When ever this happens we found the code to have a deadlock. users
never saw it until they cross the eager->roundevous threshold.
Yes you can disable shared memory with:
mpirun --mca btl ^sm
Or you can try increasing the eager limit.
ompi_info --param btl sm
MCA btl: parameter "btl_sm_eager_limit" (current value:
"4096")
You can modify this limit at run time, I think (can't test it right
now) it is just:
mpirun --mca btl_sm_eager_limit 40960
I think you can also in tweaking these values use env Vars in place
of putting it all in the mpirun line:
export OMPI_MCA_btl_sm_eager_limit=40960
See:
http://www.open-mpi.org/faq/?category=tuning
Brock Palen
www.umich.edu/~brockp
Center for Advanced Computing
bro...@umich.edu
(734)936-1985
On Dec 5, 2008, at 12:22 PM, Justin wrote:
Hi,
We are currently using OpenMPI 1.3 on Ranger for large processor
jobs (8K+). Our code appears to be occasionally deadlocking at
random within point to point communication (see stacktrace below).
This code has been tested on many different MPI versions and as far
as we know it does not contain a deadlock. However, in the past we
have ran into problems with shared memory optimizations within MPI
causing deadlocks. We can usually avoid these by setting a few
environment variables to either increase the size of shared memory
buffers or disable shared memory optimizations all together. Does
OpenMPI have any known deadlocks that might be causing our
deadlocks? If are there any work arounds? Also how do we disable
shared memory within OpenMPI?
Here is an example of where processors are hanging:
#0 0x00002b2df3522683 in mca_btl_sm_component_progress () from /
opt/apps/intel10_1/openmpi/1.3/lib/openmpi/mca_btl_sm.so
#1 0x00002b2df2cb46bf in mca_bml_r2_progress () from /opt/apps/
intel10_1/openmpi/1.3/lib/openmpi/mca_bml_r2.so
#2 0x00002b2df0032ea4 in opal_progress () from /opt/apps/intel10_1/
openmpi/1.3/lib/libopen-pal.so.0
#3 0x00002b2ded0d7622 in ompi_request_default_wait_some () from /
opt/apps/intel10_1/openmpi/1.3//lib/libmpi.so.0
#4 0x00002b2ded109e34 in PMPI_Waitsome () from /opt/apps/intel10_1/
openmpi/1.3//lib/libmpi.so.0
Thanks,
Justin
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