Yep, there are indeed two progress threads running - and no, you cannot disable
them. They are, however, “blocked” so they aren’t eating any cycles during
normal operation unless an event that requires their attention wakes them up.
So they shouldn’t interfere with your app.
> On Aug 4, 2016, at 4:23 PM, Jaime Arteaga <jandres...@gmail.com> wrote:
>
> Hi:
>
> When running a simple MPI program in the form of:
>
> int main()
> {
> ...
> MPI_Init();
> ...
> sleep(10);
> ...
> MPI_Finalize();
> ...
> }
>
> Two threads, additionally to the master, can be seen when using gstack:
>
>
> Thread 3 (Thread 0x7f2238a6c700 (LWP 106578)):
> #0 0x00007f223a869783 in epoll_wait () from /lib64/libc.so.6
> #1 0x00007f223a268983 in epoll_dispatch (base=0x1be76c0, tv=<optimized out>)
> at epoll.c:407
> #2 0x00007f223a26c3d0 in opal_libevent2022_event_base_loop (base=0x1be76c0,
> flags=1) at event.c:1630
> #3 0x00007f2238a91b9d in progress_engine () from
> ../openmpi-2.0.0/lib/openmpi/mca_pmix_pmix112.so
> #4 0x00007f223ab3bdf5 in start_thread () from /lib64/libpthread.so.0
> #5 0x00007f223a8691ad in clone () from /lib64/libc.so.6
> Thread 2 (Thread 0x7f2233fff700 (LWP 106579)):
> #0 0x00007f223a85eb7d in poll () from /lib64/libc.so.6
> #1 0x00007f223a274736 in poll_dispatch (base=0x1be8bd0, tv=0x7f2233ffeea0)
> at poll.c:165
> #2 0x00007f223a26c3d0 in opal_libevent2022_event_base_loop (base=0x1be8bd0,
> flags=1) at event.c:1630
> #3 0x00007f223a23115e in progress_engine () from
> .../openmpi-2.0.0/lib/libopen-pal.so.20
> #4 0x00007f223ab3bdf5 in start_thread () from /lib64/libpthread.so.0
> #5 0x00007f223a8691ad in clone () from /lib64/libc.so.6
> Thread 1 (Thread 0x7f223b23e740 (LWP 106577)):
> #0 0x00007f223a83048d in nanosleep () from /lib64/libc.so.6
> #1 0x00007f223a830324 in sleep () from /lib64/libc.so.6
> #2 0x0000000000400acb in main (argc=1, argv=0x7fffd6e7b498)
>
> What are these threads designation? Are they progress threads?
>
> Also, if I'd wanted to disable the extra threads, so there was only one
> thread (the master one), how could I do it?
>
>
> Info:
>
> OpenMPI used: 2.0.0
>
> Command used: mpirun -machinefile ~/hostfile --n 2 --map-by node ./test
>
> Thanks!
>
> Jaime
>
>
>
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