From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: Re: Strange spikes using linux-rt kernel Date: Mon, 6 Jul 2009 17:30:38 +0200 (CEST) Message-ID: References: <190013.60215.qm@web112503.mail.gq1.yahoo.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Nicholas Mc Guire , linux-rt-users@vger.kernel.org To: Pedro R Return-path: Received: from www.tglx.de ([62.245.132.106]:41177 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750874AbZGFPar (ORCPT ); Mon, 6 Jul 2009 11:30:47 -0400 In-Reply-To: <190013.60215.qm@web112503.mail.gq1.yahoo.com> Sender: linux-rt-users-owner@vger.kernel.org List-ID: Pedro, please do not top post and please fix your mailer to do proper linewraps at around 78 chars. On Fri, 3 Jul 2009, Pedro R wrote: > The posixcputmr/0 and watchdog/0 seem to be running at a higher > priority! Is this normal? Yes, but they do not interfere and are not the cause of your latency problems. > I looked at the distribution of the jitter and these are very rare > spikes. I ran cyclictest with 5 threads for 30000 cycles and the > delay is always around 10-35 us except when there is a spike, which > goes from 1000 to 7000us. These spikes are one-time ocurrences - > they only last for one sample and sometimes only one of the threads > is delayed, on other occasions 2 or 3 threads are delayed... Can you please add "nohz=off" to the kernel command line and check whether the problem persists ? Thanks, tglx