From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Angielski Subject: Re: preempt rt in commercial use Date: Tue, 14 Sep 2010 10:21:52 -0400 Message-ID: <4C8F8500.5070002@theptrgroup.com> References: <201009141317.13439@zigzag.lvk.cs.msu.su> <20100914094411.GB10841@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Cc: Raz , "Nikita V. Youshchenko" , linux-rt-users To: Robert Schwebel Return-path: Received: from mail.theptrgroup.com ([71.178.251.9]:60395 "EHLO mail.theptrgroup.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752391Ab0INOcw (ORCPT ); Tue, 14 Sep 2010 10:32:52 -0400 In-Reply-To: <20100914094411.GB10841@pengutronix.de> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On 09/14/2010 05:44 AM, Robert Schwebel wrote: > On Tue, Sep 14, 2010 at 11:24:21AM +0200, Raz wrote: >> anyone can say preempt rt is hard real time? > > Hard realtime has something to do with how you define "missing the > deadline". If somebody cuts the cable of your roboter controller in the > factory hall, the system misses the deadline. So it is all about > probabilities: hard realtime systems have a very, very low probability > of missing the deadline. However, in real life systems, it is> 0%. > > So yes, if you talk about real world, it is hard realtime. No. Preempt rt it's not hard realtime. But most people/companies who think they need hard realtime really don't. They can live with soft realtime and have a really low probability of missing deadlines and having long latencies. For these people, the preempt rt is adequate. -- Jeff Angielski The PTR Group www.theptrgroup.com