diff -up ./byterun/sys.h.orig ./byterun/sys.h
--- ./byterun/sys.h.orig	2007-02-25 13:38:36.000000000 +0100
+++ ./byterun/sys.h	2007-10-03 15:42:18.000000000 +0200
@@ -27,4 +27,6 @@ CAMLextern value caml_sys_exit (value);
 
 extern char * caml_exe_name;
 
+double caml_tick (void);
+
 #endif /* CAML_SYS_H */
diff -up ./byterun/minor_gc.c.orig ./byterun/minor_gc.c
--- ./byterun/minor_gc.c.orig	2005-09-22 16:21:50.000000000 +0200
+++ ./byterun/minor_gc.c	2007-10-03 15:42:18.000000000 +0200
@@ -27,6 +27,9 @@
 #include "roots.h"
 #include "signals.h"
 
+#include "alloc.h"
+#include "sys.h"
+
 asize_t caml_minor_heap_size;
 CAMLexport char *caml_young_start = NULL, *caml_young_end = NULL;
 CAMLexport char *caml_young_ptr = NULL, *caml_young_limit = NULL;
@@ -35,6 +38,20 @@ CAMLexport value **caml_ref_table_ptr = 
 static asize_t ref_table_size, ref_table_reserve;
 int caml_in_minor_collection = 0;
 
+static int caml_gc_timing;
+double caml_gc_time = 0.;
+
+CAMLprim value caml_get_gc_time (value unit)
+{
+  return caml_copy_double (caml_gc_time);
+}
+
+CAMLprim value caml_set_gc_timing (value v)
+{
+  caml_gc_timing = Bool_val (v);
+  return Val_unit;
+}
+
 void caml_set_minor_heap_size (asize_t size)
 {
   char *new_heap;
@@ -217,8 +234,13 @@ void caml_empty_minor_heap (void)
 */
 CAMLexport void caml_minor_collection (void)
 {
+  double t_start, t_end;
+
   intnat prev_alloc_words = caml_allocated_words;
 
+  if (caml_gc_timing)
+    t_start = caml_tick ();
+
   caml_empty_minor_heap ();
 
   caml_stat_promoted_words += caml_allocated_words - prev_alloc_words;
@@ -229,6 +251,12 @@ CAMLexport void caml_minor_collection (v
   caml_final_do_calls ();
 
   caml_empty_minor_heap ();
+
+  if (caml_gc_timing) 
+    {
+      t_end = caml_tick ();
+      caml_gc_time += t_end - t_start;
+    }
 }
 
 CAMLexport value caml_check_urgent_gc (value extra_root)
diff -up ./byterun/sys.c.orig ./byterun/sys.c
--- ./byterun/sys.c.orig	2007-03-01 14:37:39.000000000 +0100
+++ ./byterun/sys.c	2007-10-03 15:42:18.000000000 +0200
@@ -344,3 +344,54 @@ CAMLprim value caml_sys_read_directory(v
   caml_ext_table_free(&tbl, 1);
   CAMLreturn(result);
 }
+
+
+#include <math.h>
+static long dumb_gettime (clockid_t i, struct timespec *ts)
+{
+  double t = clock () / (double) CLOCKS_PER_SEC;
+  ts->tv_sec  = t;
+  ts->tv_nsec = (t - floor(t)) * 1e9;
+  return 0;
+}
+
+static long (* gettime)(clockid_t, struct timespec *);
+
+#include <dlfcn.h>
+static void init_gettime ()
+{
+  void *h;
+  h = dlopen ("librt.so", RTLD_LAZY);
+  if (! h)
+    goto fail;
+  dlerror ();
+  *(void **)(&gettime) = dlsym (h, "clock_gettime");
+  if (dlerror () != NULL)
+    {
+      dlclose (h);
+      goto fail;
+    }
+  return;
+
+ fail:
+  gettime = dumb_gettime;
+}
+
+
+double caml_tick ()
+{
+  struct timespec tp;
+
+  if (! gettime)
+    init_gettime();
+
+  if (gettime (CLOCK_PROCESS_CPUTIME_ID, &tp))
+    abort();
+
+  return tp.tv_sec + (1.e-9) * tp.tv_nsec;
+}
+
+CAMLprim value caml_get_tick (value unit)
+{
+  return caml_copy_double (caml_tick ());
+}