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Date: Thu, 26 Aug 2010 04:12:10 +0200
From: =?utf-8?B?TWljaGHFgiBOYXphcmV3aWN6?= <m.nazarewicz@samsung.com>
Subject: Re: [PATCH/RFCv4 0/6] The Contiguous Memory Allocator framework
In-reply-to: <20100826095857.5b821d7f.kamezawa.hiroyu@jp.fujitsu.com>
To: Andrew Morton <akpm@linux-foundation.org>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hans Verkuil <hverkuil@xs4all.nl>, Daniel Walker <dwalker@codeaurora.org>,
        Russell King <linux@arm.linux.org.uk>,
        Jonathan Corbet <corbet@lwn.net>,
        Peter Zijlstra <peterz@infradead.org>,
        Pawel Osciak <p.osciak@samsung.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        linux-kernel@vger.kernel.org,
        FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>, linux-mm@kvack.org,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Zach Pfeffer <zpfeffer@codeaurora.org>,
        Mark Brown <broonie@opensource.wolfsonmicro.com>,
        Mel Gorman <mel@csn.ul.ie>, linux-media@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        Marek Szyprowski <m.szyprowski@samsung.com>
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On Thu, 26 Aug 2010 02:58:57 +0200, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> Hmm, you may not like this..but how about following kind of interface ?
>
> Now, memoyr hotplug supports following operation to free and _isolate_
> memory region.
> 	# echo offline > /sys/devices/system/memory/memoryX/state
>
> Then, a region of memory will be isolated. (This succeeds if there are free
> memory.)
>
> Add a new interface.
>
> 	% echo offline > /sys/devices/system/memory/memoryX/state
> 	# extract memory from System RAM and make them invisible from buddy allocator.
>
> 	% echo cma > /sys/devices/system/memory/memoryX/state
> 	# move invisible memory to cma.

At this point I need to say that I have no experience with hotplug memory but
I think that for this to make sense the regions of memory would have to be
smaller.  Unless I'm misunderstanding something, the above would convert
a region of sizes in order of GiBs to use for CMA.

-- 
Best regards,                                        _     _
| Humble Liege of Serenely Enlightened Majesty of  o' \,=./ `o
| Computer Science,  Michał "mina86" Nazarewicz       (o o)
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