On Sun, May 17, 2020, at 12:22 PM, Glyph wrote:
In the one case that may be complicated I think that pinning Twisted will be acceptable, since the service in question is a process supervisor without direct external exposure. Well in that case I'll just do my best to add lots of goodies (posix_spawn support!) that will make you want to upgrade that to current twisted and python 3.8 :).
Oh it's not for lack of wanting. :-) The service in question is actually spawning Python processes, so posix_spawn support doesn't seem likely to help much: fork() + exec() is a drop in the bucket compared to Python imports, particularly in Python 3 (I'm hoping to explore oxidized-importer [1] to help with this at some point). If looking improve process management in Twisted, I think that the lowest-hanging fruit is to watch children with pidfd, rather than reaping all children on SIGCHLD. This O(n) reaping --- one waitpid() call per running process --- starts to consume substantial CPU. IIRC it pegged a core at 20,000 processes or so. ---Tom [1]: https://pypi.org/project/oxidized-importer/