Support python -Xcpu_count= feature for container environment. · Issue #109595 · python/cpython (original) (raw)
Feature or enhancement
As #80235, there are requests for isolating CPU count in k8s or container environment, and this is a very important feature these days. (Practically my corp, a lot of workloads are running under container environments, and controlling CPU count is very important to resolve busy neighborhood issues)
There were a lot of discussions, and following the cgroup spec requires a lot of complexity and performance issues (due to fallback).
JDK 21 chooses not to depend on CPU Shares to compute active processor count and they choose to use -XX:ActiveProcessorCount=<n>.
see: https://bugs.openjdk.org/browse/JDK-8281571
I think that this strategy will be worth using from the CPython side too.
So if the user executes the python with -Xcpu_count=3option os.cpu_count will return 3, instead of the actual CPU count that was calculated from os.cpu_count.