Livelock seen on current with threaded processes

From: Kevin Oberman <oberman_at_es.net>
Date: Sun, 05 Jun 2005 20:20:25 -0700
I am running current on an IBM T30 with P4m CPU_at_1.8 GHz and 512
MB. ATA100 disk (5400 RPM).

When I run some threaded codes, I see the system response slow
badly. I've tried 4BSD, ULE, and PREEMPTION without seeing any real
difference.

For a long time I was unable to repeat the problem reliably, but now I
have an easy way to do it.

I run transcode on a video file to convert it to divx4 using the xvid4
library. I do this with nice set to 10 and top confirms that it is set
to 10. At various times, the system starts locking up. Windows won't
refresh. Shell commands never execute (nor do keys echo) in some windows
including syscons vtys. If my gkrellm is still alive (and it usually
is), I see the system at 97% CPU and nothing else busy. There is a bit a
disk I/O but not much.

If I wait until the transcode operation completes, the system quickly
returns to normal. This effectively precludes doing anything on the system
while transcode is running which is a real pain since it typically
transcodes at only about 5 framed per second and takes a long time to
transcode 5 minute video clips.

Has anyone else seen this? There was a recent thread on some similar
problems on stable, but I can't say if they are really the same. Since
nice does not seem to help, I am really suspicious it's a threading
issue of some sort, but I am far from sure.
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman_at_es.net			Phone: +1 510 486-8634
Received on Mon Jun 06 2005 - 01:20:26 UTC

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