linux-kernel - Re: [PATCH 0/3] cpu: idle state framework for offline CPUs.

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Message-ID: <20090809120836.GB1338@ucw.cz>
Date:	Sun, 9 Aug 2009 14:08:36 +0200
From:	Pavel Machek <pavel@....cz>
To:	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Cc:	Shaohua Li <shaohua.li@...el.com>,
	Gautham R Shenoy <ego@...ibm.com>,
	Joel Schopp <jschopp@...tin.ibm.com>,
	"Brown, Len" <len.brown@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Balbir Singh <balbir@...ibm.com>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...e.hu>,
	Dipankar Sarma <dipankar@...ibm.com>,
	"Darrick J. Wong" <djwong@...ibm.com>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] cpu: idle state framework for offline CPUs.

Hi!

> > > Also, approaches such as [1] can make use of this
> > > extended infrastructure instead of putting the CPU to an arbitrary C-state
> > > when it is offlined, thereby providing the system administrator a rope to hang
> > > himself with should he feel the need to do so.
> > I didn't see the reason why administrator needs to know which state offline cpu
> > should stay. Don't know about powerpc side, but in x86 side, it appears deepest
> > C-state is already preferred.
> 
> Yes that is what we would expect, but the deepest sleep state may be
> restricted by BIOS or other system level parameters.  This was the
> main objection to Venki's deepest sleep state for offline cpus
> patch.

'May be restricted'? Kernel already needs to know about that
restriction, just do the right thing...

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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