On Sat, Oct 02, 2010 at 01:37:42PM -0700, Zack Weinberg wrote: > I wrote a test MPI program that just calls MPI_Probe() once - this > should block forever, since there are no sends happening. When run > with > > $ mpirun -np 2 ./a.out > > MPI_Probe never returns and the processes spin through poll(), which > is what I originally reported. So far so good. If I change the > invocation to > > $ mpirun -np 2 --mca mpi_yield_when_idle 1 ./a.out > > the behavior is the same, except that the processes alternate between > poll() and sched_yield(). This doesn't help anything; the scheduler > is still being thrashed, and the CPU is not allowed to go idle. [In > fact, my understanding of the Linux scheduler is that a zero-timeout > poll() counts as a yield, so "Aggressive" mode isn't even doing > anything constructive!] > > The desired behavior is for an idle cluster's processes to BLOCK in > poll(). So mpi_yield_when_idle does not do what I want. > > Also, putting "mpi_yield_when_idle = 1" into > ~/.openmpi/mca-params.conf has no effect, contra the documentation -- > this perhaps ought to be its own bug. (I can set MCA parameters for R > with environment variables, but that's not nearly as convenient as the > host file.)
I'm out of ideas here. Jeff, could you please comment on the issue? You can find the full log here: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=598553 Thanks in advance! Best regards, Manuel -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
