Re: 2.4.17 RAID-1 EXT3 reliable to hang....

From: Andrew Morton (akpm@zip.com.au)
Date: Mon Jan 07 2002 - 03:49:30 EST


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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