Parallel performance drops off a cliff

[Neil Mitchell]

Hi,

Using one benchmark I have, which doesn't create any threads, I have:

$ benchmark +RTS -Nx

x             time (Seconds)
1              2
2              2
3              2
4              3
5              3
6              3
7              3
8              aborted after 2 minutes

This is using GHC 6.10.2 on Windows XP, 2 processors. Is this a known
bug, or should I try and replicate it? (benchmark is fairly big and
very dependent on internal things, but I suspect the dramatic
performance slowdown is unlikely to be related to these bits).

Thanks

Neil