Feature #21797
Updated by moznion (Taiki Kawakami) about 3 hours ago
Currently, `Etc.nprocessors` ignores cgroup CPU quotas. This causes issues in containers where CPU limits differ from the host CPU count.
I have written a gem for this purpose (https://github.com/moznion/maxprocs-ruby), but it would be preferable if the Ruby core implementation respected cgroup configuration.
Additionally, concurrent-ruby provides similar functionality, but if the language itself offered this capability, language users would not need to implement it individually.
And some parts of the Ruby language handle the number of processors using hard-coded values (e.g., https://github.com/ruby/ruby/blob/8efaf5e6b6a25e0d237f3d71b75865661ae98268/thread_pthread.c#L1737-L1738), so this could also be useful for Ruby language development.
Extending `Etc.nprocessors` to respect cgroups is one option, but that would be a breaking change, so adding a new API (e.g., `Etc.cpu_quota` or something?) might be a better approach.
## Prior Art
- Go 1.25: runtime GOMAXPROCS (Issue [#73193](https://github.com/golang/go/issues/73193))
- [uber-go/automaxprocs](https://github.com/uber-go/automaxprocs)
- [concurrent-ruby](https://github.com/ruby-concurrency/concurrent-ruby): https://github.com/ruby-concurrency/concurrent-ruby/blob/129cf004294af68ac53e53a2f1197621b303570a/lib/concurrent-ruby/concurrent/utility/processor_counter.rb