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GH-126491: Lower heap size limit with faster marking (GH-127519)

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* Faster marking of reachable objects

* Changes calculation of work to do and work done.

* Merges transitive closure calculations
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Mark Shannon 2024-12-06 10:46:59 +00:00 • committed by GitHub
parent 8b7c194c7b
commit 023b7d2141
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6 changed files with 212 additions and 247 deletions
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50
InternalDocs/garbage_collector.md
View file

@ -199,22 +199,22 @@ unreachable:
```pycon
>>> import gc
>>>
>>>
>>> class Link:
... def __init__(self, next_link=None):
... self.next_link = next_link
...
...
>>> link_3 = Link()
>>> link_2 = Link(link_3)
>>> link_1 = Link(link_2)
>>> link_3.next_link = link_1
>>> A = link_1
>>> del link_1, link_2, link_3
>>>
>>>
>>> link_4 = Link()
>>> link_4.next_link = link_4
>>> del link_4
>>>
>>>
>>> # Collect the unreachable Link object (and its .__dict__ dict).
>>> gc.collect()
2
@ -459,11 +459,11 @@ specifically in a generation by calling `gc.collect(generation=NUM)`.
>>> # Create a reference cycle.
>>> x = MyObj()
>>> x.self = x
>>>
>>>
>>> # Initially the object is in the young generation.
>>> gc.get_objects(generation=0)
[..., <__main__.MyObj object at 0x7fbcc12a3400>, ...]
>>>
>>>
>>> # After a collection of the youngest generation the object
>>> # moves to the old generation.
>>> gc.collect(generation=0)
@ -515,6 +515,44 @@ increment. All objects directly referred to from those stack frames are
added to the working set.
Then the above algorithm is repeated, starting from step 2.
Determining how much work to do
-------------------------------
We need to do a certain amount of work to enusre that garbage is collected,
but doing too much work slows down execution.
To work out how much work we need to do, consider a heap with `L` live objects
and `G0` garbage objects at the start of a full scavenge and `G1` garbage objects
at the end of the scavenge. We don't want the amount of garbage to grow, `G1 ≤ G0`, and
we don't want too much garbage (say 1/3 of the heap maximum), `G0 ≤ L/2`.
For each full scavenge we must visit all objects, `T == L + G0 + G1`, during which
`G1` garbage objects are created.
The number of new objects created `N` must be at least the new garbage created, `N ≥ G1`,
assuming that the number of live objects remains roughly constant.
If we set `T == 4*N` we get `T > 4*G1` and `T = L + G0 + G1` => `L + G0 > 3G1`
For a steady state heap (`G0 == G1`) we get `L > 2G0` and the desired garbage ratio.
In other words, to keep the garbage fraction to 1/3 or less we need to visit
4 times as many objects as are newly created.
We can do better than this though. Not all new objects will be garbage.
Consider the heap at the end of the scavenge with `L1` live objects and `G1`
garbage. Also, note that `T == M + I` where `M` is the number of objects marked
as reachable and `I` is the number of objects visited in increments.
Everything in `M` is live, so `I ≥ G0` and in practice `I` is closer to `G0 + G1`.
If we choose the amount of work done such that `2*M + I == 6N` then we can do
less work in most cases, but are still guaranteed to keep up.
Since `I ≳ G0 + G1` (not strictly true, but close enough)
`T == M + I == (6N + I)/2` and `(6N + I)/2 ≳ 4G`, so we can keep up.
The reason that this improves performance is that `M` is usually much larger
than `I`. If `M == 10I`, then `T ≅ 3N`.
Finally, instead of using a fixed multiple of 8, we gradually increase it as the
heap grows. This avoids wasting work for small heaps and during startup.
