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gh-115103: Implement delayed free mechanism for free-threaded builds (#115367)

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This adds `_PyMem_FreeDelayed()` and supporting functions. The
`_PyMem_FreeDelayed()` function frees memory with the same allocator as
`PyMem_Free()`, but after some delay to ensure that concurrent lock-free
readers have finished.
This commit is contained in:
Sam Gross 2024-02-20 13:04:37 -05:00 • committed by GitHub
parent d207c7cd5a
commit e3ad6ca56f
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8 changed files with 226 additions and 0 deletions
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3
Python/pylifecycle.c
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@ -1837,6 +1837,9 @@ finalize_interp_clear(PyThreadState *tstate)
finalize_interp_types(tstate->interp);
/* Free any delayed free requests immediately */
_PyMem_FiniDelayed(tstate->interp);
/* finalize_interp_types may allocate Python objects so we may need to
abandon mimalloc segments again */
_PyThreadState_ClearMimallocHeaps(tstate);

6
Python/pystate.c
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@ -617,6 +617,7 @@ init_interpreter(PyInterpreterState *interp,
#ifdef Py_GIL_DISABLED
_Py_brc_init_state(interp);
#endif
llist_init(&interp->mem_free_queue.head);
for (int i = 0; i < _PY_MONITORING_UNGROUPED_EVENTS; i++) {
interp->monitors.tools[i] = 0;
}
@ -1353,6 +1354,7 @@ init_threadstate(_PyThreadStateImpl *_tstate,
// Initialize biased reference counting inter-thread queue
_Py_brc_init_thread(tstate);
#endif
llist_init(&_tstate->mem_free_queue);
if (interp->stoptheworld.requested || _PyRuntime.stoptheworld.requested) {
// Start in the suspended state if there is an ongoing stop-the-world.
@ -1574,6 +1576,7 @@ PyThreadState_Clear(PyThreadState *tstate)
// don't call _PyInterpreterState_SetNotRunningMain() yet.
tstate->on_delete(tstate->on_delete_data);
}
#ifdef Py_GIL_DISABLED
// Each thread should clear own freelists in free-threading builds.
struct _Py_object_freelists *freelists = _Py_object_freelists_GET();
@ -1583,6 +1586,9 @@ PyThreadState_Clear(PyThreadState *tstate)
_Py_brc_remove_thread(tstate);
#endif
// Merge our queue of pointers to be freed into the interpreter queue.
_PyMem_AbandonDelayed(tstate);
_PyThreadState_ClearMimallocHeaps(tstate);
tstate->_status.cleared = 1;