From patchwork Mon Jun 21 18:49:22 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 12335499 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 C51C2C49EA6 for ; Mon, 21 Jun 2021 18:49:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B1DD86124B for ; Mon, 21 Jun 2021 18:49:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231806AbhFUSwM (ORCPT ); Mon, 21 Jun 2021 14:52:12 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:47090 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231822AbhFUSwK (ORCPT ); Mon, 21 Jun 2021 14:52:10 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1624301395; 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=DbRAbt176tzzAPvmL6EJFKHvZbyfzjJzu5p9Px+k+1U=; b=egl4NWDHqO8CdsbqKzGmgJGKIXSJoyADopypbEMapaG2Bu39IYJeOuEht7izSZ3vTn1w+7 k5RKIScHWmKv6m4tn5n27t+yZoqemv1K04yr3B1zKlP7Z48Ze5K5kBSiZvcOHjTfsW1gQ8 8zfob1hkKAwAKQkWzhoOKORCBUX9Yqg= 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-229-Me0X6NnkPiauoPL9LJfamQ-1; Mon, 21 Jun 2021 14:49:53 -0400 X-MC-Unique: Me0X6NnkPiauoPL9LJfamQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id CD86C800D62; Mon, 21 Jun 2021 18:49:51 +0000 (UTC) Received: from llong.com (ovpn-114-127.rdu2.redhat.com [10.10.114.127]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7C4B25D9CA; Mon, 21 Jun 2021 18:49:50 +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 v2 4/6] cgroup/cpuset: Allow non-top parent partition root to distribute out all CPUs Date: Mon, 21 Jun 2021 14:49:22 -0400 Message-Id: <20210621184924.27493-5-longman@redhat.com> In-Reply-To: <20210621184924.27493-1-longman@redhat.com> References: <20210621184924.27493-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 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 | 90 +++++++++++++++++++++++++++++------------- 1 file changed, 63 insertions(+), 27 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 1a4b90e70e68..01b861b97a40 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -268,6 +268,11 @@ static inline int is_partition_root(const struct cpuset *cs) return cs->partition_root_state > 0; } +static inline int cpuset_has_tasks(const struct cpuset *cs) +{ + return cs->css.cgroup->nr_populated_csets; +} + static struct cpuset top_cpuset = { .flags = ((1 << CS_ONLINE) | (1 << CS_CPU_EXCLUSIVE) | (1 << CS_MEM_EXCLUSIVE)), @@ -1174,21 +1179,31 @@ 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 && cpuset_has_tasks(parent)) + return -EINVAL; + cpumask_copy(tmp->addmask, cpuset->cpus_allowed); adding = true; } else if (cmd == partcmd_disable) { @@ -1219,9 +1234,10 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, adding = cpumask_andnot(tmp->addmask, tmp->addmask, parent->subparts_cpus); /* - * Return error if parent's effective_cpus could become empty. + * Return error if parent's effective_cpus could become empty + * and there are tasks in the parent. */ - if (adding && + if (adding && cpuset_has_tasks(parent) && cpumask_equal(parent->effective_cpus, tmp->addmask)) { if (!deleting) return -EINVAL; @@ -1237,12 +1253,13 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, } /* - * Return error if effective_cpus becomes empty or any CPU - * distributed to child partitions is deleted. + * Return error if effective_cpus becomes empty with tasks + * or any CPU distributed to child partitions is deleted. */ if (deleting && (cpumask_intersects(tmp->delmask, cpuset->subparts_cpus) || - cpumask_equal(tmp->delmask, cpuset->effective_cpus))) + (cpumask_equal(tmp->delmask, cpuset->effective_cpus) && + cpuset_has_tasks(cpuset)))) return -EBUSY; } else { /* @@ -1263,7 +1280,8 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, parent->effective_cpus); part_error = (is_partition_root(cpuset) && !parent->nr_subparts_cpus) || - cpumask_equal(tmp->addmask, parent->effective_cpus); + (cpumask_equal(tmp->addmask, parent->effective_cpus) && + cpuset_has_tasks(parent)); } if (cmd == partcmd_update) { @@ -1364,9 +1382,15 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp) /* * If it becomes empty, inherit the effective mask of the - * parent, which is guaranteed to have some CPUs. + * parent, which is guaranteed to have some CPUs unless + * it is a partition root that has explicitly distributed + * out all its CPUs. */ if (is_in_v2_mode() && cpumask_empty(tmp->new_cpus)) { + if (is_partition_root(cp) && + cpumask_equal(cp->cpus_allowed, cp->subparts_cpus)) + goto update_parent_subparts; + cpumask_copy(tmp->new_cpus, parent->effective_cpus); if (!cp->use_parent_ecpus) { cp->use_parent_ecpus = true; @@ -1388,6 +1412,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp) continue; } +update_parent_subparts: /* * update_parent_subparts_cpumask() should have been called * for cs already in update_cpumask(). We should also call @@ -1458,7 +1483,8 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp) */ cpumask_andnot(cp->effective_cpus, cp->effective_cpus, cp->subparts_cpus); - WARN_ON_ONCE(cpumask_empty(cp->effective_cpus)); + WARN_ON_ONCE(cpumask_empty(cp->effective_cpus) && + cpuset_has_tasks(cp)); } spin_unlock_irq(&callback_lock); @@ -1787,7 +1813,7 @@ static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems) cp->effective_mems = *new_mems; spin_unlock_irq(&callback_lock); - WARN_ON(!is_in_v2_mode() && + WARN_ON_ONCE(!is_in_v2_mode() && !nodes_equal(cp->mems_allowed, cp->effective_mems)); update_tasks_nodemask(cp); @@ -2201,6 +2227,13 @@ 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) @@ -3067,7 +3100,8 @@ hotplug_update_tasks(struct cpuset *cs, struct cpumask *new_cpus, nodemask_t *new_mems, bool cpus_updated, bool mems_updated) { - if (cpumask_empty(new_cpus)) + /* A partition root is allowed to have empty effective cpus */ + if (cpumask_empty(new_cpus) && !is_partition_root(cs)) cpumask_copy(new_cpus, parent_cs(cs)->effective_cpus); if (nodes_empty(*new_mems)) *new_mems = parent_cs(cs)->effective_mems; @@ -3136,22 +3170,24 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp) /* * In the unlikely event that a partition root has empty - * effective_cpus, we will have to force any child partitions, - * if present, to become invalid by setting nr_subparts_cpus to 0 - * without causing itself to become invalid. + * effective_cpus with tasks, we will have to force any child + * partitions, if present, to become invalid by setting + * nr_subparts_cpus to 0 without causing itself to become invalid. */ if (is_partition_root(cs) && cs->nr_subparts_cpus && - cpumask_empty(&new_cpus)) { + cpumask_empty(&new_cpus) && cpuset_has_tasks(cs)) { cs->nr_subparts_cpus = 0; cpumask_clear(cs->subparts_cpus); compute_effective_cpumask(&new_cpus, cs, parent); } /* - * If empty effective_cpus or zero nr_subparts_cpus or its parent - * becomes erroneous, we have to transition it to the erroneous state. + * If empty effective_cpus with tasks or zero nr_subparts_cpus or + * its parent becomes erroneous, we have to transition it to the + * erroneous state. */ - if (is_partition_root(cs) && (cpumask_empty(&new_cpus) || + if (is_partition_root(cs) && + ((cpumask_empty(&new_cpus) && cpuset_has_tasks(cs)) || (parent->partition_root_state == PRS_ERROR) || !parent->nr_subparts_cpus)) { update_parent_subparts_cpumask(cs, partcmd_disable,