From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752192AbdGVNug (ORCPT ); Sat, 22 Jul 2017 09:50:36 -0400 Received: from mail-qk0-f174.google.com ([209.85.220.174]:36370 "EHLO mail-qk0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750873AbdGVNue (ORCPT ); Sat, 22 Jul 2017 09:50:34 -0400 Date: Sat, 22 Jul 2017 09:50:30 -0400 From: Tejun Heo To: Waiman Long Cc: Li Zefan , Johannes Weiner , Peter Zijlstra , Ingo Molnar , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, pjt@google.com, luto@amacapital.net, efault@gmx.de, torvalds@linux-foundation.org, guro@fb.com Subject: Re: [PATCH v2 2/4] cgroup: Allow bypass mode in subtree_control Message-ID: <20170722135030.GC3329631@devbig577.frc2.facebook.com> References: <1500669293-21792-1-git-send-email-longman@redhat.com> <1500669293-21792-3-git-send-email-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1500669293-21792-3-git-send-email-longman@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Waiman. On Fri, Jul 21, 2017 at 04:34:51PM -0400, Waiman Long wrote: > The special prefix '#' attached to a controller name can now be written > into the cgroup.subtree_control file to set that controller in bypass > mode in all the child cgroups. The controller will show up in the > children's cgroup.controllers file, but the corresponding control knobs > will be absent. However, that controller can be enabled or bypassed > in its children by writing to their respective subtree_control files. > > This mode can be useful to non-domain controllers or controllers where > there are costs to each additional layer of hierarchy. This mode will > also allow more freedom in how each controller can shape its effective > hierarchy independent of each others. While this continues to be an interesting idea. I'm still having a bit of hard time with the change. The biggest blocks are * As raised a couple times before, how would this work in terms of resource ownership and delegation? The last time we spoke about this, I felt that we were mostly talking past each other. I think it'd really help to think about / explain how this would work with delegation to clarify who owns what. * While the idea is interesting, I think we need more concrete usecases to justify the addition and make sure that we aren't doing something misguided. Can you please illustrate / give examples of how this would be useful? Thanks. -- tejun