GeezerVison is showing github.com — gh-129813, PEP 782: Use PyBytesWriter in _socket by vstinner · Pull Request #139097 · python/cpython
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vstinner
commented
Sep 18, 2025
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edited by bedevere-app
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Replace PyBytes_FromStringAndSize(NULL, size) and _PyBytes_Resize() with the new public PyBytesWriter API.
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Replace PyBytes_FromStringAndSize(NULL, size) and _PyBytes_Resize()
with the new public PyBytesWriter API.
vstinner
commented
Sep 18, 2025
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edited
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Micro-benchmark:
import pyperf
import socket
s1, s2 = socket.socketpair()
loops = 100
size = 1
def func():
s1.sendall(b'x' * (size * loops))
for _ in range(loops):
s = s2.recv(size)
if len(s) != size:
raise Exception
runner = pyperf.Runner()
runner.bench_func('bench', func, inner_loops=loops)
s1.close()
s2.close()
Result:
size=1: Mean +- std dev: [ref] 803 ns +- 12 ns -> [pep782] 769 ns +- 12 ns: 1.04x faster.
size=1_000: Mean +- std dev: [ref] 1.14 us +- 0.02 us -> [pep782] 1.15 us +- 0.03 us: 1.01x slower
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Another micro-benchmark:
import pyperf
import socket
s1, s2 = socket.socketpair()
def func(size):
s1.sendall(b'x' * size)
s = s2.recv(size)
if len(s) != size:
raise Exception
runner = pyperf.Runner()
for size in (1, 10, 100, 1000, 10_000, 100_000):
runner.bench_func(f'recv {size:,}B', func, size)
s1.close()
s2.close()
Result:
| Benchmark |
ref |
pep782 |
| recv 1B |
2.29 us |
2.19 us: 1.05x faster |
| recv 10B |
2.36 us |
2.29 us: 1.03x faster |
| recv 100B |
2.41 us |
2.34 us: 1.03x faster |
| recv 1,000B |
2.85 us |
2.73 us: 1.04x faster |
| recv 10,000B |
4.89 us |
4.95 us: 1.01x slower |
| Geometric mean |
(ref) |
1.02x faster |
Benchmark hidden because not significant (1): recv 100,000B
The benchmark is not reliable :-( If I run it again, I get different result:
| Benchmark |
ref |
pep782 |
| recv 1B |
2.22 us |
2.17 us: 1.02x faster |
| recv 100B |
2.27 us |
2.33 us: 1.03x slower |
| recv 100,000B |
25.0 us |
25.2 us: 1.01x slower |
| Geometric mean |
(ref) |
1.00x slower |
Benchmark hidden because not significant (3): recv 10B, recv 1,000B, recv 10,000B
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This introduced some refleaks.
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This introduced some refleaks.
Ooops, thanks for the report! I wrote #139151 to fix it.
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