linux-kernel - Re: [PATCH 07/11] Memory compaction core

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Message-ID: <20100324105707.GC21147@csn.ul.ie>
Date:	Wed, 24 Mar 2010 10:57:08 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Adam Litke <agl@...ibm.com>, Avi Kivity <avi@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 07/11] Memory compaction core

On Wed, Mar 24, 2010 at 11:10:14AM +0900, Minchan Kim wrote:
> On Wed, Mar 24, 2010 at 10:53 AM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@...fujitsu.com> wrote:
> > On Wed, 24 Mar 2010 10:47:41 +0900
> > Minchan Kim <minchan.kim@...il.com> wrote:
> >
> >> On Wed, Mar 24, 2010 at 10:03 AM, KAMEZAWA Hiroyuki
> >> <kamezawa.hiroyu@...fujitsu.com> wrote:
> >> > On Tue, 23 Mar 2010 12:25:42 +0000
> >> > Mel Gorman <mel@....ul.ie> wrote:
> >> >
> >> >> This patch is the core of a mechanism which compacts memory in a zone by
> >> >> relocating movable pages towards the end of the zone.
> >> >>
> >> >> A single compaction run involves a migration scanner and a free scanner.
> >> >> Both scanners operate on pageblock-sized areas in the zone. The migration
> >> >> scanner starts at the bottom of the zone and searches for all movable pages
> >> >> within each area, isolating them onto a private list called migratelist.
> >> >> The free scanner starts at the top of the zone and searches for suitable
> >> >> areas and consumes the free pages within making them available for the
> >> >> migration scanner. The pages isolated for migration are then migrated to
> >> >> the newly isolated free pages.
> >> >>
> >> >> Signed-off-by: Mel Gorman <mel@....ul.ie>
> >> >> Acked-by: Rik van Riel <riel@...hat.com>
> >> >> Reviewed-by: Minchan Kim <minchan.kim@...il.com>
> >> >
> >> > I think lru_add_drain() or lru_add_drain_all() should be called somewhere
> >> > when we do __isolate_lru_page(). But it's (_all is) slow....
> >> >
> >>
> >> migrate_prep does it.
> >>

Yep.

> > Thanks.
> >
> > Hmm...then, lru_add_drain_all() is called at each (32page migrate) itelation.
> > Isn't it too slow to be called in such frequency ?
> 
> I agree. We can move migrate_prep in compact_zone.
> 

Indeed we can. It's moved now.

Thanks

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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