Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 28 Aug 2002 12:45:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 28 Aug 2002 12:45:29 -0400 Received: from [195.185.133.146] ([195.185.133.146]:61451 "HELO gateway.hottinger.de") by vger.kernel.org with SMTP id ; Wed, 28 Aug 2002 12:45:28 -0400 Message-ID: From: "Wessler, Siegfried" To: "'linux-kernel@vger.kernel.org'" Subject: AW: interrupt latency Date: Wed, 28 Aug 2002 18:49:41 +0200 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2653.19) Content-Type: text/plain; charset="iso-8859-1" Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1694 Lines: 44 Hello again, > Alan Cox [mailto:alan@lxorguk.ukuu.org.uk] wrote: > > I would expect port 0x378 on any modern PC to be on the X-bus > not on ISA Right, so it is fast enough for a quick test. Actually I don't know where this thread has lead us. Was it really me who typed the reference line? Anyhow. :-> When I was talking about interrupt latency, I ment this: I do a hardware interrupt, use it as trigger on an oscilloscope, then measure how long it takes until the printer port showbit shows up. (Ha! An oscilloscope is fine for timing measurements!) The printer port is handled first in the irq_function of my driver. That kind of "latency" I was talking about. The jitter I get (because of NMI functions and more) I can guess by changing the persistance of the oscilloscope. And to those who think that the printer port might be to slow for that kind of measurement, I did the same with a showbit I set on a PCI device (a PLD I know the inside). That one is nanoseconds fast, so no relevant delay. Okay, the kernel takes at least 8 microseconds time to "tell" the kernel driver function that an interrupt is there. So my question still is: How should I trace thru the kernel source after a hardware interrupt is there? (I am running a Pentium-like ETX with 266 MHz CPU clock. Single CPU.) But thanks for all helps, hints and interesting discusses! Siegfried Wessler. BTW: You can get down to 1ms jiffies without RT Linux easily ;-) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/