From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH v10 2/9] cpuset: Add new v2 cpuset.sched.domain_root flag Date: Wed, 20 Jun 2018 16:27:35 +0200 Message-ID: <20180620142735.GM2494@hirez.programming.kicks-ass.net> References: <1529295249-5207-1-git-send-email-longman@redhat.com> <1529295249-5207-3-git-send-email-longman@redhat.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=eMGX/vsz54Q4caqt50tNX8W2/XJte3L4ED1D2DYi3DM=; b=NTy23Fnsf7WLUGXDCU7Zw7jvu 1M4RHZa6VjWMn91F72ExcFloyGANed3g6cq6XvBzm8yPXCl4S4CBQykPADUjAeyX2odDPvAm0QQz6 yfxE7hqrJIbMtIDuYQO4oLeMDbDLHv/vUfqq93ZG9Y8df2nE8U2Ldw4mIGoJc+QAbYPVrMdKgmRiu 51JP9eVTIm7Ivyx2WSRrpLyubjbWfUhd1cvrBMQXeSXBz+U1yasuhs80zQY94T1MBG5MgkAtKVHq4 R0WtHHtz+UBNsed6zSZFwR2aYtFXi6CnktqZKGvIlj1FPjQNCs2k2jWcRWjE6tt7KUyS37zVp/8ue Content-Disposition: inline In-Reply-To: <1529295249-5207-3-git-send-email-longman@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: 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 , Patrick Bellasi On Mon, Jun 18, 2018 at 12:14:01PM +0800, Waiman Long wrote: > + cpuset.sched.domain_root Why are we calling this a domain_root and not a partition? > + 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 "1" (on). This flag is set by the parent > + and is not delegatable. You still haven't answered: https://lkml.kernel.org/r/20180531094943.GG12180@hirez.programming.kicks-ass.net the question stands. > + If set, it indicates that the current cgroup is the root of a > + new scheduling domain or partition that comprises itself and > + all its descendants except those that are scheduling domain > + roots themselves and their descendants. The root cgroup is > + always a scheduling domain root. > + > + There are constraints on where this flag can be set. It can > + only be set in a cgroup if all the following conditions are true. > + > + 1) The "cpuset.cpus" is not empty and the list of CPUs are > + exclusive, i.e. they are not shared by any of its siblings. > + 2) The "cpuset.cpus" is also a proper subset of the parent's > + "cpuset.cpus.effective". > + 3) The parent cgroup is a scheduling domain root. > + 4) There is no child cgroups with cpuset enabled. This is > + for eliminating corner cases that have to be handled if such > + a condition is allowed. > + > + 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. > + > + A parent scheduling domain root cgroup cannot distribute > + all its CPUs to its child scheduling domain root cgroups. > + There must be at least one cpu left in the parent scheduling > + domain root cgroup.