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Subject: [OMPI users] Number of file handles limiting the number off processes?
From: Samuel Sarholz (sarholz_at_[hidden])
Date: 2008-07-10 08:04:12


Hi,

mpiexec seems to need a file handle per started process.
By default the number of file handles is set to 1024 here, thus I can
start about 900 something processes.

With higher numbers I get
mca_oob_tcp_accept: accept() failed: Too many open files (24).

If I decrease the file handles on the shell I run mpiexec from, I get
the error with less processes. However no MPI process is started on the
local machine.

The first thing I am wondering about is the TCP because Infiniband is
used for communication.
And secondly what are the files/connections used for?

Do I really have to set the file handles to 5000 (and to 32000 in a few
years) for large MPI programs or is there a workaround?

Another thing that I don't get is that the problem only arises if I
start an MPI program.
mpiexec -np 2000 hostname
works fine.

best regards,
Samuel