From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 20 Sep 2001 05:10:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 20 Sep 2001 05:10:33 -0400 Received: from unthought.net ([212.97.129.24]:54404 "HELO mail.unthought.net") by vger.kernel.org with SMTP id ; Thu, 20 Sep 2001 05:10:24 -0400 Date: Thu, 20 Sep 2001 11:10:48 +0200 From: =?iso-8859-1?Q?Jakob_=D8stergaard?= To: David Hajek Cc: linux-kernel@vger.kernel.org Subject: Re: high cpu load with sw raid1 Message-ID: <20010920111048.B17066@unthought.net> Mail-Followup-To: =?iso-8859-1?Q?Jakob_=D8stergaard?= , David Hajek , linux-kernel@vger.kernel.org In-Reply-To: <20010920102616.A2753@pida.ulita.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit User-Agent: Mutt/1.2i In-Reply-To: <20010920102616.A2753@pida.ulita.cz>; from david@atrey.karlin.mff.cuni.cz on Thu, Sep 20, 2001 at 10:26:16AM +0200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 20, 2001 at 10:26:16AM +0200, David Hajek wrote: > Hi, > > I have linux box with 70GB SW Raid1. This box runs for half > a year without problems but now I meet the high cpu load > problems. I suspect that it can be caused by not enough > free disk space on this md device. I see following: > > 1 GB free - load > 5 > 5 GB free - load < 1 RAID does not know about "free space" (that is a filesystem thing), so that would be either some strange interaction between the filesystem and lower layers, or a measurement error - I guess. High fragmentation could lead to extra filesystem activity, but that's not really something the RAID can influence. > > I have to notice that this box is rather under heavy load > (1 GB cvs tree, nfs homes etc.) My question is whether this > load can depend on available disk space because I do not > see any suspect processes that can cause such a high load. > > Kernel: 2.2.19 > Patches: lfs + md + ide > RH6.2 + glibc-2.2.12 Please check that your disks are using DMA (hdparm /dev/hdX). You should see something like: [root@eagle /root]# hdparm /dev/hda /dev/hda: multcount = 16 (on) I/O support = 0 (default 16-bit) unmaskirq = 0 (off) using_dma = 1 (on) <=========== INDICATES DMA keepsettings = 0 (off) nowerr = 0 (off) readonly = 0 (off) readahead = 8 (on) geometry = 782/128/63, sectors = 6306048, start = 0 Without DMA you will see high CPU load from accessing the disks, regardless of free space. -- ................................................................ : jakob@unthought.net : And I see the elder races, : :.........................: putrid forms of man : : Jakob Østergaard : See him rise and claim the earth, : : OZ9ABN : his downfall is at hand. : :.........................:............{Konkhra}...............: