Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756638AbaAHNEp (ORCPT ); Wed, 8 Jan 2014 08:04:45 -0500 Received: from merlin.infradead.org ([205.233.59.134]:57387 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755890AbaAHNEn (ORCPT ); Wed, 8 Jan 2014 08:04:43 -0500 Date: Wed, 8 Jan 2014 14:04:07 +0100 From: Peter Zijlstra To: Morten Rasmussen Cc: Alex Shi , Vincent Guittot , Dietmar Eggemann , "linux-kernel@vger.kernel.org" , "mingo@kernel.org" , "pjt@google.com" , "cmetcalf@tilera.com" , "tony.luck@intel.com" , "preeti@linux.vnet.ibm.com" , "linaro-kernel@lists.linaro.org" , "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: <20140108130407.GE31570@twins.programming.kicks-ass.net> References: <20140106163123.GN31570@twins.programming.kicks-ass.net> <20140107132220.GZ31570@twins.programming.kicks-ass.net> <20140107141059.GY3694@twins.programming.kicks-ass.net> <20140107154154.GH2936@e103034-lin> <20140107204951.GD2480@laptop.programming.kicks-ass.net> <52CD0D12.6020108@linaro.org> <20140108083716.GA7572@laptop.programming.kicks-ass.net> <20140108125228.GJ2936@e103034-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140108125228.GJ2936@e103034-lin> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 08, 2014 at 12:52:28PM +0000, Morten Rasmussen wrote: > If I remember correctly, Alex used the rq runnable_avg_sum (in rq->avg) > for this. It is the most obvious choice, but it takes ages to reach > 100%. > > #define LOAD_AVG_MAX_N 345 > > Worst case it takes 345 ms from the system is becomes fully utilized > after a long period of idle until the rq runnable_avg_sum reaches 100%. > > An unweigthed version of cfs_rq->runnable_load_avg and blocked_load_avg > wouldn't have that delay. Right.. not sure we want to involve blocked load on the utilization metric, but who knows maybe that does make sense. But yes, we need unweighted runnable_avg. > Also, if we are changing the load balance behavior when all cpus are > fully utilized We already have this tipping point. See all the has_capacity bits. But yes, it'd get more involved I suppose. > we may need to think about cases where the load is > hovering around the saturation threshold. But I don't think that is > important yet. Yah.. I'm going to wait until we have a fail case that can give us some guidance before really pondering this though :-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/