From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [PATCH v8 3/6] cpuset: Add cpuset.sched.load_balance flag to v2 Date: Fri, 25 May 2018 10:45:14 -0400 Message-ID: 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> <5f409ed7-3850-f1ea-58cf-4326605d1570@redhat.com> <20180525094050.GB30654@e110439-lin> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180525094050.GB30654@e110439-lin> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Patrick Bellasi Cc: Juri Lelli , 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 On 05/25/2018 05:40 AM, Patrick Bellasi wrote: > On 24-May 11:22, Waiman Long wrote: >> 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 > I always a bit confused by the usage of "scheduling domain", which > overlaps with the SD concept from the scheduler standpoint. It is supposed to mimic SD concept of scheduler. > > AFAIU a cpuset sched domain is not granted to be turned into an > actual scheduler SD, am I wrong? > > If that's the case, why not better disambiguate these two concept by > calling the cpuset one a "cpus partition" or eventually "cpuset domain"? Good point. Peter has similar comment. I will probably change the name and clarifying it better in the documentation. Cheers, Longman