diff -r 9dd59c32e7f0 Modules/_testcapimodule.c
--- a/Modules/_testcapimodule.c	Wed Jan 13 17:08:33 2016 +0100
+++ b/Modules/_testcapimodule.c	Wed Jan 13 17:09:19 2016 +0100
@@ -3584,6 +3584,49 @@ dict_set_version(PyObject *self, PyObjec
     Py_RETURN_NONE;
 }
 
+static PyObject *
+guard_benchmark(PyObject *self, PyObject *args)
+{
+    _PyTime_t before, after, dt, best;
+    Py_ssize_t run, nrun = 100, loop, nloop = 10 * 1000 * 1000;
+    PyObject *dict, *key;
+    PyFuncGuardObject *guard;
+
+    if (!PyArg_ParseTuple(args, "O!O!O!",
+                          &PyDict_Type, &dict,
+                          &PyUnicode_Type, &key,
+                          &PyFuncGuard_Type, &guard))
+        return NULL;
+
+    best = 0;
+    for (run=0; run < nrun; run++) {
+        before = _PyTime_GetMonotonicClock();
+        for (loop=0; loop<nloop; loop++) {
+#if 0
+            PyObject *res = PyObject_GetItem(dict, key);
+            if (res == NULL)
+                return NULL;
+            Py_DECREF(res);
+#elif 0
+            PyObject *res = PyDict_GetItem(dict, key);
+            if (res == NULL)
+                return NULL;
+#else
+            int res = guard->check((PyObject *)guard, NULL, 0, 0);
+            if (res)
+                return NULL;
+#endif
+        }
+        after = _PyTime_GetMonotonicClock();
+
+        dt = after - before;
+        if (best == 0 || dt < best)
+            best = dt;
+    }
+
+    return PyFloat_FromDouble(_PyTime_AsSecondsDouble(best) / nloop);
+}
+
 
 static PyMethodDef TestMethods[] = {
     {"raise_exception",         raise_exception,                 METH_VARARGS},
@@ -3763,6 +3806,7 @@ static PyMethodDef TestMethods[] = {
     {"get_recursion_depth", get_recursion_depth, METH_NOARGS},
     {"dict_get_version", dict_get_version, METH_VARARGS},
     {"dict_set_version", dict_set_version, METH_VARARGS},
+    {"guard_benchmark", guard_benchmark, METH_VARARGS},
     {NULL, NULL} /* sentinel */
 };