From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: preempt rt in commercial use Date: Wed, 15 Sep 2010 07:58:12 -0700 Message-ID: <20100915145812.GB2544@linux.vnet.ibm.com> References: <201009141317.13439@zigzag.lvk.cs.msu.su> <20100914094411.GB10841@pengutronix.de> <4C8F8500.5070002@theptrgroup.com> <4C90C093.4070607@disco.unimib.it> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Pradyumna Sampath , Jeff Angielski , Robert Schwebel , Raz , "Nikita V. Youshchenko" , linux-rt-users To: Sergio Ruocco Return-path: Received: from e7.ny.us.ibm.com ([32.97.182.137]:58485 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753840Ab0IOO6P (ORCPT ); Wed, 15 Sep 2010 10:58:15 -0400 Received: from d01relay05.pok.ibm.com (d01relay05.pok.ibm.com [9.56.227.237]) by e7.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id o8FEhZSC024091 for ; Wed, 15 Sep 2010 10:43:35 -0400 Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay05.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o8FEwEL2127434 for ; Wed, 15 Sep 2010 10:58:14 -0400 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id o8FEwEFL010327 for ; Wed, 15 Sep 2010 10:58:14 -0400 Content-Disposition: inline In-Reply-To: <4C90C093.4070607@disco.unimib.it> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Wed, Sep 15, 2010 at 02:48:19PM +0200, Sergio Ruocco wrote: > Pradyumna Sampath wrote: > > I agree. Hard, soft ... far too qualitative for a discussion like > > this. Numbers, test cases and applications determine different > > meanings of these words. > > Right. Hard and Soft realtime discussions end up always in useless > infinite loops. The *applications*' *requirements* are hard or soft. > > These requirements reflect in the OS, the CPU, the IO devices, and more > typically a convolution of all of them, depending on what the > application does, i.e., the actual sequence of computations, OS > syscalls, IO operations and so on... I did a Linux Journal article on this topic a few years ago: http://www.linuxjournal.com/article/9361 I also did a portion of a short course on this topic last year: http://www.rdrop.com/users/paulmck/scalability/paper/ACACES2009/4-LKRT.2009.07.16a.pdf http://www.rdrop.com/users/paulmck/scalability/paper/ACACES2009/5-AppRT.2009.07.17b.pdf Thanx, Paul > > Top copy a phrase from one of the presentations from dresden. > > Which presentation? I am curious to read it. > > > Real-time need not always be real fast. > > "Real fast is not real-time" is a catchy phrase which comes from this > very old workshop: > > http://www.langston.com/Papers/uk.pdf > > I used it to motivate an investigation in the real-time properties of a > "real fast" microkernel: > > http://www.hindawi.com/journals/es/2008/234710.abs.html > > Have fun! > > Sergio > -- > To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html