Re: CMA broken in next-20120926

[Thierry Reding]

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@xxxxxxx>
> > 
> > linux-next + this patch alone also works for me.
> > 
> > Tested-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
> 
> 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.

Thierry

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