strange performance problem

[Dominic Fandrey]

When I build openoffice with NUMOFPROCESSES=4 the system starts to act 
unresponsive after some time on my Core2 Duo, very similar to a single core 
system running make -j. However if I set

debug.vfscache=0

the system immediately becomes responsive again. After resetting 
debug.vfscache to 1 the system _remains_ responsive. I'm considering to put

debug.vfscache=0
debug.vfscache=1

into my sysctl.conf. Whatever causes this behaviour, I doubt it is intended.