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GH-139951: Fix major GC performance regression #140262

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Merged
markshannon merged 6 commits into from
Oct 21, 2025
Merged

GH-139951: Fix major GC performance regression #140262

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2e8d020
Fix major GC performance regression
markshannon Oct 16, 2025
6c78c01
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markshannon Oct 17, 2025
c5836be
Address review comments
markshannon Oct 20, 2025
bde53f4
Up limit to 100000
markshannon Oct 20, 2025
1c2030a
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markshannon Oct 20, 2025
698e5f5
Address review comments
markshannon Oct 21, 2025
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Address review comments
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@markshannon
markshannon committed Oct 21, 2025
commit 698e5f5a4aae788896d5196e957c6d8681eca5af
3 changes: 1 addition & 2 deletions Include/internal/pycore_gc.h
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Expand Up @@ -244,8 +244,7 @@ static inline void _PyObject_GC_TRACK(
"object is in generation which is garbage collected",
filename, lineno, __func__);

PyThreadState *tstate = _PyThreadState_GET();
struct _gc_runtime_state *gcstate = &tstate->interp->gc;
struct _gc_runtime_state *gcstate = &_PyInterpreterState_GET()->gc;
PyGC_Head *generation0 = &gcstate->young.head;
PyGC_Head *last = (PyGC_Head*)(generation0->_gc_prev);
_PyGCHead_SET_NEXT(last, gc);
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2 changes: 1 addition & 1 deletion Misc/NEWS.d/next/Core_and_Builtins/2025-10-17-18-03-12.gh-issue-139951.IdwM2O.rst
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Expand Up @@ -2,6 +2,6 @@ Fixes a regression in GC performance for a growing heap composed mostly of
small tuples.

* Counts number of actually tracked objects, instead of trackable objects.
This ensures that untracking tuples has the desired effect of reducing GC overhead
This ensures that untracking tuples has the desired effect of reducing GC overhead.
* Does not track most untrackable tuples during creation.
This prevents large numbers of small tuples causing excessive GCs.
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