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

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Date:	Fri, 17 Apr 2009 17:48:54 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Ryo Tsuruta <ryov@...inux.co.jp>, 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 17:00:16 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:

> 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.
> 

Can't this work sanely ?
Hmm, endian is obstacle ?
==
	sturct page_cgroup {
		union {
			struct {
				unsigned long memcg_field:16;
				unsigned long blockio_field:16;
			} field;
			unsigned long flags; /* unsigned long is not 32bits */
		} flags;
	}
==

Thanks,
-Kame





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