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

[Jeffrey Racine]

Hi David.

Thanks for your response. With the 4BSD scheduler, things run as
expected... lam with 2 processors always fires up cpu 0 and 1 and
distributes the load evenly...
                                                                                
  PID USERNAME PRI NICE   SIZE    RES STATE  C   TIME   WCPU    CPU
COMMAND
  838 jracine  101    0  5632K  2012K CPU0   0   0:02 58.94%  5.62%
n_lam
  839 jracine  101    0  5616K  1968K RUN    1   0:02 57.91%  5.52%
n_lam

-- Jeff

On Mon, 2004-04-19 at 23:32, David O'Brien wrote:
> 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