[Haskell-cafe] Strange parallel behaviour with Ubuntu Karmic / GHC 6.10.4

Neil Brown nccb2 at kent.ac.uk
Mon Nov 16 04:38:29 EST 2009

Michael Lesniak wrote:
> Hello,
> I've written a smaller example which reproduces the unusual behaviour.
> Should I open a GHC-Ticket, too?

I get these results:

$ time ./Temp +RTS -N1 -RTS 16

real    0m16.010s
user    0m10.869s
sys    0m5.144s

$ time ./Temp +RTS -N2 -RTS 16

real    0m12.794s
user    0m13.341s
sys    0m7.136s

Looking at top, the second version used ~160% CPU time (i.e. it was 
using both cores fairly well).  So I don't think I get the same bad 
behaviour as you.  Those sys times look high by the way -- I guess it's 
all the calls to getTime?  I wonder if that number might be causing the 
problem; can you replicate it with lower sys times?



More information about the Haskell-Cafe mailing list