From 7ccacb220d99662b626c8bc63b00a27eaf604f0c Mon Sep 17 00:00:00 2001 From: Sam Gross Date: Mon, 29 Apr 2024 14:36:02 -0400 Subject: gh-117783: Immortalize objects that use deferred reference counting (#118112) Deferred reference counting is not fully implemented yet. As a temporary measure, we immortalize objects that would use deferred reference counting to avoid multi-threaded scaling bottlenecks. This is only performed in the free-threaded build once the first non-main thread is started. Additionally, some tests, including refleak tests, suppress this behavior. --- Python/gc_free_threading.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) (limited to 'Python/gc_free_threading.c') diff --git a/Python/gc_free_threading.c b/Python/gc_free_threading.c index 9cf0e989d09..8c0940d8f06 100644 --- a/Python/gc_free_threading.c +++ b/Python/gc_free_threading.c @@ -704,6 +704,12 @@ _PyGC_Init(PyInterpreterState *interp) { GCState *gcstate = &interp->gc; + if (_Py_IsMainInterpreter(interp)) { + // gh-117783: immortalize objects that would use deferred refcounting + // once the first non-main thread is created. + gcstate->immortalize.enable_on_thread_created = 1; + } + gcstate->garbage = PyList_New(0); if (gcstate->garbage == NULL) { return _PyStatus_NO_MEMORY(); @@ -1781,6 +1787,30 @@ custom_visitor_wrapper(const mi_heap_t *heap, const mi_heap_area_t *area, return true; } +// gh-117783: Immortalize objects that use deferred reference counting to +// temporarily work around scaling bottlenecks. +static bool +immortalize_visitor(const mi_heap_t *heap, const mi_heap_area_t *area, + void *block, size_t block_size, void *args) +{ + PyObject *op = op_from_block(block, args, false); + if (op != NULL && _PyObject_HasDeferredRefcount(op)) { + _Py_SetImmortal(op); + op->ob_gc_bits &= ~_PyGC_BITS_DEFERRED; + } + return true; +} + +void +_PyGC_ImmortalizeDeferredObjects(PyInterpreterState *interp) +{ + struct visitor_args args; + _PyEval_StopTheWorld(interp); + gc_visit_heaps(interp, &immortalize_visitor, &args); + interp->gc.immortalize.enabled = 1; + _PyEval_StartTheWorld(interp); +} + void PyUnstable_GC_VisitObjects(gcvisitobjects_t callback, void *arg) { -- cgit v1.2.3