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Issue #20540: Fix a performance regression (vs. Python 3.2) when layering a multiprocessing Connection over a TCP socket.

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For small payloads, Nagle's algorithm would introduce idle delays before the entire transmission of a message.
This commit is contained in:
Antoine Pitrou 2014-02-08 23:05:52 +01:00
commit 0c1e31ab1e
2 changed files with 21 additions and 6 deletions
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22
Lib/multiprocessing/connection.py
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@ -395,13 +395,23 @@ class Connection(_ConnectionBase):
return buf
def _send_bytes(self, buf):
# For wire compatibility with 3.2 and lower
n = len(buf)
self._send(struct.pack("!i", n))
# The condition is necessary to avoid "broken pipe" errors
# when sending a 0-length buffer if the other end closed the pipe.
if n > 0:
self._send(buf)
# For wire compatibility with 3.2 and lower
header = struct.pack("!i", n)
if n > 16384:
# The payload is large so Nagle's algorithm won't be triggered
# and we'd better avoid the cost of concatenation.
chunks = [header, buf]
elif n > 0:
# Issue # 20540: concatenate before sending, to avoid delays due
# to Nagle's algorithm on a TCP socket.
chunks = [header + buf]
else:
# This code path is necessary to avoid "broken pipe" errors
# when sending a 0-length buffer if the other end closed the pipe.
chunks = [header]
for chunk in chunks:
self._send(chunk)
def _recv_bytes(self, maxsize=None):
buf = self._recv(4)