Date: Fri, 24 May 2013 08:16:30 +0000 (GMT)
From: MyungJoo Ham <myungjoo.ham@samsung.com>
Subject: Re: Re: [RFC v2 0/3][TESTS] LAB: Support for Legacy Application
 Booster governor - tests results
To: Viresh Kumar <viresh.kumar@linaro.org>,
        Lukasz Majewski <l.majewski@samsung.com>
Cc: =?euc-kr?Q?=C0=CC=C1=BE=C8=AD?= <jonghwa3.lee@samsung.com>,
        "Rafael J. Wysocky" <rjw@sisk.pl>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "cpufreq@vger.kernel.org" <cpufreq@vger.kernel.org>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        Vicent Guittot <vincent.guittot@linaro.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Lukasz Majewski <l.majewski@majess.pl>
Reply-to: myungjoo.ham@samsung.com
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> On 24 May 2013 11:26, Lukasz Majewski <l.majewski@samsung.com> wrote:
> >> > On 22 May 2013 15:57, Lukasz Majewski <l.majewski@samsung.com>
> > As you wished, I've provided relevant data for overclocking.
> >
> > Would you be so kind and comment on them?
> 
> I was about to reply ... was busy with some other backlog :)
> 
> >> 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.
> 
> Hmm... So its ultraclear that higher clock rates have given us better
> performance numbers, obviously at the cost of power.
> 
> Now, why don't we simply add this high end frequency in the available
> frequencies list? And then ondemand can set it whenever the load is
> high? Why do we need additional core support for it?


It is because we cannot use the frequency if there are more running cores.
We can use such frequencies only if the # cores is limited.
(We do not want conventional performance/ondemand/conservative to use
such frequencies.)


Cheers,
MyungJoo

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