From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Lezcano Subject: Re: [RFC PATCH 3/3] idle: store the idle state index in the struct rq Date: Fri, 31 Jan 2014 16:37:30 +0100 Message-ID: <52EBC33A.6080101@linaro.org> References: <1391090962-15032-1-git-send-email-daniel.lezcano@linaro.org> <1391090962-15032-4-git-send-email-daniel.lezcano@linaro.org> <20140130153150.GD5002@laptop.programming.kicks-ass.net> <52EA7D8A.6080604@linaro.org> <20140130163501.GG5002@laptop.programming.kicks-ass.net> <52EA8B07.6020206@linaro.org> <20140131090230.GM5002@laptop.programming.kicks-ass.net> <52EB6F65.8050008@linux.vnet.ibm.com> <52EBBC23.8020603@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-wg0-f48.google.com ([74.125.82.48]:39236 "EHLO mail-wg0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932082AbaAaPhd (ORCPT ); Fri, 31 Jan 2014 10:37:33 -0500 Received: by mail-wg0-f48.google.com with SMTP id x13so9201509wgg.27 for ; Fri, 31 Jan 2014 07:37:32 -0800 (PST) In-Reply-To: <52EBBC23.8020603@linux.intel.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Arjan van de Ven , Preeti U Murthy , Peter Zijlstra , Len Brown Cc: Preeti Murthy , nicolas.pitre@linaro.org, mingo@redhat.com, Thomas Gleixner , "Rafael J. Wysocki" , LKML , "linux-pm@vger.kernel.org" , Lists linaro-kernel On 01/31/2014 04:07 PM, Arjan van de Ven wrote: >>>> >>>> Hence I think this patch would make sense only with additional >>>> information >>>> like exit_latency or target_residency is present for the scheduler= =2E >>>> The idle >>>> state index alone will not be sufficient. >>> >>> Alternatively, can we enforce sanity on the cpuidle infrastructure = to >>> make the index naturally ordered? If not, please explain why :-) >> >> The commit id 71abbbf856a0e70 says that there are SOCs which could h= ave >> their target_residency and exit_latency values change at runtime. Th= is >> commit thus removed the ordering of the idle states according to the= ir >> target_residency/exit_latency. Adding Len and Arjan to the CC. > > the ARM folks wanted a dynamic exit latency, so.... it makes much mor= e > sense > to me to store the thing you want to use (exit latency) than the numb= er > of the state. > > more than that, you can order either by target residency OR by exit > latency, > if you sort by one, there is no guarantee that you're also sorted by = the > other IMO, it would be preferable to store the index for the moment as we are= =20 integrating cpuidle with the scheduler. The index allows to access more= =20 informations. Then when everything is fully integrated we can improve=20 the result, no ? > (for example, you can on a hardware level make a "fast exit" state, a= nd > burn power for this faster exit, > which means your break even gets longer to recoup this extra power > compared to the same state without > the fast exit) > --=20 Linaro.org =E2=94=82 Open source software fo= r ARM SoCs =46ollow Linaro: Facebook | Twitter | Blog