gh-114312: Collect stats for unlikely events (GH-114493)

3 files changed, 30 insertions, 0 deletions

diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 0d5eec0..261622a 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -605,6 +605,12 @@ init_interp_create_gil(PyThreadState *tstate, int gil)
     _PyEval_InitGIL(tstate, own_gil);
 }
 
+static int
+builtins_dict_watcher(PyDict_WatchEvent event, PyObject *dict, PyObject *key, PyObject *new_value)
+{
+    RARE_EVENT_INC(builtin_dict);
+    return 0;
+}
 
 static PyStatus
 pycore_create_interpreter(_PyRuntimeState *runtime,
@@ -1266,6 +1272,14 @@ init_interp_main(PyThreadState *tstate)
         }
     }
 
+    if ((interp->rare_events.builtins_dict_watcher_id = PyDict_AddWatcher(&builtins_dict_watcher)) == -1) {
+        return _PyStatus_ERR("failed to add builtin dict watcher");
+    }
+
+    if (PyDict_Watch(interp->rare_events.builtins_dict_watcher_id, interp->builtins) != 0) {
+        return _PyStatus_ERR("failed to set builtin dict watcher");
+    }
+
     assert(!_PyErr_Occurred(tstate));
 
     return _PyStatus_OK();
@@ -1592,6 +1606,10 @@ static void
 finalize_modules(PyThreadState *tstate)
 {
     PyInterpreterState *interp = tstate->interp;
+
+    // Stop collecting stats on __builtin__ modifications during teardown
+    PyDict_Unwatch(interp->rare_events.builtins_dict_watcher_id, interp->builtins);
+
     PyObject *modules = _PyImport_GetModules(interp);
     if (modules == NULL) {
         // Already done
diff --git a/Python/pystate.c b/Python/pystate.c
index 548c77b..c9b5213 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -2616,6 +2616,7 @@ _PyInterpreterState_SetEvalFrameFunc(PyInterpreterState *interp,
     if (eval_frame != NULL) {
         _Py_Executors_InvalidateAll(interp);
     }
+    RARE_EVENT_INC(set_eval_frame_func);
     interp->eval_frame = eval_frame;
 }
 
diff --git a/Python/specialize.c b/Python/specialize.c
index 13e0440..a9efbe0 100644
--- a/Python/specialize.c
+++ b/Python/specialize.c
@@ -268,6 +268,16 @@ print_optimization_stats(FILE *out, OptimizationStats *stats)
 }
 
 static void
+print_rare_event_stats(FILE *out, RareEventStats *stats)
+{
+    fprintf(out, "Rare event (set_class): %" PRIu64 "\n", stats->set_class);
+    fprintf(out, "Rare event (set_bases): %" PRIu64 "\n", stats->set_bases);
+    fprintf(out, "Rare event (set_eval_frame_func): %" PRIu64 "\n", stats->set_eval_frame_func);
+    fprintf(out, "Rare event (builtin_dict): %" PRIu64 "\n", stats->builtin_dict);
+    fprintf(out, "Rare event (func_modification): %" PRIu64 "\n", stats->func_modification);
+}
+
+static void
 print_stats(FILE *out, PyStats *stats)
 {
     print_spec_stats(out, stats->opcode_stats);
@@ -275,6 +285,7 @@ print_stats(FILE *out, PyStats *stats)
     print_object_stats(out, &stats->object_stats);
     print_gc_stats(out, stats->gc_stats);
     print_optimization_stats(out, &stats->optimization_stats);
+    print_rare_event_stats(out, &stats->rare_event_stats);
 }
 
 void