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gh-110481: Implement biased reference counting #110764

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Merged
corona10 merged 8 commits into from
Oct 30, 2023
Merged

gh-110481: Implement biased reference counting #110764

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94bfbde
Remove trailing commas in _PyObject_HEAD_INIT and _PyVarObject_HEAD_INIT
colesbury Oct 4, 2023
b1cb396
Implement biased reference counting
colesbury Sep 13, 2023
425d570
Add blurb
colesbury Oct 12, 2023
8c68c78
Changes from review:
colesbury Oct 19, 2023
86892d9
Fix compile errors from rebasing on main
colesbury Oct 19, 2023
3c85ca1
Fix typo
colesbury Oct 20, 2023
c6c6ec6
Add missing guards
colesbury Oct 20, 2023
ac2c957
Add TODOs for missing Py_DECREF specializations
colesbury Oct 24, 2023
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Fix typo
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@colesbury @corona10
colesbury authored and corona10 committed Oct 30, 2023
commit 3c85ca12a73636fa040482a77e3119a4d76477cc
2 changes: 1 addition & 1 deletion Include/internal/pycore_object.h
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Original file line number Diff line number Diff line change
Expand Up @@ -106,7 +106,7 @@ static inline void _Py_RefcntAdd(PyObject* op, Py_ssize_t n)
#if !defined(Py_NOGIL)
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@markshannon markshannon Oct 23, 2023

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Is this worth the extra code?
_Py_RefcntAdd is only used in list_repeat and tuplerepeat. Multiplying tuples and lists by ints is hardly a common operation.
Would it perhaps make more sense to remove _Py_RefcntAdd and use plain Py_INCREF in those functions?
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@colesbury colesbury Oct 23, 2023

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Are you suggesting removing _Py_RefcntAdd in general or just for Py_NOGIL?
op->ob_refcnt += n;
#else
if (_Py_IsOnwedByCurrentThread(op)) {
if (_Py_IsOwnedByCurrentThread(op)) {
uint32_t local = op->ob_ref_local;
Py_ssize_t refcnt = (Py_ssize_t)local + n;
# if PY_SSIZE_T_MAX > UINT32_MAX
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10 changes: 5 additions & 5 deletions Include/object.h
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Expand Up @@ -263,7 +263,7 @@ _Py_ThreadId(void)

#if defined(Py_NOGIL) && !defined(Py_LIMITED_API)
static inline Py_ALWAYS_INLINE int
_Py_IsOnwedByCurrentThread(PyObject *ob)
_Py_IsOwnedByCurrentThread(PyObject *ob)
{
return ob->ob_tid == _Py_ThreadId();
}
Expand Down Expand Up @@ -340,7 +340,7 @@ static inline void Py_SET_REFCNT(PyObject *ob, Py_ssize_t refcnt) {
#if !defined(Py_NOGIL)
ob->ob_refcnt = refcnt;
#else
if (_Py_IsOnwedByCurrentThread(ob)) {
if (_Py_IsOwnedByCurrentThread(ob)) {
// Set local refcount to desired refcount and shared refcount to zero,
// but preserve the shared refcount flags.
assert(refcnt < UINT32_MAX);
Expand Down Expand Up @@ -738,7 +738,7 @@ static inline Py_ALWAYS_INLINE void Py_INCREF(PyObject *op)
if (new_local == 0) {
return;
}
if (_Py_IsOnwedByCurrentThread(op)) {
if (_Py_IsOwnedByCurrentThread(op)) {
_Py_atomic_store_uint32_relaxed(&op->ob_ref_local, new_local);
}
else {
Expand Down Expand Up @@ -805,7 +805,7 @@ static inline void Py_DECREF(const char *filename, int lineno, PyObject *op)
}
_Py_DECREF_STAT_INC();
_Py_DECREF_DecRefTotal();
if (_Py_IsOnwedByCurrentThread(op)) {
if (_Py_IsOwnedByCurrentThread(op)) {
if (local == 0) {
_Py_NegativeRefcount(filename, lineno, op);
}
Expand All @@ -829,7 +829,7 @@ static inline void Py_DECREF(PyObject *op)
return;
}
_Py_DECREF_STAT_INC();
if (_Py_IsOnwedByCurrentThread(op)) {
if (_Py_IsOwnedByCurrentThread(op)) {
local--;
_Py_atomic_store_uint32_relaxed(&op->ob_ref_local, local);
if (local == 0) {
Expand Down