linux-kernel - Re: [PATCH 1/2][v2] mm: add notifier in pageblock isolation for balloon drivers

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Message-ID: <20091009202304.GB19114@austin.ibm.com>
Date:	Fri, 9 Oct 2009 15:23:04 -0500
From:	Robert Jennings <rcj@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Mel Gorman <mel@....ul.ie>, Ingo Molnar <mingo@...e.hu>,
	Badari Pulavarty <pbadari@...ibm.com>,
	Brian King <brking@...ux.vnet.ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Gerald Schaefer <geralds@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linuxppc-dev@...abs.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 1/2][v2] mm: add notifier in pageblock isolation for
	balloon drivers

* Andrew Morton (akpm@...ux-foundation.org) wrote:
> On Fri, 2 Oct 2009 13:44:58 -0500
> Robert Jennings <rcj@...ux.vnet.ibm.com> wrote:
> 
> > Memory balloon drivers can allocate a large amount of memory which
> > is not movable but could be freed to accomodate memory hotplug remove.
> > 
> > Prior to calling the memory hotplug notifier chain the memory in the
> > pageblock is isolated.  If the migrate type is not MIGRATE_MOVABLE the
> > isolation will not proceed, causing the memory removal for that page
> > range to fail.
> > 
> > Rather than failing pageblock isolation if the the migrateteype is not
> > MIGRATE_MOVABLE, this patch checks if all of the pages in the pageblock
> > are owned by a registered balloon driver (or other entity) using a
> > notifier chain.  If all of the non-movable pages are owned by a balloon,
> > they can be freed later through the memory notifier chain and the range
> > can still be isolated in set_migratetype_isolate().
> 
> The patch looks sane enough to me.
> 
> I expect that if the powerpc and s390 guys want to work on CMM over the
> next couple of months, they'd like this patch merged into 2.6.32.  It's
> a bit larger and more involved than one would like, but I guess we can
> do that if suitable people (Mel?  Kamezawa?) have had a close look and
> are OK with it.
>
> What do people think?

I'd love to get it in 2.6.32 if that's possible.  I have gone over the 
comments from Mel and Kamezawa I produced a new patchset.  I just
finished testing it (and I also tested with
CONFIG_MEMORY_HOTPLUG_SPARSE=n) and it will be posted shortly.

> 
> Has it been carefully compile- and run-time tested with
> CONFIG_MEMORY_HOTPLUG_SPARSE=n?

Yes, I have compiled the kernel CONFIG_MEMORY_HOTPLUG_SPARSE=n and made
sure that we didn't have any problems.

--Robert Jennings
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