Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264760AbTFLFyl (ORCPT ); Thu, 12 Jun 2003 01:54:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264762AbTFLFyl (ORCPT ); Thu, 12 Jun 2003 01:54:41 -0400 Received: from h2.prohosting.com.ua ([217.106.231.81]:17794 "EHLO h2.prohosting.com.ua") by vger.kernel.org with ESMTP id S264760AbTFLFyg (ORCPT ); Thu, 12 Jun 2003 01:54:36 -0400 From: Artemio To: Mark Hahn Subject: Re: SMP question Date: Thu, 12 Jun 2003 08:42:42 +0300 User-Agent: KMail/1.5 References: In-Reply-To: MIME-Version: 1.0 Content-Disposition: inline Message-Id: <200306120841.08809.artemio@artemio.net> Cc: Linux Kernel Mailing List Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - h2.prohosting.com.ua X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [0 0] / [0 0] X-AntiAbuse: Sender Address Domain - artemio.net Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2160 Lines: 67 Hello! > > I'm building a hard real-time Linux (RTLinux) system on a 2x Xeon > > machine. If > > then LKML is not the place for you. RTLinux is a fork of "real" linux. Well, those guys seem to have success on the same machines that I fail. I even used *their* .config file to compile a kernel, but I still fail. > well, talk to the rtlinux people. considering what rtlinux changes from > real linux, this hang is not a big surprise. Yes, rtlinux runs linux kernel as it's idle thread, and it messes up the system - I mean it becomes more difficult to make it work if it doesn't work. > > So, I have to deside between these two: > > > > - Run rtlinux and hard-realtime applications on a kernel without SMP > > support. How much performance will I loose this way? Is SMP *THAT* > > critical? > > huh? it's not critical at all. though if you have two processors, > you've just wasted several hundred dollars unless you run SMP. :-) > > - Run all tasks in a usual way, no hard realtime, but with SMP support. > > why do you think you need rtlinux-type realtime? Hmm... Nice question. We are to run many applications that will be mission-critical. That's why we decided to make them in hard-realtime. The other way is probably making low-priority kernel threads by usual means. But I think hard-realtime will give us more performance. > > Also, if I turn hyperthreading off, how will it influence the system with > > SMP support? Without SMP support? > > HT is just hardware-supported multithreading - imagine that you have > the same old processor, except that the CPU's instruction-dispatcher > is reading from two instruction streams. HT doesn't add any new resources, > just shares a single CPU among two threads. Got it. > I suspect the design of rtlinux is inherently incompatible with HT. I will try turning HT off and running RTLinux. Thank you very much for your reply! Artemio. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/