linux-kernel - Re: CMA broken in next-20120926

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Message-ID: <20120928103815.GA15219@avionic-0098.mockup.avionic-design.de>
Date:	Fri, 28 Sep 2012 12:38:15 +0200
From:	Thierry Reding <thierry.reding@...onic-design.de>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Peter Ujfalusi <peter.ujfalusi@...com>,
	Minchan Kim <minchan@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Subject: Re: CMA broken in next-20120926

On Fri, Sep 28, 2012 at 12:32:07PM +0200, Thierry Reding wrote:
> On Fri, Sep 28, 2012 at 11:27:28AM +0100, Mel Gorman wrote:
> > On Fri, Sep 28, 2012 at 11:48:25AM +0300, Peter Ujfalusi wrote:
> > > Hi,
> > > 
> > > On 09/28/2012 11:37 AM, Mel Gorman wrote:
> > > >> I hope this patch fixes the bug. If this patch fixes the problem
> > > >> but has some problem about description or someone has better idea,
> > > >> feel free to modify and resend to akpm, Please.
> > > >>
> > > > 
> > > > A full revert is overkill. Can the following patch be tested as a
> > > > potential replacement please?
> > > > 
> > > > ---8<---
> > > > mm: compaction: Iron out isolate_freepages_block() and isolate_freepages_range() -fix1
> > > > 
> > > > CMA is reported to be broken in next-20120926. Minchan Kim pointed out
> > > > that this was due to nr_scanned != total_isolated in the case of CMA
> > > > because PageBuddy pages are one scan but many isolations in CMA. This
> > > > patch should address the problem.
> > > > 
> > > > This patch is a fix for
> > > > mm-compaction-acquire-the-zone-lock-as-late-as-possible-fix-2.patch
> > > > 
> > > > Signed-off-by: Mel Gorman <mgorman@...e.de>
> > > 
> > > linux-next + this patch alone also works for me.
> > > 
> > > Tested-by: Peter Ujfalusi <peter.ujfalusi@...com>
> > 
> > Thanks Peter. I expect it also works for Thierry as I expect you were
> > suffering the same problem but obviously confirmation of that would be nice.
> 
> I've been running a few tests and indeed this solves the obvious problem
> that the coherent pool cannot be created at boot (which in turn caused
> the ethernet adapter to fail on Tegra).
> 
> However I've been working on the Tegra DRM driver, which uses CMA to
> allocate large chunks of framebuffer memory and these are now failing.
> I'll need to check if Minchan's patch solves that problem as well.

Indeed, with Minchan's patch the DRM can allocate the framebuffer
without a problem. Something else must be wrong then.

Thierry

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