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Fixed #33865 -- Optimized LimitedStream wrapper.

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The current implementation of LimitedStream is slow because .read()
performs an extra copy into a buffer and .readline() performs two
extra copies. The stream being wrapped is already typically a BytesIO
object so this is unnecessary.

This implementation has largely been untouched for 12 years and,
inspired by a simpler implementation in werkzeug, it was possible to
achieve the following performance improvement:

LimitedStream.read() (single line):
  Mean +- std dev: [bench_limitedstream-main] 286 ns +- 6 ns
  -> [bench_limitedstream-patch] 227 ns +- 6 ns: 1.26x faster
LimitedStream.readline() (single line):
  Mean +- std dev: [bench_limitedstream-main] 507 ns +- 11 ns
  -> [bench_limitedstream-patch] 232 ns +- 8 ns: 2.18x faster
LimitedStream.read(8192) (single line):
  Mean +- std dev: [bench_limitedstream-main] 360 ns +- 8 ns
  -> [bench_limitedstream-patch] 297 ns +- 6 ns: 1.21x faster
LimitedStream.readline(8192) (single line):
  Mean +- std dev: [bench_limitedstream-main] 602 ns +- 10 ns
  -> [bench_limitedstream-patch] 305 ns +- 10 ns: 1.98x faster
LimitedStream.read() (multiple lines):
  Mean +- std dev: [bench_limitedstream-main] 290 ns +- 5 ns
  -> [bench_limitedstream-patch] 236 ns +- 6 ns: 1.23x faster
LimitedStream.readline() (multiple lines):
  Mean +- std dev: [bench_limitedstream-main] 517 ns +- 19 ns
  -> [bench_limitedstream-patch] 239 ns +- 7 ns: 2.16x faster
LimitedStream.read(8192) (multiple lines):
  Mean +- std dev: [bench_limitedstream-main] 363 ns +- 8 ns
  -> [bench_limitedstream-patch] 311 ns +- 11 ns: 1.17x faster
LimitedStream.readline(8192) (multiple lines):
  Mean +- std dev: [bench_limitedstream-main] 601 ns +- 12 ns
  -> [bench_limitedstream-patch] 308 ns +- 7 ns: 1.95x faster

Geometric mean: 1.59x faster
This commit is contained in:
Nick Pope
2022-07-22 21:08:10 +01:00
committed by Mariusz Felisiak
parent 57f5669d23
commit b47f2f5b90
4 changed files with 43 additions and 49 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
tests/builtin_server/tests.py
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@@ -81,7 +81,7 @@ class WSGIFileWrapperTests(TestCase):
def test_file_wrapper_uses_sendfile(self):
env = {"SERVER_PROTOCOL": "HTTP/1.0"}
handler = FileWrapperHandler(None, BytesIO(), BytesIO(), env)
handler = FileWrapperHandler(BytesIO(), BytesIO(), BytesIO(), env)
handler.run(wsgi_app_file_wrapper)
self.assertTrue(handler._used_sendfile)
self.assertEqual(handler.stdout.getvalue(), b"")
@@ -89,7 +89,7 @@ class WSGIFileWrapperTests(TestCase):
def test_file_wrapper_no_sendfile(self):
env = {"SERVER_PROTOCOL": "HTTP/1.0"}
handler = FileWrapperHandler(None, BytesIO(), BytesIO(), env)
handler = FileWrapperHandler(BytesIO(), BytesIO(), BytesIO(), env)
handler.run(wsgi_app)
self.assertFalse(handler._used_sendfile)
self.assertEqual(handler.stdout.getvalue().splitlines()[-1], b"Hello World!")
@@ -102,7 +102,7 @@ class WSGIFileWrapperTests(TestCase):
response when file_wrapper is used.
"""
env = RequestFactory().get("/fileresponse/").environ
handler = FileWrapperHandler(None, BytesIO(), BytesIO(), env)
handler = FileWrapperHandler(BytesIO(), BytesIO(), BytesIO(), env)
handler.run(get_internal_wsgi_application())
# Sendfile is used only when file_wrapper has been used.
self.assertTrue(handler._used_sendfile)
@@ -119,7 +119,7 @@ class WSGIFileWrapperTests(TestCase):
@override_settings(ROOT_URLCONF="builtin_server.urls")
def test_file_response_call_request_finished(self):
env = RequestFactory().get("/fileresponse/").environ
handler = FileWrapperHandler(None, BytesIO(), BytesIO(), env)
handler = FileWrapperHandler(BytesIO(), BytesIO(), BytesIO(), env)
with mock.MagicMock() as signal_handler:
request_finished.connect(signal_handler)
handler.run(get_internal_wsgi_application())