Skip to content

gh-148906: fix scaling of descriptors on free-threading #148915

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
kumaraditya303 wants to merge 2 commits into
base: main
Choose a base branch
from
+32 −5
Open

gh-148906: fix scaling of descriptors on free-threading #148915

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
83193b5
fix scaling of descriptors on free-threading
kumaraditya303 Apr 23, 2026
dabfd09
drc only for descriptors
kumaraditya303 Apr 23, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
20 changes: 15 additions & 5 deletions Objects/typeobject.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6289,6 +6289,13 @@ _PyType_LookupStackRefAndVersion(PyTypeObject *type, PyObject *name, _PyStackRef

PyObject *res_obj = PyStackRef_AsPyObjectBorrow(*out);
#if Py_GIL_DISABLED
// Optimistically enable deferred refcounting on descriptors
Copy link
Copy Markdown
Contributor

@colesbury colesbury Apr 23, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Can we do this in type_setattro? That seems like a more logical place to me, and it's where we enable deferred reference counting on function objects.

Copy link
Copy Markdown
Contributor Author

@kumaraditya303 kumaraditya303 Apr 24, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Wouldn't that only work when the descriptor is assigned to the class after class is already created?

if (res_obj != NULL &&
PyType_IS_GC(Py_TYPE(res_obj)) &&
!_PyObject_HasDeferredRefcount(res_obj) &&
Py_TYPE(res_obj)->tp_descr_get != NULL) {
PyUnstable_Object_EnableDeferredRefcount(res_obj);
}
update_cache_gil_disabled(entry, name, version_tag, res_obj);
#else
PyObject *old_value = update_cache(entry, name, version_tag, res_obj);
Expand Down Expand Up @@ -10995,10 +11002,12 @@ static PyObject *
slot_tp_descr_get(PyObject *self, PyObject *obj, PyObject *type)
{
PyTypeObject *tp = Py_TYPE(self);
PyObject *get;

get = _PyType_LookupRef(tp, &_Py_ID(__get__));
if (get == NULL) {
PyThreadState *tstate = _PyThreadState_GET();
_PyCStackRef cref;
_PyThreadState_PushCStackRef(tstate, &cref);
_PyType_LookupStackRefAndVersion(tp, &_Py_ID(__get__), &cref.ref);
if (PyStackRef_IsNull(cref.ref)) {
_PyThreadState_PopCStackRef(tstate, &cref);
#ifndef Py_GIL_DISABLED
/* Avoid further slowdowns */
if (tp->tp_descr_get == slot_tp_descr_get)
Expand All @@ -11010,9 +11019,10 @@ slot_tp_descr_get(PyObject *self, PyObject *obj, PyObject *type)
obj = Py_None;
if (type == NULL)
type = Py_None;
PyObject *get = PyStackRef_AsPyObjectBorrow(cref.ref);
PyObject *stack[3] = {self, obj, type};
PyObject *res = PyObject_Vectorcall(get, stack, 3, NULL);
Py_DECREF(get);
_PyThreadState_PopCStackRef(tstate, &cref);
return res;
}

Expand Down
17 changes: 17 additions & 0 deletions Tools/ftscalingbench/ftscalingbench.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -279,6 +279,23 @@ def staticmethod_call():
for _ in range(1000 * WORK_SCALE):
obj.my_staticmethod()


class MyDescriptor:
def __get__(self, obj, objtype=None):
return 42

def __set__(self, obj, value):
pass

class MyClassWithDescriptor:
attr = MyDescriptor()

@register_benchmark
def descriptor():
obj = MyClassWithDescriptor()
for _ in range(1000 * WORK_SCALE):
obj.attr

@register_benchmark
def deepcopy():
x = {'list': [1, 2], 'tuple': (1, None)}
Expand Down
Loading