Speed up Simulink model which uses a Matlab function block

Hello,

I would like to speed up the running of my Simulink model that uses a Matlab function block. Without that function block my model runs fine and fast. When running the function in isolation, I timed it to 0.07s using tic/toc. But when I include the function block in my Simulink model, it runs very slow (even when the function block is not connected to anything).

Is that a normal behavior or is there anything to improve?

Thanks!