linux-kernel - Re: The performance and behaviour of the anti-fragmentation related patches

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Message-Id: <20070302135243.ada51084.akpm@linux-foundation.org>
Date:	Fri, 2 Mar 2007 13:52:43 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Rik van Riel <riel@...hat.com>
Cc:	Bill Irwin <bill.irwin@...cle.com>,
	Christoph Lameter <clameter@...r.sgi.com>,
	Mel Gorman <mel@...net.ie>, npiggin@...e.de, mingo@...e.hu,
	jschopp@...tin.ibm.com, arjan@...radead.org,
	torvalds@...ux-foundation.org, mbligh@...igh.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: The performance and behaviour of the anti-fragmentation related
 patches

On Fri, 02 Mar 2007 16:19:19 -0500
Rik van Riel <riel@...hat.com> wrote:

> Bill Irwin wrote:
> > On Fri, Mar 02, 2007 at 01:23:28PM -0500, Rik van Riel wrote:
> >> With 32 CPUs diving into the page reclaim simultaneously,
> >> each trying to scan a fraction of memory, this is disastrous
> >> for performance.  A 256GB system should be even worse.
> > 
> > Thundering herds of a sort pounding the LRU locks from direct reclaim
> > have set off the NMI oopser for users here.
> 
> Ditto here.

Opterons?

> The main reason they end up pounding the LRU locks is the
> swappiness heuristic.  They scan too much before deciding
> that it would be a good idea to actually swap something
> out, and with 32 CPUs doing such scanning simultaneously...

What kernel version?
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