From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick Bellasi Subject: Re: [PATCH v8 3/6] cpuset: Add cpuset.sched.load_balance flag to v2 Date: Fri, 25 May 2018 10:40:50 +0100 Message-ID: <20180525094050.GB30654@e110439-lin> 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> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <5f409ed7-3850-f1ea-58cf-4326605d1570@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Waiman Long 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 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. 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"? -- #include Patrick Bellasi