On Fri, Dec 01, 2006 at 11:51:24AM +0100, Peter Kjellstrom wrote: > This might be a bit naive but, if you spawn two procs on a dual core dual > socket system then the linux kernel should automagically schedule them this > way.
No, we checked this for OpenMP and MPI, and in both cases wiring the processes to cores was significantly better. The Linux scheduler (still) tends to migrate processes to the wrong core when OS threads and processes wake up and go back to sleep. Just like the OpenMPI guys, we don't have a clever solution for the "what if the user wants to have 2 OpenMP or MPI jobs share the same node?" Well, I have a plan, but it's annoying to implement. -- greg
