gh-126703: add freelist for ints with small number of digits

Include/internal/pycore_freelist_state.h

@@ -18,6 +18,7 @@ extern "C" {
 #  define Py_floats_MAXFREELIST 100
 #  define Py_complexes_MAXFREELIST 100
 #  define Py_ints_MAXFREELIST 100
+#  define PyLong_MAXSAVESIZE 6     // Keep freelists for all ints with less than this number of digits
 #  define Py_slices_MAXFREELIST 1
 #  define Py_ranges_MAXFREELIST 6
 #  define Py_range_iters_MAXFREELIST 6
@@ -46,8 +47,8 @@ struct _Py_freelist {
 struct _Py_freelists {
     struct _Py_freelist floats;
     struct _Py_freelist complexes;
-    struct _Py_freelist ints;
     struct _Py_freelist tuples[PyTuple_MAXSAVESIZE];
+    struct _Py_freelist ints[PyLong_MAXSAVESIZE];
     struct _Py_freelist lists;
     struct _Py_freelist list_iters;
     struct _Py_freelist tuple_iters;

Misc/NEWS.d/next/Core_and_Builtins/2025-02-04-10-53-18.gh-issue-126703.RpjKez.rst

@@ -0,0 +1 @@
+Increase usage of freelist for :class:`int` allocation.

Objects/longobject.c

@@ -155,6 +155,29 @@ long_normalize(PyLongObject *v)
 # define MAX_LONG_DIGITS ((INT64_MAX-1) / PyLong_SHIFT)
 #endif
 
+static inline int
+maybe_freelist_push(PyObject *self)
+{
+    assert(PyLong_CheckExact(self));
+
+    PyLongObject *op = (PyLongObject *)self;
+    Py_ssize_t ndigits = _PyLong_DigitCount(op);
+
+    /* A value that normalized to zero still owns a buffer of at least one
+     * digit (long_alloc always allocates max(size, 1) digits), so it can be
+     * reused as a 1-digit int.  Bucketing it at index 0 would strand it:
+     * long_alloc never requests bucket 0 (it clamps ndigits to >= 1). */
+    if (ndigits == 0) {
+        ndigits = 1;
+    }
+
+    if (ndigits < PyLong_MAXSAVESIZE) {
+        return _Py_FREELIST_PUSH(ints[ndigits], self, Py_ints_MAXFREELIST);
+    }
+    return 0;
+}
+
+
 static PyLongObject *
 long_alloc(Py_ssize_t size)
 {
@@ -169,8 +192,8 @@ long_alloc(Py_ssize_t size)
      * assume that there is always at least one digit present. */
     Py_ssize_t ndigits = size ? size : 1;
 
-    if (ndigits == 1) {
-        result = (PyLongObject *)_Py_FREELIST_POP(PyLongObject, ints);
+    if (ndigits < PyLong_MAXSAVESIZE ) {
+        result = (PyLongObject *)_Py_FREELIST_POP(PyLongObject, ints[ndigits]);
     }
     if (result == NULL) {
         /* Number of bytes needed is: offsetof(PyLongObject, ob_digit) +
@@ -253,7 +276,7 @@ _PyLong_FromMedium(sdigit x)
     assert(!IS_SMALL_INT(x));
     assert(is_medium_int(x));
 
-    PyLongObject *v = (PyLongObject *)_Py_FREELIST_POP(PyLongObject, ints);
+    PyLongObject *v = (PyLongObject *)_Py_FREELIST_POP(PyLongObject, ints[1]);
     if (v == NULL) {
         v = PyObject_Malloc(sizeof(PyLongObject));
         if (v == NULL) {
@@ -334,7 +357,7 @@ medium_from_stwodigits(stwodigits x)
     if(!is_medium_int(x)) {
         return PyStackRef_NULL;
     }
-    PyLongObject *v = (PyLongObject *)_Py_FREELIST_POP(PyLongObject, ints);
+    PyLongObject *v = (PyLongObject *)_Py_FREELIST_POP(PyLongObject, ints[1]);
     if (v == NULL) {
         v = PyObject_Malloc(sizeof(PyLongObject));
         if (v == NULL) {
@@ -3640,11 +3663,10 @@ _PyLong_ExactDealloc(PyObject *self)
         _Py_SetImmortal(self);
         return;
     }
-    if (_PyLong_IsCompact((PyLongObject *)self)) {
-        _Py_FREELIST_FREE(ints, self, PyObject_Free);
-        return;
+
+    if (!maybe_freelist_push(self)) {
+        PyObject_Free(self);
     }
-    PyObject_Free(self);
 }
 
 static void
@@ -3660,10 +3682,13 @@ long_dealloc(PyObject *self)
         _Py_SetImmortal(self);
         return;
     }
-    if (PyLong_CheckExact(self) && _PyLong_IsCompact((PyLongObject *)self)) {
-        _Py_FREELIST_FREE(ints, self, PyObject_Free);
+    if (PyLong_CheckExact(self))  {
+        if (!maybe_freelist_push(self)) {
+            PyObject_Free(self);
+        }
         return;
     }
+
     Py_TYPE(self)->tp_free(self);
 }
 

Objects/object.c

@@ -932,6 +932,9 @@
     for (Py_ssize_t i = 0; i < PyTuple_MAXSAVESIZE; i++) {
         clear_freelist(&freelists->tuples[i], is_finalization, free_object);
     }
+    for (Py_ssize_t i = 0; i < PyLong_MAXSAVESIZE; i++) {
+        clear_freelist(&freelists->ints[i], is_finalization, free_object);
+    }
     clear_freelist(&freelists->lists, is_finalization, free_object);
     clear_freelist(&freelists->list_iters, is_finalization, free_object);
     clear_freelist(&freelists->tuple_iters, is_finalization, free_object);
@@ -951,7 +954,7 @@
     }
     clear_freelist(&freelists->unicode_writers, is_finalization, PyMem_Free);
     clear_freelist(&freelists->bytes_writers, is_finalization, PyMem_Free);
     clear_freelist(&freelists->ints, is_finalization, free_object);
     clear_freelist(&freelists->pycfunctionobject, is_finalization, PyObject_GC_Del);
     clear_freelist(&freelists->pycmethodobject, is_finalization, PyObject_GC_Del);
     clear_freelist(&freelists->pymethodobjects, is_finalization, free_object);