From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756221AbeDKUfz (ORCPT ); Wed, 11 Apr 2018 16:35:55 -0400 Received: from mail-wm0-f44.google.com ([74.125.82.44]:53523 "EHLO mail-wm0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754135AbeDKUft (ORCPT ); Wed, 11 Apr 2018 16:35:49 -0400 X-Google-Smtp-Source: AIpwx48UOFngjr84VfkKt1XO153CyDbmnpgv6lcdgAQwuqQyW3+PuwazcNNehGLg5gHIPoMIWmFXTQ== Subject: Re: Problem with commit 31e77c93e432 "sched/fair: Update blocked load when newly idle" To: Vincent Guittot Cc: Dietmar Eggemann , "Peter Zijlstra (Intel)" , Ingo Molnar , Linux Kernel Mailing List , "Rafael J. Wysocki" References: <20180324064627.GA10884@linaro.org> <6b151c56-9ead-7bbe-d1b7-b0e6d69c0d7f@arm.com> <796bbd7b-8512-7370-28c9-0f082dc3f287@gmail.com> <95fe50be-cc8b-4345-7333-cdf656fad2a7@gmail.com> From: Heiner Kallweit Message-ID: Date: Wed, 11 Apr 2018 22:35:42 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 11.04.2018 um 19:00 schrieb Vincent Guittot: > Hi Heiner, > > On 9 April 2018 at 19:33, Heiner Kallweit wrote: >> Am 06.04.2018 um 18:03 schrieb Vincent Guittot: >>> Hi Heiner, >>> >>> On 30 March 2018 at 10:37, Heiner Kallweit wrote: >>>> Am 30.03.2018 um 08:50 schrieb Vincent Guittot: >>>>> On 29 March 2018 at 19:40, Heiner Kallweit wrote: >>>>>> Am 29.03.2018 um 09:41 schrieb Vincent Guittot: >>>>> >>>>>>> >>>>>>> I'm finally not so sure that i have the right set up to reproduce the >>>>>>> problem as I haven't been able to reproduce it since. >>>>>>> >>>>>>> Heiner, >>>>>>> >>>>>>> How fast the problem happens on your board ? >>>>>>> Are you doing anything specific on the console that trigger the problem ? >>>>>>> >>>>>> Hi Vincent, >>>>>> >>>>>> the lag when working on the console is constantly there, the "rcu_preempt >>>>>> detected stalls" happens after several hours (so far always within 24h) >>>>>> w/o any triggering event I would be aware of. It occured also when the >>>>>> system was idle at that point in time. >>>>> >>>>> Ok, so I don't have the problem on my hikey as the console never lag >>>>> on my setup. >>>>> >>>>> Can you send me the config of your kernel ? I'd like to check if you >>>>> have enable something that could trigger such problem >>>>> >>>> Sure, he we go. I also add a system log. >>> >>> Thanks for the config. I have used it for my setup but I can't >>> reproduce your regression. My platforms stay stable so I probably >>> missing something. Are you facing similar problem with other platforms >>> or only this celeron based platform ? >>> >>> I have reviewed the code but don't see any obvious place in the patch >>> that can generate the problem. Nevertheless, would you mind to try the >>> patch below ? It's a blind test to try to narrow the problem. >>> >>> Thanks >>> >> Hi Vincent, >> >> I tried again with today's linux-next and it's much better. The lag isn't >> completely gone but it's much less annoying. Every ~30 secs the console >> hangs for about half a second, that's much less frequent than before. > > That's interesting because nothing related to commit > 31e77c93e432dec79c7d90b888bbfc3652592741 has been merged recently > AFAICT > >> >> I saw some patches from Rafael have been merged in the last days. >> Maybe they improved the situation. > > Yes, Peter mentions in another thread that lastest Rafael's patches > avoid stopping tick when entering short idle thus reducing the time to > enter idle. commit 31e77 is adding some background activity when > entering idle so it can be that we take too much time > > You also mentioned that the CPU was relatively slow on the platform. > Can you try to use cpufreq performance governor instead of ondemand ? > The system uses intel_pstate scaling driver, so only powersave and performance are available. Min/max frequency are 600MHz / 1100 MHz. I didn't really notice a difference when switching between both modes. Regards, Heiner > I'm also going to prepare a patch for adding some trace in the code to > highlight the problem > > Thanks, > Vincent > >> >> Regards, Heiner >> > > [snip] > >> >