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gh-111968: Use per-thread slice_cache in free-threading #113972

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Jan 15, 2024
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gh-111968: Use per-thread slice_cache in free-threading #113972

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b05b359
gh-111968: Use per-thread slice_cahce in free-threading
corona10 Jan 12, 2024
ac5cdb8
Address code review
corona10 Jan 12, 2024
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9 changes: 9 additions & 0 deletions Include/internal/pycore_freelist.h
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Expand Up @@ -59,10 +59,19 @@ struct _Py_float_state {
#endif
};

struct _Py_slice_state {
#ifdef WITH_FREELISTS
/* Using a cache is very effective since typically only a single slice is
created and then deleted again. */
PySliceObject *slice_cache;
#endif
};

typedef struct _Py_freelist_state {
struct _Py_float_state float_state;
struct _Py_tuple_state tuple_state;
struct _Py_list_state list_state;
struct _Py_slice_state slice_state;
} _PyFreeListState;
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@erlend-aasland @colesbury
IMO, we should rename _PyFreeListState if we consider slice_cache is not freelist :)
Do you have any good suggestion?

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It's basically a freelist of max-length 1 🤷

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In that case, let's maintain the current naming. (Changing is quite stressful)


#ifdef __cplusplus
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1 change: 1 addition & 0 deletions Include/internal/pycore_gc.h
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Expand Up @@ -249,6 +249,7 @@ extern void _Py_ClearFreeLists(_PyFreeListState *state, int is_finalization);
extern void _PyTuple_ClearFreeList(_PyFreeListState *state, int is_finalization);
extern void _PyFloat_ClearFreeList(_PyFreeListState *state, int is_finalization);
extern void _PyList_ClearFreeList(_PyFreeListState *state, int is_finalization);
extern void _PySlice_ClearCache(_PyFreeListState *state);
extern void _PyDict_ClearFreeList(PyInterpreterState *interp);
extern void _PyAsyncGen_ClearFreeLists(PyInterpreterState *interp);
extern void _PyContext_ClearFreeList(PyInterpreterState *interp);
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3 changes: 0 additions & 3 deletions Include/internal/pycore_interp.h
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Expand Up @@ -187,9 +187,6 @@ struct _is {
struct _Py_long_state long_state;
struct _dtoa_state dtoa;
struct _py_func_state func_state;
/* Using a cache is very effective since typically only a single slice is
created and then deleted again. */
PySliceObject *slice_cache;

struct _Py_tuple_state tuple;
struct _Py_dict_state dict_state;
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2 changes: 1 addition & 1 deletion Include/internal/pycore_sliceobject.h
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Expand Up @@ -11,7 +11,7 @@ extern "C" {

/* runtime lifecycle */

extern void _PySlice_Fini(PyInterpreterState *);
extern void _PySlice_Fini(_PyFreeListState *);

extern PyObject *
_PyBuildSlice_ConsumeRefs(PyObject *start, PyObject *stop);
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26 changes: 15 additions & 11 deletions Objects/sliceobject.c
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Expand Up @@ -103,16 +103,20 @@ PyObject _Py_EllipsisObject = _PyObject_HEAD_INIT(&PyEllipsis_Type);

/* Slice object implementation */


void _PySlice_Fini(PyInterpreterState *interp)
void _PySlice_ClearCache(_PyFreeListState *state)
{
PySliceObject *obj = interp->slice_cache;
PySliceObject *obj = state->slice_state.slice_cache;
if (obj != NULL) {
interp->slice_cache = NULL;
state->slice_state.slice_cache = NULL;
PyObject_GC_Del(obj);
}
}

void _PySlice_Fini(_PyFreeListState *state)
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This is identical to _PySlice_ClearCache. Do we need both functions? If you want to keep both names, maybe have one call the other.

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Let's keep both names; I don't want to confuse people who work on the default build.

{
_PySlice_ClearCache(state);
}

/* start, stop, and step are python objects with None indicating no
index is present.
*/
Expand All @@ -122,11 +126,11 @@ _PyBuildSlice_Consume2(PyObject *start, PyObject *stop, PyObject *step)
{
assert(start != NULL && stop != NULL && step != NULL);

PyInterpreterState *interp = _PyInterpreterState_GET();
_PyFreeListState *state = _PyFreeListState_GET();
PySliceObject *obj;
if (interp->slice_cache != NULL) {
obj = interp->slice_cache;
interp->slice_cache = NULL;
if (state->slice_state.slice_cache != NULL) {
obj = state->slice_state.slice_cache;
state->slice_state.slice_cache = NULL;
_Py_NewReference((PyObject *)obj);
}
else {
Expand Down Expand Up @@ -354,13 +358,13 @@ Create a slice object. This is used for extended slicing (e.g. a[0:10:2]).");
static void
slice_dealloc(PySliceObject *r)
{
PyInterpreterState *interp = _PyInterpreterState_GET();
_PyFreeListState *state = _PyFreeListState_GET();
_PyObject_GC_UNTRACK(r);
Py_DECREF(r->step);
Py_DECREF(r->start);
Py_DECREF(r->stop);
if (interp->slice_cache == NULL) {
interp->slice_cache = r;
if (state->slice_state.slice_cache == NULL) {
state->slice_state.slice_cache = r;
}
else {
PyObject_GC_Del(r);
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4 changes: 1 addition & 3 deletions Python/pylifecycle.c
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Expand Up @@ -1752,15 +1752,13 @@ finalize_interp_types(PyInterpreterState *interp)
_PyUnicode_ClearInterned(interp);

_PyDict_Fini(interp);

_PySlice_Fini(interp);

_PyUnicode_Fini(interp);

_PyFreeListState *state = _PyFreeListState_GET();
_PyTuple_Fini(state);
_PyList_Fini(state);
_PyFloat_Fini(state);
_PySlice_Fini(state);

#ifdef Py_DEBUG
_PyStaticObjects_CheckRefcnt(interp);
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1 change: 1 addition & 0 deletions Python/pystate.c
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Expand Up @@ -1549,6 +1549,7 @@ PyThreadState_Clear(PyThreadState *tstate)
// Each thread should clear own freelists in free-threading builds.
_PyFreeListState *freelist_state = &((_PyThreadStateImpl*)tstate)->freelist_state;
_Py_ClearFreeLists(freelist_state, 0);
_PySlice_ClearCache(freelist_state);
#endif

_PyThreadState_ClearMimallocHeaps(tstate);
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