linux-kernel - Re: RFC: THE OFFLINE SCHEDULER

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Message-ID: <alpine.LFD.2.00.0908282231260.19335@localhost.localdomain>
Date:	Fri, 28 Aug 2009 22:34:16 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Christoph Lameter <cl@...ux-foundation.org>
cc:	Gregory Haskins <ghaskins@...ell.com>,
	Rik van Riel <riel@...hat.com>,
	Chris Friesen <cfriesen@...tel.com>,
	raz ben yehuda <raziebe@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>, mingo@...e.hu,
	peterz@...radead.org, maximlevitsky@...il.com, efault@....de,
	wiseman@...s.biu.ac.il, linux-kernel@...r.kernel.org,
	linux-rt-users@...r.kernel.org
Subject: Re: RFC: THE OFFLINE SCHEDULER

On Fri, 28 Aug 2009, Christoph Lameter wrote:

> On Fri, 28 Aug 2009, Thomas Gleixner wrote:
> 
> > The statistics stuff needs to be tackled anyway as we need to offload
> > the sched accounting to some other cpu.
> 
> The vm statisticcs in mm/vmstat.c are different from the sched accounting.

I know, but the problem is basically the same. Delegate the stats to
someone else.
 
> > What slab queue stuff is running on timers and cannot be switched off
> > in such a context?
> 
> slab does run a timer every 2 second to age queues. If there was activity
> then there can be a relatively long time in which we periodically throw
> out portions of the cached data.

Right, but why does that affect a CPU which is marked "I'm not
involved in that game" ?
 
> > Device specific stuff should not happen on such a CPU when there is no
> > device handled on it.
> 
> The device may periodically check for conditions that require action.

Errm. The device is associated to some other CPU, so why would it
require action on an isolated one ? Or are you talking about a device
which is associated to that isolated CPU ?

Thanks,

	tglx

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