From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751349AbdFASox (ORCPT ); Thu, 1 Jun 2017 14:44:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46896 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751078AbdFASov (ORCPT ); Thu, 1 Jun 2017 14:44:51 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com AB6383DBDE Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=longman@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com AB6383DBDE Subject: Re: [RFC PATCH v2 11/17] cgroup: Implement new thread mode semantics To: Peter Zijlstra , Tejun Heo 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> <20170601151045.xhsv7jauejjis3mi@hirez.programming.kicks-ass.net> Cc: 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 From: Waiman Long Organization: Red Hat Message-ID: Date: Thu, 1 Jun 2017 14:44:48 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <20170601151045.xhsv7jauejjis3mi@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Thu, 01 Jun 2017 18:44:51 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/01/2017 11:10 AM, Peter Zijlstra wrote: > 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. One of the changes that I proposed in my patches was to get rid of the no internal process constraint. I think that will solve a big part of the container invariant problem that we have with cgroup v2. Cheers, Longman