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 13:51:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 27 May 2002 13:51:12 -0400 Received: from pc2-cwma1-5-cust12.swa.cable.ntl.com ([80.5.121.12]:56303 "EHLO irongate.swansea.linux.org.uk") by vger.kernel.org with ESMTP id ; Mon, 27 May 2002 13:51:11 -0400 Subject: Re: interrupt latency/700microsecs From: Alan Cox To: Muthal Sangam Cc: linux-kernel@vger.kernel.org In-Reply-To: Content-Type: text/plain Content-Transfer-Encoding: 7bit X-Mailer: Ximian Evolution 1.0.3 (1.0.3-6) Date: 27 May 2002 19:53:46 +0100 Message-Id: <1022525626.11859.307.camel@irongate.swansea.linux.org.uk> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2002-05-27 at 17:30, 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 :-) In X with a matrox G200 I've observed processor stalls in excess of 1mS so Im not actually much suprised.