cbworkloadgen gives no message about Thread when set -r as 0

I create a default bucket in cluster and use the following command:
./cbworkloadgen -r 0 -i 10000 -n 10.5.2.22:8091

When the process finishes, there is no message output like
"Thread 0 - average set time : 0.0025092941005 seconds , min : 0.000411033630371 seconds,
max : 0.0308890342712 seconds , operation timeouts 0"

The number of items generate is correct, 0, BTW