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Date: Wed, 22 Aug 2012 12:35:08 +0100
From: Matthew Garrett <mjg59@srcf.ucam.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>, Alex Shi <alex.shi@intel.com>,
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Paul Turner <pjt@google.com>
Subject: Re: [discussion]sched: a rough proposal to enable power saving in
 scheduler
Message-ID: <20120822113508.GA19152@srcf.ucam.org>
References: <20120820181651.GA737@srcf.ucam.org>
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On Wed, Aug 22, 2012 at 11:10:13AM +0200, Ingo Molnar wrote:
> 
> * Matthew Garrett <mjg59@srcf.ucam.org> wrote:
> 
> > [...]
> >
> > Our power consumption is worse than under other operating 
> > systems is almost entirely because only one of our three GPU 
> > drivers implements any kind of useful power management. [...]
> 
> ... and because our CPU frequency and C state selection logic is 
> doing pretty much the worst possible decisions (on x86 at 
> least).

You have figures showing that our C state residence is worse than, say, 
Windows? Because my own testing says that we're way better at that. 
Could we be better? Sure. Is it why we're worse? No.

> Regardless, you cannot possibly seriously suggest that because 
> there's even greater suckage elsewhere for some workloads we 
> should not even bother with improving the situation here.

I'm enthusiastic about improving the scheduler's behaviour. I'm 
unenthusiastic about putting in automatic hacks related to AC state.

-- 
Matthew Garrett | mjg59@srcf.ucam.org
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