linux-kernel - Re: [PATCH v3 1/3] cpufreq: ondemand: Change the calculation of target frequency

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Date:	Fri, 14 Jun 2013 01:04:25 +0300
From:	Stratos Karafotis <stratosk@...aphore.gr>
To:	Borislav Petkov <bp@...en8.de>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>, Borislav Petkov <bp@...e.de>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-pm@...r.kernel.org,
	cpufreq@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] cpufreq: ondemand: Change the calculation of target
 frequency

On 06/14/2013 12:40 AM, Borislav Petkov wrote:
> On Fri, Jun 14, 2013 at 12:22:18AM +0300, Stratos Karafotis wrote:
>> Please let me share some more test results using aim9 benchmark suite:
>> https://docs.google.com/spreadsheet/ccc?key=0AnMfNYUV1k0ddDdGdlJyUHpqT2xGY1lBOEt2UEVnNlE&usp=sharing
>>
>> Each test was running for 10sec.
>> Total execution time with and without the patch was almost identical, which is
>> expected since the tests in aim9 run for a specific period.
>> The energy during the test run was increased by 0.43% with the patch.
>> The performance was increased by 1.25% (average) with this patch.
> 
> Not bad. However, exec_test and fork_test are kinda unexpected with such
> a high improvement percentage. Happen to have an explanation?
> 
> FWIW, if we don't find any serious perf/power regressions with
> this patch, I'd say it is worth applying even solely for the code
> simplification it brings.
> 

Although, I'm not sure about the unexpected improvement, I confirm this 
(run again the test). Also, there is important improvement in 
Directory searches (+5.79%), Disk Copies (+1.19%), shell scripts 
(1.20%, 1.51%, 2.38%) and tcp/udp tests (3.62%, 1.41%).

I believe that ondemand has better performance with this patch in 
medium loads. Maybe these operations produce small to medium loads (lower
than up_threshold) and push the CPU to medium frequencies. Without the
patch CPU stays longer to min frequency.

Thanks,
Stratos

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