From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Hounschell Subject: Re: Latency Problems with 2.6.31/PREEMPT_RT on a 1.2GHz Celeron Date: Sat, 19 Dec 2009 06:34:00 -0500 Message-ID: <4B2CBA28.1030405@cfl.rr.com> References: <4B2BB45A.9040909@mantatest.com> Reply-To: dmarkh@cfl.rr.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: linux-rt-users@vger.kernel.org, Scott Gilbertson To: Vladimir Cotfas Return-path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.123]:39864 "EHLO cdptpa-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750958AbZLSLeE (ORCPT ); Sat, 19 Dec 2009 06:34:04 -0500 In-Reply-To: <4B2BB45A.9040909@mantatest.com> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On 12/18/2009 11:56 AM, Vladimir Cotfas wrote: > All, > > I have a a driver that must process an interrupt every 100 uS without > missing any. I am having latency issues and I am looking for some help > debugging my problem. > You'll probably never get this working reliably with the RT kernel. Latencies are more deterministic with the RT kernel but slightly higher. You'll have better luck with a vanilla kernel running your app in run level 4. And then even better luck running on an SMP machine isolating your process and IRQ to a single processor. And stay away from the VGA console. You have better luck with faster hardware too. Mark