From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id A00AF7D08A for ; Tue, 2 Oct 2018 20:44:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726731AbeJCD3i (ORCPT ); Tue, 2 Oct 2018 23:29:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59070 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726517AbeJCD3i (ORCPT ); Tue, 2 Oct 2018 23:29:38 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 902F7C025D20; Tue, 2 Oct 2018 20:44:27 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-55.bos.redhat.com [10.18.17.55]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6543D648AB; Tue, 2 Oct 2018 20:44:23 +0000 (UTC) Subject: Re: [PATCH v12 9/9] cpuset: Support forced turning off of partition flag To: Tejun Heo Cc: Li Zefan , Johannes Weiner , Peter Zijlstra , 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: <1535380884-31308-1-git-send-email-longman@redhat.com> <1535380884-31308-10-git-send-email-longman@redhat.com> <20180827164004.GE3978217@devbig004.ftw2.facebook.com> <0daf1f43-2292-0281-3ab8-aef20d0475dc@redhat.com> <20181002200627.GI270328@devbig004.ftw2.facebook.com> From: Waiman Long Organization: Red Hat Message-ID: <9d356cf9-0256-338c-0854-cf52c5d0f8fe@redhat.com> Date: Tue, 2 Oct 2018 16:44:22 -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: <20181002200627.GI270328@devbig004.ftw2.facebook.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Tue, 02 Oct 2018 20:44:27 +0000 (UTC) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 10/02/2018 04:06 PM, Tejun Heo wrote: > Hello, Waiman. > > My apologies for the delay. > > On Mon, Aug 27, 2018 at 01:50:18PM -0400, Waiman Long wrote: >> My current code has explicitly assumed the following relationship for >> partition root. >> >> cpus_allowed = effective_cpus + reserved_cpus >> >> Also effective_cpus cannot be empty. Specifically, cpus_allowed has to >> be equal to effective_cpus before a cpuset can be made a partition root. >> >> Any changes that break the above conditions will turn off the partition >> flag forcefully. The only exception is cpu offlining where cpus_allowed >>> effective_cpus + reserved_cpus can happen. >> One reason for doing so is because reserved_cpus is hidden. So the main >> way to infer that is to do cpus_allowed - effective_cpus. >> >> It is probably doable to make cpus_allowed >= effective_cpus + >> reserved_cpus in general, but we may need to expose reserved_cpus as a >> read-only file, for instance. There may also be other complications that >> we will need to take care of if this is supported. My current preference >> is to not doing that unless there is compelling reason to do so. > So, if we're gonna make this hierarchical, I think it probably would > be better to go in all the way. It's kinda weird to mix the two > approaches - the normal cpuset operation following the usual > convention (it'd be really great to fix the removal part too) and > parition code doing something else. > > I think adding another interface file should be fine here. > > Thanks. > OK, I will revise the patch to make it work without the removal part. Thanks, Longman