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=-8.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 679A5C43214 for ; Sat, 28 Aug 2021 01:14:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 49D7C60F4C for ; Sat, 28 Aug 2021 01:14:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232973AbhH1BPC (ORCPT ); Fri, 27 Aug 2021 21:15:02 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:21167 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232763AbhH1BO6 (ORCPT ); Fri, 27 Aug 2021 21:14:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1630113246; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=nj7lN9b3OW9PxFPw9p3QaG1rQrZn9spoM1KJO1HMw1U=; b=A4dzNDypRsANDa1pVg1DfcJKC3AeuzVqI/F2sN9U5WyLrRgudYokmWn6/FKp29JdUtpDNU OGw349B1vwMuvYMNMev+arKbHt1fAAgPZ1aRSdSemGsBd0tfpZTPP4W2ECt8avwlCJKjgq ekctGLWwbBEl2uru6xbRluuaPsqoHzE= Received: from mail-qv1-f71.google.com (mail-qv1-f71.google.com [209.85.219.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-585-ZdXJXCLVN6q8Xt25nxMlhw-1; Fri, 27 Aug 2021 21:14:04 -0400 X-MC-Unique: ZdXJXCLVN6q8Xt25nxMlhw-1 Received: by mail-qv1-f71.google.com with SMTP id ib9-20020a0562141c8900b003671c3a1243so1146281qvb.21 for ; Fri, 27 Aug 2021 18:14:04 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:subject:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=nj7lN9b3OW9PxFPw9p3QaG1rQrZn9spoM1KJO1HMw1U=; b=QSabHgjDMmbDWqIQtiDmCPqlQpOcb4MXjnNyEbks+2h3LpL7JYzjsaWt3KVBYwEAIs f9YeiIxd6ok5GIqSsxngeFxN/jOI8jizPb3c33X2Cg24oZHulbtvZ7GFWnGb+dkiVO4t tGmdqIFR9bQZ7FgvIOFxqAUA7nyjXFcMzDPHK0BfEyEsKrqHmV4cW+6YQf6TRgCooH6V 0CWMt7ZA8IUrRy3JLtIiDVyAVKLT84gOojvNieK0mNHQwZM4TKNXjjTre7NYPfB9sFEt KbCCoCNYa/0ecClim5+76zVm/TQnU/nIhv3TpRJPy5rOJk+j+dOnCEG1h7mv00/bcmuY YhQA== X-Gm-Message-State: AOAM532TvAQv4dw9oyxyuACiG0MozrjwoimSOc64o5YRgMeXCUnrx9uS zq2lGhdfRk1Ty/hflZwcYooH4ic9UTeWUEeBDcrcj9zsvcm+rjU6aWR8WS1DpSyeyASHipamt62 aaW4L7qDtX/CLo+Qv9td2ND3V X-Received: by 2002:a37:652:: with SMTP id 79mr12078383qkg.197.1630113244161; Fri, 27 Aug 2021 18:14:04 -0700 (PDT) X-Google-Smtp-Source: ABdhPJykNQoi0T51RsUXHOgq9qN2JS1S6X7N+wT1bH2pmiiItHjdiaYmsBmA5yoKxviFq81ypmmOdA== X-Received: by 2002:a37:652:: with SMTP id 79mr12078348qkg.197.1630113243925; Fri, 27 Aug 2021 18:14:03 -0700 (PDT) Received: from llong.remote.csb ([2601:191:8500:76c0::cdbc]) by smtp.gmail.com with ESMTPSA id 21sm6009570qkk.51.2021.08.27.18.14.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 27 Aug 2021 18:14:02 -0700 (PDT) From: Waiman Long X-Google-Original-From: Waiman Long Subject: Re: [PATCH v7 5/6] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst To: Tejun Heo , Waiman Long Cc: Zefan Li , Johannes Weiner , Jonathan Corbet , Shuah Khan , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, Andrew Morton , Roman Gushchin , Phil Auld , Peter Zijlstra , Juri Lelli , Frederic Weisbecker , Marcelo Tosatti , =?UTF-8?Q?Michal_Koutn=c3=bd?= References: <20210825213750.6933-1-longman@redhat.com> <20210825213750.6933-6-longman@redhat.com> <32e27fcc-32f1-b26c-ae91-9e03f7e433af@redhat.com> <392c3724-f583-c7fc-cfa1-a3f1665114c9@redhat.com> Message-ID: Date: Fri, 27 Aug 2021 21:14:01 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/27/21 7:35 PM, Tejun Heo wrote: > Hello, > > On Fri, Aug 27, 2021 at 06:50:10PM -0400, Waiman Long wrote: >> The cpu exclusivity rule is due to the setting of CPU_EXCLUSIVE bit. This is >> a pre-existing condition unless you want to change how the >> cpuset.cpu_exclusive works. >> >> So the new rules will be: >> >> 1) The "cpuset.cpus" is not empty and the list of CPUs are exclusive. > Empty cpu list can be considered an exclusive one. It doesn't make sense to me to have a partition with no cpu configured at all. I very much prefer the users to set cpuset.cpus first before turning it into a partition. > >> 2) The parent cgroup is a partition root (can be an invalid one). > Does this mean a partition parent can't stop being a partition if one or > more of its children become partitions? If so, it violates the rule that a > descendant shouldn't be able to restrict what its ancestors can do. No. As I said in the documentation, transitioning from partition root to member is allowed. Against, it is illogical to allow a cpuset to become a potential partition if it parent is not even a partition root at all. In the case that the parent is reverted back to a member, the child partitions will stay invalid forever unless the parent become a valid partition again. > >> 3) The "cpuset.cpus" is a subset of the parent's cpuset.cpus.allowed. > Why not just go by effective? This would mean that a parent can't withdraw > CPUs from its allowed set once descendants are configured. Restrictions like > this are fine when the entire hierarchy is configured by a single entity but > become awkward when configurations are multi-tiered, automated and dynamic. The original rule is to be based on effective cpus. However, to properly handle the case of allowing offlined cpus to be included in the partition, I have to change it to cpu_allowed instead. I can certainly change it back to effective if you prefer. > >> 4) No child cgroup with cpuset enabled. > idk, maybe? I'm having a hard time seeing the point in adding these > restrictions when the state transitions are asynchronous anyway. Would it > help if we try to separate what's absoluately and technically necessary and > what seems reasonable or high bar and try to justify why each of the latter > should be added? This rule is there mainly for ease of implementation. Otherwise, I need to add additional code to handle the conversion of child cpusets which can be rather complex and require a lot more debugging. This rule will no longer apply once the cpuset becomes a partition root. Cheers, Longman