linux-kernel - Re: [PATCH] powerpc: Enable DEEPNAP power savings mode on 970MP

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Date:	Thu, 5 Oct 2006 21:25:15 +0200
From:	Michael Buesch <mb@...sch.de>
To:	Olof Johansson <olof@...om.net>
Cc:	paulus@...ba.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...abs.org
Subject: Re: [PATCH] powerpc: Enable DEEPNAP power savings mode on 970MP

On Thursday 05 October 2006 06:41, Olof Johansson wrote:
> Hi,
> 
> Without this patch, on an idle system I get:
> 
> cpu-power-0:21.638
> cpu-power-1:27.102
> cpu-power-2:29.343
> cpu-power-3:25.784
> Total: 103.8W
> 
> With this patch:
> 
> cpu-power-0:11.730
> cpu-power-1:17.185
> cpu-power-2:18.547
> cpu-power-3:17.528
> Total: 65.0W
> 
> If I lower HZ to 100, I can get it as low as:
> 
> cpu-power-0:10.938
> cpu-power-1:16.021
> cpu-power-2:17.245
> cpu-power-3:16.145
> Total: 60.2W
> 
> Another (older) Quad G5 went from 54W to 39W at HZ=250.
> 
> Coming back out of Deep Nap takes 40-70 cycles longer than coming back
> from just Nap (which already takes quite a while). I don't think it'll
> be a performance issue (interrupt latency on an idle system), but in
> case someone does measurements feel free to report them.
> 
> 
> Signed-off-by: Olof Johansson <olof@...om.net>

Acked-by: Michael Buesch <mb@...sch.de>

I am running DEEPNAP on my Quad since quite some time and I
did not see any problems.
It saves quite a bit of power (I think it was about 20W for me when
I measured it)
That's really worth it.

-- 
Greetings Michael.
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