From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [PATCH v10 2/9] cpuset: Add new v2 cpuset.sched.domain_root flag Date: Fri, 22 Jun 2018 11:00:03 +0800 Message-ID: <1eb82b46-aa97-2ada-5196-5d7fc1cda87d@redhat.com> References: <1529295249-5207-1-git-send-email-longman@redhat.com> <1529295249-5207-3-git-send-email-longman@redhat.com> <20180620142735.GM2494@hirez.programming.kicks-ass.net> <20180621092013.GU2494@hirez.programming.kicks-ass.net> Mime-Version: 1.0 Content-Transfer-Encoding: 8BIT Return-path: In-Reply-To: <20180621092013.GU2494@hirez.programming.kicks-ass.net> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Peter Zijlstra Cc: Tejun Heo , Li Zefan , Johannes Weiner , Ingo Molnar , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kernel-team@fb.com, pjt@google.com, luto@amacapital.net, Mike Galbraith , torvalds@linux-foundation.org, Roman Gushchin , Juri Lelli , Patrick Bellasi On 06/21/2018 05:20 PM, Peter Zijlstra wrote: > On Thu, Jun 21, 2018 at 03:58:06PM +0800, Waiman Long wrote: > >> As for the inconsistency between the real root and the container root, >> this is true for almost all the controllers. So it is a generic problem. >> One possible solution is to create a kind a pseudo root cgroup for the >> container that looks and feels like a real root. But is there really a >> need to do that? > I don't really know. I thought the idea was to make containers > indistinguishable from a real system. Now I know we're really rather far > away from that in reality, and I really have no clue how important all > that is. That will certainly be the ideal. > It all depends on how exactly this works; is it like I assumed, that > this file is owned by the parent instead of the current directory? And > that if you namespace this, you have an effective read-only file? Yes, that is right. > Then fixing the inconsistency is trivial; simply provide a read-only > file for the actual root cgroup too. > > And if the solution is trivial, I don't see a good reason not to do it. Do you mean providing a flag like READONLY_AT_ROOT so that it will be read-only at the real root? That is an cgroup architectural decision that needs input from Tejun. Anyway, this issue is not specific to this patchset and I would like to break it out as a separate discussion independent of this patchset. Cheers, Longman