Optimization: reusing fields to save memory
===========================================

14
Lib/test/test_gc.py
View file

@ -1161,27 +1161,19 @@ class IncrementalGCTests(unittest.TestCase):
return head
head = make_ll(1000)
count = 1000
# There will be some objects we aren't counting,
# e.g. the gc stats dicts. This test checks
# that the counts don't grow, so we try to
# correct for the uncounted objects
# This is just an estimate.
CORRECTION = 20
enabled = gc.isenabled()
gc.enable()
olds = []
initial_heap_size = _testinternalcapi.get_tracked_heap_size()
for i in range(20_000):
iterations = max(20_000, initial_heap_size)
for i in range(iterations):
newhead = make_ll(20)
count += 20
newhead.surprise = head
olds.append(newhead)
if len(olds) == 20:
new_objects = _testinternalcapi.get_tracked_heap_size() - initial_heap_size
self.assertLess(new_objects, 27_000, f"Heap growing. Reached limit after {i} iterations")
self.assertLess(new_objects, initial_heap_size/2, f"Heap growing. Reached limit after {i} iterations")
del olds[:]
if not enabled:
gc.disable()

4
Objects/dictobject.c
View file

@ -7064,9 +7064,7 @@ int
PyObject_VisitManagedDict(PyObject *obj, visitproc visit, void *arg)
{
PyTypeObject *tp = Py_TYPE(obj);
if((tp->tp_flags & Py_TPFLAGS_MANAGED_DICT) == 0) {
return 0;
}
assert(tp->tp_flags & Py_TPFLAGS_MANAGED_DICT);
if (tp->tp_flags & Py_TPFLAGS_INLINE_VALUES) {
PyDictValues *values = _PyObject_InlineValues(obj);
if (values->valid) {

69
Objects/genobject.c
View file

@ -882,25 +882,7 @@ PyTypeObject PyGen_Type = {
gen_methods, /* tp_methods */
gen_memberlist, /* tp_members */
gen_getsetlist, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
0, /* tp_init */
0, /* tp_alloc */
0, /* tp_new */
0, /* tp_free */
0, /* tp_is_gc */
0, /* tp_bases */
0, /* tp_mro */
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
0, /* tp_del */
0, /* tp_version_tag */
_PyGen_Finalize, /* tp_finalize */
.tp_finalize = _PyGen_Finalize,
};
static PyObject *
@ -1242,24 +1224,7 @@ PyTypeObject PyCoro_Type = {
coro_methods, /* tp_methods */
coro_memberlist, /* tp_members */
coro_getsetlist, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
0, /* tp_init */
0, /* tp_alloc */
0, /* tp_new */
0, /* tp_free */
0, /* tp_is_gc */
0, /* tp_bases */
0, /* tp_mro */
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
0, /* tp_del */
0, /* tp_version_tag */
_PyGen_Finalize, /* tp_finalize */
.tp_finalize = _PyGen_Finalize,
};
static void
@ -1464,7 +1429,6 @@ typedef struct _PyAsyncGenWrappedValue {
(assert(_PyAsyncGenWrappedValue_CheckExact(op)), \
_Py_CAST(_PyAsyncGenWrappedValue*, (op)))
static int
async_gen_traverse(PyObject *self, visitproc visit, void *arg)
{
@ -1673,24 +1637,7 @@ PyTypeObject PyAsyncGen_Type = {
async_gen_methods, /* tp_methods */
async_gen_memberlist, /* tp_members */
async_gen_getsetlist, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
0, /* tp_init */
0, /* tp_alloc */
0, /* tp_new */
0, /* tp_free */
0, /* tp_is_gc */
0, /* tp_bases */
0, /* tp_mro */
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
0, /* tp_del */
0, /* tp_version_tag */
_PyGen_Finalize, /* tp_finalize */
