On Thu, Jul 18, 2013 at 08:33:37AM -0700, Ralph Castain wrote: > > On Jul 18, 2013, at 8:17 AM, "David Goodell (dgoodell)" <dgood...@cisco.com> > wrote: > > > On Jul 18, 2013, at 9:53 AM, Ralph Castain <r...@open-mpi.org> wrote: > > > >> On Jul 18, 2013, at 7:05 AM, David Goodell (dgoodell) <dgood...@cisco.com> > >> wrote: > >> > >>> On Jul 18, 2013, at 8:06 AM, Ralph Castain <r...@open-mpi.org> wrote: > >>> > >>>> That's a good point, and a bad behavior. IIRC, it results from the MPI > >>>> Forum's adoption of the MPI-T requirement that stipulates we must allow > >>>> access to all control and performance variables at startup so they can > >>>> be externally seen/manipulated. > >>> > >>> Minor nit: MPI_T does not require this. However, it does recommend that > >>> you offer users access to as many variables as possible as early as > >>> reasonably possible for the convenience and control of the user. > >>> > >>> If an implementation chooses to offer 5% of the possible > >>> control/performance variables to the user just before MPI_Finalize, > >>> that's still a valid MPI_T implementation. But it may not be a very > >>> useful one... > >> > >> The problem here is one of use vs startup performance. George is quite > >> correct with his concerns - this behavior would have been a serious > >> problem for RoadRunner, for example, where we had a small IO channel > >> feeding a lot of nodes. It will definitely become an issue at exascale > >> where IO bandwidth and memory will be at a premium. > > > > My point was not that the performance concerns were unfounded. Rather, I > > wanted to point out that the "load everything" behavior is not a hard > > requirement from the MPI standard, so we have room for different > > implementation choices/tradeoffs. > > I understood - I was more just pointing out the potential performance issue > of load everything. However, Nathan has addressed it by pointing out that the > problem is my aged, fading memory.
So, I think what I can take from this discussion to to make the following changes to ompi_info: - Make --all without a --level option imply --level 9. - Allow the user to modify this behavior by specifying a level: ex --all --level 5 would print every variable up to level 5. I will make these changes today and CMR them into 1.7.3 unless there are any objections. -Nathan
