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Fixes issue #19929: Call os.read with 32768 within subprocess.Popen

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communicate rather than 4096 for efficiency.  A microbenchmark shows
Linux and OS X both using ~50% less cpu time this way.
This commit is contained in:
Gregory P. Smith 2013-12-08 10:56:07 -08:00
parent 6976104a36
commit 589ecda56e
2 changed files with 5 additions and 1 deletions
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2
Lib/subprocess.py
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@ -1654,7 +1654,7 @@ class Popen(object):
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)

4
Misc/NEWS
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@ -18,6 +18,10 @@ Core and Builtins
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.