From patchwork Thu Jun 3 21:24:14 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 454384 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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS 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 E6654C47096 for ; Thu, 3 Jun 2021 21:25:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D40716140A for ; Thu, 3 Jun 2021 21:25:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230261AbhFCV0u (ORCPT ); Thu, 3 Jun 2021 17:26:50 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:28083 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230246AbhFCV0r (ORCPT ); Thu, 3 Jun 2021 17:26:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622755501; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:in-reply-to:in-reply-to:references:references; bh=WUGY8sYtZzxYZSnhBIxuLuhJwQQu5J4ornFBXmTKadM=; b=Af/VFunv8bLg8P3LHrJXykFOPRhvACz2cpXYpnCb8Bbdb6UjXXYXR/EmhCnu13K9+vnX10 AH683zInpi9ED/TNvgFB2inovknZvTrSNi9xMRQw0EbGqgZvYdImrLxfGQ/4z7WBltsnNW HE6yFS30M5QFKPcuqZHGbOrjGTDmHyI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-345-xF1QuBkwN4mkdbG0TiNQ1g-1; Thu, 03 Jun 2021 17:24:59 -0400 X-MC-Unique: xF1QuBkwN4mkdbG0TiNQ1g-1 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id 44E498030A1; Thu, 3 Jun 2021 21:24:57 +0000 (UTC) Received: from llong.com (ovpn-116-222.rdu2.redhat.com [10.10.116.222]) by smtp.corp.redhat.com (Postfix) with ESMTP id E26DF614FD; Thu, 3 Jun 2021 21:24:55 +0000 (UTC) From: Waiman Long To: Tejun Heo , Zefan Li , Johannes Weiner , Jonathan Corbet , Shuah Khan Cc: 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 , Waiman Long Subject: [PATCH 3/5] cgroup/cpuset: Allow non-top parent partition root to distribute out all CPUs Date: Thu, 3 Jun 2021 17:24:14 -0400 Message-Id: <20210603212416.25934-4-longman@redhat.com> In-Reply-To: <20210603212416.25934-1-longman@redhat.com> References: <20210603212416.25934-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Currently, a parent partition root cannot distribute all its CPUs to child partition roots with no CPUs left. However in some use cases, a management application may want to create a parent partition root as a management unit with no task associated with it and has all its CPUs distributed to various child partition roots dynamically according to their needs. Leaving a cpu in the parent partition root in such a case is now a waste. To accommodate such use cases, a parent partition root can now have all its CPUs distributed to its child partition roots as long as: 1) it is not the top cpuset; and 2) there is no task directly associated with the parent. Once an empty parent partition root is formed, no new task can be moved into it. Signed-off-by: Waiman Long --- kernel/cgroup/cpuset.c | 44 +++++++++++++++++++++++++++++------------- 1 file changed, 31 insertions(+), 13 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 78dd6c91dcd6..ef19eb317fef 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1117,7 +1117,7 @@ enum subparts_cmd { * cpus_allowed can be granted or an error code will be returned. * * For partcmd_disable, the cpuset is being transofrmed from a partition - * root back to a non-partition root. any CPUs in cpus_allowed that are in + * root back to a non-partition root. Any CPUs in cpus_allowed that are in * parent's subparts_cpus will be taken away from that cpumask and put back * into parent's effective_cpus. 0 should always be returned. * @@ -1172,21 +1172,31 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, if ((cmd != partcmd_update) && css_has_online_children(&cpuset->css)) return -EBUSY; - /* - * Enabling partition root is not allowed if not all the CPUs - * can be granted from parent's effective_cpus or at least one - * CPU will be left after that. - */ - if ((cmd == partcmd_enable) && - (!cpumask_subset(cpuset->cpus_allowed, parent->effective_cpus) || - cpumask_equal(cpuset->cpus_allowed, parent->effective_cpus))) - return -EINVAL; - /* * A cpumask update cannot make parent's effective_cpus become empty. */ adding = deleting = false; if (cmd == partcmd_enable) { + bool parent_is_top_cpuset = !parent_cs(parent); + bool no_cpu_in_parent = cpumask_equal(cpuset->cpus_allowed, + parent->effective_cpus); + /* + * Enabling partition root is not allowed if not all the CPUs + * can be granted from parent's effective_cpus. If the parent + * is the top cpuset, at least one CPU must be left after that. + */ + if (!cpumask_subset(cpuset->cpus_allowed, parent->effective_cpus) || + (parent_is_top_cpuset && no_cpu_in_parent)) + return -EINVAL; + + /* + * A non-top parent can be left with no CPU as long as there + * is no task directly associated with the parent. For such + * a parent, no new task can be moved into it. + */ + if (no_cpu_in_parent && parent->css.cgroup->nr_populated_csets) + return -EINVAL; + cpumask_copy(tmp->addmask, cpuset->cpus_allowed); adding = true; } else if (cmd == partcmd_disable) { @@ -1208,9 +1218,10 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, adding = cpumask_andnot(tmp->addmask, tmp->addmask, parent->subparts_cpus); /* - * Return error if the new effective_cpus could become empty. + * Return error if the new effective_cpus could become empty + * and there are tasks in the parent. */ - if (adding && + if (adding && parent->css.cgroup->nr_populated_csets && cpumask_equal(parent->effective_cpus, tmp->addmask)) { if (!deleting) return -EINVAL; @@ -2181,6 +2192,13 @@ static int cpuset_can_attach(struct cgroup_taskset *tset) (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))) goto out_unlock; + /* + * On default hierarchy, task cannot be moved to a cpuset with empty + * effective cpus. + */ + if (is_in_v2_mode() && cpumask_empty(cs->effective_cpus)) + goto out_unlock; + cgroup_taskset_for_each(task, css, tset) { ret = task_can_attach(task, cs->cpus_allowed); if (ret)