[3.14] GH-139951: Fix major GC performance regression. Backport of GH-140262 (GH-140447)

* Count number of actually tracked objects, instead of trackable objects. This ensures that untracking tuples has the desired effect of reducing GC overhead
* Do not track most untrackable tuples during creation. This prevents large numbers of small tuples causing execessive GCs.

Objects/tupleobject.c

@@ -156,6 +156,18 @@ _PyTuple_MaybeUntrack(PyObject *op)
     _PyObject_GC_UNTRACK(op);
 }
 
+/* Fast, but conservative check if an object maybe tracked
+   May return true for an object that is not tracked,
+   Will always return true for an object that is tracked.
+   This is a temporary workaround until _PyObject_GC_IS_TRACKED
+   becomes fast and safe to call on non-GC objects.
+*/
+static bool
+maybe_tracked(PyObject *ob)
+{
+    return _PyType_IS_GC(Py_TYPE(ob));
+}
+
 PyObject *
 PyTuple_Pack(Py_ssize_t n, ...)
 {
@@ -163,6 +175,7 @@ PyTuple_Pack(Py_ssize_t n, ...)
     PyObject *o;
     PyObject **items;
     va_list vargs;
+    bool track = false;
 
     if (n == 0) {
         return tuple_get_empty();
@@ -177,10 +190,15 @@ PyTuple_Pack(Py_ssize_t n, ...)
     items = result->ob_item;
     for (i = 0; i < n; i++) {
         o = va_arg(vargs, PyObject *);
+        if (!track && maybe_tracked(o)) {
+            track = true;
+        }
         items[i] = Py_NewRef(o);
     }
     va_end(vargs);
-    _PyObject_GC_TRACK(result);
+    if (track) {
+        _PyObject_GC_TRACK(result);
+    }
     return (PyObject *)result;
 }
 
@@ -377,11 +395,17 @@ _PyTuple_FromArray(PyObject *const *src, Py_ssize_t n)
         return NULL;
     }
     PyObject **dst = tuple->ob_item;
+    bool track = false;
     for (Py_ssize_t i = 0; i < n; i++) {
         PyObject *item = src[i];
+        if (!track && maybe_tracked(item)) {
+            track = true;
+        }
         dst[i] = Py_NewRef(item);
     }
-    _PyObject_GC_TRACK(tuple);
+    if (track) {
+        _PyObject_GC_TRACK(tuple);
+    }
     return (PyObject *)tuple;
 }
 
@@ -396,10 +420,17 @@ _PyTuple_FromStackRefStealOnSuccess(const _PyStackRef *src, Py_ssize_t n)
         return NULL;
     }
     PyObject **dst = tuple->ob_item;
+    bool track = false;
     for (Py_ssize_t i = 0; i < n; i++) {
-        dst[i] = PyStackRef_AsPyObjectSteal(src[i]);
+        PyObject *item = PyStackRef_AsPyObjectSteal(src[i]);
+        if (!track && maybe_tracked(item)) {
+            track = true;
+        }
+        dst[i] = item;
+    }
+    if (track) {
+        _PyObject_GC_TRACK(tuple);
     }
-    _PyObject_GC_TRACK(tuple);
     return (PyObject *)tuple;
 }