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

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Message-Id: <20110428181046.b81635ce.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 28 Apr 2011 18:10:46 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Johannes Weiner <hannes@...xchg.org>
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, 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.

Thanks,
-Kame

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