linux-kernel - Re: Default zone_reclaim_mode = 1 on NUMA kernel is bad forfile/email/web servers

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Date:	Mon, 4 Oct 2010 12:43:27 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
cc:	Christoph Lameter <cl@...ux.com>, Mel Gorman <mel@....ul.ie>,
	Rob Mueller <robm@...tmail.fm>, linux-kernel@...r.kernel.org,
	Bron Gondwana <brong@...tmail.fm>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: Default zone_reclaim_mode = 1 on NUMA kernel is bad forfile/email/web
 servers

On Mon, 4 Oct 2010, KOSAKI Motohiro wrote:

> 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.
> 
>   * a master process which reads config files and manages the other
>     process
>   * multiple imapd processes, one per connection
>   * multiple pop3d processes, one per connection
>   * multiple lmtpd processes, one per connection
>   * periodical "cleanup" processes.
> 
> Then, there are thousands of independent processes. The problem is,
> recent Intel motherboard turn on zone_reclaim_mode by default and
> traditional prefork model software don't work fine on it.
> Unfortunatelly, Such model is still typical one even though 21th
> century. We can't ignore them.
> 
> This patch raise zone_reclaim_mode threshold to 30. 30 don't have
> specific meaning. but 20 mean one-hop QPI/Hypertransport and such
> relatively cheap 2-4 socket machine are often used for tradiotional
> server as above. The intention is, their machine don't use
> zone_reclaim_mode.
> 
> Note: ia64 and Power have arch specific RECLAIM_DISTANCE definition.
> then this patch doesn't change such high-end NUMA machine behavior.
> 
> Cc: Mel Gorman <mel@....ul.ie>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Bron Gondwana <brong@...tmail.fm>
> Cc: Robert Mueller <robm@...tmail.fm>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>

Acked-by: David Rientjes <rientjes@...gle.com>

We already do this, but I guess it never got pushed to mainline.
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