From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 27 May 2002 12:43:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 27 May 2002 12:43:20 -0400 Received: from holomorphy.com ([66.224.33.161]:55721 "EHLO holomorphy") by vger.kernel.org with ESMTP id ; Mon, 27 May 2002 12:43:19 -0400 Date: Mon, 27 May 2002 09:43:03 -0700 From: William Lee Irwin III To: Muthal Sangam Cc: linux-kernel@vger.kernel.org Subject: Re: interrupt latency/700microsecs Message-ID: <20020527164303.GP14918@holomorphy.com> Mail-Followup-To: William Lee Irwin III , Muthal Sangam , linux-kernel@vger.kernel.org In-Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Description: brief message Content-Disposition: inline User-Agent: Mutt/1.3.25i Organization: The Domain of Holomorphy Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 27, 2002 at 08:30:06PM +0400, Muthal Sangam wrote: > On kernel 2.4.7, AMDK6 @ 450MHz processor, is it possible to get latency > fluctuations of upto 700microsecs for running the timer interrupt, due to > interrupts being disabled ? > I am using the time stamp counter and reading it at the start of the timer > interrupt and measuring the cycles elapsed between two inovocations of it. > The number of cycles elapsed is ~4500225, but sometimes it increases to as > high as 4848032. Can i conclude that this difference is due to interrupts > being disabled in critical sections ? ( I think i am making some mistake :-) IIRC there have been prior reports of excessive interrupt disablement in 2.4.x, and also IIRC it was reported against a more recent kernel. I think it was suspected there are bug(s) where some code is leaving interrupts off and someone later unconditionally turns them back on. Any chance you could upgrade to a more recent kernel and try to reproduce there? There have been a number of critical bugfixes since 2.4.7 (and although none are particularly pertinent to this issue, people would probably rather field bug reports for 2.4.19-pre* than 2.4.7). Cheers, Bill