linux-kernel - Re: + restore-missing-sysfs-max_cstate-attr.patch added to -mm tree

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Date:	Fri, 30 Nov 2007 19:18:16 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Mark Lord <lkml@....ca>
Cc:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>, abelay@...ell.com,
	lenb@...nel.org, mlord@...ox.com, rjw@...k.pl,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: + restore-missing-sysfs-max_cstate-attr.patch added to -mm tree

On Fri, 30 Nov 2007 22:14:08 -0500
Mark Lord <lkml@....ca> wrote:

> > in -mm there is.. the QoS stuff allows you to set maximum tolerable
> ..
> 
> That's encouraging, I think, but not for 2.6.24.
> 
> > latency. If your app cant take any latency, you should set those...
> > and the side effect is that the kernel will not do long-latency
> > C-states or P-state transitions..
> ..
> 
> I don't mind the cpufreq changing (actually, I want it to drop in
> cpugfreq to save power and keep the fan off), but the C-states just
> kill this app.
> 
> The app is VMware.  I force the max_state=1 when launching,

ah but then its' even easier... and can be done in 2.6.24 already.
VMWare after all has a kernel module, and the latency stuff is in
2.6.23 and 2.6.24 available inside the kernel already.

> 
> I'm not sure about C?? -- it could be C8 or even be C2 or whatever.
> I suppose I should find out, but that really takes a lot of fuss
> (hours) to measure, and isn't strictly repeatable.

(also hope you don't have one of those AMD machines where the bios
turns C1 into C2/C3/etc behind the OSes back ;-)


-- 
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