linux-kernel - Re: [discussion]sched: a rough proposal to enable power saving in scheduler

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Date:	Tue, 21 Aug 2012 09:05:26 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Vincent Guittot <vincent.guittot@...aro.org>
CC:	Matthew Garrett <mjg59@...f.ucam.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	svaidy@...ux.vnet.ibm.com, Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [discussion]sched: a rough proposal to enable power saving in
 scheduler

On 08/20/2012 11:47 PM, Vincent Guittot wrote:

> On 16 August 2012 07:03, Alex Shi <alex.shi@...el.com> wrote:
>> On 08/16/2012 12:19 AM, Matthew Garrett wrote:
>>
>>> On Mon, Aug 13, 2012 at 08:21:00PM +0800, Alex Shi wrote:
>>>
>>>> power aware scheduling), this proposal will adopt the
>>>> sched_balance_policy concept and use 2 kind of policy: performance, power.
>>>
>>> Are there workloads in which "power" might provide more performance than
>>> "performance"? If so, don't use these terms.
>>>
>>
>>
>> Power scheme should no chance has better performance in design.
> 
> A side effect of packing small tasks on one core is that you always
> use the core with the lowest C-state which will minimize the wake up
> latency so you can sometime get better results than performance mode
> which will try to use a other core in another cluster which will take
> more time to wake up that waiting for the end of the current task.
> 


Sure. some scenario packing tasks into smaller domain will bring
performance benefit.
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