Re: Improved multiprocessor usage on amd64

On Mon, Sep 15, 2008 at 07:36:04PM -0500, Stephen Montgomery-Smith wrote:
> 
> ... and each thread is a loop of the form
> 
> while (1) {
>   wait until told to start;
>   do massive amounts of floating point arithmetic (only additions and
> multiplications) on large arrays;
>   tell the master process that you are done;
> }
> 
> >Do you have about as many threads as processor or more?
> 
> Both ways.  The time difference between the two approaches is negligible.
> 

Are you using ULE?  With my MPI applications, if the number of
launched processes exceeds the number of cpus by 1, ULE falls
through the floor.  I have a nagging feeling that there is 
a problem with cpu affinity.

http://lists.freebsd.org/pipermail/freebsd-current/2008-July/086917.html

-- 
Steve