gh-115605 Use QSBR technique for list_new/free

corona10 · corona10 · commit de494744d4a9 · 2024-02-24T15:46:06.000+09:00
diff --git a/Objects/listobject.c b/Objects/listobject.c
@@ -31,12 +31,12 @@ get_list_freelist(void)
 }
 #endif
 
+#ifdef Py_GIL_DISABLED
 static size_t
 list_good_size(Py_ssize_t size)
 {
     // 4, 8, 16, 24, 32, 40, 48, 64, 80, ...
     // NOTE: we add one here so that the rounding accounts for the "allocated"
-    // field in _PyListArray.
     size_t reqsize = (size_t)size + 1;
     if (reqsize <= 4) {
         reqsize = 4;
@@ -67,6 +67,7 @@ list_allocate_items(size_t capacity)
     PyObject **items = PyMem_Malloc(capacity * sizeof(PyObject *));
     return items;
 }
+#endif
 
 static PyListObject *
 list_new(Py_ssize_t size)
@@ -699,7 +700,7 @@ list_repeat(PyObject *aa, Py_ssize_t n)
 }
 
 static void
-list_clear(PyListObject *a)
+list_clear_impl(PyListObject *a, bool is_resize)
 {
     PyObject **items = a->ob_item;
     if (items == NULL) {
@@ -716,16 +717,31 @@ list_clear(PyListObject *a)
         Py_XDECREF(items[i]);
     }
     // TODO: Use QSBR technique, if the list is shared between threads,
-    PyMem_Free(items);
-
+#ifdef Py_GIL_DISABLED
+    bool use_qsbr = is_resize && _PyObject_GC_IS_SHARED(a);
+#else
+    bool use_qsbr = false;
+#endif
+    if (use_qsbr) {
+        _PyMem_FreeDelayed(items);
+    }
+    else {
+        PyMem_Free(items);
+    }
     // Note that there is no guarantee that the list is actually empty
     // at this point, because XDECREF may have populated it indirectly again!
 }
 
+static void
+list_clear(PyListObject *a)
+{
+    list_clear_impl(a, true);
+}
+
 static int
 list_clear_slot(PyObject *self)
 {
-    list_clear((PyListObject *)self);
+    list_clear_impl((PyListObject *)self, false);
     return 0;
 }
 
