Date: Tue, 22 Dec 2009 20:57:43 +0100
From: Arjan van de Ven <arjan@infradead.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Salman Qazi <sqazi@google.com>, linux-kernel@vger.kernel.org,
       linux-pm@lists.linux-foundation.org,
       Andrew Morton <akpm@linux-foundation.org>,
       Michael Rubin <mrubin@google.com>, Taliver Heath <taliver@google.com>
Subject: Re: RFC: A proposal for power capping through forced idle in the
 Linux  Kernel
Message-ID: <20091222205743.4b6cf677@infradead.org>
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	<20091214161922.6f252492@infradead.org>
	<1261511304.4937.116.camel@laptop>
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On Tue, 22 Dec 2009 20:48:24 +0100
Peter Zijlstra <peterz@infradead.org> wrote:

> On Mon, 2009-12-14 at 16:19 -0800, Arjan van de Ven wrote:
> 
> > I like the general idea, I have one request (that I didn't see
> > quite in your explanation): Please make sure that all cpus in the
> > system do their idle injection at the same time, so that memory can
> > go into power saving mode as well during this time etc etc...
> 
> And then you're going to ask that it scales too, right? :-)
> 
> Gang-scheduling is inherently non scalable, be it for idle time or
> not.

well... there's many ways to do this... one option is to agree, ahead
of time, which jiffies values you're going to do the idle thing on.
Say every 100 jiffies where jiffies % 100 is 0....

then the scalability thing isn't a big deal.. and you still do it all
at the same time. Or at least "enough" at the same time for it to not
matter


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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