[Python-Dev] [Python-checkins] cpython: Switch subprocess stdin to a socketpair, attempting to fix issue #19293 (AIX (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Wed Oct 23 11:58:49 CEST 2013

Le Tue, 22 Oct 2013 10:54:03 +0200, Victor Stinner <victor.stinner at gmail.com> a écrit :

Hi,

Would it be possible to use os.pipe() on all OSes except AIX? Pipes and socket pairs may have minor differences, but some applications may rely on these minor differences. For example, is the buffer size the same? For example, in test.support, we have two constants: PIPEMAXSIZE (4 MB) and SOCKMAXSIZE (16 MB).

For the record, pipe I/O seems a little faster than socket I/O under Linux:

$ ./python -m timeit -s "import os, socket; a,b = socket.socketpair(); r=a.fileno(); w=b.fileno(); x=b'x'*1000" "os.write(w, x); os.read(r, 1000)" 1000000 loops, best of 3: 1.1 usec per loop

$ ./python -m timeit -s "import os, socket; a,b = socket.socketpair(); x=b'x'*1000" "a.sendall(x); b.recv(1000)" 1000000 loops, best of 3: 1.02 usec per loop

$ ./python -m timeit -s "import os; r, w = os.pipe(); x=b'x'*1000" "os.write(w, x); os.read(r, 1000)" 1000000 loops, best of 3: 0.82 usec per loop

Regards

Antoine.

Victor 2013/10/22 guido.van.rossum <python-checkins at python.org>: > http://hg.python.org/cpython/rev/2a0bda8d283d > changeset: 86557:2a0bda8d283d > user: Guido van Rossum <guido at dropbox.com> > date: Mon Oct 21 20:37:14 2013 -0700 > summary: > Switch subprocess stdin to a socketpair, attempting to fix issue > #19293 (AIX hang). > > files: > Lib/asyncio/unixevents.py | 29 +++++++++- > Lib/test/testasyncio/testunixevents.py | 7 ++ > 2 files changed, 32 insertions(+), 4 deletions(-) > > > diff --git a/Lib/asyncio/unixevents.py b/Lib/asyncio/unixevents.py > --- a/Lib/asyncio/unixevents.py > +++ b/Lib/asyncio/unixevents.py > if stdin == subprocess.PIPE: > self.pipes[STDIN] = None > + # Use a socket pair for stdin, since not all platforms > + # support selecting read events on the write end of a > + # socket (which we use in order to detect closing of > the > + # other end). Notably this is needed on AIX, and works > + # just fine on other platforms. > + stdin, stdinw = self.loop.socketpair() > if stdout == subprocess.PIPE: > self.pipes[STDOUT] = None > if stderr == subprocess.PIPE:

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