Kubilay Kocak e4c2b30ce8 lang/python{27,35,36,37,38}: Add closefrom(2) support ... A single close(fd) syscall is cheap, but when MAXFDS (maximum file descriptor number) is high, the loop calling close(fd) on each file descriptor can take several milliseconds. The default value of subprocess.Popen "close_fds" parameter changed to True in Python 3. Compared to Python 2, close_fds=True can make Popen 10x slower: see bpo-37790 [1] The present workaround on FreeBSD to improve performance is to load and mount the fdescfs kernel module, but this is not enabled by default. This change adds minimum viable (and upstreamable) closefrom(2) syscall support to Python's subprocess and posix modules, improving performance significantly for loads that involve working with many processes, such as diffoscope, ansible, and many others. For additional optimizations, upstream recently (3.8) landed posix_spawn(2) support [3] and has stated that they will adopt close_range(2) after Linux merges it [4]. Linux/FreeBSD developers are already collaborating on ensuring compatible implementations, with FreeBSD's implementation pending in D21627. [5] Thank you emaste, cem, kevans for providing analysis, input, clarifications, comms/upstream support and patches. [1] https://bugs.python.org/issue37790 [2] https://bugs.python.org/issue38061 [3] https://bugs.python.org/issue35537 [4] https://lwn.net/Articles/789023/ [5] https://reviews.freebsd.org/D21627 Additional References: https://bugs.python.org/issue8052 https://bugs.python.org/issue11284 https://bugs.python.org/issue13788 https://bugs.python.org/issue1663329 https://www.python.org/dev/peps/pep-0446/ PR: 242274, 221700 Submitted by: kevans (emaste, cem) Approved by: koobs (python (maintainer), santa)		2019-11-29 10:55:00 +00:00
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files	lang/python{27,35,36,37,38}: Add closefrom(2) support	2019-11-29 10:55:00 +00:00
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Makefile	lang/python{27,35,36,37,38}: Add closefrom(2) support	2019-11-29 10:55:00 +00:00
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