This counter displays the total number of times arguments and return values have been marshaled from managed to unmanaged ...

This counter displays the total number of times arguments and return values have been marshaled from managed to unmanaged code and vice versa since the start of the application. This counter is not incremented if the stubs are inlined. (Stubs are responsible for marshalling arguments and return values). Stubs usually get inlined if the marshalling overhead is small.