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Date: Mon, 07 Jan 2002 00:49:30 -0800
From: Andrew Morton <akpm@zip.com.au>
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To: Oliver Paukstadt <pstadt@stud.fh-heilbronn.de>
CC: Matti Aarnio <matti.aarnio@zmailer.org>,
        Linux-Kernel <linux-kernel@vger.kernel.org>,
        linux-raid@vger.kernel.org
Subject: Re: 2.4.17 RAID-1 EXT3  reliable to hang....
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Oliver Paukstadt wrote:
> 
> Heavy traffic on ext3 seems to cause short system freezes.

This could be due to disk request elevator latency and VM imbalance.
Your application has a page dropped due to the competing write activity,
and it takes ages to be restored, due to the write activity.
 
> Seems only to happen on 2 or more processor boxes.

In which case the above theory is wrong.
 
> I'm not deep into kernel nor ext3, but how is the journal flushed if
> full?

Nothing special, really - we just pump a stream of data out to disk.
While this is happening, other processes can still attach data to the
journal without getting blocked.  Up to a point.  Our handling of this
is a bit sudden at present.  Some people have reported benefit from
radically decreasing the buffer flushtimes. See Daniel Robbins' article
at http://www-106.ibm.com/developerworks/linux/library/l-fs8/ for this.
Yes, improvements are needed in this area.  Not only in ext3.

You haven't really defined "freeze", but it's certainly different
from Matti's freeze.

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