gmm-verbose

gmm-verbose is a variable defined in `gmm-utils.el'.
Its value is

7

Documentation:
Integer that says how verbose gmm should be.
The higher the number, the more messages will flash to say what
it did. At zero, it will be totally mute; at five, it will
display most important messages; and at ten, it will keep on
jabbering all the time.

You can customize this variable.