linux-kernel - Re: power-efficient scheduling design

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Message-ID: <51C47377.2000208@linux.intel.com>
Date:	Fri, 21 Jun 2013 08:38:31 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Morten Rasmussen <morten.rasmussen@....com>
CC:	David Lang <david@...g.hm>, Ingo Molnar <mingo@...nel.org>,
	"alex.shi@...el.com" <alex.shi@...el.com>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"preeti@...ux.vnet.ibm.com" <preeti@...ux.vnet.ibm.com>,
	"vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
	"efault@....de" <efault@....de>, "pjt@...gle.com" <pjt@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	"len.brown@...el.com" <len.brown@...el.com>,
	"corbet@....net" <corbet@....net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	Catalin Marinas <Catalin.Marinas@....com>
Subject: Re: power-efficient scheduling design

On 6/21/2013 1:50 AM, Morten Rasmussen wrote:
>> ypically.
> A hint when a task is moved to a new cpu is too late if the migration
> shouldn't have happened at all. If the scheduler knows that the cpu is
> able to switch to a higher p-state it can decide to wait for the p-state
> change instead of migrating the task and waking up another cpu.
>

oops sorry I misread your mail (lack of early coffee I suppose)

I can see your point of having a thing for "did we ask for all the performance
we could ask for" prior to doing a load balance (although, for power efficiency,
if you have two tasks that could run in parallel, it's usually better to
run them in parallel... so likely we should balance anyway)
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