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Date: Thu, 14 May 2009 16:05:07 -0400 (EDT)
From: Christoph Lameter <cl@linux-foundation.org>
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To: Robin Holt <holt@sgi.com>
cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH 4/4] zone_reclaim_mode is always 0 by default
In-Reply-To: <20090513152256.GM7601@sgi.com>
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References: <20090513120155.5879.A69D9226@jp.fujitsu.com> <20090513120729.5885.A69D9226@jp.fujitsu.com> <20090513152256.GM7601@sgi.com>
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Not having zone reclaim on a NUMA system often means that per node
allocations will fall back. Optimized node local allocations become very
difficult for the page allocator. If the latency penalties are not
significant then this may not matter. The larger the system, the larger
the NUMA latencies become.

One possibility would be to disable zone reclaim for low node numbers.
Eanble it only if more than 4 nodes exist?