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Sender: Tejun Heo <htejun@gmail.com>
Date:   Wed, 2 Dec 2020 13:53:00 -0500
From:   Tejun Heo <tj@kernel.org>
To:     Peter Zijlstra <peterz@infradead.org>
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Subject: Re: [PATCH -tip 26/32] sched: Add a second-level tag for nested
 CGroup usecase
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Hello,

On Wed, Dec 02, 2020 at 09:02:11AM +0100, Peter Zijlstra wrote:
> > the user might only want subsets of {B, C, D, E} to share.  For
> > instance, the user might only want {B,C} and {D, E} to share.  One way
> > to solve this would be to allow the user to write the group cookie
> > directly.  However, this interface would need to be restricted to
> > privileged users, since otherwise the cookie could be configured to
> > share with any arbitrary cgroup.  The purpose of the 'color' field is
> > to expose a portion of the cookie that can be modified by a
> > non-privileged user in order to achieve this sharing goal.
> > 
> > If this doesn't seem like a useful case, I'm happy to drop this patch
> > from the series to unblock it.
> 
> Well, the traditional cgroup way of doing that would be to:
> 
>          A
> 	/ \
>        T1 T2
>       / \
>      B   C
> 
> And tag T1 if you want B,C to share.
> 
> So me the color thing reads like an end-run around the cgroup hierarchy.

+1

and please cc me on cgroup related changes.

Thanks.

-- 
tejun