.tp_finalize = _PyGen_Finalize,
};
@ -1935,16 +1882,6 @@ PyTypeObject _PyAsyncGenASend_Type = {
PyObject_SelfIter, /* tp_iter */
async_gen_asend_iternext, /* tp_iternext */
async_gen_asend_methods, /* tp_methods */
0, /* tp_members */
0, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
0, /* tp_init */
0, /* tp_alloc */
0, /* tp_new */
.tp_finalize = async_gen_asend_finalize,
};

13
Objects/typeobject.c
View file

@ -2355,6 +2355,16 @@ subtype_traverse(PyObject *self, visitproc visit, void *arg)
return 0;
}
static int
plain_object_traverse(PyObject *self, visitproc visit, void *arg)
{
PyTypeObject *type = Py_TYPE(self);
assert(type->tp_flags & Py_TPFLAGS_MANAGED_DICT);
Py_VISIT(type);
return PyObject_VisitManagedDict(self, visit, arg);
}
static void
clear_slots(PyTypeObject *type, PyObject *self)
{
@ -4147,6 +4157,9 @@ type_new_descriptors(const type_new_ctx *ctx, PyTypeObject *type)
assert((type->tp_flags & Py_TPFLAGS_MANAGED_DICT) == 0);
type->tp_flags |= Py_TPFLAGS_MANAGED_DICT;
type->tp_dictoffset = -1;
if (type->tp_basicsize == sizeof(PyObject)) {
type->tp_traverse = plain_object_traverse;
}
}
type->tp_basicsize = slotoffset;

309
Python/gc.c
View file

@ -1277,18 +1277,13 @@ gc_list_set_space(PyGC_Head *list, int space)
* space faster than objects are added to the old space.
*
* Each young or incremental collection adds a number of
* objects, S (for survivors) to the old space, and
* incremental collectors scan I objects from the old space.
* I > S must be true. We also want I > S * N to be where
* N > 1. Higher values of N mean that the old space is
* new objects (N) to the heap, and incremental collectors
* scan I objects from the old space.
* I > N must be true. We also want I > N * K to be where
* K > 2. Higher values of K mean that the old space is
* scanned more rapidly.
* The default incremental threshold of 10 translates to
* N == 1.4 (1 + 4/threshold)
*/
/* Divide by 10, so that the default incremental threshold of 10
* scans objects at 1% of the heap size */
#define SCAN_RATE_DIVISOR 10
#define SCAN_RATE_DIVISOR 5
static void
add_stats(GCState *gcstate, int gen, struct gc_collection_stats *stats)
@ -1330,71 +1325,78 @@ gc_collect_young(PyThreadState *tstate,
validate_spaces(gcstate);
}
#ifndef NDEBUG
static inline int
IS_IN_VISITED(PyGC_Head *gc, int visited_space)
{
assert(visited_space == 0 || other_space(visited_space) == 0);
return gc_old_space(gc) == visited_space;
}
#endif
struct container_and_flag {
PyGC_Head *container;
typedef struct work_stack {
PyGC_Head *top;
int visited_space;
intptr_t size;
};
} WorkStack;
/* A traversal callback for adding to container) */
/* Remove gc from the list it is currently in and push it to the stack */
static inline void
push_to_stack(PyGC_Head *gc, WorkStack *stack)
{
PyGC_Head *prev = GC_PREV(gc);
PyGC_Head *next = GC_NEXT(gc);
_PyGCHead_SET_NEXT(prev, next);
_PyGCHead_SET_PREV(next, prev);
_PyGCHead_SET_PREV(gc, stack->top);
stack->top = gc;
}
static inline PyGC_Head *
pop_from_stack(WorkStack *stack)
{
PyGC_Head *gc = stack->top;
stack->top = _PyGCHead_PREV(gc);
return gc;
}
/* append list `from` to `stack`; `from` becomes an empty list */
