From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH 12/12] cfq-iosched: add hierarchical cfq_group statistics
Date: Tue, 18 Dec 2012 14:26:33 -0500
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To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
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On Tue, Dec 18, 2012 at 11:21:55AM -0800, Tejun Heo wrote:
> On Tue, Dec 18, 2012 at 02:18:54PM -0500, Vivek Goyal wrote:
> > > Yeah, hmmm, maybe we should add another set of counters to carry stats
> > > from dead ones?  Avoiding hierarchical accounting overhead in hot path
> > > while remembering by-gones shouldn't be that hard.  Will work on that.
> > 
> > So are you planning to migrate the stats to parent when a cgroup is being
> > deleted?  That should make sure we don't do hierarhical update.
> 
> Yeah, something like that.  The current statistics being !hierarchical
> means that we need to keep them separate from the actual stats, so
> it'll end up with another set of stats.  Kinda nasty but I don't see
> any better way out.

Separate stats for hierarchical migration make sense to me.

Thanks
Vivek