LAM MPI on dual processor opteron box sees only one cpu...

[David O'Brien]

On Mon, Apr 12, 2004 at 09:04:24AM -0400, Jeffrey Racine wrote:
> Hi Roland.
> 
> I do get CPU #1 launched. This is not the problem.
> 
> The problem appears to be with the way that current is scheduling.
> 
> With mpirun np 2 I get the job running on CPU 0 (two instances on one
> proc). However, it turns out that with np 4 I get the job running on CPU
> 0 and 1 though with 4 instances (and associated overhead). Here is top
> for np 4... notice that in the C column it is using both procs.
> 
>   PID USERNAME PRI NICE   SIZE    RES STATE  C   TIME   WCPU    CPU
> COMMAND
> 96090 jracine  131    0  7148K  2172K CPU1   1   0:19 44.53% 44.53%
> n_lam
> 96088 jracine  125    0  7148K  2172K RUN    0   0:18 43.75% 43.75%
> n_lam
> 96089 jracine  136    0  7148K  2172K RUN    1   0:19 42.19% 42.19%
> n_lam
> 96087 jracine  135    0  7188K  2248K RUN    0   0:19 41.41% 41.41%
> n_lam
> 
> 
> One run (once when I rebooted lam) did allocate the job correctly with
> np 2, but this is not in general the case. On other systems I use,
> however, they correctly farm out np 2 to CPU 0 and 1...
> 
> Thanks, and any suggestions welcome.

1. Please don't top-post -- it looses context.  This is a Unix list, not
   Mikeysoft one.

2. Have you tried with the 4.4BSD scheduler vs. the "ULE" scheduler?
   To test, replace:
        options 	SCHED_ULE		# ULE scheduler
   with
        options 	SCHED_4BSD		#4BSD scheduler

-- David