From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263426AbTDVXNR (ORCPT ); Tue, 22 Apr 2003 19:13:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263472AbTDVXNQ (ORCPT ); Tue, 22 Apr 2003 19:13:16 -0400 Received: from taka.swcp.com ([198.59.115.12]:1284 "EHLO taka.swcp.com") by vger.kernel.org with ESMTP id S263426AbTDVXNP (ORCPT ); Tue, 22 Apr 2003 19:13:15 -0400 Date: Tue, 22 Apr 2003 17:23:16 -0600 From: Trammell Hudson To: linux-kernel@vger.kernel.org Subject: gettimeofday running backwards on 2.4.20 Message-ID: <20030422232316.GF20108@osbox.osresearch.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org [ Please cc hudson@osresearch.net on any replies. Thank you! ] A few months ago I noticed gettimeofday running backwards on dual Pentium II and dual Pentium Pro systems with 2.4.18. Based on postings made to linux-kernel in June of 2002, I upgraded to 2.4.20 and the problem seemed to go away: http://groups.google.com/groups?threadm=3D16DE83.3060409@tiscalinet.it Just recently my NAS benchmarks and MPI latency tests showed bizarre results, so I pulled out my test program and am seeing the same problems again. It seems that roughly 50 in 1 million calls go backwards, even with 2.4.20. Occasionally it is 4295 seconds (very consistently that value), but most of them are just a few microseconds backwards. No error code is returned from the system call either. No NTP or rdate type services are running. My test program can be seen here: http://www.swcp.com/~hudson/gettimeofday.c Interestingly, it only happens on the compute nodes with NFS root. The service node has booted from a local SCSI disk and is serving roughly 140 compute nodes without any timing bugs. service:~/tflop-linux: ssh node-181 uname -a \; cat /proc/cpuinfo Linux node-181 2.4.20 #73 SMP Mon Apr 21 14:06:49 MDT 2003 i686 unknown processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 3 model name : Pentium II (Klamath) stepping : 2 cpu MHz : 333.356 cache size : 512 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr bogomips : 665.19 processor : 1 vendor_id : GenuineIntel cpu family : 6 model : 3 model name : Pentium II (Klamath) stepping : 2 cpu MHz : 333.356 cache size : 512 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr bogomips : 665.19 Trammell -- -----|----- hudson@osresearch.net W 240-283-1700 *>=====[]L\ hudson@rotomotion.com M 505-463-1896 ' -'-`- http://www.swcp.com/~hudson/ KC5RNF