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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 40AB3C433F5 for ; Wed, 27 Apr 2022 02:34:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 86D026B0073; Tue, 26 Apr 2022 22:34:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 81C106B0075; Tue, 26 Apr 2022 22:34:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6E4D36B0078; Tue, 26 Apr 2022 22:34:28 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.a.hostedemail.com [64.99.140.24]) by kanga.kvack.org (Postfix) with ESMTP id 5ED196B0073 for ; Tue, 26 Apr 2022 22:34:28 -0400 (EDT) Received: from smtpin24.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 34806282A5 for ; 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Tue, 26 Apr 2022 22:34:23 -0400 X-MC-Unique: qaEU4A3LP2-mlluaJGPavg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 66E63101AA44; Wed, 27 Apr 2022 02:34:22 +0000 (UTC) Received: from [10.22.16.78] (unknown [10.22.16.78]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8E3AC40D282D; Wed, 27 Apr 2022 02:34:21 +0000 (UTC) Message-ID: <4c6847ba-4c8d-9776-a065-684a8b95130b@redhat.com> Date: Tue, 26 Apr 2022 22:34:21 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH v2] cgroup/cpuset: Remove cpus_allowed/mems_allowed setup in cpuset_init_smp() Content-Language: en-US To: Feng Tang Cc: Tejun Heo , Zefan Li , Johannes Weiner , "cgroups@vger.kernel.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , Michal Hocko , "Hansen, Dave" , "Huang, Ying" , "stable@vger.kernel.org" References: <20220425155505.1292896-1-longman@redhat.com> <20220426032337.GA84190@shbuild999.sh.intel.com> <20220427010654.GC84190@shbuild999.sh.intel.com> From: Waiman Long In-Reply-To: <20220427010654.GC84190@shbuild999.sh.intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.11.54.2 X-Rspamd-Queue-Id: 4DAC0180058 X-Stat-Signature: 6docwnhimcxubwuicgagr3soz56x96pf X-Rspam-User: Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="jUNOAz/L"; spf=none (imf24.hostedemail.com: domain of longman@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=longman@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspamd-Server: rspam09 X-HE-Tag: 1651026864-505011 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 4/26/22 21:06, Feng Tang wrote: > On Tue, Apr 26, 2022 at 10:58:21PM +0800, Waiman Long wrote: >> On 4/25/22 23:23, Feng Tang wrote: >>> Hi Waiman, >>> >>> On Mon, Apr 25, 2022 at 11:55:05AM -0400, Waiman Long wrote: >>>> There are 3 places where the cpu and node masks of the top cpuset can >>>> be initialized in the order they are executed: >>>> 1) start_kernel -> cpuset_init() >>>> 2) start_kernel -> cgroup_init() -> cpuset_bind() >>>> 3) kernel_init_freeable() -> do_basic_setup() -> cpuset_init_smp() >>>> >>>> The first cpuset_init() function just sets all the bits in the masks. >>>> The last one executed is cpuset_init_smp() which sets up cpu and node >>>> masks suitable for v1, but not v2. cpuset_bind() does the right setup >>>> for both v1 and v2. >>>> >>>> For systems with cgroup v2 setup, cpuset_bind() is called once. For >>>> systems with cgroup v1 setup, cpuset_bind() is called twice. It is >>>> first called before cpuset_init_smp() in cgroup v2 mode. Then it is >>>> called again when cgroup v1 filesystem is mounted in v1 mode after >>>> cpuset_init_smp(). >>>> >>>> [ 2.609781] cpuset_bind() called - v2 = 1 >>>> [ 3.079473] cpuset_init_smp() called >>>> [ 7.103710] cpuset_bind() called - v2 = 0 >>> I run some test, on a server with centOS, this did happen that >>> cpuset_bind() is called twice, first as v2 during kernel boot, >>> and then as v1 post-boot. >>> >>> However on a QEMU running with a basic debian rootfs image, >>> the second call of cpuset_bind() didn't happen. >> The first time cpuset_bind() is called in cgroup_init(), the kernel >> doesn't know if userspace is going to mount v1 or v2 cgroup. By default, >> it is assumed to be v2. However, if userspace mounts the cgroup v1 >> filesystem for cpuset, cpuset_bind() will be run at this point by >> rebind_subsystem() to set up cgroup v1 environment and >> cpus_allowed/mems_allowed will be correctly set at this point. Mounting >> the cgroup v2 filesystem, however, does not cause rebind_subsystem() to >> run and hence cpuset_bind() is not called again. >> >> Is the QEMU setup not mounting any cgroup filesystem at all? If so, does >> it matter whether v1 or v2 setup is used? > When I got the cpuset binding error report, I tried first on qemu to > reproduce and failed (due to there was no memory hotplug), then I > reproduced it on a real server. For both system, I used "cgroup_no_v1=all" > cmdline parameter to test cgroup-v2, could this be the reason? (TBH, > this is the first time I use cgroup-v2). > > Here is the info dump: > > # mount | grep cgroup > tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755) > cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/lib/systemd/systemd-cgroups-agent,name=systemd) > > #cat /proc/filesystems | grep cgroup > nodev cgroup > nodev cgroup2 > > Thanks, > Feng For cgroup v2, cpus_allowed should be set to cpu_possible_mask and mems_allowed to node_possible_map as is done in the first invocation of cpuset_bind(). That is the correct behavior. Cheers, Longman