Date: Fri, 17 Apr 2009 17:00:16 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: Ryo Tsuruta <ryov@valinux.co.jp>
Cc: yoshikawa.takuya@oss.ntt.co.jp, righi.andrea@gmail.com, menage@google.com,
       balbir@linux.vnet.ibm.com, guijianfeng@cn.fujitsu.com,
       agk@sourceware.org, akpm@linux-foundation.org, axboe@kernel.dk,
       baramsori72@gmail.com, chlunde@ping.uio.no, dave@linux.vnet.ibm.com,
       dpshah@google.com, eric.rannaud@gmail.com, fernando@oss.ntt.co.jp,
       taka@valinux.co.jp, lizf@cn.fujitsu.com, matt@bluehost.com,
       dradford@bluehost.com, ngupta@google.com, randy.dunlap@oracle.com,
       roberto@unbit.it, s-uchida@ap.jp.nec.com, subrata@linux.vnet.ibm.com,
       containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/9] bio-cgroup controller
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On Fri, 17 Apr 2009 16:22:01 +0900 (JST)
Ryo Tsuruta <ryov@valinux.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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