static void
move_list_to_stack(PyGC_Head *from, WorkStack *stack)
{
if (!gc_list_is_empty(from)) {
PyGC_Head *from_head = GC_NEXT(from);
PyGC_Head *from_tail = GC_PREV(from);
_PyGCHead_SET_PREV(from_head, stack->top);
stack->top = from_tail;
gc_list_init(from);
}
}
static inline void
move_to_stack(PyObject *op, WorkStack *stack, int visited_space)
{
assert(op != NULL);
if (_PyObject_IS_GC(op)) {
PyGC_Head *gc = AS_GC(op);
if (_PyObject_GC_IS_TRACKED(op) &&
gc_old_space(gc) != visited_space) {
assert(!_Py_IsImmortal(op));
gc_flip_old_space(gc);
push_to_stack(gc, stack);
}
}
}
static void
move_unvisited(PyObject *op, WorkStack *stack, int visited_space)
{
move_to_stack(op, stack, visited_space);
}
#define MOVE_UNVISITED(O, T, V) if ((O) != NULL) move_unvisited((O), (T), (V))
/* A traversal callback for adding to container */
static int
visit_add_to_container(PyObject *op, void *arg)
{
OBJECT_STAT_INC(object_visits);
struct container_and_flag *cf = (struct container_and_flag *)arg;
int visited = cf->visited_space;
assert(visited == get_gc_state()->visited_space);
if (!_Py_IsImmortal(op) && _PyObject_IS_GC(op)) {
PyGC_Head *gc = AS_GC(op);
if (_PyObject_GC_IS_TRACKED(op) &&
gc_old_space(gc) != visited) {
gc_flip_old_space(gc);
gc_list_move(gc, cf->container);
cf->size++;
}
}
WorkStack *stack = (WorkStack *)arg;
assert(stack->visited_space == get_gc_state()->visited_space);
move_to_stack(op, stack, stack->visited_space);
return 0;
}
static intptr_t
expand_region_transitively_reachable(PyGC_Head *container, PyGC_Head *gc, GCState *gcstate)
{
struct container_and_flag arg = {
.container = container,
.visited_space = gcstate->visited_space,
.size = 0
};
assert(GC_NEXT(gc) == container);
while (gc != container) {
/* Survivors will be moved to visited space, so they should
* have been marked as visited */
assert(IS_IN_VISITED(gc, gcstate->visited_space));
PyObject *op = FROM_GC(gc);
assert(_PyObject_GC_IS_TRACKED(op));
if (_Py_IsImmortal(op)) {
PyGC_Head *next = GC_NEXT(gc);
gc_list_move(gc, &get_gc_state()->permanent_generation.head);
gc = next;
continue;
}
traverseproc traverse = Py_TYPE(op)->tp_traverse;
(void) traverse(op,
visit_add_to_container,
&arg);
gc = GC_NEXT(gc);
}
return arg.size;
}
/* Do bookkeeping for a completed GC cycle */
static void
completed_scavenge(GCState *gcstate)
@ -1420,54 +1422,62 @@ completed_scavenge(GCState *gcstate)
gc_list_set_space(&gcstate->old[not_visited].head, not_visited);
}
assert(gc_list_is_empty(&gcstate->old[visited].head));
gcstate->work_to_do = 0;
gcstate->phase = GC_PHASE_MARK;
}
static intptr_t
move_to_reachable(PyObject *op, PyGC_Head *reachable, int visited_space)
static void
frame_move_unvisited(_PyInterpreterFrame *frame, WorkStack *stack, int visited_space)
{
if (op != NULL && !_Py_IsImmortal(op) && _PyObject_IS_GC(op)) {
PyGC_Head *gc = AS_GC(op);
if (_PyObject_GC_IS_TRACKED(op) &&
gc_old_space(gc) != visited_space) {
gc_flip_old_space(gc);
gc_list_move(gc, reachable);
return 1;
_PyStackRef *locals = frame->localsplus;
_PyStackRef *sp = frame->stackpointer;
if (frame->f_locals != NULL) {
move_unvisited(frame->f_locals, stack, visited_space);
}
