[mvapich-discuss] MV2_CPU_MAPPING in 1.2-rc1

[Manfred Muecke]

Hi,

I tried to test the user defined CPU (Core) Mapping (as described in
http://mvapich.cse.ohio-state.edu/support/user_guide_mvapich2-1.2rc1.html#x1-320006.8),
but fail to see any effect.

I work on a Sun Cluster with two DualCore Opterons per node, Infiniband
interconnect and running Solaris 10 1/06. Some time ago, I wrote a small
DTrace script showing task migration of my application. Running the
application with four processes on a single node (four cores) without the
use of MV2_CPU_MAPPING results in each process being assigned to a
different node but with the processes migrating happily back and forth
every few milliseconds. Below is a snippet of the output for a single
process.

    49052us pid: 4379: cpu1 -> cpu3
    60327us pid: 4379: cpu3 -> cpu0
    64067us pid: 4379: cpu0 -> cpu1
    68705us pid: 4379: cpu1 -> cpu0
    70325us pid: 4379: cpu0 -> cpu1
    72929us pid: 4379: cpu1 -> cpu0
    73176us pid: 4379: cpu0 -> cpu3

With MVAPICH 1.0, I succeeded to get rid of the task migration using
VIADEV_CPU_MAPPING.

Now with MVAPICH2 1.2rc1 (the first version of MVAPICH2 supporting CPU
mapping - thanks a lot, BTW), I tried again:
"mpdrun -np 4 -env MV2_ENABLE_AFFINITY 1 -env MV2_CPU_MAPPING 0:1:2:3 a.out"
which results in the following output (again for a single process only):

    79040us pid: 4438: cpu2 -> cpu3
    79662us pid: 4438: cpu3 -> cpu2
    83276us pid: 4438: cpu2 -> cpu3
    97615us pid: 4438: cpu3 -> cpu1
    98513us pid: 4438: cpu1 -> cpu3
    99471us pid: 4438: cpu3 -> cpu1
    99794us pid: 4438: cpu1 -> cpu0

Again, the tasks migrate every few milliseconds. It seems like setting
MV2_CPU_MAPPING has no effect on my system.

What is your preffered way of verifying this functionality? Do you have
any suggestions on other parameters in my configuration to check?

Thanks, Manfred



-- 
Manfred Mücke
Research Lab Computational Technologies and Applications
rlcta.univie.ac.at      Lenaugasse 2, 1080 Wien, AUSTRIA