Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261648AbTILCBM (ORCPT ); Thu, 11 Sep 2003 22:01:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261652AbTILCBM (ORCPT ); Thu, 11 Sep 2003 22:01:12 -0400 Received: from mail006.syd.optusnet.com.au ([211.29.132.63]:14048 "EHLO mail006.syd.optusnet.com.au") by vger.kernel.org with ESMTP id S261648AbTILCBL (ORCPT ); Thu, 11 Sep 2003 22:01:11 -0400 From: Peter Chubb MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <16225.10465.132753.695040@wombat.chubb.wattle.id.au> Date: Fri, 12 Sep 2003 12:01:05 +1000 To: Rick Lindsley Cc: Peter Chubb , linux-kernel@vger.kernel.org Subject: Re: [PATCH] schedstat-2.6.0-test5-A1 measuring process scheduling latency In-Reply-To: <200309120102.h8C12NV07347@owlet.beaverton.ibm.com> References: <16225.5591.442410.58842@wombat.chubb.wattle.id.au> <200309120102.h8C12NV07347@owlet.beaverton.ibm.com> X-Mailer: VM 7.14 under 21.4 (patch 13) "Rational FORTRAN" XEmacs Lucid Comments: Hyperbole mail buttons accepted, v04.18. X-Face: GgFg(Z>fx((4\32hvXq<)|jndSniCH~~$D)Ka:P@e@JR1P%Vr}EwUdfwf-4j\rUs#JR{'h# !]])6%Jh~b$VA|ALhnpPiHu[-x~@<"@Iv&|%R)Fq[[,(&Z'O)Q)xCqe1\M[F8#9l8~}#u$S$Rm`S9% \'T@`:&8>Sb*c5d'=eDYI&GF`+t[LfDH="MP5rwOO]w>ALi7'=QJHz&y&C&TE_3j! Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1437 Lines: 32 >>>>> "Rick" == Rick Lindsley writes: Rick> I'm not sure that it's any less or more intrusive, but it's at Rick> least another way of doing the same thing. So since you've Rick> taken some measurements, what's the length of time you find your Rick> process waits to hit the processor after getting the I/O it Rick> needs? What's the time it seems to wait when it skips (what's Rick> the cutoff at which you hear a skip versus don't hear one?) In short, time on the run queue is negligeable. Time spend waiting for disk I/O is extensive. If you look at the graph, you'll see each disk I/O takes 0.8 seconds, which is about the same as the skip. This is on ReiserFS 2.6, laptop (4000RPM) disk, but attached to mains power. There's a massive difference between the behaviour with hdparm -u1 and hdparm -u0 --- I don't see skips with -u1, and the time the disk light is on is much reduced. This puts my problem in the IDE layer somewhere -- which means it may not be the same problem others are seeing. -- Dr Peter Chubb http://www.gelato.unsw.edu.au peterc AT gelato.unsw.edu.au You are lost in a maze of BitKeeper repositories, all slightly different. - 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/