linux-kernel - Re: [RFC PATCH 0/3] Fix SLQB on memoryless configurations V2

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Message-ID: <alpine.DEB.1.10.0909211412050.3106@V090114053VZO-1>
Date:	Mon, 21 Sep 2009 14:17:40 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Mel Gorman <mel@....ul.ie>
cc:	Nick Piggin <npiggin@...e.de>,
	Pekka Enberg <penberg@...helsinki.fi>,
	heiko.carstens@...ibm.com, sachinp@...ibm.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Tejun Heo <tj@...nel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [RFC PATCH 0/3] Fix SLQB on memoryless configurations V2

On Mon, 21 Sep 2009, Mel Gorman wrote:
> Can you spot if there is something fundamentally wrong with patch 2? I.e. what
> is wrong with treating the closest node as local instead of only the
> closest node?

Depends on the way locking is done for percpu queues (likely lockless).
A misidentification of the numa locality of an object may result in locks
not being taken that should have been taken.

> > Or just allow SLQB for !NUMA configurations and merge it now.
> >
>
> Forcing SLQB !NUMA will not rattle out any existing list issues
> unfortunately :(.

But it will make SLQB work right in permitted configurations. The NUMA
issues can then be fixed later upstream.


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