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 67030C48BE6 for ; Thu, 10 Jun 2021 19:22:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 52EA761246 for ; Thu, 10 Jun 2021 19:22:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230083AbhFJTXz (ORCPT ); Thu, 10 Jun 2021 15:23:55 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:21789 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230232AbhFJTXv (ORCPT ); Thu, 10 Jun 2021 15:23:51 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623352914; 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=DVG4CWGfyu4y0g9i2OCoAuUtkr+80/M03bPDGkS4TS8=; b=KrmRPXTQzgcO01RxmExyB/c/8VLB/qa3V4z+12QANBuu1neQI+ONGRiBe9rfO3Dgk9vprf zhzFySb7gd8RSMbu6pd4vPLZATtD+gtaMKN5acximHIWBeXtWdzD+o3qWeNk4TKUtCMth1 8+xBul22Y5wXyPAlTXCBPQ6IvJnKDuw= Received: from mail-qt1-f197.google.com (mail-qt1-f197.google.com [209.85.160.197]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-283-fGiOXAsHOc2hZkX3wPpxEg-1; Thu, 10 Jun 2021 15:21:53 -0400 X-MC-Unique: fGiOXAsHOc2hZkX3wPpxEg-1 Received: by mail-qt1-f197.google.com with SMTP id a5-20020ac84d850000b029024998e61d00so488204qtw.14 for ; Thu, 10 Jun 2021 12:21:53 -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=DVG4CWGfyu4y0g9i2OCoAuUtkr+80/M03bPDGkS4TS8=; b=ZZ88p+zyRTOOFsHIg2DNriAYIdEB9mLREESsTQ9LZYnB6fuLdnlQXcHpSz2syByUEy poEHabtwBrpoGeSnd7lK3dSstFyVWE/7smkLg5OBgk3MsgElAQhm9BoCUsfs3f1FzaHY iEK+p1mN7omh4etrMbcaHsUWie2l4LaX8W9V4PxwGnCxnuLwPrkA0U9DISbH3zkepp0r 6BLnpbw37adl6hY3CvE3MuEkBgZjbogay+35GeyFXFT/4m36JpF88c90lflw1+vFzj8B C3sINSmyu5K+nzX6A5z3AFsecQcodrYZl9Wo/RHfbgzMrRsWH06kmd56MJI+1BYqlmF/ 6csA== X-Gm-Message-State: AOAM531AviVMHvQqj4fcMJ5QwywnPn8mYaUeMuowgXuyEDNurT5Z60XO WkyPvBVmGVkWB8VUzDlFxgUFLzoFkUcECwPWqO/2UDHsVDXPzVRCBZXXOYF2vi/JEoyzX2VTDiH I6fm17x2ZPhT0VZkY8gOHrefM X-Received: by 2002:ac8:45cd:: with SMTP id e13mr342455qto.45.1623352913270; Thu, 10 Jun 2021 12:21:53 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzeiZS804EdnkmC4YoAIb9fvGvqBRkzaFwj/cd9U44QFCAH/4ydLc0o5CPvxlig3jZUdN2jTQ== X-Received: by 2002:ac8:45cd:: with SMTP id e13mr342442qto.45.1623352913114; Thu, 10 Jun 2021 12:21:53 -0700 (PDT) Received: from llong.remote.csb ([2601:191:8500:76c0::cdbc]) by smtp.gmail.com with ESMTPSA id s7sm3033177qkp.35.2021.06.10.12.21.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 10 Jun 2021 12:21:52 -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: Date: Thu, 10 Jun 2021 15:21:51 -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-kernel@vger.kernel.org On 6/10/21 3:00 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. > Also, can we change isolcpus to create a default cgroup hierarchy > instead of being the fugly hack that it is? I really hate isolcpus with > a passion, it needs to die. > That is probably doable assuming that we can allow cpuset v2 to have a non-load balanced partition. Depending on which cpuset version is set up, we can automatically set up a isolated subdirectory under / to contain cpus that are isolated. However, that will be a follow-on patch after this one. Cheers, Longman