Implement zero copy writes in StreamWriter

[bdraco]

python/cpython#91166 made writelines zero copy for Python 3.12+.

finishing a chunk has a lot of memcpy. Even if zero copy isn't implement for old python it will use b"".join() since it has a more efficient implementation in https://github.com/python/cpython/blob/91f4908798074db6c41925b4417bee1f933aca93/Objects/stringlib/join.h#L36 vs constructing a new bytes string for every add operation #9838 shows the bytes join is also faster, just not as fast as the zero copy write

[codspeed-hq]

CodSpeed Performance Report

Merging #9839 will improve performances by 53.25%

_{Comparing zerocopy_writes (d482e66) with master (fabf388)}

Summary

⚡ 2 improvements
✅ 22 untouched benchmarks

Benchmarks breakdown

	Benchmark	master	zerocopy_writes	Change
⚡	test_one_hundred_get_requests_with_30000_chunked_payload[pyloop]	48.2 ms	44 ms	+9.43%
⚡	test_one_hundred_get_requests_with_512kib_chunked_payload[pyloop]	262.5 ms	171.3 ms	+53.25%

[bdraco]

Well that was much better than expected.

We don't have a benchmark for compressed payloads here. We should add that as well

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.70%. Comparing base (2b135a8) to head (d482e66).
Report is 2 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #9839   +/-   ##
=======================================
  Coverage   98.70%   98.70%           
=======================================
  Files         118      118           
  Lines       36174    36261   +87     
  Branches     4297     4311   +14     
=======================================
+ Hits        35706    35793   +87     
  Misses        315      315           
  Partials      153      153           

Flag	Coverage Δ
CI-GHA	98.59% <100.00%> (+<0.01%)	⬆️
OS-Linux	98.28% <100.00%> (+<0.01%)	⬆️
OS-Windows	96.08% <100.00%> (+<0.01%)	⬆️
OS-macOS	97.36% <100.00%> (-0.01%)	⬇️
Py-3.10.11	97.21% <100.00%> (+<0.01%)	⬆️
Py-3.10.15	97.76% <100.00%> (+<0.01%)	⬆️
Py-3.11.10	97.81% <100.00%> (+<0.01%)	⬆️
Py-3.11.9	97.26% <100.00%> (-0.01%)	⬇️
Py-3.12.7	98.34% <100.00%> (+<0.01%)	⬆️
Py-3.13.0	98.33% <100.00%> (+0.04%)	⬆️
Py-3.9.13	97.13% <100.00%> (+<0.01%)	⬆️
Py-3.9.20	97.68% <100.00%> (+0.01%)	⬆️
Py-pypy7.3.16	97.30% <100.00%> (+<0.01%)	⬆️
VM-macos	97.36% <100.00%> (-0.01%)	⬇️
VM-ubuntu	98.28% <100.00%> (+<0.01%)	⬆️
VM-windows	96.08% <100.00%> (+<0.01%)	⬆️

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[asvetlov]

Yeah, many years ago transport.writelines(...) was implemented as transport.write(b''.join(lines)).

Now it utilizes sendmsg() which is more efficient than memcpy() + send()

[bdraco]

Still needs a test for a large compressed payload without chunked that is large enough to ensure compress and flush both output a payload

[patchback]

Backport to 3.11: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply a9a0d84 on top of patchback/backports/3.11/a9a0d849bd4ad65724710662e73f29f1e968bfe6/pr-9839

Backporting merged PR #9839 into master

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git remote add upstream https://github.com/aio-libs/aiohttp.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.11/a9a0d849bd4ad65724710662e73f29f1e968bfe6/pr-9839 upstream/3.11

4. Now, cherry-pick PR Implement zero copy writes in StreamWriter #9839 contents into that branch:

   $ git cherry-pick -x a9a0d849bd4ad65724710662e73f29f1e968bfe6

   If it'll yell at you with something like fatal: Commit a9a0d849bd4ad65724710662e73f29f1e968bfe6 is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x a9a0d849bd4ad65724710662e73f29f1e968bfe6

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Implement zero copy writes in StreamWriter #9839 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.11/a9a0d849bd4ad65724710662e73f29f1e968bfe6/pr-9839

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.