linux-kernel - Re: [RFC PATCH v4 00/14] sched: packing small tasks

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Message-ID: <CAKfTPtCwdw1mYpWRFbPo9zT=9vFANpJyubh1eX-0vJLqrqizgA@mail.gmail.com>
Date:	Fri, 26 Apr 2013 17:40:27 +0200
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Arjan van de Ven <arjan@...ux.intel.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	LAK <linux-arm-kernel@...ts.infradead.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Paul Turner <pjt@...gle.com>,
	Santosh <santosh.shilimkar@...com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	Chander Kashyap <chander.kashyap@...aro.org>,
	"cmetcalf@...era.com" <cmetcalf@...era.com>,
	"tony.luck@...el.com" <tony.luck@...el.com>,
	Alex Shi <alex.shi@...el.com>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Len Brown <len.brown@...el.com>,
	Amit Kucheria <amit.kucheria@...aro.org>,
	Jonathan Corbet <corbet@....net>,
	Lukasz Majewski <l.majewski@...sung.com>
Subject: Re: [RFC PATCH v4 00/14] sched: packing small tasks

On 26 April 2013 17:00, Arjan van de Ven <arjan@...ux.intel.com> wrote:
> On 4/25/2013 10:23 AM, Vincent Guittot wrote:
>>
>> Hi,
>>
>> This patchset takes advantage of the new per-task load tracking that is
>> available in the kernel for packing the tasks in as few as possible
>> CPU/Cluster/Core. It has got 2 packing modes:
>> -The 1st mode packs the small tasks when the system is not too busy. The
>> main
>> goal is to reduce the power consumption in the low system load use cases
>> by
>> minimizing the number of power domain that are enabled but it also keeps
>> the
>> default behavior which is performance oriented.
>> -The 2nd mode packs all tasks in as few as possible power domains in order
>> to
>> improve the power consumption of the system but at the cost of possible
>> performance decrease because of the increase of the rate of ressources
>> sharing
>> compared to the default mode.
>
>
>
> so I got to ask the hard question; what percentage of system level (not just
> cpu level)
> power consumption gain can you measure (pick your favorite workload)...
>

I haven't system level figures for my patches but only for the cpu
subsystem. If we use the MP3 results in the back of my mail, they show
an improvement of 37 % (113/178) for the CPU subsystem of the
platform. If we assume that the CPU subsystem contributes 25% of an
embedded system power consumption (this can vary across platform
depending of the use of HW accelerator but it should be a almost fair
percentage), the patch can impact the power consumption on up to 9%.

> on x86 (even on the low power stuff) I expect this to be very far into the
> noise
> (since we have per core power gates, and power transitions are pretty fast)
>
> you have some numbers in the back of your mail, but it's hard for me to get
> a conclusion out of
> that (they either measure only cpu power, or are just vague in general)
>
>
> --
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