Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751522AbaKGJln (ORCPT ); Fri, 7 Nov 2014 04:41:43 -0500 Received: from mail-wi0-f173.google.com ([209.85.212.173]:44741 "EHLO mail-wi0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750993AbaKGJlk (ORCPT ); Fri, 7 Nov 2014 04:41:40 -0500 Message-ID: <545C9244.6040508@linaro.org> Date: Fri, 07 Nov 2014 10:35:00 +0100 From: Daniel Lezcano User-Agent: Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Preeti U Murthy CC: "Rafael J. Wysocki" , Nicolas Pitre , "linux-pm@vger.kernel.org" , LKML , Peter Zijlstra , Lists linaro-kernel , patches@linaro.org Subject: Re: [PATCH V2 1/5] sched: idle: cpuidle: Check the latency req before idle References: <1414054881-17713-1-git-send-email-daniel.lezcano@linaro.org> <544FE787.8090108@linaro.org> <54504A60.2090908@linux.vnet.ibm.com> <545A3414.7030500@linaro.org> <545AF424.2070302@linux.vnet.ibm.com> <545B7AAC.3020309@linaro.org> <545C4AA4.7010904@linux.vnet.ibm.com> In-Reply-To: <545C4AA4.7010904@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/07/2014 05:29 AM, Preeti U Murthy wrote: > On 11/06/2014 07:12 PM, Daniel Lezcano wrote: >> >> Preeti, >> >> I am wondering if we aren't going to a false debate. >> >> If the latency_req is 0, we should just poll and not enter in any idle >> state even if one has zero exit latency. With a zero latency req, we >> want full reactivity on the system, not enter an idle state with all the >> computation in the menu governor, no ? >> >> I agree this patch changes the behavior on PowerPC, but only if the >> latency_req is set to zero. I don't think we are worried about power >> saving when setting this value. >> >> Couldn't the patch accepted as it is for the sake of consistency on all >> the platform and then we optimize cleanly for the special latency zero >> case ? > > Alright Daniel, you can go ahead. I was thinking this patch through and > now realize that, like you point out the logic will only get complicated > with all the additional hack. > > But would it be possible to add the weak arch_cpu_idle_loop() call for > the cases where latency requirement is 0 like you had suggested earlier > ? This would ensure the polling logic does not break on PowerPC and we > don't bother the governor even. I will add the function in the core > PowerPC code. If arch does not define this function it will fall back to > cpu_idle_loop(). Fair enough? Yes, sounds good. I will add the weak function as the first patch in the series. Thanks for your reviews. -- Daniel -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- 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/