Issue #21797 has been updated by moznion (Taiki Kawakami). 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, 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/t...), 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 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/129cf004294af68ac53... ---------------------------------------- Feature #21797: Make Etc.nprocessors cgroup-aware on Linux https://bugs.ruby-lang.org/issues/21797#change-115818 * Author: moznion (Taiki Kawakami) * Status: Open ---------------------------------------- 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. Extending `Etc.nprocessors` to respect cgroups is one option, but that would be a breaking change, so adding a new API 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/129cf004294af68ac53... -- https://bugs.ruby-lang.org/

Issue #21797 has been updated by osyoyu (Daisuke Aritomo). It'd be nice if `RUBY_MAX_CPU` would be autoconfigured based on this, just like Go 1.25 `GOMAXPROCS`. Its default value is currently fixed to 8, but not many cloud containers have 8 cores worth of processors. https://github.com/ruby/ruby/blob/8efaf5e6b6a25e0d237f3d71b75865661ae98268/t... ---------------------------------------- Feature #21797: Make Etc.nprocessors cgroup-aware on Linux https://bugs.ruby-lang.org/issues/21797#change-115823 * Author: moznion (Taiki Kawakami) * Status: Open ---------------------------------------- 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/t...), 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/129cf004294af68ac53... -- https://bugs.ruby-lang.org/

Issue #21797 has been updated by moznion (Taiki Kawakami). osyoyu (Daisuke Aritomo) wrote in #note-4:

It'd be nice if `RUBY_MAX_CPU` would be autoconfigured based on this, just like Go 1.25 `GOMAXPROCS`.

Its default value is currently fixed to 8, but not many cloud containers have 8 cores worth of processors. https://github.com/ruby/ruby/blob/8efaf5e6b6a25e0d237f3d71b75865661ae98268/t...

This sounds very good, but it should probably be a separate ticket though. nobu (Nobuyoshi Nakada) wrote in #note-5:

How about https://github.com/ruby/etc/tree/linux-cgroup-from-maxprocs?

Thank you for your quick action. I left a comment on the pull request; overall, it looks good. ---------------------------------------- Feature #21797: Make Etc.nprocessors cgroup-aware on Linux https://bugs.ruby-lang.org/issues/21797#change-115836 * Author: moznion (Taiki Kawakami) * Status: Open ---------------------------------------- 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/t...), 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/129cf004294af68ac53... -- https://bugs.ruby-lang.org/

Issue #21797 has been updated by moznion (Taiki Kawakami). Thank you for your comments. Let me summarize the discussion. ### 1. Introducing a new API under `Etc` Introducing a method such as `Etc.cpu_quota`, which returns `Float | nil`, seems reasonable. ### 2. Changing the behavior of `Etc.nprocessors` Changing the behavior of `Etc.nprocessors` to respect cgroup-based values and fall back to the original logic when cgroups are unavailable. This would be a breaking change, but it would likely be beneficial for most use cases, and the negative impact should be minimal. ### 3. Injecting the number of actually available CPUs into `RUBY_MAX_CPU` This would be useful, but it should be handled as a separate ticket after this one is resolved. ### 4. Implementation approach Which is preferred: pure Ruby as a part of `ruby/etc` or C? --- What do you think? ---------------------------------------- Feature #21797: Make Etc.nprocessors cgroup-aware on Linux https://bugs.ruby-lang.org/issues/21797#change-115844 * Author: moznion (Taiki Kawakami) * Status: Open ---------------------------------------- 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/t...), 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/129cf004294af68ac53... -- https://bugs.ruby-lang.org/

Issue #21797 has been updated by moznion (Taiki Kawakami).

What would be the value of nprocessor in this case?, e.g. if cpu_quotais 0.5, what does nprocessors return? cpu_quota.ceil?

I think it depends on the decision, but either floor or ceil should be fine (for reference, Go’s `GOMAXPROCS` has used ceil since 1.25). In any case, it would be better if the logic were configurable.

Which is preferred: pure Ruby as a part of ruby/etc or C?

I agree with this. It sounds like it should be implemented under `ruby/etc`. By the way, @osyoyu was interested in using this function in `ruby/thread_pthread.c`, but is it sufficient for Ruby to set the value in the `RUBY_MAX_CPU` environment variable automatically? In other words, do we actually need to use this function directly in the C layer? ---------------------------------------- Feature #21797: Make Etc.nprocessors cgroup-aware on Linux https://bugs.ruby-lang.org/issues/21797#change-115889 * Author: moznion (Taiki Kawakami) * Status: Open ---------------------------------------- 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/t...), 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/129cf004294af68ac53... -- https://bugs.ruby-lang.org/