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McKenney" , Tim Chen , Oleg Rombakh Subject: Re: [PATCH -tip 26/32] sched: Add a second-level tag for nested CGroup usecase Message-ID: References: <20201117232003.3580179-1-joel@joelfernandes.org> <20201117232003.3580179-27-joel@joelfernandes.org> <20201125134237.GZ2414@hirez.programming.kicks-ass.net> <20201202080211.GD3021@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201202080211.GD3021@hirez.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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