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Sat Jul 27 00:18:40 CEST 2013 · https://mail.python.org/pipermail/python-dev/2013-July/127613.html

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)

Victor

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