linux-kernel - Re: -mm merge plans -- anti-fragmentation

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Date:	Fri, 13 Jul 2007 10:02:46 -0700
From:	"Nish Aravamudan" <nish.aravamudan@...il.com>
To:	"Andy Whitcroft" <apw@...dowen.org>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Mel Gorman" <mel@...net.ie>, npiggin@...e.de, kenchen@...gle.com,
	jschopp@...tin.ibm.com, kamezawa.hiroyu@...fujitsu.com,
	a.p.zijlstra@...llo.nl, y-goto@...fujitsu.com, clameter@....com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: -mm merge plans -- anti-fragmentation

On 7/13/07, Andy Whitcroft <apw@...dowen.org> wrote:
> Andrew Morton wrote:
> > On Tue, 10 Jul 2007 11:20:43 +0100
> > mel@...net.ie (Mel Gorman) wrote:
> >
> >>> create-the-zone_movable-zone.patch
> >>> allow-huge-page-allocations-to-use-gfp_high_movable.patch
> >>> handle-kernelcore=-generic.patch
> >>>
> >>>  Mel's moveable-zone work.  In a similar situation.  We need to stop whatever
> >>>  we're doing and get down and work out what we're going to do with all this
> >>>  stuff.
> >>>
> >> Whatever about grouping pages by mobility, I would like to see these go
> >> through. They have a real application for hugetlb pool resizing where the
> >> administrator knows the range of hugepages that will be required but doesn't
> >> want to waste memory when the required number of hugepages is small. I've
> >> cc'd Kenneth Chen as I believe he has run into this problem recently where
> >> I believe partitioning memory would have helped. He'll either confirm or deny.
> >
> > Still no decision here, really.
> >
> > Should we at least go for
> >
> > add-__gfp_movable-for-callers-to-flag-allocations-from-high-memory-that-may-be-migrated.patch
> > create-the-zone_movable-zone.patch
> > allow-huge-page-allocations-to-use-gfp_high_movable.patch
> > handle-kernelcore=-generic.patch
> >
> > in 2.6.23?
>
> These patches are pretty simple and self-contained utilising the
> existing zone infrastructure.  They provide a significant degree of
> placement control when configured, which gives a lot of the benefits of
> grouping-pages-by-mobility.  Merging these would seem like a low-risk
> option.
>
> Having a degree of placement control as delivered by ZONE_MOVABLE
> greatly increases the effectiveness of lumpy reclaim at higher orders.
> These patches plus lumpy would (IMO) provide a good base for further
> development.  In particular I would envisage better usability for
> hugepage users in terms of simpler configuration.

This is also where I (as a libhugetlbfs maintainer/developer) see
these patches being very helpful (for example, see Adam Litke's recent
posting on resizing the hugepage pool dynamically). Making hugepages
"easier" to use -- and in this case that means more likely to
successfully resize the hugepage pool at run-time -- is a good thing.

> I would like to see ZONE_MOVABLE and lumpy considered for 2.6.23.

Ack.

Thanks,
Nish
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