Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754377AbbBTOe2 (ORCPT ); Fri, 20 Feb 2015 09:34:28 -0500 Received: from foss-mx-na.foss.arm.com ([217.140.108.86]:44265 "EHLO foss-mx-na.foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753936AbbBTOe1 (ORCPT ); Fri, 20 Feb 2015 09:34:27 -0500 Date: Fri, 20 Feb 2015 14:35:31 +0000 From: Morten Rasmussen To: Vincent Guittot Cc: Peter Zijlstra , "mingo@kernel.org" , "linux-kernel@vger.kernel.org" , "preeti@linux.vnet.ibm.com" , "kamalesh@linux.vnet.ibm.com" , "riel@redhat.com" , "efault@gmx.de" , "nicolas.pitre@linaro.org" , Dietmar Eggemann , "linaro-kernel@lists.linaro.org" Subject: Re: [PATCH RESEND v9 00/10] sched: consolidation of CPU capacity and usage Message-ID: <20150220143531.GF22059@e105550-lin.cambridge.arm.com> References: <1421316570-23097-1-git-send-email-vincent.guittot@linaro.org> <20150219124940.GA22059@e105550-lin.cambridge.arm.com> <20150220113447.GO5029@twins.programming.kicks-ass.net> <20150220115241.GE22059@e105550-lin.cambridge.arm.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 Content-Length: 1822 Lines: 35 On Fri, Feb 20, 2015 at 02:13:21PM +0000, Vincent Guittot wrote: > On 20 February 2015 at 12:52, Morten Rasmussen wrote: > > On Fri, Feb 20, 2015 at 11:34:47AM +0000, Peter Zijlstra wrote: > >> On Thu, Feb 19, 2015 at 12:49:40PM +0000, Morten Rasmussen wrote: > >> > >> > Also, it still not clear why patch 10 uses relative capacity reduction > >> > instead of absolute capacity available to CFS tasks. > >> > >> As present in your asymmetric big and small systems? Yes it would be > >> unfortunate to migrate a task to an idle small core when the big core is > >> still faster, even if reduced by rt/irq work. > > > > Yes, exactly. I don't think it would cause any harm for symmetric cases > > to use absolute capacity instead. Am I missing something? > > If absolute capacity is used, we will trig an active load balance from > little to big core each time a little has got 1 task and a big core is > idle whereas we only want to trig an active migration is the src_cpu's > capacity that is available for the cfs task is significantly reduced > by rt tasks. > > I can mix absolute and relative tests by 1st testing that the capacity > of the src is reduced and then ensure that the dst_cpu has more > absolute capacity than src_cpu If we use absolute capacity and check if the source cpu is fully utilized, wouldn't that work? We want to migrate the task if it is currently being restricted by the available capacity (due to rt/irq work, being a little cpu, or both) and if there is a destination cpu with more absolute capacity available. No? -- 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/