From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: Re: 2.6.33.7-rt29 PREEMPT_RT worse latency than PREEMPT_DESKTOP on AT91? Date: Wed, 15 Sep 2010 18:08:27 +0200 (CEST) Message-ID: References: <4C72A438.2080301@cgglobal.com> <4C90E959.80306@cgglobal.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: "linux-rt-users@vger.kernel.org" To: Agustin Ferrin Pozuelo Return-path: Received: from www.tglx.de ([62.245.132.106]:40802 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752701Ab0IOQIf (ORCPT ); Wed, 15 Sep 2010 12:08:35 -0400 In-Reply-To: <4C90E959.80306@cgglobal.com> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Wed, 15 Sep 2010, Agustin Ferrin Pozuelo wrote: > On 27/08/10 11:35, Thomas Gleixner wrote: > > On Mon, 23 Aug 2010, Agustin Ferrin Pozuelo wrote: > Sorry, my test setup is not very comprehensive at the moment. I have some > overnight/overweekend results at hand with millions of loops: > > PREEMPT-DESKTOP: > root@at91sam9263cpc:~# time cyclictest -i 70000 -p 80 -h 700 -r Oh, you are running cyclictest with a signal based timer and relative time. Any reason for this ? What happens if you change the command line to cyclictest -i 70000 -p 80 -n > I am assuming context switching is more expensive on PREEMPT-RT under ARM9, > where it seems already a bit expensive. No, the context switch is equally expensive, but signal delivery might be a bit more overhead on -RT Thanks, tglx