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From: "jesk" <jesk@killall.org>
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Date: Wed, 21 Jul 2004 01:46:12 +0200
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cc: Robert Watson <rwatson@freebsd.org>
Subject: Re: I/O or Threading Suffer
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hi,
i figured out that the performanceloss only really occur if the process is
heavily writing on the filesystem.
dd if=/dev/zero of=/dev/null bs=128k doesnt hurt much in responsetime
of parallel processes, but when dd operates on the filesystem with of=foo
every process will be affect in executiontime.
a simple ps or ls meanwhile dding onto the disk will be hang for dozen of
seconds.

i tested it with 4BSD and ULE with and without Preemption.