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GeezerVison is showing github.com — bpo-38061: subprocess uses closefrom() on FreeBSD by vstinner · Pull Request #19697 · python/cpython

bpo-38061: subprocess uses closefrom() on FreeBSD #19697

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Merged
vstinner merged 1 commit into python:master from vstinner:subprocess_closefrom
Apr 24, 2020

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bpo-38061: subprocess uses closefrom() on FreeBSD #19697

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bpo-38061: subprocess uses closefrom() on FreeBSD
vstinner Apr 23, 2020
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4 changes: 4 additions & 0 deletions 4 Doc/whatsnew/3.9.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -471,6 +471,10 @@ Optimizations
until the main thread handles signals.
(Contributed by Victor Stinner in :issue:`40010`.)

* Optimize the :mod:`subprocess` module on FreeBSD using ``closefrom()``.
(Contributed by Ed Maste, Conrad Meyer, Kyle Evans, Kubilay Kocak and Victor
Stinner in :issue:`38061`.)


Build and C API Changes
=======================
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11 changes: 11 additions & 0 deletions 11 Misc/NEWS.d/next/Library/2020-04-24-01-55-00.bpo-38061.XmULB3.rst
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@@ -0,0 +1,11 @@
Optimize the :mod:`subprocess` module on FreeBSD using ``closefrom()``.
A single ``close(fd)`` syscall is cheap, but when ``sysconf(_SC_OPEN_MAX)`` is
high, the loop calling ``close(fd)`` on each file descriptor can take several
milliseconds.

The workaround on FreeBSD to improve performance was to load and mount the
fdescfs kernel module, but this is not enabled by default.

Initial patch by Ed Maste (emaste), Conrad Meyer (cem), Kyle Evans (kevans) and
Kubilay Kocak (koobs):
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@koobs koobs Apr 24, 2020

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Can remove this, full credit to Ed, Conrad & Kyle

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@vstinner vstinner Apr 24, 2020

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Even if you didn't write the patch directly, you helped to get it packaged. Thanks @koobs, you deserved to be credited ;-)

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=242274
8 changes: 7 additions & 1 deletion 8 Modules/_posixsubprocess.c
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Expand Up @@ -264,9 +264,15 @@ _close_fds_by_brute_force(long start_fd, PyObject *py_fds_to_keep)
start_fd = keep_fd + 1;
}
if (start_fd <= end_fd) {
#if defined(__FreeBSD__)
/* Any errors encountered while closing file descriptors are ignored */
closefrom(start_fd);
#else
for (fd_num = start_fd; fd_num < end_fd; ++fd_num) {
close(fd_num);
/* Ignore errors */
(void)close(fd_num);
}
#endif
}
}

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