linux-kernel - Re: RFC: THE OFFLINE SCHEDULER

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Message-ID: <alpine.DEB.1.10.0908311520500.26046@V090114053VZO-1>
Date:	Mon, 31 Aug 2009 15:22:19 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	jim owens <jowens@...com>
cc:	Thomas Gleixner <tglx@...utronix.de>,
	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 Sat, 29 Aug 2009, jim owens wrote:

> From other HPC people, I know the "no noise in my math application"
> requirement.  But that means the user code that is running on the
> CPU must not do anything that wakes the kernel.  Not even page faults,
> so they pin the memory at job start.

Right.

> Anything the user code does that needs kernel statistics or
> kernel action is "I must fix my user code", or "I accept that
> the noise is necessary".
>
> So we don't need to offload stats to other CPUs, stats are not needed.

Stats updates are performed if needed or not. Same with slab expiration.
Thats why its necessary to Offline the cpu.
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