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

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Message-ID: <CADZ9YHjLzNtR+EVQYbutV034T8zrPr52D6mMGLQL3VgaxnemAw@mail.gmail.com>
Date:	Thu, 16 Aug 2012 04:58:29 +0600
From:	Rakib Mullick <rakib.mullick@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Alex Shi <alex.shi@...el.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	vincent.guittot@...aro.org, 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 Wed, Aug 15, 2012 at 8:55 PM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> On Wed, 2012-08-15 at 20:24 +0600, Rakib Mullick wrote:
>> How do you plan to test this power saving scheme? Using powertop? Or,
>> is there any other tools?
>
> We should start out simple enough that we can validate it by looking at
> task placement by hand, eg. 4 tasks on a dual socket quad-core, should
> only keep one socket awake.
>
Yeah, that's what we can do "task placement", that's what scheduler is
known for :).

> We can also add an power aware evaluator to Linsched (another one of
> those things that needs getting sorted).
>
> And yeah, someone running with a power meter is of course king.
>
> _BUT_ we shouldn't go off the wall with power meters as that very
> quickly gets very specific to the system being measured.
>
> We should really keep this thing as simple as possible while still
> providing some benefit for all various architectures without tons of per
> arch knobs and knowhow.

Perhaps this is because, there's no well sorted specification from
various arch, to properly deal with power saving from scheduler's POV.
Actually, this is what I wasn't really sure whether there's any
documentation of how scheduler should work to save power.

Thanks,
Rakib
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