Date: Mon, 21 Sep 2009 14:17:40 -0400 (EDT)
From: Christoph Lameter <cl@linux-foundation.org>
To: Mel Gorman <mel@csn.ul.ie>
cc: Nick Piggin <npiggin@suse.de>, Pekka Enberg <penberg@cs.helsinki.fi>,
       heiko.carstens@de.ibm.com, sachinp@in.ibm.com,
       linux-kernel@vger.kernel.org, linux-mm@kvack.org,
       Tejun Heo <tj@kernel.org>,
       Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [RFC PATCH 0/3] Fix SLQB on memoryless configurations V2
In-Reply-To: <20090921180739.GT12726@csn.ul.ie>
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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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