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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6353CD13D1 for ; Mon, 18 Sep 2023 07:07:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240016AbjIRHHh (ORCPT ); Mon, 18 Sep 2023 03:07:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52764 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240071AbjIRHHV (ORCPT ); Mon, 18 Sep 2023 03:07:21 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id A97E712A; Mon, 18 Sep 2023 00:07:12 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5ACF31FB; Mon, 18 Sep 2023 00:07:49 -0700 (PDT) Received: from [10.34.100.121] (e126645.nice.arm.com [10.34.100.121]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CFE513F5A1; Mon, 18 Sep 2023 00:07:10 -0700 (PDT) Message-ID: <9777f0d2-2fdf-41cb-bd01-19c52939ef42@arm.com> Date: Mon, 18 Sep 2023 09:07:04 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.0 Subject: Re: [PATCH 1/1] cgroup/cpuset: Rebuild sched domains if isolated partition changed Content-Language: en-US To: Waiman Long , linux-kernel@vger.kernel.org Cc: rui.zhang@intel.com, aaron.lu@intel.com, Zefan Li , Tejun Heo , Johannes Weiner , cgroups@vger.kernel.org References: <20230915154505.363754-1-pierre.gondois@arm.com> <20230915154505.363754-2-pierre.gondois@arm.com> <5e513c72-7198-a55e-6e2b-a811d5529284@redhat.com> From: Pierre Gondois In-Reply-To: <5e513c72-7198-a55e-6e2b-a811d5529284@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Longman, On 9/17/23 18:51, Waiman Long wrote: > On 9/15/23 11:45, Pierre Gondois wrote: >> When an isolated parition is created, the sched domains (sds) are >> rebuilt and the sds of the isolated CPUs are detached. This only >> happens at the creation of the isolated parition. Updating >> the cpuset of the partition doesn't rebuild the sds: >> >> To reproduce: >> # ls /sys/kernel/debug/sched/domains/cpu0/ >> domain0 >> # ls /sys/kernel/debug/sched/domains/cpu1/ >> domain0 >> # >> # mkdir cgroup >> # mount -t cgroup2 none cgroup/ >> # mkdir cgroup/A1/ >> # echo "+cpuset" > cgroup/cgroup.subtree_control >> # echo 0-3 > cgroup/A1/cpuset.cpus >> # echo isolated > cgroup/A1/cpuset.cpus.partition >> # >> # ls /sys/kernel/debug/sched/domains/cpu0/ >> # ls /sys/kernel/debug/sched/domains/cpu1/ >> # >> # echo 0 > cgroup/A1/cpuset.cpus >> # ls /sys/kernel/debug/sched/domains/cpu0/ >> # ls /sys/kernel/debug/sched/domains/cpu1/ >> # >> >> Here CPU1 should have a sched domain re-attached. >> >> Signed-off-by: Pierre Gondois >> --- >> kernel/cgroup/cpuset.c | 12 ++++++++---- >> 1 file changed, 8 insertions(+), 4 deletions(-) >> >> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c >> index 58e6f18f01c1..e3eb27ff9b68 100644 >> --- a/kernel/cgroup/cpuset.c >> +++ b/kernel/cgroup/cpuset.c >> @@ -1680,11 +1680,15 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, >> * empty cpuset is changed, we need to rebuild sched domains. >> * On default hierarchy, the cpuset needs to be a partition >> * root as well. >> + * Also rebuild sched domains if the cpuset of an isolated >> + * partition changed. >> */ >> - if (!cpumask_empty(cp->cpus_allowed) && >> - is_sched_load_balance(cp) && >> - (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) || >> - is_partition_valid(cp))) >> + if ((!cpumask_empty(cp->cpus_allowed) && >> + is_sched_load_balance(cp) && >> + (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) || >> + is_partition_valid(cp))) || >> + (cp->partition_root_state == PRS_ISOLATED || >> + cp->partition_root_state == PRS_INVALID_ISOLATED)) >> need_rebuild_sched_domains = true; >> >> rcu_read_lock(); > > Thanks for spotting the problem and sending out a patch to fix it. > However, it should be done in the update_cpumask(). The sched_domain > rebuild in update_cpumasks_hier() is supposed to be used for impacted > descendant cpusets lower down in the hierarchy. > > Anyway, I believe this problem should have been fixed in commit > a86ce68078b2 ("cgroup/cpuset: Extract out CS_CPU_EXCLUSIVE & > CS_SCHED_LOAD_BALANCE handling") recently merged into the v6.6 kernel. > Would you mind testing the latest upstream kernel to see if this problem > is gone or not? Yes right, v6.6-rc2 kernel doesn't have this issue. My bad for not updating it ... However I think the second issue described in the cover letter can still be reproduced on v6.6-rc2. This present patch was not aiming to fix it though. Commands: # mkdir cgroup # mount -t cgroup2 none cgroup/ # mkdir cgroup/A1 cgroup/B1 # echo "+cpuset" > cgroup/cgroup.subtree_control # echo 0-3 > cgroup/A1/cpuset.cpus # echo isolated > cgroup/A1/cpuset.cpus.partition # echo 4-6 > cgroup/B1/cpuset.cpus # cat cgroup/A1/cpuset.cpus.partition isolated # echo 0-4 > cgroup/A1/cpuset.cpus # cat cgroup/A1/cpuset.cpus.partition isolated invalid (Cpu list in cpuset.cpus not exclusive) # echo 0-3 > cgroup/A1/cpuset.cpus # cat cgroup/A1/cpuset.cpus.partition isolated invalid (Cpu list in cpuset.cpus not exclusive) Cgroup A1 should be a valid isolated partition once its CPUs become exclusive again I believe, Regards, Pierre > > Thanks, > Longman >