From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E8B41ECDFBB for ; Fri, 20 Jul 2018 16:19:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AB8EB20652 for ; Fri, 20 Jul 2018 16:19:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AB8EB20652 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387992AbeGTRIa convert rfc822-to-8bit (ORCPT ); Fri, 20 Jul 2018 13:08:30 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:47998 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2387855AbeGTRIa (ORCPT ); Fri, 20 Jul 2018 13:08:30 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6D72A81A4EA6; Fri, 20 Jul 2018 16:19:30 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-175.bos.redhat.com [10.18.17.175]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8A7FA2026D69; Fri, 20 Jul 2018 16:19:29 +0000 (UTC) Subject: Re: [PATCH v11 7/9] cpuset: Expose cpus.effective and mems.effective on cgroup v2 root To: Tejun Heo , Peter Zijlstra Cc: 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 References: <20180703155823.GS533219@devbig577.frc2.facebook.com> <20180719135224.GE2494@hirez.programming.kicks-ass.net> <1107494a-9667-df58-dcac-9366e969dc3a@redhat.com> <20180719153045.GT72677@devbig577.frc2.facebook.com> <20180719165201.GU72677@devbig577.frc2.facebook.com> <20180720113121.GJ2476@hirez.programming.kicks-ass.net> <20180720114549.GY72677@devbig577.frc2.facebook.com> <20180720154454.GR2494@hirez.programming.kicks-ass.net> <20180720155613.GB1934745@devbig577.frc2.facebook.com> From: Waiman Long Organization: Red Hat Message-ID: <4857a9db-ebf5-24f8-c42d-d795f5c75854@redhat.com> Date: Fri, 20 Jul 2018 12:19:29 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20180720155613.GB1934745@devbig577.frc2.facebook.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Content-Language: en-US X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.8]); Fri, 20 Jul 2018 16:19:30 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.8]); Fri, 20 Jul 2018 16:19:30 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'longman@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/20/2018 11:56 AM, Tejun Heo wrote: > Hello, Peter. > > On Fri, Jul 20, 2018 at 05:44:54PM +0200, Peter Zijlstra wrote: >>> The currently proposed implementation is somewhere in the middle. It >>> kinda gets there by restricting a partition to be a child of another >>> partition, which may be okay but it does make the whole delegation >>> mechanism less useful. >> So the implementation does not set ownership of the 'partition' file to >> that of the parent directory? Because _that_ is what I understood from >> Waiman (many versions ago). And that _does_ allow delegation to work >> nicely. > So, that part isn't the problem. The problem is that if we allow > partitioning nested further away from ancestor, the descendant would > be able to take away reources from the removed ancestor. Waiman > avoids this problem by only allowing partitions to nest but then it's > kinda weird cuz it's just a separate tree. The rationale behind the current design is that a parent is allowed to create a child partition if it fully owns all the cpus it has. That is true only if it is a partition itself. IOW, making a cpuset a partition won't affect any ancestors other than the parent. >>>>> 2. take away any given cpu from ist subtree. >>>> I really hate this obsession of yours and doubly so for partitions. But >>>> why would this currently not be allowed? >>> Well, sorry that you hate it. It's a fundamental architectural >>> constraint. If it can't satisfy that, it should't be in cgroup. >> So is hierarchical behaviour; but you seem willing to forgo that. > Well, we do have root or first-level only things. Things just need to > be properly delegatable when they're hierarchical (and things should > be hierarchical only when that actually means something). While not > desirable, considering the history, accomodating this specific usage > that way seems acceptable to me. I am not against the idea of making it hierarchical eventually. I am just hoping to get thing going by merging the patchset in its current form and then we can make it hierarchical in a followup patch. Cheers, Longman