linux-kernel - Re: Over-eager swapping

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Date:	Wed, 18 Aug 2010 16:58:25 +0100
From:	Chris Webb <chris@...chsys.com>
To:	Lee Schermerhorn <Lee.Schermerhorn@...com>
Cc:	Wu Fengguang <fengguang.wu@...el.com>,
	Minchan Kim <minchan.kim@...il.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andi Kleen <andi@...stfloor.org>,
	Christoph Lameter <cl@...ux-foundation.org>
Subject: Re: Over-eager swapping

Lee Schermerhorn <Lee.Schermerhorn@...com> writes:

> On Wed, 2010-08-18 at 23:21 +0800, Wu Fengguang wrote:
> > Andi, Christoph and Lee:
> > 
> > This looks like an "unbalanced NUMA memory usage leading to premature
> > swapping" problem.
> 
> What is the value of the vm.zone_reclaim_mode sysctl?  If it is !0, the
> system will go into zone reclaim before allocating off-node pages.
> However, it shouldn't "swap" in this case unless (zone_reclaim_mode & 4)
> != 0.  And even then, zone reclaim should only reclaim file pages, not
> anon.  In theory...

Hi. This is zero on all our machines:

# sysctl vm.zone_reclaim_mode
vm.zone_reclaim_mode = 0

Cheers,

Chris.
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