From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755470AbaAFRPf (ORCPT ); Mon, 6 Jan 2014 12:15:35 -0500 Received: from fw-tnat.austin.arm.com ([217.140.110.23]:59942 "EHLO collaborate-mta1.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751115AbaAFRPe (ORCPT ); Mon, 6 Jan 2014 12:15:34 -0500 Date: Mon, 6 Jan 2014 17:15:30 +0000 From: Morten Rasmussen To: Peter Zijlstra Cc: Dietmar Eggemann , Vincent Guittot , "linux-kernel@vger.kernel.org" , "mingo@kernel.org" , "pjt@google.com" , "cmetcalf@tilera.com" , "tony.luck@intel.com" , "alex.shi@linaro.org" , "preeti@linux.vnet.ibm.com" , "linaro-kernel@lists.linaro.org" , "rjw@sisk.pl" , "paulmck@linux.vnet.ibm.com" , "corbet@lwn.net" , "tglx@linutronix.de" , "len.brown@intel.com" , "arjan@linux.intel.com" , "amit.kucheria@linaro.org" , "james.hogan@imgtec.com" , "schwidefsky@de.ibm.com" , "heiko.carstens@de.ibm.com" Subject: Re: [RFC] sched: CPU topology try Message-ID: <20140106171530.GC2936@e103034-lin> References: <20131105222752.GD16117@laptop.programming.kicks-ass.net> <1387372431-2644-1-git-send-email-vincent.guittot@linaro.org> <52B87149.4010801@arm.com> <20140106162813.GM31570@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140106162813.GM31570@twins.programming.kicks-ass.net> 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 On Mon, Jan 06, 2014 at 04:28:13PM +0000, Peter Zijlstra wrote: > On Mon, Dec 23, 2013 at 06:22:17PM +0100, Dietmar Eggemann wrote: > > I'm not sure if the idea to create a dedicated sched_domain level for every > > topology flag representing a specific functionality will scale. From the > > perspective of energy-aware scheduling we need e.g. energy costs (P and C > > state) which can only be populated towards the scheduler via an additional > > sub-struct and additional function arch_sd_energy() like depicted in > > Morten's email: > > > > [2] lkml.org/lkml/2013/11/14/102 > > That lkml.org link is actually not working for me (blank page -- maybe > lkml.org is on the blink again). > > That said, I yet have to sit down and think about the P state stuff, but > I was thinking we need some rudimentary domain support for that. > > For instance, the big-little thingies seem share their P state per > cluster, so we need a domain at that level to hang some state off of -- > which we actually have in this case. But we need to ensure we do have > it -- somehow. Is there any examples of frequency domains not matching the span of a sched_domain? I would have thought that we would have a matching sched_domain to hang the P and C state information from for most systems. If not, we could just add it. I don't think it is safe to assume that big-little always has cluster P-states. It is implementation dependent. But the most obvious alternative would be to have per-cpu P-states in which case we would also have a matching sched_domain.