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gh-132657: Avoid locks and refcounts in frozenset operations #136107

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Merged
merged 5 commits into from
Aug 30, 2025
+26 −10
Merged

gh-132657: Avoid locks and refcounts in frozenset operations #136107

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e630b64
Avoid locks are and refcounts in frozenset operatins
eendebakpt Jun 27, 2025
40d2d29
avoid table check
eendebakpt Jun 29, 2025
10aed73
📜🤖 Added by blurb_it.
blurb-it[bot] Jul 9, 2025
574e0f4
Merge branch 'main' into frozenset_specialization
eendebakpt Aug 14, 2025
7b4240e
Merge branch 'main' into frozenset_specialization
eendebakpt Aug 30, 2025
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-07-09-21-27-14.gh-issue-132657.kSA8R3.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Improve performance of :class:`frozenset` by removing locks in the free-threading build.
35 changes: 25 additions & 10 deletions Objects/setobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,8 @@ set_lookkey(PySetObject *so, PyObject *key, Py_hash_t hash)
int probes;
int cmp;

int frozenset = PyFrozenSet_CheckExact(so);

while (1) {
entry = &so->table[i];
probes = (i + LINEAR_PROBES <= mask) ? LINEAR_PROBES: 0;
Expand All @@ -102,13 +104,20 @@ set_lookkey(PySetObject *so, PyObject *key, Py_hash_t hash)
&& unicode_eq(startkey, key))
return entry;
table = so->table;
Py_INCREF(startkey);
cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);
Py_DECREF(startkey);
if (cmp < 0)
return NULL;
if (table != so->table || entry->key != startkey)
return set_lookkey(so, key, hash);
if (frozenset) {
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@eendebakpt eendebakpt Jun 29, 2025 •
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Note: the special case for unicode a couple of lines above was introduced to avoid the check on mutated tables. See commit eendebakpt@93035c4 that moved the code inline.

With the check for an exact frozenset we avoid the same checks.

cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);
if (cmp < 0)
return NULL;
} else {
// incref startkey because it can be removed from the set by the compare
Py_INCREF(startkey);
cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);
Py_DECREF(startkey);
if (cmp < 0)
return NULL;
if (table != so->table || entry->key != startkey)
return set_lookkey(so, key, hash);
}
if (cmp > 0)
return entry;
mask = so->mask;
Expand Down Expand Up @@ -2235,10 +2244,16 @@ set_contains_lock_held(PySetObject *so, PyObject *key)
int
_PySet_Contains(PySetObject *so, PyObject *key)
{
assert(so);

int rv;
Py_BEGIN_CRITICAL_SECTION(so);
rv = set_contains_lock_held(so, key);
Py_END_CRITICAL_SECTION();
if (PyFrozenSet_CheckExact(so)) {
rv = set_contains_lock_held(so, key);
} else {
Py_BEGIN_CRITICAL_SECTION(so);
rv = set_contains_lock_held(so, key);
Py_END_CRITICAL_SECTION();
}
return rv;
}

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