Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264516AbTFKWVN (ORCPT ); Wed, 11 Jun 2003 18:21:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264605AbTFKWVM (ORCPT ); Wed, 11 Jun 2003 18:21:12 -0400 Received: from mail.webmaster.com ([216.152.64.131]:22448 "EHLO shell.webmaster.com") by vger.kernel.org with ESMTP id S264516AbTFKWVC (ORCPT ); Wed, 11 Jun 2003 18:21:02 -0400 From: "David Schwartz" To: "Artemio" , "Linux Kernel Mailing List" Subject: RE: SMP question Date: Wed, 11 Jun 2003 15:34:44 -0700 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.6604 (9.0.2911.0) In-Reply-To: <200306112313.30903.artemio@artemio.net> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Importance: Normal Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1666 Lines: 48 > Hello! > > > How much performance will I loose this way? Is SMP *THAT* critical? > > > > You will lose about half your CPU power. > Hmmm... So, you mean uni-processor Linux kernel can't see two > processors as > one "big" processor? Don't we wish. No, two processors is two processors. > > > Also, if I turn hyperthreading off, how will it influence the > > > system with SMP > > > support? Without SMP support? > > In a system with more than one physical CPU, hyperthreading > > is not that > > big of a performance boost. > Okay, I will try turning hyperthreding off and see if RTLinux > keeps hanging > the machine. It sounds like you're experiencing a bug. You can do this kind of testing to help determine the 'envelope' of the bug (that is, under what circumstances it appears and under what circumstances it doesn't appear), however this is not a substitute for fixing the bug. ;) Even if you find a configuration that doesn't show the bug, you still should work with the RTLinux guys to track down the bug and get it fixed. If, for example, it's due to unreliable hardware, turning off hyperthreading might hide it but it will still be lurking there. RTLinux might be hanging because of problems with the code you're running. Thinks like deadlock and priority inversion can become much more obvious in an SMP machine, but can definitely still happen in a UP machine, just much less often. DS - 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/