PyObject *func = PyStackRef_AsPyObjectBorrow(frame->f_funcobj);
move_unvisited(func, stack, visited_space);
while (sp > locals) {
sp--;
_PyStackRef ref = *sp;
if (!PyStackRef_IsNull(ref)) {
PyObject *op = PyStackRef_AsPyObjectBorrow(ref);
if (!_Py_IsImmortal(op)) {
move_unvisited(op, stack, visited_space);
}
}
}
return 0;
}
static intptr_t
mark_all_reachable(PyGC_Head *reachable, PyGC_Head *visited, int visited_space)
static Py_ssize_t
move_all_transitively_reachable(WorkStack *stack, PyGC_Head *visited, int visited_space)
{
// Transitively traverse all objects from reachable, until empty
struct container_and_flag arg = {
.container = reachable,
.visited_space = visited_space,
.size = 0
};
while (!gc_list_is_empty(reachable)) {
PyGC_Head *gc = _PyGCHead_NEXT(reachable);
Py_ssize_t objects_marked = 0;
while (stack->top != NULL) {
PyGC_Head *gc = pop_from_stack(stack);
assert(gc_old_space(gc) == visited_space);
gc_list_move(gc, visited);
gc_list_append(gc, visited);
objects_marked++;
PyObject *op = FROM_GC(gc);
traverseproc traverse = Py_TYPE(op)->tp_traverse;
(void) traverse(op,
visit_add_to_container,
&arg);
assert(PyObject_IS_GC(op));
assert(_PyObject_GC_IS_TRACKED(op));
if (_Py_IsImmortal(op)) {
_PyObject_GC_UNTRACK(op);
}
else {
traverseproc traverse = Py_TYPE(op)->tp_traverse;
(void) traverse(op, visit_add_to_container, stack);
}
}
gc_list_validate_space(visited, visited_space);
return arg.size;
return objects_marked;
}
static intptr_t
mark_stacks(PyInterpreterState *interp, PyGC_Head *visited, int visited_space, bool start)
{
PyGC_Head reachable;
gc_list_init(&reachable);
Py_ssize_t objects_marked = 0;
WorkStack stack;
stack.top = NULL;
stack.visited_space = visited_space;
// Move all objects on stacks to reachable
_PyRuntimeState *runtime = &_PyRuntime;
HEAD_LOCK(runtime);
@ -1480,27 +1490,7 @@ mark_stacks(PyInterpreterState *interp, PyGC_Head *visited, int visited_space, b
frame = frame->previous;
continue;
}
_PyStackRef *locals = frame->localsplus;
_PyStackRef *sp = frame->stackpointer;
objects_marked += move_to_reachable(frame->f_locals, &reachable, visited_space);
PyObject *func = PyStackRef_AsPyObjectBorrow(frame->f_funcobj);
objects_marked += move_to_reachable(func, &reachable, visited_space);
while (sp > locals) {
sp--;
if (PyStackRef_IsNull(*sp)) {
continue;
}
PyObject *op = PyStackRef_AsPyObjectBorrow(*sp);
if (!_Py_IsImmortal(op) && _PyObject_IS_GC(op)) {
PyGC_Head *gc = AS_GC(op);
if (_PyObject_GC_IS_TRACKED(op) &&
gc_old_space(gc) != visited_space) {
gc_flip_old_space(gc);
objects_marked++;
gc_list_move(gc, &reachable);
}
}
}
frame_move_unvisited(frame, &stack, visited_space);
if (!start && frame->visited) {
// If this frame has already been visited, then the lower frames
// will have already been visited and will not have changed
@ -1513,31 +1503,31 @@ mark_stacks(PyInterpreterState *interp, PyGC_Head *visited, int visited_space, b
ts = PyThreadState_Next(ts);
HEAD_UNLOCK(runtime);
}
objects_marked += mark_all_reachable(&reachable, visited, visited_space);
assert(gc_list_is_empty(&reachable));
Py_ssize_t objects_marked = move_all_transitively_reachable(&stack, visited, visited_space);
