From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751553AbeCTUWx (ORCPT ); Tue, 20 Mar 2018 16:22:53 -0400 Received: from mail-yw0-f180.google.com ([209.85.161.180]:35047 "EHLO mail-yw0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751411AbeCTUWu (ORCPT ); Tue, 20 Mar 2018 16:22:50 -0400 X-Google-Smtp-Source: AG47ELuUheBuSBten7gGT3cQ47E/j4C93gAUq1O9cigjuaNLw8UuVWjl9XNYuviQbSc6WPOzlLariQ== Date: Tue, 20 Mar 2018 13:22:47 -0700 From: Tejun Heo To: Waiman Long Cc: 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, efault@gmx.de, torvalds@linux-foundation.org, Roman Gushchin Subject: Re: [PATCH v5 2/2] cpuset: Add cpuset.flags control knob to v2 Message-ID: <20180320202247.GQ519464@devbig577.frc2.facebook.com> References: <1521148842-15486-1-git-send-email-longman@redhat.com> <1521148842-15486-3-git-send-email-longman@redhat.com> <20180319162654.GR2943022@devbig577.frc2.facebook.com> <8e553b7e-cab6-1b5d-9110-cc5770ae16c4@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Waiman. On Tue, Mar 20, 2018 at 04:12:25PM -0400, Waiman Long wrote: > After some thought, I am planning to impose the following additional > constraints on how sched_load_balance works in v2. > > 1) sched_load_balance will be made hierarchical, the child will inherit > the flag from its parent. > 2) cpu_exclusive will be implicitly associated with sched_load_balance. > IOW, sched_load_balance => !cpu_exclusive, and !sched_load_balance => > cpu_exclusive. > 3) sched_load_balance cannot be 1 on a child if it is 0 on the parent. > > With these changes, sched_load_balance will have to be set by the parent > and so will not be delegatable. Please let me know your thought on that. So, for configurations, we usually don't let them interact across hierarchy because that can lead to configurations surprise-changing and delegated children locking the parent into the current config. This case could be different and as long as we always guarantee that an ancestor isn't limited by its descendants in what it can configure, it should be okay (e.g. an ancestor should always be able to turn on sched_load_balance regardless of how the descendants are configured). Hmmm... can you explain why sched_load_balance needs to behave this way? Thanks. -- tejun