From: Arnd Bergmann <arnd@arndb.de>
To: Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [Linaro-mm-sig] [PATCH 08/10] mm: cma: Contiguous 
 =?iso-8859-1?q?Memory=09Allocator?= added
Date: Wed, 22 Jun 2011 15:39:23 +0200
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Cc: "'Hans Verkuil'" <hverkuil@xs4all.nl>,
        "'Daniel Walker'" <dwalker@codeaurora.org>,
        "'Jesse Barker'" <jesse.barker@linaro.org>,
        "'Mel Gorman'" <mel@csn.ul.ie>,
        "'KAMEZAWA Hiroyuki'" <kamezawa.hiroyu@jp.fujitsu.com>,
        linux-kernel@vger.kernel.org,
        "'Michal Nazarewicz'" <mina86@mina86.com>,
        linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org,
        "'Kyungmin Park'" <kyungmin.park@samsung.com>,
        "'Ankita Garg'" <ankita@in.ibm.com>,
        "'Andrew Morton'" <akpm@linux-foundation.org>,
        linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org
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On Wednesday 22 June 2011, Marek Szyprowski wrote:
> Sounds really good, but it might be really hard to implemnt, at least for
> CMA, because it needs to tweak parameters of memory management internal 
> structures very early, when buddy allocator has not been activated yet.

Why that? I would expect you can do the same that hugepages (used to) do
and just attempt high-order allocations. If they succeed, you can add them
as a CMA region and free them again, into the movable set of pages, otherwise
you just fail the  request from user space when the memory is already
fragmented.
 
> > These essentially fight over the same memory (though things are slightly
> > different with dynamic hugepages), and they all face the same basic problem
> > of getting as much for themselves without starving the other three.
> 
> I'm not sure we can solve all such issues in the first version. Maybe we should
> first have each of the above fully working in mainline separately and then
> start the integration works.

Yes, makes sense. We just need to be careful not to introduce user-visible
interfaces that we cannot change any more in the process.

	Arnd
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