Date: Mon, 8 May 2006 13:13:45 +0200
From: Erik Mouw <erik@harddisk-recovery.com>
To: Andrew Morton <akpm@osdl.org>
Cc: Jason Schoonover <jasons@pioneer-pra.com>, linux-kernel@vger.kernel.org
Subject: Re: High load average on disk I/O on 2.6.17-rc3
Message-ID: <20060508111345.GA1875@harddisk-recovery.com>
References: <200605051010.19725.jasons@pioneer-pra.com> <20060507095039.089ad37c.akpm@osdl.org>
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On Sun, May 07, 2006 at 09:50:39AM -0700, Andrew Morton wrote:
> This is probably because the number of pdflush threads slowly grows to its
> maximum.  This is bogus, and we seem to have broken it sometime in the past
> few releases.  I need to find a few quality hours to get in there and fix
> it, but they're rare :(
> 
> It's pretty harmless though.  The "load average" thing just means that the
> extra pdflush threads are twiddling thumbs waiting on some disk I/O -
> they'll later exit and clean themselves up.  They won't be consuming
> significant resources.

Not completely harmless. Some daemons (sendmail, exim) use the load
average to decide if they will allow more work. A local user could
create a mail DoS by just copying a couple of large files around.
Zeniv.linux.org.uk mail went down due to this. See
http://lkml.org/lkml/2006/3/28/70 .


Erik

-- 
+-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 --
| Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands
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