[Python-Dev] Inherance of file descriptor and handles on Windows (PEP 446)

[Guido van Rossum]

On Fri, Jul 26, 2013 at 9:26 PM, Gregory P. Smith <greg at krypto.org> wrote:
>
> On Fri, Jul 26, 2013 at 3:23 PM, Antoine Pitrou <solipsis at pitrou.net> wrote:
>>
>> On Sat, 27 Jul 2013 00:18:40 +0200
>> Victor Stinner <victor.stinner at gmail.com> wrote:
>> > 2013/7/26 Antoine Pitrou <solipsis at pitrou.net>:
>> > > On Fri, 26 Jul 2013 22:17:47 +0200
>> > >> """
>> > >> On Linux, setting the close-on-flag has a low overhead on
>> > >> performances. Results of bench_cloexec.py on Linux 3.6:
>> > >>
>> > >> - close-on-flag not set: 7.8 us
>> > >> - O_CLOEXEC: 1% slower (7.9 us)
>> > >> - ioctl(): 3% slower (8.0 us)
>> > >> - fcntl(): 3% slower (8.0 us)
>> > >> """
>> > >
>> > > You aren't answering my question: slower than what?
>> >
>> > Ah, you didn't understand the labels. bench_cloexec.py runs a
>> > benchmark on os.open(path, os.O_RDONLY, cloexec=False) and
>> > os.open(path, os.O_RDONLY, cloexec=True) with different implementation
>> > of making the file descriptor non-inheritable.
>> >
>> > close-on-flag not set: 7.8 us
>> > => C code: open(path, O_RDONLY)
>> >
>> > O_CLOEXEC: 1% slower (7.9 us)
>> > => C code: open(path, O_RDONLY|CLOEXEC)
>> > => 1% slower than open(path, O_RDONLY)
>> >
>> > ioctl(): 3% slower (8.0 us)
>> > => C code: fd=open(path, O_RDONLY); ioctl(fd, FIOCLEX, 0)
>> > => 3% slower than open(path, O_RDONLY)
>> >
>> > fcntl(): 3% slower (8.0 us)
>> > => C code: fd=open(path, O_RDONLY); flags = fcntl(fd, F_GETFD);
>> > fcntl(fd, F_SETFD, flags | FD_CLOEXEC)
>> > => 3% slower than open(path, O_RDONLY)
>>
>> Ok, so I think this it is a totally reasonable compromise.
>>
>> People who bother about a 3% slowdown when calling os.open() can
>> optimize the hell out of their code using Cython for all I care :-)
>>
>
> +1  ;)
>
> and +1 for making the sane default of noinherit / cloexec /
> whatever-others-call-it by default for all fds/handles ever opened by
> Python. It stops ignoring the issue (ie: the status quo of matching the
> default behavior of C as defined in the 1970s)... That is a GOOD thing. :)

Do we even need a new PEP, or should we just do it? Or can we adapt
Victor's PEP 446?

-- 
--Guido van Rossum (python.org/~guido)