On Monday, 18 May 2020 22:21:16 BST Tom Most wrote:
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).
Would putting all the .pyc/.pyo into a zip file help with the import problem? You only have one file to open, the .zip, and no compile as its only .pyc/.pyo.
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.
Why not waitpid for all children (pid=0 or pid=-1) in a single call? Barry
---Tom