From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261598AbVFMPBh (ORCPT ); Mon, 13 Jun 2005 11:01:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261593AbVFMPBh (ORCPT ); Mon, 13 Jun 2005 11:01:37 -0400 Received: from mx2.elte.hu ([157.181.151.9]:64914 "EHLO mx2.elte.hu") by vger.kernel.org with ESMTP id S261590AbVFMPBb (ORCPT ); Mon, 13 Jun 2005 11:01:31 -0400 Date: Mon, 13 Jun 2005 17:00:21 +0200 From: Ingo Molnar To: Karim Yaghmour Cc: Kristian Benoit , linux-kernel@vger.kernel.org, paulmck@us.ibm.com, 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, rpm@xenomai.org, Thomas Gleixner Subject: Re: PREEMPT_RT vs ADEOS: the numbers, part 1 Message-ID: <20050613150021.GA5891@elte.hu> References: <42AA6A6B.5040907@opersys.com> <20050611191448.GA24152@elte.hu> <42AB662B.4010104@opersys.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <42AB662B.4010104@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: > Ingo Molnar wrote: > > how were interrupt response times measured, precisely? What did the > > target (measured) system have to do to respond to an interrupt? Did you > > use the RTC to measure IRQ latencies? > > The logger used two TSC values. One prior to shooting the interrupt to > the target, and one when receiving the response. Responding to an > interrupt meant that a driver was hooked to the target's parallel port > interrupt and simply acted by toggling an output pin on the parallel > port, which in turn was hooked onto the logger's parallel port in a > similar fashion. [...] FYI, there's a new feature in the -V0.7.48-25 (and later) -RT patches that implements this: CONFIG_LPPTEST. It is a simple standalone driver and userspace utility from Thomas Gleixner that can be used to measure the IRQ-latency of the system over a null-modem-parallel-cable. to use it, enable CONFIG_LPPEST in the .config [disable CONFIG_PARPORT first], boot the kernel on both the target and the host systems, and then run the scripts/testlpp utility on the host system which will measure latencies and will do a maximum-search. (the driver assumes normal LPT1 PC layout - 0x378/IRQ7) Ingo