Issue #4688: Add a heuristic so that tuples and dicts containing only
untrackable objects are not tracked by the garbage collector. This can
reduce the size of collections and therefore the garbage collection overhead
on long-running programs, depending on their particular use of datatypes.
(trivia: this makes the "binary_trees" benchmark from the Computer Language
Shootout 40% faster)
diff --git a/Include/objimpl.h b/Include/objimpl.h
index ef47218..55186b1 100644
--- a/Include/objimpl.h
+++ b/Include/objimpl.h
@@ -285,6 +285,17 @@
g->gc.gc_next = NULL; \
} while (0);
+/* True if the object is currently tracked by the GC. */
+#define _PyObject_GC_IS_TRACKED(o) \
+ ((_Py_AS_GC(o))->gc.gc_refs != _PyGC_REFS_UNTRACKED)
+
+/* True if the object may be tracked by the GC in the future, or already is.
+ This can be useful to implement some optimizations. */
+#define _PyObject_GC_MAY_BE_TRACKED(obj) \
+ (PyObject_IS_GC(obj) && \
+ (!PyTuple_CheckExact(obj) || _PyObject_GC_IS_TRACKED(obj)))
+
+
PyAPI_FUNC(PyObject *) _PyObject_GC_Malloc(size_t);
PyAPI_FUNC(PyObject *) _PyObject_GC_New(PyTypeObject *);
PyAPI_FUNC(PyVarObject *) _PyObject_GC_NewVar(PyTypeObject *, Py_ssize_t);