linux-kernel - Re: [RFC] [PATCH 0/6] Provide cgroup isolation for buffered writes.

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Date:	Wed, 9 Mar 2011 10:19:40 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Justin TerAvest <teravest@...gle.com>, m-ikeda@...jp.nec.com,
	jaxboe@...ionio.com, linux-kernel@...r.kernel.org,
	ryov@...inux.co.jp, taka@...inux.co.jp, righi.andrea@...il.com,
	guijianfeng@...fujitsu.com, balbir@...ux.vnet.ibm.com,
	ctalbott@...gle.com, nauman@...gle.com, mrubin@...gle.com
Subject: Re: [RFC] [PATCH 0/6] Provide cgroup isolation for buffered writes.

On Wed, Mar 09, 2011 at 02:22:37PM +0900, KAMEZAWA Hiroyuki wrote:
[..]

> B) I wonder why the information cannot be recorded in page->private.
>    When page has buffers, you can record the information to buffer struct.
>    About swapio (if you take care of), you can record information to bio.
> 

This sounds very interesting. I am not a vm guy hence I have no idea in
what situations page->private is used and is it ok, to introduce one
more user of it. But if it works, then getting rid of this dependency
on page_cgroup is a huge plug, IMHO.

> Anyway, thank you for the work. And please join the discussion and explain
> "Without it, we didn't see much isolation improvement." with real data.

Agreed. AFAICS, this piece is not going to help much until and unless
we have upper layers fixed (per cgroup dirty ratio and cgroup aware writeout).
So once those two are fixed and in kernel, it will pave the way for
this piece to go in.

Thanks
Vivek
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