diff options
| -rw-r--r-- | Lib/multiprocessing/connection.py | 22 | ||||
| -rw-r--r-- | Misc/NEWS | 5 |
2 files changed, 21 insertions, 6 deletions
diff --git a/Lib/multiprocessing/connection.py b/Lib/multiprocessing/connection.py index 8ad6fd5..09ec4fc 100644 --- a/Lib/multiprocessing/connection.py +++ b/Lib/multiprocessing/connection.py @@ -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) @@ -27,6 +27,11 @@ Core and Builtins Library ------- +- Issue #20540: Fix a performance regression (vs. Python 3.2) when layering + a multiprocessing Connection over a TCP socket. For small payloads, Nagle's + algorithm would introduce idle delays before the entire transmission of a + message. + - Issue #16983: the new email header parsing code will now decode encoded words that are (incorrectly) surrounded by quotes, and register a defect. |