[Python-checkins] cpython (3.3): Fixes issue #19929: Call os.read with 32768 within subprocess.Popen

gregory.p.smith python-checkins at python.org
Sun Dec 8 19:58:40 CET 2013


http://hg.python.org/cpython/rev/03a056c3b88e
changeset:   87838:03a056c3b88e
branch:      3.3
parent:      87836:5ca6e8af0aab
user:        Gregory P. Smith <greg at krypto.org>
date:        Sun Dec 08 10:56:07 2013 -0800
summary:
  Fixes issue #19929: Call os.read with 32768 within subprocess.Popen
communicate rather than 4096 for efficiency.  A microbenchmark shows
Linux and OS X both using ~50% less cpu time this way.

files:
  Lib/subprocess.py |  2 +-
  Misc/NEWS         |  4 ++++
  2 files changed, 5 insertions(+), 1 deletions(-)


diff --git a/Lib/subprocess.py b/Lib/subprocess.py
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -1654,7 +1654,7 @@
                             if self._input_offset >= len(self._input):
                                 close_unregister_and_remove(fd)
                     elif mode & select_POLLIN_POLLPRI:
-                        data = os.read(fd, 4096)
+                        data = os.read(fd, 32768)
                         if not data:
                             close_unregister_and_remove(fd)
                         self._fd2output[fd].append(data)
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -18,6 +18,10 @@
 Library
 -------
 
+- Issue #19929: Call os.read with 32768 within subprocess.Popen.communicate
+  rather than 4096 for efficiency.  A microbenchmark shows Linux and OS X
+  both using ~50% less cpu time this way.
+
 - Issue #19506: Use a memoryview to avoid a data copy when piping data
   to stdin within subprocess.Popen.communicate.  5-10% less cpu usage.
 

-- 
Repository URL: http://hg.python.org/cpython


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