From owner-cvs-all Mon Dec 24 1:14:17 2001 Delivered-To: cvs-all@freebsd.org Received: from zibbi.icomtek.csir.co.za (zibbi.icomtek.csir.co.za [146.64.24.58]) by hub.freebsd.org (Postfix) with ESMTP id A8F0A37B405; Mon, 24 Dec 2001 01:14:07 -0800 (PST) Received: (from jhay@localhost) by zibbi.icomtek.csir.co.za (8.11.6/8.11.6) id fBO9DlH39063; Mon, 24 Dec 2001 11:13:47 +0200 (SAT) (envelope-from jhay) From: John Hay Message-Id: <200112240913.fBO9DlH39063@zibbi.icomtek.csir.co.za> Subject: Re: cvs commit: src/sys/dev/sio sio.c In-Reply-To: <83382.1009180276@critter.freebsd.dk> from Poul-Henning Kamp at "Dec 24, 2001 08:51:16 am" To: phk@critter.freebsd.dk (Poul-Henning Kamp) Date: Mon, 24 Dec 2001 11:13:46 +0200 (SAT) Cc: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org X-Mailer: ELM [version 2.4ME+ PL54 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-cvs-all@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG > In message <20011224162247.B85044@gsmx07.alcatel.com.au>, Peter Jeremy writes: > > >>My guess would be that only four people in the project who have > >>ever measured our interrupt latency: Bruce, Louie, Warner and me. > > > >That's definitely an under-estimate. Andrew Gallatin posted his > >latency measurements on a Alpha h/w. I think I've seen one or two > >other people indicate that they'd made measurements on -hackers. I've > >also done some limited latency testing on both i386 and Alpha's. > > Sorry, but I don't think so. The only measurements I have seen which > document the _actual_ interrupt latency are from the above people. > > I have seen people measuring the spread of interrupt latency, but > that is not the same as the interrupt latency. > > To explain the difference more graphically: Measuring the interrupt > latency means measuring the distance from bulls-eye to the hole in > a target, measuring the spread means looking at how close the holes > are on a blank sheet target. > > Very few people have hardware that allows them to see where the > bulls-eye actually is. (Cost ~= USD1000). Or a two channel oscilloscope, preferably a storage version. :-) Or a logic analyser. Both are maybe more expensive, but much more common. John -- John Hay -- John.Hay@icomtek.csir.co.za To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message