From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 178727D062 for ; Thu, 24 May 2018 15:25:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S970645AbeEXPWQ (ORCPT ); Thu, 24 May 2018 11:22:16 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:45038 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S966472AbeEXPWQ (ORCPT ); Thu, 24 May 2018 11:22:16 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6666BBB43D; Thu, 24 May 2018 15:22:15 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-81.bos.redhat.com [10.18.17.81]) by smtp.corp.redhat.com (Postfix) with ESMTP id 286D82023580; Thu, 24 May 2018 15:22:14 +0000 (UTC) Subject: Re: [PATCH v8 3/6] cpuset: Add cpuset.sched.load_balance flag to v2 To: Juri Lelli Cc: Tejun Heo , Li Zefan , Johannes Weiner , Peter Zijlstra , Ingo Molnar , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kernel-team@fb.com, pjt@google.com, luto@amacapital.net, Mike Galbraith , torvalds@linux-foundation.org, Roman Gushchin References: <1526590545-3350-1-git-send-email-longman@redhat.com> <1526590545-3350-4-git-send-email-longman@redhat.com> <20180524143614.GC3948@localhost.localdomain> <4bd31510-4f73-e263-8dc1-5edb0fe63b59@redhat.com> <20180524151656.GD3948@localhost.localdomain> From: Waiman Long Organization: Red Hat Message-ID: <5f409ed7-3850-f1ea-58cf-4326605d1570@redhat.com> Date: Thu, 24 May 2018 11:22:13 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20180524151656.GD3948@localhost.localdomain> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Thu, 24 May 2018 15:22:15 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Thu, 24 May 2018 15:22:15 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'longman@redhat.com' RCPT:'' Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 05/24/2018 11:16 AM, Juri Lelli wrote: > On 24/05/18 11:09, Waiman Long wrote: >> On 05/24/2018 10:36 AM, Juri Lelli wrote: >>> On 17/05/18 16:55, Waiman Long wrote: >>> >>> [...] >>> >>>> + A parent cgroup cannot distribute all its CPUs to child >>>> + scheduling domain cgroups unless its load balancing flag is >>>> + turned off. >>>> + >>>> + cpuset.sched.load_balance >>>> + A read-write single value file which exists on non-root >>>> + cpuset-enabled cgroups. It is a binary value flag that accepts >>>> + either "0" (off) or a non-zero value (on). This flag is set >>>> + by the parent and is not delegatable. >>>> + >>>> + When it is on, tasks within this cpuset will be load-balanced >>>> + by the kernel scheduler. Tasks will be moved from CPUs with >>>> + high load to other CPUs within the same cpuset with less load >>>> + periodically. >>>> + >>>> + When it is off, there will be no load balancing among CPUs on >>>> + this cgroup. Tasks will stay in the CPUs they are running on >>>> + and will not be moved to other CPUs. >>>> + >>>> + The initial value of this flag is "1". This flag is then >>>> + inherited by child cgroups with cpuset enabled. Its state >>>> + can only be changed on a scheduling domain cgroup with no >>>> + cpuset-enabled children. >>> [...] >>> >>>> + /* >>>> + * On default hierachy, a load balance flag change is only allowed >>>> + * in a scheduling domain with no child cpuset. >>>> + */ >>>> + if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) && balance_flag_changed && >>>> + (!is_sched_domain(cs) || css_has_online_children(&cs->css))) { >>>> + err = -EINVAL; >>>> + goto out; >>>> + } >>> The rule is actually >>> >>> - no child cpuset >>> - and it must be a scheduling domain >>> >>> Right? >> Yes, because it doesn't make sense to have a cpu in one cpuset that has >> loading balance off while, at the same time, in another cpuset with load >> balancing turned on. This restriction is there to make sure that the >> above condition will not happen. I may be wrong if there is a realistic >> use case where the above condition is desired. > Yep, makes sense to me. > > Maybe add the second condition to the comment and documentation. Sure. Will do. -Longman -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html