assert(stack.top == NULL);
return objects_marked;
}
static intptr_t
mark_global_roots(PyInterpreterState *interp, PyGC_Head *visited, int visited_space)
{
PyGC_Head reachable;
gc_list_init(&reachable);
Py_ssize_t objects_marked = 0;
objects_marked += move_to_reachable(interp->sysdict, &reachable, visited_space);
objects_marked += move_to_reachable(interp->builtins, &reachable, visited_space);
objects_marked += move_to_reachable(interp->dict, &reachable, visited_space);
WorkStack stack;
stack.top = NULL;
stack.visited_space = visited_space;
MOVE_UNVISITED(interp->sysdict, &stack, visited_space);
MOVE_UNVISITED(interp->builtins, &stack, visited_space);
MOVE_UNVISITED(interp->dict, &stack, visited_space);
struct types_state *types = &interp->types;
for (int i = 0; i < _Py_MAX_MANAGED_STATIC_BUILTIN_TYPES; i++) {
objects_marked += move_to_reachable(types->builtins.initialized[i].tp_dict, &reachable, visited_space);
objects_marked += move_to_reachable(types->builtins.initialized[i].tp_subclasses, &reachable, visited_space);
MOVE_UNVISITED(types->builtins.initialized[i].tp_dict, &stack, visited_space);
MOVE_UNVISITED(types->builtins.initialized[i].tp_subclasses, &stack, visited_space);
}
for (int i = 0; i < _Py_MAX_MANAGED_STATIC_EXT_TYPES; i++) {
objects_marked += move_to_reachable(types->for_extensions.initialized[i].tp_dict, &reachable, visited_space);
objects_marked += move_to_reachable(types->for_extensions.initialized[i].tp_subclasses, &reachable, visited_space);
MOVE_UNVISITED(types->for_extensions.initialized[i].tp_dict, &stack, visited_space);
MOVE_UNVISITED(types->for_extensions.initialized[i].tp_subclasses, &stack, visited_space);
}
objects_marked += mark_all_reachable(&reachable, visited, visited_space);
assert(gc_list_is_empty(&reachable));
Py_ssize_t objects_marked = move_all_transitively_reachable(&stack, visited, visited_space);
assert(stack.top == NULL);
return objects_marked;
}
@ -1549,39 +1539,35 @@ mark_at_start(PyThreadState *tstate)
PyGC_Head *visited = &gcstate->old[gcstate->visited_space].head;
Py_ssize_t objects_marked = mark_global_roots(tstate->interp, visited, gcstate->visited_space);
objects_marked += mark_stacks(tstate->interp, visited, gcstate->visited_space, true);
gcstate->work_to_do -= objects_marked;
gcstate->phase = GC_PHASE_COLLECT;
validate_spaces(gcstate);
return objects_marked;
}
/* See InternalDocs/garbage_collector.md for more details. */
#define MAX_HEAP_PORTION_MULTIPLIER 5
#define MARKING_PROGRESS_MULTIPLIER 2
static intptr_t
assess_work_to_do(GCState *gcstate)
{
/* The amount of work we want to do depends on three things.
/* The amount of work we want to do depends on two things.
* 1. The number of new objects created
* 2. The growth in heap size since the last collection
* 3. The heap size (up to the number of new objects, to avoid quadratic effects)
*
* For a steady state heap, the amount of work to do is three times the number
* of new objects added to the heap. This ensures that we stay ahead in the
* worst case of all new objects being garbage.
*
* This could be improved by tracking survival rates, but it is still a
* large improvement on the non-marking approach.
