Simple C call time benchmark

build.sh

#!/bin/sh
set -e
ocamlfind query bench || opam install bench
ocamlfind ocamlopt -linkpkg -o foo foo-c.c foo.ml -package unix,bench

foo-c.c

#include <caml/memory.h>

static int x = 0;

void foo_test(value nothing)
{
  CAMLparam0();
  ++x;
  CAMLreturn0;
 }

value foo_info(value nothing)
{
  CAMLparam0();
  CAMLreturn(Val_int(x));
}

foo.ml

external foo : unit -> unit = "foo_test"
external info : unit -> int = "foo_info"

let main () =
  Printf.printf "counter before: %d\n%!" (info ());
  Bench.bench [("call c function", foo)];
  Printf.printf "counter after: %d\n%!" (info ())

let _ = main ()