CAN overhead

What kind of overhead are people seeing when making CAN call?

We used CAN to control our flywheel. mostly for phyiscal wiring reasons, but I was expecting that CAN would be light wieght on the cRIO also, with the encoder work being done on the Jaguar. However simply setting speeds to the motor seemed to bump out CPU usage up by 20% to 25%. Is this just network overhead of the CAN bus, was the code going down error paths that I just didn’t notice?

details:
Programming in Labview
CAN connected by RS232
2 Jaguars each with 1 encoder
Jaguars programming set to RPM mode, 1 call to set speeed, 1 call to GetStatus in telop vi

Take a look at this thread.
http://chiefdelphi.com/forums/showthread.php?t=103977&highlight=CAN+bandwidth