linux-kernel - Re: [PATCH 5/6 v4] cfq-iosched: CFQ group hierarchical scheduling and use

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Message-ID: <20110216180628.GF14653@redhat.com>
Date:	Wed, 16 Feb 2011 13:06:28 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Divyesh Shah <dpshah@...gle.com>
Cc:	Gui Jianfeng <guijianfeng@...fujitsu.com>,
	Jens Axboe <axboe@...nel.dk>,
	Shaohua Li <shaohua.li@...el.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Chad Talbott <ctalbott@...gle.com>
Subject: Re: [PATCH 5/6 v4] cfq-iosched: CFQ group hierarchical scheduling
 and use_hierarchy interface

On Wed, Feb 16, 2011 at 09:28:07AM -0800, Divyesh Shah wrote:
> On Wed, Feb 16, 2011 at 9:22 AM, Divyesh Shah <dpshah@...gle.com> wrote:
> > On Tue, Feb 15, 2011 at 5:44 PM, Gui Jianfeng
> > <guijianfeng@...fujitsu.com> wrote:
> >> Hmm, it seems memcg aggregating stats in parent group.
> >> But do we really need to do that in kernel? I think it's easier to do it in
> >> userland, and it makes kernel much simpler.
> >>
> >
> > I would prefer having stats aggregated up the hierarchy. One trick we
> > used at Google earlier was to do lazy updates for most stats. So we
> 
> Note that this was on ancient version of the blkio controller :). As
> Vivek mentioned,
> it may be ok to add the hierarchical accounting later.

One improvement we can probably do is make accounting per cpu and make
it lockless.

Thanks
Vivek
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