From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthias Meier Subject: Re: Long max latencies on Wandbaord / Freescale i.MX6 Date: Thu, 1 Oct 2015 10:08:18 +0200 Message-ID: <560CE9F2.4010401@gmx.net> References: <5606677A.1020705@gmx.net> <560A3020.5090909@gmx.net> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit To: "linux-rt-users@vger.kernel.org" Return-path: Received: from mout.gmx.net ([212.227.15.15]:65146 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755246AbbJAIIV (ORCPT ); Thu, 1 Oct 2015 04:08:21 -0400 Received: from localhost.localdomain ([213.188.224.136]) by mail.gmx.com (mrgmx003) with ESMTPSA (Nemesis) id 0M9JYE-1ZnZiX1eIw-00ChJ4 for ; Thu, 01 Oct 2015 10:08:19 +0200 In-Reply-To: Sender: linux-rt-users-owner@vger.kernel.org List-ID: PROVE_LOCKING is not so bad I thought finally I guess my latency problem is caused by a spurious interrupt on a unused mmc slot causing heavy load when using PROVE_LOCKING ... Here a little more in detail what I did: Disabling CONFIG_PROVE_LOCKING together with a lot other debug options as Thomas proposed indeed gave max latencies in the range of 100us - at least most of the time... After adding besides 'hackbench' additional heavy network load via the on-board WiFi interface, the max latency raised further and finally I the kernel fired a backtrace which ended in a "Disabling IRQ #284" /proc/interrupts indeed shows a hugh amout of interrupts on mmc1 although I don't use mmc1 at all (the Wandboard boots via mmc0) (possible a pullup config is missing at the mmc interfaces?) After reboot I tried to stop the spurious interrupts by inserting a sd-card on mmc1 but this does not work - still high interrupts. Now I'm trying to disable mmc1 and mmc2 completely which is not as easy as I thought: via sysfs it seems not to be possible and via DT I think I would have to modify all imx6* DTS files of all imx6 boards - otherwise the dtbs does not compile... Is there a simple solution to disable either a single interrupt or a individual mmc interface from userspace? Thanks, Matthias