Free threading scaling bottleneck in sys.intern() #146041
Description
Bug report
Calling sys.intern() on a string that's not interned acquires the interpreter-wide interned_mutex. This can lead to scaling bottlenecks either due to explicit sys.intern() calls or indirectly because PyObject_SetAttr calls _PyUnicode_InternMortal.
We should avoid the lock acquisition if there is an interned copy already present in the interned_dict.
For example:
_ATTR_PREFIX = "bench"
@register_benchmark
def setattr_non_interned():
prefix = _ATTR_PREFIX
obj = MyObject()
for _ in range(1000 * WORK_SCALE):
setattr(obj, f"{prefix}_a", None)
setattr(obj, f"{prefix}_b", None)
setattr(obj, f"{prefix}_c", None)This came up when looking at Django scaling bottlenecks.