Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752942AbbBXLdf (ORCPT ); Tue, 24 Feb 2015 06:33:35 -0500 Received: from service87.mimecast.com ([91.220.42.44]:47232 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752732AbbBXLdd convert rfc822-to-8bit (ORCPT ); Tue, 24 Feb 2015 06:33:33 -0500 Message-ID: <54EC61A2.5010702@arm.com> Date: Tue, 24 Feb 2015 11:33:54 +0000 From: Dietmar Eggemann User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Vincent Guittot , Morten Rasmussen 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" , "linaro-kernel@lists.linaro.org" Subject: Re: [PATCH RESEND v9 05/10] sched: make scale_rt invariant with frequency References: <1421316570-23097-1-git-send-email-vincent.guittot@linaro.org> <1421316570-23097-6-git-send-email-vincent.guittot@linaro.org> <20150219165241.GL5029@twins.programming.kicks-ass.net> <20150219171824.GC22059@e105550-lin.cambridge.arm.com> In-Reply-To: X-OriginalArrivalTime: 24 Feb 2015 11:33:28.0183 (UTC) FILETIME=[B570E070:01D05025] X-MC-Unique: 115022411333101301 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1979 Lines: 47 On 24/02/15 10:21, Vincent Guittot wrote: > On 19 February 2015 at 18:18, Morten Rasmussen wrote: >> On Thu, Feb 19, 2015 at 04:52:41PM +0000, Peter Zijlstra wrote: >>> On Thu, Jan 15, 2015 at 11:09:25AM +0100, Vincent Guittot wrote: [...] >> Agreed. I think it is reasonable to assume that the arch code >> implementing arch_scale_freq_capacity() does it's best to make it fast >> for the particular architecture. Since the scaling factor to be returned >> by the function may be obtained in different ways for different >> architectures the caching should be done on the arch side. >> >>> But lets see, I've yet to see an actual implementation of it; and its >>> got that sd argument, curious what you're going to do with that. >> >> So we do have an RFC implementation for ARM already which I posted in >> December and is also included in the rather large RFC posting I did some >> weeks ago. That one basically reads two atomic variables and returns the >> ratio between the two. I have yet to benchmark how horribly expensive it >> is though. The sd argument is ignored. We might actually not need it at >> all? > > For consistency across all arch_scale_xx_capacity, i would prefer to > keep the same prototype interface (struct sched_domain *sd, int cpu) > even if it's not used ofr now Agreed. Once we call arch_scale_xx_capacity [xx = freq, cpu] in the PELT code (i.e. w/ sd = NULL) we have to make sure that default_scale_cpu_capacity() can be called w/ sd = NULL too for platforms which are not providing their own arch_scale_cpu_capacity() function. It's already part of '[RFCv3 PATCH 00/48] sched: Energy cost model for energy-aware scheduling' https://lkml.org/lkml/2015/2/4/573 [...] -- 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/