linux-kernel - Re: [RFC][PATCH] big continuous memory allocator v2

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Date:	Tue, 7 Sep 2010 17:25:59 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	"linux-mm\@kvack.org" <linux-mm@...ck.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	"minchan.kim\@gmail.com" <minchan.kim@...il.com>,
	Mel Gorman <mel@....ul.ie>,
	"kosaki.motohiro\@jp.fujitsu.com" <kosaki.motohiro@...fujitsu.com>
Subject: Re: [RFC][PATCH] big continuous memory allocator v2

On Tue, 07 Sep 2010 09:29:21 +0200
Andi Kleen <andi@...stfloor.org> wrote:

> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> writes:
> 
> > This is a page allcoator based on memory migration/hotplug code.
> > passed some small tests, and maybe easier to read than previous one.
> 
> Maybe I'm missing context here, but what is the use case for this?
> 

I hear some drivers want to allocate xxMB of continuous area.(camera?)
Maybe embeded guys can answer the question.

> If this works well enough the 1GB page code for x86, which currently
> only supports allocating at boot time due to the MAX_ORDER problem,
> could be moved over to runtime allocation. This would make
> GB pages a lot nicer to use.
> 
> I think it would still need declaring a large moveable
> area at boot right? (but moveable area is better than
> prereserved memory)
> 
Right.  

I think a main use-case is using allocation-at-init rather than boot
option. If modules can allocate a big chunk in __init_module() at boot,
boot option will not be necessary and it will be user friendly.
I think there are big free space before application starts running.

If on-demand loading of modules are required, it's safe to use MOVABLE zones.

> On the other hand I'm not sure the VM is really up to speed
> in managing such large areas.
> 

Thanks,
-Kame

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