The direct modex operation is slow, especially at scale for even modestly-connected applications. Likewise, blocking in MPI_Init while we wait for a full modex to complete takes too long. However, as George pointed out, there is a middle ground here. We could kickoff the modex operation in the background, and then trap any modex_recv's until the modex completes and the data is delivered. For most non-benchmark apps, this may prove to be the best of the available options as they are likely to perform other (non-communicating) setup operations after MPI_Init, and so there is a reasonable chance that the modex will actually be done before the first modex_recv gets called.
Once we get instant-on-enabled hardware, this won't be necessary. Clearly, zero time will always out-perform the time spent doing a modex. However, this provides a decent compromise in the interim.
This PR changes the default settings of a few relevant params to make "background modex" the default behavior:
* pmix_base_async_modex -> defaults to true
* pmix_base_collect_data -> continues to default to true (no change)
* async_mpi_init - defaults to true. Note that the prior code attempted to base the default setting of this value on the setting of pmix_base_async_modex. Unfortunately, the pmix value isn't set prior to setting async_mpi_init, and so that attempt failed to accomplish anything.
The logic in MPI_Init is:
* if async_modex AND collect_data are set, AND we have a non-blocking fence available, then we execute the background modex operation
* if async_modex is set, but collect_data is false, then we simply skip the modex entirely - no fence is performed
* if async_modex is not set, then we block until the fence completes (regardless of collecting data or not)
* if we do NOT have a non-blocking fence (e.g., we are not using PMIx), then we always perform the full blocking modex operation.
* if we do perform the background modex, and the user requested the barrier be performed at the end of MPI_Init, then we check to see if the modex has completed when we reach that point. If it has, then we execute the barrier. However, if the modex has NOT completed, then we block until the modex does complete and skip the extra barrier. So we never perform two barriers in that case.
HTH
Ralph
Signed-off-by: Ralph Castain <rhc@open-mpi.org>
Follow on to 7bd2de9960419422a4591f4b5d286f1f911a0a47: move setting
the iov_limit to 1 earlier in the startup sequence.
Signed-off-by: Jeff Squyres <jsquyres@cisco.com>
The usNIC BTL does not use more than 1 iov, so be sure to set it to 1
so that we don't allocate cq/rq/sq entries based on a default (i.e.,
>1) number of iovs per entry.
Signed-off-by: Jeff Squyres <jsquyres@cisco.com>
This PR renames the common library for OFI libfabric from
libfabric to ofi. There are a number of reasons this
is good to do:
1) its shorter and replaces 9 characters with three for
function names for what may eventually be a fairly extensive interface
2) OFI is the term used for MTL and RML components that use
the OFI libfabric interface
3) A planned OSC component will also use the OFI term.
4) Other HPC libraries that can use OFI libfabric tend to use
the term "ofi" internally and also in their configure options
relevant to OFI libfabric (i.e. MPICH/CH4, Intel MPI, Sandia SHMEM)
There seem to be comments in places in the Open MPI source
code that indicate that this common library will be going away.
Far from it as we will want to be able to share things like
AV objects between OMPI and possibly OSHMEM components that
use the OFI libfabric interface.
This PR also adds a synonym to the --with-libfabric(-libdir)
configury options: --with-ofi and with-ofi-libdir.
Signed-off-by: Howard Pritchard <howardp@lanl.gov>
This commit recategorizes several mpirun arguments,
and moves the information for mpirun --help arguments
to the bottom of the general help message. I also
added the OPAL_CMD_LINE_OTYPE field to two commands
that were missed initially because they were not
in the same area as the others.
Signed-off-by: Nathaniel Graham <ngraham@lanl.gov>
since Open MPI now requires a C99, and ptrdiff_t type is part of C99,
there is no more need for the abstract OPAL_PTRDIFF_TYPE type.
Thanks George, Nathan and Paul for the help.
Signed-off-by: Gilles Gouaillardet <gilles@rist.or.jp>
since Open MPI now requires a C99, and ptrdiff_t type is part of C99,
there is no more need for the abstract OPAL_PTRDIFF_TYPE type.
Signed-off-by: Gilles Gouaillardet <gilles@rist.or.jp>
* Complete rewrite of opal_pointer_array
Instead of a cache oblivious linear search use a bits array
to speed up the management of the free space. As a result we
slightly increase the memory used by the structure, but we get a
significant boost in performance.
Signed-off-by: George Bosilca <bosilca@icl.utk.edu>
* Do not register datatypes in the f2c translation table.
The registration is now done up into the Fortran layer, by
forcing a call to MPI_Type_c2f.
Signed-off-by: George Bosilca <bosilca@icl.utk.edu>
With this, libs (e.g., "-ldl") are not added to the wrapper LIBS
flags. This may work on some platforms, but on at least RHEL 7.3, it
does not (i.e., compiling MPI applications fails because it can't find
dlopen).
Signed-off-by: Jeff Squyres <jsquyres@cisco.com>
So that we can stop asking common questions like "What version of Open
MPI are you using?", etc.
[skip ci]
bot:notest
Signed-off-by: Jeff Squyres <jsquyres@cisco.com>
