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Improve performance of exception raise #160473
Description
Feature or enhancement
At the end of _PyErr_SetObject() the value is a normalized BaseException instance. The function still took a new reference to Py_TYPE(value) and fetched the value's traceback, only for _PyErr_Restore() to set that traceback back on the same object, store the value and drop the type again. Instead we can call _PyErr_SetRaisedException() directly.
Benchmarks
Default build, single thread:
| Benchmark | base | patch |
|---|---|---|
raise E / except E (heap type) |
174 ns | 171 ns: 1.02x faster |
raise E('message') / except E |
210 ns | 205 ns: 1.02x faster |
raise KeyError(1) / except KeyError (static type) |
192 ns | 176 ns: 1.09x faster |
d[1] / except KeyError (raised from C) |
177 ns | 170 ns: 1.04x faster |
f() / except E (raise through a frame) |
290 ns | 284 ns: 1.02x faster |
| Geometric mean | (ref) | 1.04x faster |
The gain is within binary layout noise range, but in the right direction.
Free-threaded build, N threads each running try: raise E / except E: pass with E defined
by the main thread:
| case | 1 thr | 2 thr | 4 thr | 8 thr |
|---|---|---|---|---|
ctl: isinstance(b, A) |
1.00 | 1.00 | 1.00 | 1.00 |
raise E / except E |
1.03-1.04 | 1.12-1.15 | 1.34-1.44 | 1.60-1.70 |
Has this already been discussed elsewhere?
This is a minor feature, which does not need previous discussion elsewhere
Links to previous discussion of this feature:
No response
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