Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755077Ab3EBJMg (ORCPT ); Thu, 2 May 2013 05:12:36 -0400 Received: from mail-bk0-f46.google.com ([209.85.214.46]:58212 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751986Ab3EBJMe (ORCPT ); Thu, 2 May 2013 05:12:34 -0400 MIME-Version: 1.0 In-Reply-To: <517AA14D.7060202@linux.intel.com> References: <1366910611-20048-1-git-send-email-vincent.guittot@linaro.org> <517A969B.5040606@linux.intel.com> <517AA14D.7060202@linux.intel.com> Date: Thu, 2 May 2013 11:12:32 +0200 Message-ID: Subject: Re: [RFC PATCH v4 00/14] sched: packing small tasks From: Vincent Guittot To: Arjan van de Ven Cc: linux-kernel , LAK , "linaro-kernel@lists.linaro.org" , Peter Zijlstra , Ingo Molnar , Russell King - ARM Linux , Paul Turner , Santosh , Morten Rasmussen , Chander Kashyap , "cmetcalf@tilera.com" , "tony.luck@intel.com" , Alex Shi , Preeti U Murthy , Paul McKenney , Thomas Gleixner , Len Brown , Amit Kucheria , Jonathan Corbet , Lukasz Majewski Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3085 Lines: 78 On 26 April 2013 17:46, Arjan van de Ven wrote: >>> >>> >>> so I got to ask the hard question; what percentage of system level (not >>> just >>> cpu level) >>> power consumption gain can you measure (pick your favorite workload)... >>> >> >> I haven't system level figures for my patches but only for the cpu >> subsystem. If we use the MP3 results in the back of my mail, they show >> an improvement of 37 % (113/178) for the CPU subsystem of the >> platform. If we assume that the CPU subsystem contributes 25% of an >> embedded system power consumption (this can vary across platform >> depending of the use of HW accelerator but it should be a almost fair >> percentage), the patch can impact the power consumption on up to 9%. >> > > sadly the math tends to not work quite that easy; > memory takes significantly more power when the system is not idle than when > it is idle for example. [*] > so while reducing cpu power by making it run a bit longer (at lower > frequency or > slower core or whatever) is a pure win if you only look at the cpu, but it > may > (or may not) be a loss when looking at a whole system level. > > I've learned the hard way that you cannot just look at the cpu numbers; you > must look > at the whole-system power when playing with such tradeoffs. > > That does not mean that your patch is not useful; it very well can be, but > without having looked at whole-system power that's a very dangerous > conclusion to make. > So.. if you get a chance, I'd love to see data on a whole-system level... > even for just one workload > and one system > (playing mp3 sounds like a quite reasonable workload for such things indeed) Hi Arjan, I don't have full system power consumption but i have gathered some additional figures for mp3 use case The power consumption percentage stay similar | CA15 | CA7 | total | ------------------------------------- default | 81% | 95% | 178% | pack | 10% | 100% | 110% | agressive | 3% | 100% | 103% | ------------------------------------- I have also gathered the time when all CPUs are in low power state so the entire system can be put in low power mode (DDR in self refresh) | Time | nb / sec | average | -------------------------------------------- default | 85.5% | 296 | 2.9ms | pack | 82.5% | 253 | 3.2ms | agressive | 81.8% | 236 | 3.4ms | -------------------------------------------- We can see a decrease of the time spent in low power mode but on the other side, the number of switch to low power mode also decreases which results in the increase the average duration of low power state. Regards, Vincent > > > [*] I assume that on your ARM systems, memory goes into self refresh during > system idle just as it does on x86 > -- 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/