From owner-freebsd-questions Wed Feb 4 20:31:18 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id UAA23877 for questions-outgoing; Wed, 4 Feb 1998 20:31:18 -0800 (PST) (envelope-from owner-freebsd-questions@FreeBSD.ORG) Received: from adam.adonai.net (adam.adonai.net [207.8.83.2]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id UAA23862 for ; Wed, 4 Feb 1998 20:31:11 -0800 (PST) (envelope-from leec@adam.adonai.net) Received: from localhost (leec@localhost) by adam.adonai.net (8.8.7/8.7.3) with SMTP id WAA09741; Wed, 4 Feb 1998 22:31:05 -0600 (CST) Date: Wed, 4 Feb 1998 22:31:04 -0600 (CST) From: "Lee Crites (AEI)" To: Jean-Marc Henriette cc: freebsd-questions@FreeBSD.ORG Subject: Re: Real time capability and FreeBSD In-Reply-To: <9802041315.ZM1492@starfleet.umd.edu> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG X-To-Unsubscribe: mail to majordomo@FreeBSD.org "unsubscribe questions" On Wed, 4 Feb 1998, Jean-Marc Henriette wrote: => I am a very happy home user of FreeBSD. Now, I'm trying to get my =>work place to accept it a bit more. Is there any plans to include some =>Real Time capability to FreeBSD, or should I not even bother? I know that =>Linux has a RT version of their stuff, but I don't want to have to learn =>how to manage a linux box when FreeBSD makes it so much easier.. My first question is what do you mean by "real time" capability? Here are some possible options: 1) you want data which is manipulated by one user to be seen right away by another user; 2) you want things happening now, as opposed to at some time in the future; 3) your processes depend upon data arriving in a deterministic way every time. The first two options are what some people call "soft" real-time. I've been able to manipulate/contort many versions of un*x, including FreeBSD into handling soft-real-time quite easily. Number three is where some of the purists will probably part ways with me. I can accept a hard-real-time definition which takes time constraints into consideration. The pure definition has nothing to do with time, only the arrival of data happening in a deterministic fashion -- and, of course, on time. I focus more on the "on-time" aspect. I figure if there is a, say, +/- 30% variance from the average, and I can handle the data arriving at 130% of the average, then I'm a happy guy. The fact that the system isn't exactly deterministic in nature, coupled with what many of the purists would call a totally unacceptable variance, don't cause me any grief. So (and this is why I have gone to the trouble of explaining the above), *I* find FreeBSD capable of handling my hard-real-time application as well. FreeBSD has the capability of manipulating the priority of a process so it can hog as much of the system as it needs, which is what I exploit. Your mileage will vary. This brings me to the second question: what is it you want to do? Or, put another way, what are your real needs? Armed with that tidbit of data, I might be able to help more. Lee