Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261592AbVE3J6n (ORCPT ); Mon, 30 May 2005 05:58:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261590AbVE3J6n (ORCPT ); Mon, 30 May 2005 05:58:43 -0400 Received: from gate.corvil.net ([213.94.219.177]:261 "EHLO corvil.com") by vger.kernel.org with ESMTP id S261594AbVE3Jzb (ORCPT ); Mon, 30 May 2005 05:55:31 -0400 Message-ID: <429AE305.30502@draigBrady.com> Date: Mon, 30 May 2005 10:55:17 +0100 From: P@draigBrady.com User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.6) Gecko/20040124 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Liangchen Zheng CC: linux-kernel@vger.kernel.org Subject: Re: The values of gettimeofday() jumps. References: <000201c563ee$eed993d0$85a4c380@dream.eng.uci.edu> In-Reply-To: <000201c563ee$eed993d0$85a4c380@dream.eng.uci.edu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 955 Lines: 26 Liangchen Zheng wrote: > Hello, > We have several SMP machines (Tyan Tiger MPX motherboard, 2 > AthlonMP 1900+ CPU, linux-2.4.21-20.EL). When running some time > sensitive programs, I observed that the values of gettimeofday() jumped > sometimes on a couple of machines (other machines are fine), from > several hundreds milliseconds to a couple of seconds. That sounds like what I described here: http://lkml.org/lkml/2005/4/4/57 2 options as far as I can see. 1. Use irq affinity to bind the timer irq to a particular CPU, while using CPU affinity to bind your process to a particular CPU. 2. Change the code to maintain a last_tsc_low for each CPU. -- P?draig Brady - http://www.pixelbeat.org -- - 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/