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

Guido van Rossum guido at python.org
Sat Jul 27 00:12:18 CEST 2013

On Fri, Jul 26, 2013 at 5:08 AM, Victor Stinner <victor.stinner at gmail.com> wrote:

After having written 2 PEP on the topic, I slowly agree that make all file descriptors non-inheritable is the best compromise. It solves most, or all, issues.

Right.

The main drawback is the additionnal syscalls: on some platforms, 2 additional syscalls are need to make a file descriptor non-inheritable for each creation of file descriptor. According to my benchmark on the implementation of the PEP 433: the overhead of making a file descriptor non-inheritable is between 1% and 3% (7.8 µs => 7.9 or 8.0 µs) on Linux 3.6. http://www.python.org/dev/peps/pep-0433/#performances

Remember that this is going to be Python 3.4 and newer. AFAICT setting O_CLOEXEC on open works on OSX (at least the man page on OSX 10.8 has it), on newer Linuxes, and the equivalent on Windows. So even if it does cost an extra syscall on older systems, those systems will be obsolete before Python 3.4 becomes mainstream there. And it does look like the syscalls are pretty cheap. I also don't think I'm not particularly worried about the cost of syscalls for making a socket (non)blocking -- although we should probably avoid the second fcntl() call if the first call shows the flag is already set the way we want it.

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

More information about the Python-Dev mailing list