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Subject: [OMPI devel] Trunk Commit Heads-up: New Common Shared Memory Component
From: Samuel K. Gutierrez (samuel_at_[hidden])
Date: 2010-08-10 10:52:05


Hi,

I wanted to give everyone a heads-up about a new POSIX shared memory
component
that has been in the works for a while now and is ready to be pushed
into the
trunk.

http://bitbucket.org/samuelkgutierrez/ompi_posix_sm_new

Some highlights:
o New posix component now the new default.
        o May address some of the shared memory performance issues users
encounter
           when OMPI's session directories are inadvertently placed on a non-
local
           filesystem.
o Silent component failover.
        o In the default case, if the posix component fails initialization,
           mmap will be selected.
o The sysv component will only be queried for selection if it is
placed before
    the mmap component (for example, -mca mpi_common_sm
sysv,posix,mmap). In the
    default case, sysv will never be queried/selected.
o Per some on-list discussion, now unlinking mmaped file in both mmap
and posix
    components (see: "System V Shared Memory for Open MPI: Request for
Community
    Input and Testing" thread).
o Assuming local process homogeneity with respect to all utilized
shared
     memory facilities. That is, if one local process deems a
particular shared
     memory facility acceptable, then ALL local processes should be
able to
     utilize that facility. As it stands, this is an important point
because one
     process dictates to all other local processes which common sm
component will
     be selected based on its own, local run-time test.
o Addressed some of George's code reuse concerns.

If there are no major objections by August 17th, I'll commit the code
after the
Tuesday morning conference call.

Thanks!

--
Samuel K. Gutierrez
Los Alamos National Laboratory