diff --git a/Doc/whatsnew/3.9.rst b/Doc/whatsnew/3.9.rst index ee851706055..325121df139 100644 --- a/Doc/whatsnew/3.9.rst +++ b/Doc/whatsnew/3.9.rst @@ -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 ======================= diff --git a/Misc/NEWS.d/next/Library/2020-04-24-01-55-00.bpo-38061.XmULB3.rst b/Misc/NEWS.d/next/Library/2020-04-24-01-55-00.bpo-38061.XmULB3.rst new file mode 100644 index 00000000000..603d80b88b0 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2020-04-24-01-55-00.bpo-38061.XmULB3.rst @@ -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): +https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=242274 diff --git a/Modules/_posixsubprocess.c b/Modules/_posixsubprocess.c index 7d5a7fe17c0..60dd78d92a4 100644 --- a/Modules/_posixsubprocess.c +++ b/Modules/_posixsubprocess.c @@ -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 } }