From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262569AbVFVWwi (ORCPT ); Wed, 22 Jun 2005 18:52:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262560AbVFVWwi (ORCPT ); Wed, 22 Jun 2005 18:52:38 -0400 Received: from mx1.elte.hu ([157.181.1.137]:49363 "EHLO mx1.elte.hu") by vger.kernel.org with ESMTP id S262578AbVFVWlw (ORCPT ); Wed, 22 Jun 2005 18:41:52 -0400 Date: Thu, 23 Jun 2005 00:41:23 +0200 From: Ingo Molnar To: Karim Yaghmour Cc: "Paul E. McKenney" , Kristian Benoit , linux-kernel@vger.kernel.org, bhuey@lnxw.com, andrea@suse.de, tglx@linutronix.de, pmarques@grupopie.com, bruce@andrew.cmu.edu, nickpiggin@yahoo.com.au, ak@muc.de, sdietrich@mvista.com, dwalker@mvista.com, hch@infradead.org, akpm@osdl.org, Philippe Gerum Subject: Re: PREEMPT_RT vs I-PIPE: the numbers, part 2 Message-ID: <20050622224123.GA7658@elte.hu> References: <42B77B8C.6050109@opersys.com> <20050622011931.GF1324@us.ibm.com> <42B9845B.8030404@opersys.com> <20050622162718.GD1296@us.ibm.com> <1119460803.5825.13.camel@localhost> <20050622185019.GG1296@us.ibm.com> <20050622190422.GA6572@elte.hu> <42B9C777.8040202@opersys.com> <20050622202242.GA17301@elte.hu> <42B9D208.4080305@opersys.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <42B9D208.4080305@opersys.com> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Karim Yaghmour wrote: > > so ... give the -50-12 -RT tree a try and report back the lpptest > > results you are getting. > > First things first, we want to report back that our setup is validated > before we go onto this one. So we've modified LRTBF to do the > busy-wait thing. here's another bug in the way you are testing PREEMPT_RT irq latencies. Right now you are doing this in lrtbf-0.1a/drivers/par-test.c: if (request_irq ( PAR_TEST_IRQ, &par_test_irq_handler, #if CONFIG_PREEMPT_RT SA_NODELAY, #else //!CONFIG_PREEMPT_RT SA_INTERRUPT, #endif //PREEMPT_RT you should set the SA_INTERRUPT flag in the PREEMPT_RT case too! I.e. the relevant line above should be: SA_NODELAY | SA_INTERRUPT, otherwise par_test_irq_handler will run with interrupts enabled, opening the window for other interrupts to be injected and increasing the worst-case latency! Take a look at drivers/char/lpptest.c how to do this properly. Also, double-check that there is no IRQ 7 thread running on the PREEMPT_RT kernel, to make sure you are measuring irq latencies. Ingo