Message 351351 - Python tracker

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Author	vstinner
Recipients	vstinner
Date	2019-09-09.07:25:35
SpamBayes Score	-1.0
Marked as misclassified	Yes
Message-id	<1568013936.15.0.668992536534.issue38061@roundup.psfhosted.org>
In-reply-to

Content
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. 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. On FreeBSD, the _posixsubprocess could use closefrom() to reduce the number of syscalls. On Linux, _posixsubprocess lists the content of /proc/self/fd/ to only close open file descriptor, after fork() and before exec().

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.

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.

On FreeBSD, the _posixsubprocess could use closefrom() to reduce the number of syscalls.

On Linux, _posixsubprocess lists the content of /proc/self/fd/ to only close open file descriptor, after fork() and before exec().

History
Date	User	Action	Args
2019-09-09 07:25:36	vstinner	set	recipients: + vstinner
2019-09-09 07:25:36	vstinner	set	messageid: <1568013936.15.0.668992536534.issue38061@roundup.psfhosted.org>
2019-09-09 07:25:36	vstinner	link	issue38061 messages
2019-09-09 07:25:35	vstinner	create