@erlend-aasland Can you please take a look?

Tests / Address sanitizer (pull_request)

             ^^^^^^^^^^^
  File "/home/runner/work/cpython/cpython/Lib/urllib/request.py", line 643, in http_error_default
    raise HTTPError(req.full_url, code, msg, hdrs, fp)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
urllib.error.HTTPError: HTTP Error 404: Not Found

Unrelated

Mean +- std dev: [base] 552 ns +- 6 ns -> [vectorcall] 541 ns +- 5 ns: 1.02x faster

-11 ns is not really impressive :-(

@vstinner Updated!

@erlend-aasland Can you please take a look?

Sorry, I don't have time until earliest next weekend :(

(I remember doing similar stuff with some of the sqlite3 callbacks some months ago, but I discarded those changes because the added complexity did not outweigh the performance gain.)

@vstinner cc @erlend-aasland

Yeah the performance improvement itself is not impressive,
but considering _ctypes callback feature is widely used, doing something is better than doing nothing since it shows consistently 1-2 % improvement.
And we are fighting for 1-2 % improvement for these days :)

Yeah the performance improvement itself is not impressive, but considering _ctypes callback feature is widely used, doing something is better than doing nothing since it shows consistently 1-2 % improvement. And we are fighting for 1-2 % improvement for these days :)

My rule is that an micro-optimization is worth it if it's at least 10% faster on a micro-benchmark. On a macro-benchmark like pyperformance, smaller speedup are worth it, but I have no global rule for that.

Here I would expect to save 20 ns by avoiding the creating a tuple for positional arguments, but it's about -11 ns. Maybe "20 ns" is what I had in mind for my laptop CPU, but on your CPU, it's closer to 11 ns?

My rule is that an micro-optimization is worth it if it's at least 10% faster on a micro-benchmark.

It's not a strict rule and you're free to not follow it ;-)