From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 29505 invoked by alias); 30 May 2006 14:44:04 -0000 Received: (qmail 29465 invoked from network); 30 May 2006 14:43:56 -0000 Received: from unknown (131.234.200.2) by sourceware.org with QMTP; 30 May 2006 14:43:56 -0000 Received: (qmail 21898 invoked from network); 30 May 2006 14:43:56 -0000 Received: from unknown (HELO localhost) ([127.0.0.1]) (envelope-sender ) by localhost (qmail-ldap-1.03) with SMTP for ; 30 May 2006 14:43:56 -0000 Received: from zitmail.uni-paderborn.de ([127.0.0.1]) by localhost (zit-mailfront1 [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 21450-06 for ; Tue, 30 May 2006 16:43:55 +0200 (CEST) Received: from nb-techinf-4.cs.upb.de ([131.234.20.215]) by zitmail.uni-paderborn.de with asmtp (TLSv1:RC4-SHA:128) (Exim 4.41) id 1Fl5Rr-0005gq-WK for ecos-discuss@ecos.sourceware.org; Tue, 30 May 2006 16:43:55 +0200 Mime-Version: 1.0 (Apple Message framework v749.3) In-Reply-To: <20060530111436.GL2876@lunn.ch> References: <20060530075335.GG2876@lunn.ch> <69dd805e0605300109k5dcf7986of596c0b5f796c6b4@mail.gmail.com> <20060530081637.GH2876@lunn.ch> <20060530111436.GL2876@lunn.ch> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: Content-Transfer-Encoding: 7bit From: Enno Luebbers Date: Tue, 30 May 2006 14:44:00 -0000 To: ecos-discuss@ecos.sourceware.org X-Mailer: Apple Mail (2.749.3) Mailing-List: contact ecos-discuss-help@ecos.sourceware.org; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: ecos-discuss-owner@ecos.sourceware.org Subject: Re: [ECOS] Hard-Realtime behaviour X-SW-Source: 2006-05/txt/msg00257.txt.bz2 Hi, >> @Andrew : As we have seen most of what is necessary for hard realtime >> behaviour of eCos already is implemented. Can you help me in >> figuring out >> what is it that is missing that makes eCos soft real-time. > > What is missing? I would say the first step is to make a really good > definition of what hard realtime is. I think we can all agree that a real-time system is a deterministic system, i.e. it is _predictable_ in its timing behaviour. The distinction between hard and soft real-time, IMO, depends on the application. In a soft real-time system, some deadline misses can be tolerated - they only degrade the system's performance or service quality (think video streaming). On the other hand, a deadline miss in a hard real-time system causes a (catastrophic) system failure (think electronic brakes, engine control, etc). So, if the OS routines in eCos are sufficiently predictable (so you can for example get upper bounds on the execution time) it's actually the application (read: the way the application programmer uses eCos services) that defines whether the system is hard or soft real-time. Best, - Enno -- Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss