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gh-112075: Avoid locking shared keys on every assignment #116087

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merged 2 commits into from
Feb 29, 2024
Merged

gh-112075: Avoid locking shared keys on every assignment #116087

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22d7bfb
Avoid locking shared keys on every assignment
DinoV Feb 29, 2024
8812f5b
Assert we don't get -1 from hashing exact unicode, lock in _PyObject_…
DinoV Feb 29, 2024
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32 changes: 20 additions & 12 deletions Objects/dictobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1597,19 +1597,11 @@ insertion_resize(PyInterpreterState *interp, PyDictObject *mp, int unicode)
}

static Py_ssize_t
insert_into_splitdictkeys(PyDictKeysObject *keys, PyObject *name)
insert_into_splitdictkeys(PyDictKeysObject *keys, PyObject *name, Py_hash_t hash)
{
assert(PyUnicode_CheckExact(name));
ASSERT_KEYS_LOCKED(keys);

Py_hash_t hash = unicode_get_hash(name);
if (hash == -1) {
hash = PyUnicode_Type.tp_hash(name);
if (hash == -1) {
PyErr_Clear();
return DKIX_EMPTY;
}
}
Py_ssize_t ix = unicodekeys_lookup_unicode(keys, name, hash);
if (ix == DKIX_EMPTY) {
if (keys->dk_usable <= 0) {
Expand Down Expand Up @@ -6692,8 +6684,25 @@ _PyObject_StoreInstanceAttribute(PyObject *obj, PyDictValues *values,
assert(Py_TYPE(obj)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
Py_ssize_t ix = DKIX_EMPTY;
if (PyUnicode_CheckExact(name)) {
LOCK_KEYS(keys);
ix = insert_into_splitdictkeys(keys, name);
Py_hash_t hash = unicode_get_hash(name);
if (hash == -1) {
hash = PyUnicode_Type.tp_hash(name);
assert(hash != -1);
}

#ifdef Py_GIL_DISABLED
// Try a thread-safe lookup to see if the index is already allocated
ix = unicodekeys_lookup_unicode_threadsafe(keys, name, hash);
if (ix == DKIX_EMPTY) {
// Lock keys and do insert
LOCK_KEYS(keys);
ix = insert_into_splitdictkeys(keys, name, hash);
UNLOCK_KEYS(keys);
}
#else
ix = insert_into_splitdictkeys(keys, name, hash);
#endif

#ifdef Py_STATS
if (ix == DKIX_EMPTY) {
if (PyUnicode_CheckExact(name)) {
Expand All @@ -6709,7 +6718,6 @@ _PyObject_StoreInstanceAttribute(PyObject *obj, PyDictValues *values,
}
}
#endif
UNLOCK_KEYS(keys);
}
if (ix == DKIX_EMPTY) {
PyObject *dict = make_dict_from_instance_attributes(
Expand Down
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