linux-kernel - Re: [RFC 3/8] vmscan: make isolate_lru

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Date:	Thu, 28 Apr 2011 12:26:06 +0200
From:	Johannes Weiner <hannes@...xchg.org>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Minchan Kim <minchan.kim@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>,
	Johannes Weiner <jweiner@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [RFC 3/8] vmscan: make isolate_lru_page with filter aware

On Thu, Apr 28, 2011 at 06:10:46PM +0900, KAMEZAWA Hiroyuki wrote:
> On Thu, 28 Apr 2011 10:54:32 +0200
> Johannes Weiner <hannes@...xchg.org> wrote:
> 
> > On Wed, Apr 27, 2011 at 05:03:04PM +0900, KAMEZAWA Hiroyuki wrote:
> > > On Wed, 27 Apr 2011 01:25:20 +0900
> > > Minchan Kim <minchan.kim@...il.com> wrote:
> > > 
> > > > In some __zone_reclaim case, we don't want to shrink mapped page.
> > > > Nonetheless, we have isolated mapped page and re-add it into
> > > > LRU's head. It's unnecessary CPU overhead and makes LRU churning.
> > > > 
> > > > Of course, when we isolate the page, the page might be mapped but
> > > > when we try to migrate the page, the page would be not mapped.
> > > > So it could be migrated. But race is rare and although it happens,
> > > > it's no big deal.
> > > > 
> > > > Cc: Christoph Lameter <cl@...ux.com>
> > > > Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> > > > Cc: Mel Gorman <mgorman@...e.de>
> > > > Cc: Rik van Riel <riel@...hat.com>
> > > > Cc: Andrea Arcangeli <aarcange@...hat.com>
> > > > Signed-off-by: Minchan Kim <minchan.kim@...il.com>
> > > 
> > > 
> > > Hmm, it seems mm/memcontrol.c::mem_cgroup_isolate_pages() should be updated, too.
> > 
> > memcg reclaim always does sc->may_unmap = 1.  What is there to
> > communicate to mem_cgroup_isolate_pages?
> >
> 
> Hmm, maybe you're right and nothing to do until memcg need to support soft
> limit in zone reclaim mode. I hope no more users.

Ah, okay.  I thought I may have missed something.  Thanks for the
clarification, Kame.

Acked-by: Johannes Weiner <hannes@...xchg.org>
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