[MPICH] An idle communication process use the same CPU as computation process on multi-core chips

Yusong Wang ywang25 at aps.anl.gov
Thu Sep 13 17:41:20 CDT 2007

Hi all,

I have a program which is implemented with a master/slave model and the
master just do very little computation. In my test, the master spent
most of its time to wait other process to finish MPI_Gather
communication (confirmed with jumpshot/MPE). In several tests on
different multi-core chips (dual-core, quad-core, 8-core), I found the
master use the same amount of CPU as the slaves, which should do all the
computation. There are only two exceptions that the master use near 0%
CPU (one on Window, one on Linux), which is what I expect. The tests
were did on both Fedora Linux and Widows with MPICH2 (shm/nemesis
mpd/smpd). I don't know if it is a software/system issue or caused by
different hardware. I would think this is  (at least )related with
hardware. As with the same operating system, I got different CPU usage
(near 0% or near 100%) for the master on different multi-core nodes of
our clusters.

Is there any documents I can check out for this issue? 



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