From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935831AbeEYHPv (ORCPT ); Fri, 25 May 2018 03:15:51 -0400 Received: from merlin.infradead.org ([205.233.59.134]:36994 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934393AbeEYHPt (ORCPT ); Fri, 25 May 2018 03:15:49 -0400 Date: Fri, 25 May 2018 09:15:24 +0200 From: Peter Zijlstra To: Waiman Long Cc: Tejun Heo , Li Zefan , Johannes Weiner , 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 , Juri Lelli Subject: Re: [PATCH v8 2/6] cpuset: Add new v2 cpuset.sched.domain flag Message-ID: <20180525071524.GQ12198@hirez.programming.kicks-ass.net> References: <1526590545-3350-1-git-send-email-longman@redhat.com> <1526590545-3350-3-git-send-email-longman@redhat.com> <20180524154156.GI12198@hirez.programming.kicks-ass.net> <675f0f38-9154-4e73-1679-179eefdb7c9f@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <675f0f38-9154-4e73-1679-179eefdb7c9f@redhat.com> User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 24, 2018 at 02:53:31PM -0400, Waiman Long wrote: > On 05/24/2018 11:41 AM, Peter Zijlstra wrote: > > On Thu, May 17, 2018 at 04:55:41PM -0400, Waiman Long wrote: > >> A new cpuset.sched.domain boolean flag is added to cpuset v2. This new > >> flag indicates that the CPUs in the current cpuset should be treated > >> as a separate scheduling domain. > > The traditional name for this is a partition. > > Do you want to call it cpuset.sched.partition? That name sounds strange > to me. Let me explore the whole domain x load-balance space first. I'm thinking the two parameters are mostly redundant, but I might be overlooking something (trivial or otherwise). > >> + cpuset.sched.domain > >> + 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). > > I would be conservative and only allow 0/1. > > I stated that because echoing other integer value like 2 into the flag > file won't return any error. I will modify it to say just 0 and 1. Ah, I would make the file error on >1. Because then you can always extend the meaning afterwards because you know it won't be written to with the new value. > >> + 3) There is no child cgroups with cpuset enabled. > >> + > >> + Setting this flag will take the CPUs away from the effective > >> + CPUs of the parent cgroup. Once it is set, this flag cannot be > >> + cleared if there are any child cgroups with cpuset enabled. > > This I'm not clear on. Why? > > > That is for pragmatic reason as it is easier to code this way. We could > remove this restriction but that will make the code more complex. Best to mention that I think.