Date: Mon, 24 Dec 2001 11:13:46 +0200 (SAT) From: John Hay <jhay@icomtek.csir.co.za> To: phk@critter.freebsd.dk (Poul-Henning Kamp) Cc: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/dev/sio sio.c Message-ID: <200112240913.fBO9DlH39063@zibbi.icomtek.csir.co.za> In-Reply-To: <83382.1009180276@critter.freebsd.dk> from Poul-Henning Kamp at "Dec 24, 2001 08:51:16 am"
next in thread | previous in thread | raw e-mail | index | archive | help
> 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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200112240913.fBO9DlH39063>