bpo-40423: Optimization: use close_range(2) if available #22651
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_Py_closerange: last-minute braino, flip logic around
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It might be nicer to cache
ENOSYSthe first time we tryclose_rangeand avoid it in future_Py_closerangecalls — assuming this is ever used more than once per process, which might not be true.There was a problem hiding this comment.
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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.