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=-7.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 884C6C48BDF for ; Thu, 10 Jun 2021 19:16:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E51961403 for ; Thu, 10 Jun 2021 19:16:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230364AbhFJTSa (ORCPT ); Thu, 10 Jun 2021 15:18:30 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:35378 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230358AbhFJTS3 (ORCPT ); Thu, 10 Jun 2021 15:18:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623352592; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=liO0eMHLLQxFJzTbME5X4nacHbq/D6xkCgBqqSco7f0=; b=UKN+VJFnPT1Qyo3v1npa3BNUZAI5MynuwJj6j1bhiY7PgYNDadnJiKxiSqCfqlg+CR+/Dc +a2PtBDDqQNbbPd+VasXaEE0uJ7hI2W9T773WubC+23Di5HiXGq+fjZj3RznfOg8b2brr1 U58N3WY9z3khNJP/ah9cLwXYoHprR48= Received: from mail-qv1-f72.google.com (mail-qv1-f72.google.com [209.85.219.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-400-s_LJ4oJNNdS-bKtJA3iV8Q-1; Thu, 10 Jun 2021 15:16:31 -0400 X-MC-Unique: s_LJ4oJNNdS-bKtJA3iV8Q-1 Received: by mail-qv1-f72.google.com with SMTP id k12-20020a0cfd6c0000b029020df9543019so18630900qvs.14 for ; Thu, 10 Jun 2021 12:16:31 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:subject:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=liO0eMHLLQxFJzTbME5X4nacHbq/D6xkCgBqqSco7f0=; b=idvaBljnpfTk1foovZ1vgo9HciduqkZj1fdD1i6OmcqC6SD4cEwlq4eNdM3bQw0QGR ZeIq0ISKZhF8qFSXPcTChNQN0it9Z4j8e0k3coGMGrgWvw1iYCelILF20CA1OM8x+F53 EvyYG/mY1YO18tXAutLBetZ2GgAYiBRPdBoFKLPdtdrxITqIbypQAKTmax0/NqVQp53U NO35buFgGAfeU7JZp1VanxpVib6rHcxf2LiJyU7Mg575i2evyUTNHlHAg2zX9O4x02Qx 3CLC3ns+ddWnLP7mPd2hzmgtWSiBd/ijjz/ULxuqzJui6VRvauT8U0n+LNm4S9nt6tGa v6nA== X-Gm-Message-State: AOAM530k+JvU1cPu8VwCm8ypyjkkpoI9ITDPy+7xzB+8RGLd9WQFWMgx BETwubtjZWsYpu4L37IQdasgWMWfS+Mn9uq4c73peGTmMow5SUCnK+/hYtykEjZo5HJtelwzhZg zZ0NqPIkQy1OY3+JW7tsZ X-Received: by 2002:a37:5507:: with SMTP id j7mr104032qkb.309.1623352591111; Thu, 10 Jun 2021 12:16:31 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyAuBlSzvmN6H5oSpFj7wzJ2WHLurIlPNKFIgsipjYWbH5Grt8CtLeVfMxQOG6UnUOcx7CMDw== X-Received: by 2002:a37:5507:: with SMTP id j7mr104009qkb.309.1623352590931; Thu, 10 Jun 2021 12:16:30 -0700 (PDT) Received: from llong.remote.csb ([2601:191:8500:76c0::cdbc]) by smtp.gmail.com with ESMTPSA id 7sm2906484qkb.86.2021.06.10.12.16.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 10 Jun 2021 12:16:30 -0700 (PDT) From: Waiman Long X-Google-Original-From: Waiman Long Subject: Re: [PATCH 2/5] cgroup/cpuset: Add new cpus.partition type with no load balancing To: Peter Zijlstra 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 , Juri Lelli References: <20210603212416.25934-1-longman@redhat.com> <20210603212416.25934-3-longman@redhat.com> Message-ID: <820aff72-fce2-ac2f-88e6-787249e04308@redhat.com> Date: Thu, 10 Jun 2021 15:16:29 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 6/10/21 2:50 PM, Peter Zijlstra wrote: > On Thu, Jun 03, 2021 at 05:24:13PM -0400, Waiman Long wrote: >> 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 >> "root-nolb" is added which allows the creation of a cpuset partition with >> no load balancing. This will allow system administrators to dynamically >> adjust the size of the no load balancing partition to the current need >> of the workload without rebooting the system. > I'm confused, why do you need this? Just create a parition for each cpu. > From a management point of view, it is more cumbersome to do one cpu per partition. I have suggested this idea of 1 cpu per partition to the container developers, but they don't seem to like it. Cheers, Longman