Writing to the pml_monitoring_flush variable will set the filename of
the output file.
Stopping a session for the pml_monitoring_flush will force the
generation of the nobitoring output file (as long as the filename
is not NULL).
To reset the monitoring, une has to bind the pml_monitoring_flush to a
session.
using performance variables "pml_monitoring_messages_count" and
"pml_monitoring_messages_size"
Per Brice suggestion make all data count and message length be
uint64_t.
counting or not the collective traffic as a separate entity. The need
for such a PML is simply because the PMPI interface doesn't allow us to
identify the collective generated traffic.
