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gh-141510: Optimize PyDict_Copy() for frozendict #145509

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Merged
vstinner merged 1 commit into from
Mar 4, 2026
+41 −17
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gh-141510: Optimize PyDict_Copy() for frozendict #145509

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58 changes: 41 additions & 17 deletions Objects/dictobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -896,24 +896,20 @@ free_values(PyDictValues *values, bool use_qsbr)
PyMem_Free(values);
}

/* Consumes a reference to the keys object */
static PyObject *
new_dict(PyDictKeysObject *keys, PyDictValues *values,
Py_ssize_t used, int free_values_on_failure)
static inline PyObject *
new_dict_impl(PyDictObject *mp, PyDictKeysObject *keys,
PyDictValues *values, Py_ssize_t used,
int free_values_on_failure)
{
assert(keys != NULL);
PyDictObject *mp = _Py_FREELIST_POP(PyDictObject, dicts);
if (mp == NULL) {
mp = PyObject_GC_New(PyDictObject, &PyDict_Type);
if (mp == NULL) {
dictkeys_decref(keys, false);
if (free_values_on_failure) {
free_values(values, false);
}
return NULL;
dictkeys_decref(keys, false);
if (free_values_on_failure) {
free_values(values, false);
}
return NULL;
}
assert(Py_IS_TYPE(mp, &PyDict_Type));

mp->ma_keys = keys;
mp->ma_values = values;
mp->ma_used = used;
Expand All @@ -923,6 +919,29 @@ new_dict(PyDictKeysObject *keys, PyDictValues *values,
return (PyObject *)mp;
}

/* Consumes a reference to the keys object */
static PyObject *
new_dict(PyDictKeysObject *keys, PyDictValues *values,
Py_ssize_t used, int free_values_on_failure)
{
PyDictObject *mp = _Py_FREELIST_POP(PyDictObject, dicts);
if (mp == NULL) {
mp = PyObject_GC_New(PyDictObject, &PyDict_Type);
}
assert(mp == NULL || Py_IS_TYPE(mp, &PyDict_Type));

return new_dict_impl(mp, keys, values, used, free_values_on_failure);
}

/* Consumes a reference to the keys object */
static PyObject *
new_frozendict(PyDictKeysObject *keys, PyDictValues *values,
Py_ssize_t used, int free_values_on_failure)
{
PyDictObject *mp = PyObject_GC_New(PyDictObject, &PyFrozenDict_Type);
return new_dict_impl(mp, keys, values, used, free_values_on_failure);
}

static PyObject *
new_dict_with_shared_keys(PyDictKeysObject *keys)
{
Expand Down Expand Up @@ -4313,8 +4332,7 @@ copy_lock_held(PyObject *o, int as_frozendict)

if (Py_TYPE(mp)->tp_iter == dict_iter &&
mp->ma_values == NULL &&
(mp->ma_used >= (mp->ma_keys->dk_nentries * 2) / 3) &&
!as_frozendict)
(mp->ma_used >= (mp->ma_keys->dk_nentries * 2) / 3))
{
/* Use fast-copy if:

Expand All @@ -4334,9 +4352,15 @@ copy_lock_held(PyObject *o, int as_frozendict)
if (keys == NULL) {
return NULL;
}
PyDictObject *new = (PyDictObject *)new_dict(keys, NULL, 0, 0);
PyDictObject *new;
if (as_frozendict) {
new = (PyDictObject *)new_frozendict(keys, NULL, 0, 0);
}
else {
new = (PyDictObject *)new_dict(keys, NULL, 0, 0);
}
if (new == NULL) {
/* In case of an error, `new_dict()` takes care of
/* In case of an error, new_dict()/new_frozendict() takes care of
cleaning up `keys`. */
return NULL;
}
Expand Down
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