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gh-146527: Heap-allocate gc_stats to avoid bloating PyInterpreterState #148057

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Merged
pablogsal merged 1 commit into from
Apr 4, 2026
+24 −10
Merged

gh-146527: Heap-allocate gc_stats to avoid bloating PyInterpreterState #148057

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2 changes: 1 addition & 1 deletion Include/internal/pycore_interp_structs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -248,7 +248,7 @@ struct _gc_runtime_state {
struct gc_generation old[2];
/* a permanent generation which won't be collected */
struct gc_generation permanent_generation;
struct gc_stats generation_stats;
struct gc_stats *generation_stats;
/* true if we are currently running the collector */
int collecting;
// The frame that started the current collection. It might be NULL even when
Expand Down
6 changes: 3 additions & 3 deletions Modules/gcmodule.c
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Expand Up @@ -347,9 +347,9 @@ gc_get_stats_impl(PyObject *module)
/* To get consistent values despite allocations while constructing
the result list, we use a snapshot of the running stats. */
GCState *gcstate = get_gc_state();
stats[0] = gcstate->generation_stats.young.items[gcstate->generation_stats.young.index];
stats[1] = gcstate->generation_stats.old[0].items[gcstate->generation_stats.old[0].index];
stats[2] = gcstate->generation_stats.old[1].items[gcstate->generation_stats.old[1].index];
stats[0] = gcstate->generation_stats->young.items[gcstate->generation_stats->young.index];
stats[1] = gcstate->generation_stats->old[0].items[gcstate->generation_stats->old[0].index];
stats[2] = gcstate->generation_stats->old[1].items[gcstate->generation_stats->old[1].index];

PyObject *result = PyList_New(0);
if (result == NULL)
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15 changes: 11 additions & 4 deletions Python/gc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -177,6 +177,11 @@ _PyGC_Init(PyInterpreterState *interp)
{
GCState *gcstate = &interp->gc;

gcstate->generation_stats = PyMem_RawCalloc(1, sizeof(struct gc_stats));
if (gcstate->generation_stats == NULL) {
return _PyStatus_NO_MEMORY();
}

gcstate->garbage = PyList_New(0);
if (gcstate->garbage == NULL) {
return _PyStatus_NO_MEMORY();
Expand Down Expand Up @@ -1398,13 +1403,13 @@ static struct gc_generation_stats *
gc_get_stats(GCState *gcstate, int gen)
{
if (gen == 0) {
struct gc_young_stats_buffer *buffer = &gcstate->generation_stats.young;
struct gc_young_stats_buffer *buffer = &gcstate->generation_stats->young;
buffer->index = (buffer->index + 1) % GC_YOUNG_STATS_SIZE;
struct gc_generation_stats *stats = &buffer->items[buffer->index];
return stats;
}
else {
struct gc_old_stats_buffer *buffer = &gcstate->generation_stats.old[gen - 1];
struct gc_old_stats_buffer *buffer = &gcstate->generation_stats->old[gen - 1];
buffer->index = (buffer->index + 1) % GC_OLD_STATS_SIZE;
struct gc_generation_stats *stats = &buffer->items[buffer->index];
return stats;
Expand All @@ -1415,12 +1420,12 @@ static struct gc_generation_stats *
gc_get_prev_stats(GCState *gcstate, int gen)
{
if (gen == 0) {
struct gc_young_stats_buffer *buffer = &gcstate->generation_stats.young;
struct gc_young_stats_buffer *buffer = &gcstate->generation_stats->young;
struct gc_generation_stats *stats = &buffer->items[buffer->index];
return stats;
}
else {
struct gc_old_stats_buffer *buffer = &gcstate->generation_stats.old[gen - 1];
struct gc_old_stats_buffer *buffer = &gcstate->generation_stats->old[gen - 1];
struct gc_generation_stats *stats = &buffer->items[buffer->index];
return stats;
}
Expand Down Expand Up @@ -2299,6 +2304,8 @@ _PyGC_Fini(PyInterpreterState *interp)
GCState *gcstate = &interp->gc;
Py_CLEAR(gcstate->garbage);
Py_CLEAR(gcstate->callbacks);
PyMem_RawFree(gcstate->generation_stats);
gcstate->generation_stats = NULL;

/* Prevent a subtle bug that affects sub-interpreters that use basic
* single-phase init extensions (m_size == -1). Those extensions cause objects
Expand Down
11 changes: 9 additions & 2 deletions Python/gc_free_threading.c
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Expand Up @@ -1698,6 +1698,11 @@ _PyGC_Init(PyInterpreterState *interp)
{
GCState *gcstate = &interp->gc;

gcstate->generation_stats = PyMem_RawCalloc(1, sizeof(struct gc_stats));
if (gcstate->generation_stats == NULL) {
return _PyStatus_NO_MEMORY();
}

gcstate->garbage = PyList_New(0);
if (gcstate->garbage == NULL) {
return _PyStatus_NO_MEMORY();
Expand Down Expand Up @@ -2387,12 +2392,12 @@ static struct gc_generation_stats *
get_stats(GCState *gcstate, int gen)
{
if (gen == 0) {
struct gc_young_stats_buffer *buffer = &gcstate->generation_stats.young;
struct gc_young_stats_buffer *buffer = &gcstate->generation_stats->young;
struct gc_generation_stats *stats = &buffer->items[buffer->index];
return stats;
}
else {
struct gc_old_stats_buffer *buffer = &gcstate->generation_stats.old[gen - 1];
struct gc_old_stats_buffer *buffer = &gcstate->generation_stats->old[gen - 1];
struct gc_generation_stats *stats = &buffer->items[buffer->index];
return stats;
}
Expand Down Expand Up @@ -2831,6 +2836,8 @@ _PyGC_Fini(PyInterpreterState *interp)
GCState *gcstate = &interp->gc;
Py_CLEAR(gcstate->garbage);
Py_CLEAR(gcstate->callbacks);
PyMem_RawFree(gcstate->generation_stats);
gcstate->generation_stats = NULL;

/* We expect that none of this interpreters objects are shared
with other interpreters.
Expand Down
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