gh-122320: Limit dict key versions used by test_opcache. (gh-132961)

The `test_load_global_module()` test consumes a lot of dict key versions.
Skip the test if we have consumed half of the available versions that can be
used for the "load global" cache.

Author: nascheme

Lib/test/test_opcache.py

@@ -16,6 +16,16 @@
 _testinternalcapi = import_module("_testinternalcapi")
 
 
+def have_dict_key_versions():
+    # max version value that can be stored in the load global cache. This is
+    # determined by the type of module_keys_version and builtin_keys_version
+    # in _PyLoadGlobalCache, uint16_t.
+    max_version = 1<<16
+    # use a wide safety margin (use only half of what's available)
+    limit = max_version // 2
+    return _testinternalcapi.get_next_dict_keys_version() < limit
+
+
 class TestBase(unittest.TestCase):
     def assert_specialized(self, f, opname):
         instructions = dis.get_instructions(f, adaptive=True)
@@ -1029,6 +1039,8 @@ def write(items):
 
     @requires_specialization_ft
     def test_load_global_module(self):
+        if not have_dict_key_versions():
+            raise unittest.SkipTest("Low on dict key versions")
         def get_items():
             items = []
             for _ in range(self.ITEMS):

Modules/_testinternalcapi.c

@@ -1985,6 +1985,18 @@ gh_119213_getargs_impl(PyObject *module, PyObject *spam)
     return Py_NewRef(spam);
 }
 
+/*[clinic input]
+get_next_dict_keys_version
+[clinic start generated code]*/
+
+static PyObject *
+get_next_dict_keys_version_impl(PyObject *module)
+/*[clinic end generated code: output=e5405a509cf9d423 input=bd1cee7c6b9d3a3c]*/
+{
+    PyInterpreterState *interp = _PyInterpreterState_GET();
+    uint32_t keys_version = interp->dict_state.next_keys_version;
+    return PyLong_FromLong(keys_version);
+}
 
 static PyObject *
 get_static_builtin_types(PyObject *self, PyObject *Py_UNUSED(ignored))
@@ -2124,6 +2136,7 @@ static PyMethodDef module_functions[] = {
     {"get_tracked_heap_size", get_tracked_heap_size, METH_NOARGS},
     {"is_static_immortal", is_static_immortal, METH_O},
     {"incref_decref_delayed", incref_decref_delayed, METH_O},
+    GET_NEXT_DICT_KEYS_VERSION_METHODDEF
     {NULL, NULL} /* sentinel */
 };