> Indeed, after you defunctorize what performance penalties are left by modules?

Indeed, really depends on the context ;-).

If you don't use many operations which come from a functor application 
(compared with the number of costly operations in your application), the 
performance penalty of a functor application is probably not relevant.

However, in some cases, defunctorization may produce a good speedup, 
especially if you use massive inlining (e.g. ocamlopt -inline 1000). On 
the contrary, defunctorization may produce cache problem because the size 
of the defunctorized code may be very bigger than the size of the initial 
code.

Julien
-- 
mailto:Julien.Signoles@lri.fr ; http://www.lri.fr/~signoles
"In theory, practice and theory are the same,
but in practice they are different" (Larry McVoy)