_us and reduce the default average time interval
between consecutive frequency changes.

Make intel_pstate set transition_delay_us to 500.

Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
parent 5ed8a1c1

drivers/cpufreq/intel_pstate.c

+2 −0
Original line number Diff line number Diff line
@@ -41,6 +41,7 @@ 
#define INTEL_PSTATE_HWP_SAMPLING_INTERVAL	(50 * NSEC_PER_MSEC)



#define INTEL_CPUFREQ_TRANSITION_LATENCY	20000

#define INTEL_CPUFREQ_TRANSITION_DELAY		500



#ifdef CONFIG_ACPI

#include <acpi/processor.h>
@@ -2237,6 +2238,7 @@ static int intel_cpufreq_cpu_init(struct cpufreq_policy *policy) 
		return ret;



	policy->cpuinfo.transition_latency = INTEL_CPUFREQ_TRANSITION_LATENCY;

	policy->transition_delay_us = INTEL_CPUFREQ_TRANSITION_DELAY;

	/* This reflects the intel_pstate_get_cpu_pstates() setting. */

	policy->cur = policy->cpuinfo.min_freq;

include/linux/cpufreq.h

+7 −0
Original line number Diff line number Diff line
@@ -120,6 +120,13 @@ struct cpufreq_policy { 
	bool			fast_switch_possible;

	bool			fast_switch_enabled;



	/*

	 * Preferred average time interval between consecutive invocations of

	 * the driver to set the frequency for this policy.  To be set by the

	 * scaling driver (0, which is the default, means no preference).

	 */

	unsigned int		transition_delay_us;



	 /* Cached frequency lookup from cpufreq_driver_resolve_freq. */

	unsigned int cached_target_freq;

	int cached_resolved_idx;

kernel/sched/cpufreq_schedutil.c

+10 −5
Original line number Diff line number Diff line
@@ -494,7 +494,6 @@ static int sugov_init(struct cpufreq_policy *policy) 
{

	struct sugov_policy *sg_policy;

	struct sugov_tunables *tunables;

	unsigned int lat;

	int ret = 0;



	/* State should be equivalent to EXIT */
@@ -533,10 +532,16 @@ static int sugov_init(struct cpufreq_policy *policy) 
		goto stop_kthread;

	}



	if (policy->transition_delay_us) {

		tunables->rate_limit_us = policy->transition_delay_us;

	} else {

		unsigned int lat;



		tunables->rate_limit_us = LATENCY_MULTIPLIER;

		lat = policy->cpuinfo.transition_latency / NSEC_PER_USEC;

		if (lat)

			tunables->rate_limit_us *= lat;

	}



	policy->governor_data = sg_policy;

	sg_policy->tunables = tunables;