linux-kernel - Re: [RFC v2 0/3][TESTS] LAB: Support for Legacy Application Booster governor

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Date:	Wed, 22 May 2013 16:44:53 +0200
From:	Lukasz Majewski <l.majewski@...sung.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Jonghwa Lee <jonghwa3.lee@...sung.com>,
	"Rafael J. Wysocky" <rjw@...k.pl>, linux-kernel@...r.kernel.org,
	cpufreq@...r.kernel.org, linux-pm@...r.kernel.org,
	Vicent Guittot <vincent.guittot@...aro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Lukasz Majewski <l.majewski@...ess.pl>
Subject: Re: [RFC v2 0/3][TESTS] LAB: Support for Legacy Application Booster
 governor - tests results

Hi Viresh,

> On 22 May 2013 15:57, Lukasz Majewski <l.majewski@...sung.com> wrote:
> >> On 3 May 2013 19:37, Jonghwa Lee <jonghwa3.lee@...sung.com> wrote:
> 
> > I think, that overclocking support is crucial here. As you pointed
> > out
> > - ondemand and conservative benefit from it. Therefore, I would urge
> >   for its mainline acceptance.
> >
> > (code for reference)
> > http://thread.gmane.org/gmane.linux.kernel/1484746/match=cpufreq
> >
> > In this RFC (patch 1/3), I've decided to put the burden of
> > overclocking support to platform code (cpufreq/exynos-cpufreq.c and
> > cpufreq/exynos4x12-cpufreq.c).
> >
> > Those changes aren't intrusive for other boards/archs. Moreover
> > overclocking is closely related to processor clocking/power
> > dissipation capabilities, so SoC specific code is a good place for
> > it.
> >
> >
> > What DO need a broad acceptance is the overclocking API proposed at:
> > include/linux/cpufreq.h
> >
> > This introduces interface to which others will be bind. It
> > shouldn't be difficult to implement overclocking at other SoCs (as
> > it was proposed for Exynos).
> >
> > Feedback is welcome, since I might have overlooked oddities present
> > at other SoCs.
> 
> Hi..
> 
> I am not talking about the minute details here... for example I
> didn't like the way overclocking support is implemented... It has to
> be a bit more framework oriented then driver...
> 
> What I am thinking right now is if it is worth to add both the
> features you are trying. i.e. overclocking and LAB..
> 
> So, requested you to give some figures... of ondemand with and without
> overclocking... Leave LAB for now...
> 
> Then we can give LAB a try with above...

Test HW Exynos4412 (4 Cores):
Kernel 3.8.3

Ondemand max freq: 1.4 GHz
Overclock max freq: 1.5 GHz


Ondemand improvement with and without overclocking (called by us
TurboBoost - TB):

Dhrystone has been built according to:
http://zenit.senecac.on.ca/wiki/index.php/Dhrystone_howto
It's Makefile is also attached.
------------------------------------------------

Dhrystone	# of Threads			
		1	2	3	4
ondemand	2054794	2061855	2097902	2090592
ondemand + TB	2290076	2205882	2281368 2290076

Improvement:	10%	7%	8%	9%
-------------------------------------------------

Electric charge [C]
(Avg) [A] * [second]	# of Threads			
		1	2	3	4
ondemand	1,334	1,837	2,296	3,096
ondemand + TB	1,401	2,2025	2,907	4,34976
								
Power cost:	5%	17%	21%	29%
-------------------------------------------------

Execution time [second]	# of Threads			
		1	2	3	4
ondemand	2,827	2,8	2,787	2,872
ondemand + TB	2,622	2,694	2,667	2,76
				
				
Speedup:	-7%	-4%	-4%	-4%

-------------------------------------------------

"Real life" example:
time tar -czf linux-3.9.1.tar.gz linux-3.9.1/

		Avg current[mA]		Time[s]
Ondemand:	460			153	
Ondemand + TB:	512			144

Result:		+10%			-6%



Conclusion: 

The main use case for TB is to speed up execution of tasks packed to
one core. Other cores are then in IDLE state.

For a single core we can safely overclock, since we will not exceed its
power consumption and thermal limits.


-- 
Best regards,

Lukasz Majewski

Samsung R&D Poland (SRPOL) | Linux Platform Group

Download attachment "Makefile" of type "application/octet-stream" (2180 bytes)