Feature or enhancement

As#80235, there are requests for isolating CPU count in k8s or container environment, andthis 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=3optionos.cpu_count will return 3, instead of the actual CPU count that was calculated fromos.cpu_count.

cc@vstinner@indygreg

Linked PRs

• gh-109595: Add -Xcpu_count=<n> cmdline for container users #109667
• gh-110649: Update -Xcpu_count=<n> cmdline to support process mode #110639