linux-kernel - Re: [PATCH 3/9] bio-cgroup controller

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Message-Id: <20090417170016.5c7268f1.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 17 Apr 2009 17:00:16 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Ryo Tsuruta <ryov@...inux.co.jp>
Cc:	yoshikawa.takuya@....ntt.co.jp, righi.andrea@...il.com,
	menage@...gle.com, balbir@...ux.vnet.ibm.com,
	guijianfeng@...fujitsu.com, agk@...rceware.org,
	akpm@...ux-foundation.org, axboe@...nel.dk, baramsori72@...il.com,
	chlunde@...g.uio.no, dave@...ux.vnet.ibm.com, dpshah@...gle.com,
	eric.rannaud@...il.com, fernando@....ntt.co.jp, taka@...inux.co.jp,
	lizf@...fujitsu.com, matt@...ehost.com, dradford@...ehost.com,
	ngupta@...gle.com, randy.dunlap@...cle.com, roberto@...it.it,
	s-uchida@...jp.nec.com, subrata@...ux.vnet.ibm.com,
	containers@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/9] bio-cgroup controller

On Fri, 17 Apr 2009 16:22:01 +0900 (JST)
Ryo Tsuruta <ryov@...inux.co.jp> wrote:

> In the case where the bio-cgroup data is allocated dynamically,
>    - Sometimes quite a large amount of memory get marked dirty.
>      In this case it requires more kernel memory than that of the
>      current implementation.
>    - The operation is expansive due to memory allocations and exclusive
>      controls by such as spinlocks.
> 
> In the case where the bio-cgroup data is allocated by delayed allocation, 
>   - It makes the operation complicated and expensive, because
>     sometimes a bio has to be created in the context of other
>     processes, such as aio and swap-out operation.
> 
> I'd prefer a simple and lightweight implementation. bio-cgroup only
> needs 4bytes unlike memory controller. The reason why bio-cgroup chose
> this approach is to minimize the overhead.
> 
My point is, plz do your best to reduce memory usage here. You increase
size of page_cgroup just because you cannot increase size of struct page.
It's not be sane reason to increase size of this object.
It's a cheat in my point of view.


Thanks,
-Kame

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