linux-kernel - Re: [PATCH resend^2] mm: increase RECLAIM

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Date:	Wed, 13 Apr 2011 10:26:50 +1000
From:	"Rob Mueller" <robm@...tmail.fm>
To:	"David Rientjes" <rientjes@...gle.com>,
	"KOSAKI Motohiro" <kosaki.motohiro@...fujitsu.com>
Cc:	"LKML" <linux-kernel@...r.kernel.org>,
	"linux-mm" <linux-mm@...ck.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Christoph Lameter" <cl@...ux.com>,
	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH resend^2] mm: increase RECLAIM_DISTANCE to 30


>> Recently, Robert Mueller reported zone_reclaim_mode doesn't work
>> properly on his new NUMA server (Dual Xeon E5520 + Intel S5520UR MB).
>> He is using Cyrus IMAPd and it's built on a very traditional
>> single-process model.
>>
>
> Let's add Robert to the cc to see if this is still an issue, it hasn't
> been re-reported in over six months.

We definitely still set this in /etc/sysctl.conf on every imap server 
machine:

vm.zone_reclaim_mode = 0

I believe it still defaults to 1 otherwise. What I haven't tested is if 
leaving it at 1 still causes problems. It definitely DID previously cause 
big problems (I think that was around 2.6.34 or so).

http://blog.fastmail.fm/2010/09/15/default-zone_reclaim_mode-1-on-numa-kernel-is-bad-for-fileemailweb-servers/

I'll try changing it to 1 on a machine for 4 hours, see if it makes a 
noticeable difference and report back.

Rob

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