As a general rule for paralellization: avoid network trafic and access to physical devices. In matlab don't use too much load/save, close, figure, etc.
Useful commands in linux are w, ps, top. W shows you how many users are logged in and what they are doing.
How many matlabs are running?
for i in `seq 0 7` ; do ssh node$i "ps aux | grep -i matlab | grep -v helper | grep -v grep" ; done