From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751220AbdFAPLE (ORCPT ); Thu, 1 Jun 2017 11:11:04 -0400 Received: from merlin.infradead.org ([205.233.59.134]:55990 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751058AbdFAPLC (ORCPT ); Thu, 1 Jun 2017 11:11:02 -0400 Date: Thu, 1 Jun 2017 17:10:45 +0200 From: Peter Zijlstra To: Tejun Heo Cc: Waiman Long , Li Zefan , Johannes Weiner , Ingo Molnar , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, kernel-team@fb.com, pjt@google.com, luto@amacapital.net, efault@gmx.de Subject: Re: [RFC PATCH v2 11/17] cgroup: Implement new thread mode semantics Message-ID: <20170601151045.xhsv7jauejjis3mi@hirez.programming.kicks-ass.net> References: <1494855256-12558-1-git-send-email-longman@redhat.com> <1494855256-12558-12-git-send-email-longman@redhat.com> <20170519202624.GA15279@wtj.duckdns.org> <20170524203616.GO24798@htj.duckdns.org> <9b147a7e-fec3-3b78-7587-3890efcd42f2@redhat.com> <20170524212745.GP24798@htj.duckdns.org> <20170601145042.GA3494@htj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170601145042.GA3494@htj.duckdns.org> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 01, 2017 at 10:50:42AM -0400, Tejun Heo wrote: > Hello, Waiman. > > A short update. I tried making root special while keeping the > existing threaded semantics but I didn't really like it because we > have to couple controller enables/disables with threaded > enables/disables. I'm now trying a simpler, albeit a bit more > tedious, approach which should leave things mostly symmetrical. I'm > hoping to be able to post mostly working patches this week. I've not had time to look at any of this. But the question I'm most curious about is how cgroup-v2 preserves the container invariant. That is, each container (namespace) should look like a 'real' machine. So just like userns allows to have a uid-0 (aka root) for each container and pidns allows a pid-1 for each container, cgroupns should provide a root group for each container. And cgroup-v2 has this 'exception' (aka wart) for the root group which needs to be replicated for each namespace.