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Commit 7af1c056 authored by Stratos Karafotis's avatar Stratos Karafotis Committed by Rafael J. Wysocki
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cpufreq: conservative: Fix sampling_down_factor functionality 



sampling_down_factor tunable is unused since commit
8e677ce8 (4 years ago).

This patch restores the original functionality and documents the
tunable.

Signed-off-by: default avatarStratos Karafotis <stratosk@semaphore.gr>
Acked-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 9366d840

Documentation/cpu-freq/governors.txt

+6 −0
Original line number Diff line number Diff line
@@ -191,6 +191,12 @@ governor but for the opposite direction. For example when set to its 
default value of '20' it means that if the CPU usage needs to be below

20% between samples to have the frequency decreased.



sampling_down_factor: similar functionality as in "ondemand" governor.

But in "conservative", it controls the rate at which the kernel makes

a decision on when to decrease the frequency while running in any

speed. Load for frequency increase is still evaluated every

sampling rate.



3. The Governor Interface in the CPUfreq Core

=============================================

drivers/cpufreq/cpufreq_conservative.c

+8 −3
Original line number Diff line number Diff line
@@ -36,9 +36,9 @@ static DEFINE_PER_CPU(struct cs_cpu_dbs_info_s, cs_cpu_dbs_info); 


/*

 * 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 check, if current idle time is more than 80%, then

 * we try to decrease frequency

 * (default), then we try to increase frequency. Every sampling_rate *

 * sampling_down_factor, we check, if current idle time is more than 80%

 * (default), then we try to decrease frequency

 *

 * Any frequency increase takes it to the maximum frequency. Frequency reduction

 * happens at minimum steps of 5% (default) of maximum frequency
@@ -81,6 +81,11 @@ static void cs_check_cpu(int cpu, unsigned int load) 
		return;

	}



	/* if sampling_down_factor is active break out early */

	if (++dbs_info->down_skip < cs_tuners->sampling_down_factor)

		return;

	dbs_info->down_skip = 0;



	/*

	 * The optimal frequency is the frequency that is the lowest that can

	 * support the current CPU usage without triggering the up policy. To be