foo.erl

-module(foo).

-export([test/0,
         export_me/1]).


export_me(_N) ->
    nono.

test() ->
    A = timer:tc(fun() ->
                         erlang:function_exported(foo, export_me, 1)
                 end),
    B = timer:tc(fun() ->
                         code:which(foo)
                 end),
    {A, B}.