Pathological case identified from contest

From: Con Kolivas (conman@kolivas.net)
Date: Wed Oct 16 2002 - 21:13:40 EST


I found a pathological case in 2.5 while running contest with process_load
recently after checking the results which showed a bad result for 2.5.43-mm1:

2.5.43-mm1 101.38 72% 42 31%
2.5.43-mm1 102.90 75% 34 28%
2.5.43-mm1 504.12 14% 603 85%
2.5.43-mm1 96.73 77% 34 26%

This was very strange so I looked into it further

The default for process_load is this command:

process_load --processes $nproc --recordsize 8192 --injections 2

where $nproc=4*num_cpus

When I changed recordsize to 16384, many of the 2.5 kernels started exhibiting
the same behaviour. While the machine was apparently still alive and would
respond to my request to abort, the kernel compile would all but stop while
process_load just continued without allowing anything to happen from kernel
compilation for up to 5 minutes at a time. This doesnt happen with any 2.4 kernels.

I'm not sure what to make of this. Suggestion?

Con
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