From: "Jakob Østergaard" <jakob@unthought.net>
To: David Hajek <david@atrey.karlin.mff.cuni.cz>
Cc: linux-kernel@vger.kernel.org
Subject: Re: high cpu load with sw raid1
Date: Thu, 20 Sep 2001 11:10:48 +0200 [thread overview]
Message-ID: <20010920111048.B17066@unthought.net> (raw)
In-Reply-To: <20010920102616.A2753@pida.ulita.cz>
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
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}...............:
next prev parent reply other threads:[~2001-09-20 9:10 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-09-20 8:26 high cpu load with sw raid1 David Hajek
2001-09-20 9:10 ` Jakob Østergaard [this message]
2001-09-20 9:23 ` David Hajek
2001-09-20 10:38 ` Jakob Østergaard
2001-09-20 18:40 ` Andreas Dilger
2001-09-21 7:07 ` David Hajek
2001-09-21 8:09 ` Andreas Dilger
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