Open MPI logo

Open MPI User's Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Open MPI User's mailing list

Subject: [OMPI users] poll taking too long in open-mpi
From: Dick Kachuma (dickkachuma_at_[hidden])
Date: 2011-08-23 16:24:26

I have used gprof to profile a program that uses openmpi. The result
shows that the code spends a long time in poll (37% on 8 cores, 50% on
16 and 85% on 32). I was wondering if there is anything I can do to
reduce the time spent in poll. I cannot determine the number of calls
made to poll and exactly where they are. The bulk of my code uses
exclusively MPI_Ssend for the send and MPI_Irecv and MPI_Wait for the
receive. For instance, would there be any gain expected if I switch
from MPI_Ssend to MPI_Send? Alternatively would there be any gain in
switching to MPI_Isend/MPI_Recv instead of MPI_Ssend/MPI_Irecv?

Some details:
open-mpi 1.4.3
gcc 4.1.2
Redhat EL5 x86_64
I am using the sm and tcp btls on nodes with 8 cores (2 quad cores)
each (so 4 nodes for 32 cores).
Intel Xeon 2.7GHz