* 2. The heap size (up to a multiple of the number of new objects, to avoid quadratic effects)
*/
intptr_t scale_factor = gcstate->old[0].threshold;
if (scale_factor < 2) {
scale_factor = 2;
}
intptr_t new_objects = gcstate->young.count;
intptr_t max_heap_fraction = new_objects*3/2;
intptr_t heap_fraction = gcstate->heap_size / SCAN_RATE_DIVISOR / scale_factor;
if (heap_fraction > max_heap_fraction) {
heap_fraction = max_heap_fraction;
intptr_t max_heap_portion = new_objects * MAX_HEAP_PORTION_MULTIPLIER;
intptr_t heap_portion = gcstate->heap_size / SCAN_RATE_DIVISOR / scale_factor;
if (heap_portion > max_heap_portion) {
heap_portion = max_heap_portion;
}
gcstate->young.count = 0;
return new_objects + heap_fraction;
return new_objects + heap_portion;
}
static void
@ -1594,36 +1580,37 @@ gc_collect_increment(PyThreadState *tstate, struct gc_collection_stats *stats)
if (gcstate->phase == GC_PHASE_MARK) {
Py_ssize_t objects_marked = mark_at_start(tstate);
GC_STAT_ADD(1, objects_transitively_reachable, objects_marked);
gcstate->work_to_do -= objects_marked;
gcstate->work_to_do -= objects_marked * MARKING_PROGRESS_MULTIPLIER;
validate_spaces(gcstate);
return;
}
PyGC_Head *not_visited = &gcstate->old[gcstate->visited_space^1].head;
PyGC_Head *visited = &gcstate->old[gcstate->visited_space].head;
PyGC_Head increment;
gc_list_init(&increment);
int scale_factor = gcstate->old[0].threshold;
if (scale_factor < 2) {
scale_factor = 2;
}
intptr_t objects_marked = mark_stacks(tstate->interp, visited, gcstate->visited_space, false);
GC_STAT_ADD(1, objects_transitively_reachable, objects_marked);
gcstate->work_to_do -= objects_marked;
gcstate->work_to_do -= objects_marked * MARKING_PROGRESS_MULTIPLIER;
gc_list_set_space(&gcstate->young.head, gcstate->visited_space);
gc_list_merge(&gcstate->young.head, &increment);
PyGC_Head increment;
gc_list_init(&increment);
WorkStack working;
working.top = 0;
working.visited_space = gcstate->visited_space;
move_list_to_stack(&gcstate->young.head, &working);
Py_ssize_t increment_size = move_all_transitively_reachable(&working, &increment, gcstate->visited_space);
gc_list_validate_space(&increment, gcstate->visited_space);
Py_ssize_t increment_size = gc_list_size(&increment);
assert(working.top == NULL);
while (increment_size < gcstate->work_to_do) {
if (gc_list_is_empty(not_visited)) {
break;
}
PyGC_Head *gc = _PyGCHead_NEXT(not_visited);
gc_list_move(gc, &increment);
increment_size++;
assert(!_Py_IsImmortal(FROM_GC(gc)));
gc_set_old_space(gc, gcstate->visited_space);
increment_size += expand_region_transitively_reachable(&increment, gc, gcstate);
push_to_stack(gc, &working);
assert(!_Py_IsImmortal(FROM_GC(gc)));
increment_size += move_all_transitively_reachable(&working, &increment, gcstate->visited_space);
assert(working.top == NULL);
}
assert(increment_size == gc_list_size(&increment));
GC_STAT_ADD(1, objects_not_transitively_reachable, increment_size);
validate_list(&increment, collecting_clear_unreachable_clear);
gc_list_validate_space(&increment, gcstate->visited_space);
@ -1632,7 +1619,6 @@ gc_collect_increment(PyThreadState *tstate, struct gc_collection_stats *stats)
gc_collect_region(tstate, &increment, &survivors, stats);
gc_list_merge(&survivors, visited);
assert(gc_list_is_empty(&increment));
gcstate->work_to_do += gcstate->heap_size / SCAN_RATE_DIVISOR / scale_factor;
gcstate->work_to_do -= increment_size;
add_stats(gcstate, 1, stats);
@ -1668,6 +1654,7 @@ gc_collect_full(PyThreadState *tstate,
gcstate->old[0].count = 0;
gcstate->old[1].count = 0;
completed_scavenge(gcstate);
gcstate->work_to_do = -gcstate->young.threshold;
_PyGC_ClearAllFreeLists(tstate->interp);
validate_spaces(gcstate);
add_stats(gcstate, 2, stats);