bpo-40423: Optimization: use close_range(2) if available #22651
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gpshead
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Oct 11, 2020
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@kevans91: Status check is done, and it's a failure ❌ . |
pablogsal
reviewed
Oct 11, 2020
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@gpshead I have removed the automerge in case my previous comment is not something I am missing, feel free to add it back if everything looks ok |
pablogsal
approved these changes
Oct 11, 2020
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@kevans91: Status check is done, and it's a success ✅ . |
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cemeyer
reviewed
Oct 11, 2020
| @@ -8779,6 +8782,14 @@ void | |||
| _Py_closerange(int first, int last) | |||
| { | |||
| first = Py_MAX(first, 0); | |||
| #ifdef HAVE_CLOSE_RANGE | |||
| if (close_range(first, last, 0) == 0 || errno != ENOSYS) { | |||
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It might be nicer to cache ENOSYS the first time we try close_range and avoid it in future _Py_closerange calls — assuming this is ever used more than once per process, which might not be true.
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I implemented such cache in the PEP 446 implementation: remind if a syscall supports atomic "O_CLOEXEC" flag. See for example _Py_open_cloexec_works in Python/fileutils.c.
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In my opinion, I don't think this code path is sensitive enough to really care.
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ah, nice, I hadn't thought of caching that. good idea. (one less failed syscall attempt before the real work likely involving many syscalls gets done in this case; so not a huge deal but still worthwhile)
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For the subprocess use case, the cache will likely only be first initialized in child processes, each child process has to do the check, and so the cache is useless.
I would mostly benefit to os.closerange().
I'm fine with not adding a cache. I agree that os.closerange() is an uncommon function.
xzy3
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Oct 18, 2020
) close_range(2) should be preferred at all times if it's available, otherwise we'll use closefrom(2) if available with a fallback to fdwalk(3) or plain old loop over fd range in order of most efficient to least. [note that this version does check for ENOSYS, but currently ignores all other errors] Automerge-Triggered-By: @pablogsal
adorilson
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Mar 13, 2021
) close_range(2) should be preferred at all times if it's available, otherwise we'll use closefrom(2) if available with a fallback to fdwalk(3) or plain old loop over fd range in order of most efficient to least. [note that this version does check for ENOSYS, but currently ignores all other errors] Automerge-Triggered-By: @pablogsal
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close_range(2) should be preferred at all times if it's available, otherwise we'll use closefrom(2) if available with a fallback to fdwalk(3) or plain old loop over fd range in order of most efficient to least.
[note that this version does check for ENOSYS, but currently ignores all other errors]
https://bugs.python.org/issue40423
Automerge-Triggered-By: @pablogsal