From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269284AbUHZSS1 (ORCPT ); Thu, 26 Aug 2004 14:18:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267685AbUHZSOA (ORCPT ); Thu, 26 Aug 2004 14:14:00 -0400 Received: from viper.oldcity.dca.net ([216.158.38.4]:46760 "HELO viper.oldcity.dca.net") by vger.kernel.org with SMTP id S269197AbUHZSGN (ORCPT ); Thu, 26 Aug 2004 14:06:13 -0400 Subject: Re: Disable kscand/Normal? From: Lee Revell To: "HOLTZ, CORBIN L. (JSC-ER) (LM)" Cc: "'linux-kernel@vger.kernel.org'" In-Reply-To: References: Content-Type: text/plain Message-Id: <1093543394.5678.64.camel@krustophenia.net> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Thu, 26 Aug 2004 14:03:15 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2004-08-25 at 23:54, HOLTZ, CORBIN L. (JSC-ER) (LM) wrote: > I'm currenty > building a realtime visualization system for a Space Shuttle landing > simulator at NASA. I'm using a small network of 5 Pentium 4 computers > running RedHat's 2.4.20-31.9 kernel. I'm easily running 60 frames/second on > my systems, but I'm having a problem because the kscand/Normal thread comes > in every 25 seconds and causes me to drop a frame (very annoying). I've > looked into the kernel source and found where the kscand threads are > spawned. I also see where the 25 second period is coming from. What I'm > wondering is what would happen if I disabled the kscand/Normal thread? I've > got plenty of memory, and my process is the only thing running on the > system. Would I eventually see problems, or would I be OK since I'm not > running low on memory? What if I modified the kernel to allow me to > temporarily disable the thread while my application is running (using a > /proc file or something similar)? You should also look into Ingo Molnar's voluntary preemption patches for a more general way to do soft and even hard realtime with Linux. Con's suggestion will probably solve the kscand problem but the voluntary preemption patches provide a more general way to deal with real time constraints. Check the LKML archives for the past few months, there has been a lot of work in this area lately. Lee