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bpo-32422: Reduce lru_cache memory usage. #5008

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Dec 25, 2017
Merged

bpo-32422: Reduce lru_cache memory usage. #5008

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a505ca5
Reduce lru_cache memory usage.
methane Dec 25, 2017
153990e
Add news entry
methane Dec 25, 2017
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2017-12-25-20-22-47.bpo-32422.5H3Wq2.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
``functools.lru_cache`` uses less memory (3 words for each cached key) and
takes about 1/3 time for cyclic GC.
32 changes: 6 additions & 26 deletions Modules/_functoolsmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -677,26 +677,9 @@ typedef struct lru_list_elem {
static void
lru_list_elem_dealloc(lru_list_elem *link)
{
_PyObject_GC_UNTRACK(link);
Py_XDECREF(link->key);
Py_XDECREF(link->result);
PyObject_GC_Del(link);
}

static int
lru_list_elem_traverse(lru_list_elem *link, visitproc visit, void *arg)
{
Py_VISIT(link->key);
Py_VISIT(link->result);
return 0;
}

static int
lru_list_elem_clear(lru_list_elem *link)
{
Py_CLEAR(link->key);
Py_CLEAR(link->result);
return 0;
PyObject_Del(link);
}

static PyTypeObject lru_list_elem_type = {
Expand All @@ -720,10 +703,7 @@ static PyTypeObject lru_list_elem_type = {
0, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC, /* tp_flags */
0, /* tp_doc */
(traverseproc)lru_list_elem_traverse, /* tp_traverse */
(inquiry)lru_list_elem_clear, /* tp_clear */
Py_TPFLAGS_DEFAULT, /* tp_flags */
};


Expand Down Expand Up @@ -959,8 +939,8 @@ bounded_lru_cache_wrapper(lru_cache_object *self, PyObject *args, PyObject *kwds
}
} else {
/* Put result in a new link at the front of the queue. */
link = (lru_list_elem *)PyObject_GC_New(lru_list_elem,
&lru_list_elem_type);
link = (lru_list_elem *)PyObject_New(lru_list_elem,
&lru_list_elem_type);
if (link == NULL) {
Py_DECREF(key);
Py_DECREF(result);
Expand All @@ -970,7 +950,6 @@ bounded_lru_cache_wrapper(lru_cache_object *self, PyObject *args, PyObject *kwds
link->hash = hash;
link->key = key;
link->result = result;
_PyObject_GC_TRACK(link);
if (_PyDict_SetItem_KnownHash(self->cache, key, (PyObject *)link,
hash) < 0) {
Py_DECREF(link);
Expand Down Expand Up @@ -1151,7 +1130,8 @@ lru_cache_tp_traverse(lru_cache_object *self, visitproc visit, void *arg)
lru_list_elem *link = self->root.next;
while (link != &self->root) {
lru_list_elem *next = link->next;
Py_VISIT(link);
Py_VISIT(link->key);
Py_VISIT(link->result);
link = next;
}
Py_VISIT(self->maxsize_O);
Expand Down