[Beowulf] memory bandwidth estimation

[Olivier Marsden]

Hello everyone,
this might be a stupid question, but I haven't found a simple
answer to it yet: is there any "easy" way of looking at the memory
bandwidth that a program uses? What I basically want to know is
whether my mpi-based program would benefit from dual-core processors
or not, and this depends on whether the program's execution is badly
memory-bandwidth-limited or not.
So far I have not found anything better than looking at cpu usage thanks 
to ganglia,
or 'top' or something like that, and looking for times when the 
processors are idling,
but this method is definitely not very precise, and for all I know might 
be wrong.
Could anyone give me any suggestions?
Thanks in advance,

Olivier Marsden
Ecole Centrale de Lyon
France