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 X-Spam-Level: X-Spam-Status: No, score=-11.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,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 8FC62C4320E for ; Tue, 27 Jul 2021 11:42:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7BF9661A07 for ; Tue, 27 Jul 2021 11:42:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236484AbhG0Lmp (ORCPT ); Tue, 27 Jul 2021 07:42:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:48246 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236087AbhG0Lmn (ORCPT ); Tue, 27 Jul 2021 07:42:43 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8FF6A61A0C; Tue, 27 Jul 2021 11:42:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1627386164; bh=kScULZZCypjcOHNbhOUj9pQys0yWEAROn9wACbjozIw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=m8JyQpsRV2qnrTyHfpCN4LeYJtuQKD2lVoLcORs/LIL6Zlfk+9kyrUWwpYLWVH0zC da4SkWCfx1FBjXO9GP9sD5YcX7dwO7+aUAGptdmkKD+iau4FPQXrDqvZf/7/iOvINL hPupBomYDitrlzXqSt4tgqqnLYI2Tt1erZZv5dqLFsX+/sdb2DjELZQk74bMom9TdJ KcCDDCgKTvR9Q4BGNqRgLcv7FjGJG7qUC0JwTdOpDa+T3RxkWbzRnt7Z2YLV8sSelE imLHD8oRPKROL+Ha8NMd192W7plhwgLNv5bQ8qDVMtz8sREeVIktU/vSiCj03Wb9u+ uv+1mXNkUEojg== Date: Tue, 27 Jul 2021 13:42:41 +0200 From: Frederic Weisbecker To: Waiman Long Cc: Tejun Heo , Zefan Li , Johannes Weiner , Jonathan Corbet , Shuah Khan , 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 , Marcelo Tosatti , Michal =?iso-8859-1?Q?Koutn=FD?= Subject: Re: [PATCH v3 6/9] cgroup/cpuset: Add a new isolated cpus.partition type Message-ID: <20210727114241.GA283787@lothringen> References: <20210720141834.10624-1-longman@redhat.com> <20210720141834.10624-7-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210720141834.10624-7-longman@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 20, 2021 at 10:18:31AM -0400, Waiman Long wrote: > Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=TBD > > commit 994fb794cb252edd124a46ca0994e37a4726a100 > Author: Waiman Long > Date: Sat, 19 Jun 2021 13:28:19 -0400 > > cgroup/cpuset: Add a new isolated cpus.partition type > > Cpuset v1 uses the sched_load_balance control file to determine if load > balancing should be enabled. Cpuset v2 gets rid of sched_load_balance > as its use may require disabling load balancing at cgroup root. > > For workloads that require very low latency like DPDK, the latency > jitters caused by periodic load balancing may exceed the desired > latency limit. > > When cpuset v2 is in use, the only way to avoid this latency cost is to > use the "isolcpus=" kernel boot option to isolate a set of CPUs. After > the kernel boot, however, there is no way to add or remove CPUs from > this isolated set. For workloads that are more dynamic in nature, that > means users have to provision enough CPUs for the worst case situation > resulting in excess idle CPUs. > > To address this issue for cpuset v2, a new cpuset.cpus.partition type > "isolated" is added which allows the creation of a cpuset partition > without load balancing. This will allow system administrators to > dynamically adjust the size of isolated partition to the current need > of the workload without rebooting the system. > > Signed-off-by: Waiman Long > > Signed-off-by: Waiman Long Nice! And while we are adding a new ABI, can we take advantage of that and add a specific semantic that if a new isolated partition matches a subset of "isolcpus=", it automatically maps to it. This means that any further modification to that isolated partition will also modify the associated isolcpus= subset. Or to summarize, when we create a new isolated partition, remove the associated CPUs from isolcpus= ? Thanks.