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

Jeffrey Racine jracine at maxwell.syr.edu
Wed Apr 21 04:50:27 PDT 2004


Hi David.

It runs as fine with the 4BSD scheduler and distributes the load
evenly... here is top with 4BSD doing the scheduling...
                                                                                  PID USERNAME PRI NICE   SIZE    RES STATE  C   TIME   WCPU    CPU COMMAND
 6105 jracine  107    0  5616K  1968K CPU0   0   0:06 95.70% 21.19%
n_lam
 6104 jracine  107    0  5632K  2012K RUN    1   0:06 95.48% 21.14%
n_lam

Thanks ever so much for your kind response.

-- 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



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