linux-kernel - Re: [PATCH 0/2] Disable zone_reclaim

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Message-ID: <53445481.3030202@agliodbs.com>
Date:	Tue, 08 Apr 2014 15:56:49 -0400
From:	Josh Berkus <josh@...iodbs.com>
To:	Robert Haas <robertmhaas@...il.com>,
	Christoph Lameter <cl@...ux.com>
CC:	Vlastimil Babka <vbabka@...e.cz>, Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andres Freund <andres@...quadrant.com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>, sivanich@....com
Subject: Re: [PATCH 0/2] Disable zone_reclaim_mode by default

On 04/08/2014 03:53 PM, Robert Haas wrote:
> In an ideal world, the kernel would put the hottest pages on the local
> node and the less-hot pages on remote nodes, moving pages around as
> the workload shifts.  In practice, that's probably pretty hard.
> Fortunately, it's not nearly as important as making sure we don't
> unnecessarily hit the disk, which is infinitely slower than any memory
> bank.

Even if the kernel could do this, we would *still* have to disable it
for PostgreSQL, since our double-buffering makes our pages look "cold"
to the kernel ... as discussed.

-- 
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com
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