linux-kernel - Re: [PATCH/RFCv4 0/6] The Contiguous Memory Allocator framework

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Date:	Thu, 26 Aug 2010 10:18:57 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Michał Nazarewicz <m.nazarewicz@...sung.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hans Verkuil <hverkuil@...all.nl>,
	Daniel Walker <dwalker@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Jonathan Corbet <corbet@....net>, Mel Gorman <mel@....ul.ie>,
	Pawel Osciak <p.osciak@...sung.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	linux-kernel@...r.kernel.org,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	linux-mm@...ck.org, Kyungmin Park <kyungmin.park@...sung.com>,
	Zach Pfeffer <zpfeffer@...eaurora.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	linux-media@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH/RFCv4 0/6] The Contiguous Memory Allocator framework

On Thu, 2010-08-26 at 04:40 +0200, Michał Nazarewicz wrote:
> I think that the biggest problem is fragmentation here.  For instance,
> I think that a situation where there is enough free space but it's
> fragmented so no single contiguous chunk can be allocated is a serious
> problem.  However, I would argue that if there's simply no space left,
> a multimedia device could fail and even though it's not desirable, it
> would not be such a big issue in my eyes.
> 
> So, if only movable or discardable pages are allocated in CMA managed
> regions all should work well.  When a device needs memory discardable
> pages would get freed and movable moved unless there is no space left
> on the device in which case allocation would fail. 

If you'd actually looked at the page allocator you'd see its capable of
doing exactly that!

I has the notion of movable pages, it can defragment free space (called
compaction).

Use it!
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