From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267324AbUHSTn0 (ORCPT ); Thu, 19 Aug 2004 15:43:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267323AbUHSTnH (ORCPT ); Thu, 19 Aug 2004 15:43:07 -0400 Received: from tomts31-srv.bellnexxia.net ([209.226.175.105]:33022 "EHLO tomts31-srv.bellnexxia.net") by vger.kernel.org with ESMTP id S267311AbUHSTmw (ORCPT ); Thu, 19 Aug 2004 15:42:52 -0400 Reply-To: From: "Ivan Kalatchev" To: Subject: System time slowdown after upgrading from 2.4 to 2.6 Date: Thu, 19 Aug 2004 15:42:41 -0400 Message-ID: <000501c48624$b1ac72f0$2e646434@ivans> 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 CWS, Build 9.0.2416 (9.0.2911.0) Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi all, We have a project that uses PC-104 (ZFx86 100 MHz CPU) Linux box to acquire some seismological signals. System resides on a M-Systems DiskOnChip 2000. We have an ISA acquisition card that acquires data into FIFO buffer and triggers interrupt as soon as 341 points were acquired (then this data is read out in interrupt handler routine). System worked perfectly well when we used 2.4.18 kernel. When I printk-ed system time (do_gettimeofday) in interrupt routine, at 1kHz sampling frequency interrupts were reported every 341 msec as they should do. But after I've switched to 2.6 kernel (2.6.7 - preempted, then I tried 2.6.8 - non-preempted) time between successive interrupts at 1kHz became 335 msec, losing 6 msec at each interrupt. What is interesting, when sampling frequency is 10 kHz, with 2.4.18 kernel interrupts are reported every 34 msec, which is right, but with 2.6 kernels interrupts are coming at 28 msec interval, again losing same 6 msec! Any ideas why this might happen? Please, CC me all answers/comments posted to the list in response to this posting. Regards, Ivan Kalatchev Senior Software Developer Engineering Seismology Group Canada Inc. ISO 9001-2000 1 Hyperion Court, Kingston, Ontarion, Canada K7K 7G3 phone: (613) 548-8287 ext.247 fax: (613) 548-8917