linux-kernel - Re: [PATCH 4/4] zone_reclaim

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Message-Id: <20090524223857.0852.A69D9226@jp.fujitsu.com>
Date:	Sun, 24 May 2009 22:44:30 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	kosaki.motohiro@...fujitsu.com, Robin Holt <holt@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 4/4] zone_reclaim_mode is always 0 by default


sorry I missed this mail

> > > Even with 128 nodes and 256 cpus, I _NEVER_ see the
> > > system swapping out before allocating off node so I can certainly not
> > > reproduce the situation you are seeing.
> >
> > hmhm. but I don't think we can assume hpc workload.
> 
> System swapping due to zone reclaim? zone reclaim only reclaims unmapped
> pages so it will not swap. Maybe some bug crept in in the recent changes?
> Or you overrode the defaults for zone reclaim?

I guess he use zone_reclaim_mode=7 or similar.

However, I have to explain recent zone reclaim change. current zone reclaim is

 1. zone reclaim can make high order reclaim (by hanns)
 2. determine file-backed page by get_scan_ratio

it mean, high order allocation makes lumpy zone reclaim. and shrink_inactive_list()
don't care may_swap. then, zone_reclaim_mode=1 can makes swap-out if your
driver makes high order allocation request.



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