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 06774C433F5 for ; Wed, 27 Apr 2022 12:10:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 87BC36B0073; Wed, 27 Apr 2022 08:10:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8528A6B0078; Wed, 27 Apr 2022 08:10:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6F4106B0080; Wed, 27 Apr 2022 08:10:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.28]) by kanga.kvack.org (Postfix) with ESMTP id 620BA6B0073 for ; Wed, 27 Apr 2022 08:10:05 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay13.hostedemail.com (Postfix) with ESMTP id 3723762677 for ; Wed, 27 Apr 2022 12:10:05 +0000 (UTC) X-FDA: 79402540770.02.3432C3D Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by imf17.hostedemail.com (Postfix) with ESMTP id 944704005C for ; Wed, 27 Apr 2022 12:09:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1651061404; x=1682597404; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=UNTq8c3nGCVicANYsW9zJ0pFSSw7ENqHGTRz5ROMqyA=; b=IcuMM4uG2sWIs7oQqQnJL/jKz0aSGck6prsuMTwza4JdAghiX2b4YONo ozZPfGtzpJKAQod8ukNBpTwnT0B2jnJXaVGFAY0MvYhBlqriW09JEIFzM rbENq4iCiWgPA8RuVLy9UPUCf/dvBmp6kRhNjTcG+7Eyfc3Yu3QDSRf4q 05SZ6aJ+8vXjK19xu02s057xCwkXnY8+C7uNppxhyxYYtBnIt5B0rPFuK qtmjtrPr78d8g2LTzPKC5W9qNrgmPcV7nAI7H/BjCiGBs8k9uKJeIwaFj BbVOyJ0+kjhwwGRsrEGuEvNpDd8Em6aaBOODrME2oWmmGnNkPUJOpKe1H Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10329"; a="265432245" X-IronPort-AV: E=Sophos;i="5.90,292,1643702400"; d="scan'208";a="265432245" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Apr 2022 05:10:02 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.90,292,1643702400"; d="scan'208";a="580561887" Received: from shbuild999.sh.intel.com (HELO localhost) ([10.239.146.138]) by orsmga008.jf.intel.com with ESMTP; 27 Apr 2022 05:09:58 -0700 Date: Wed, 27 Apr 2022 20:09:58 +0800 From: Feng Tang To: Waiman Long 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" Subject: Re: [PATCH v2] cgroup/cpuset: Remove cpus_allowed/mems_allowed setup in cpuset_init_smp() Message-ID: <20220427120958.GD84190@shbuild999.sh.intel.com> References: <20220425155505.1292896-1-longman@redhat.com> <20220426032337.GA84190@shbuild999.sh.intel.com> <20220427010654.GC84190@shbuild999.sh.intel.com> <4c6847ba-4c8d-9776-a065-684a8b95130b@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4c6847ba-4c8d-9776-a065-684a8b95130b@redhat.com> X-Rspamd-Queue-Id: 944704005C X-Stat-Signature: gek8ra4qn33ujewdeie5yf11zet4ku13 Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=IcuMM4uG; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf17.hostedemail.com: domain of feng.tang@intel.com has no SPF policy when checking 134.134.136.24) smtp.mailfrom=feng.tang@intel.com X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1651061396-109126 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 Tue, Apr 26, 2022 at 10:34:21PM -0400, Waiman Long wrote: > 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. OK. For the cgroup v2 mem binding problem with hot-added nodes, I retested today, and it can't be reproduced with this patch. So feel free to add: Tested-by: Feng Tang Thanks, Feng > Cheers, > Longman >