Add an API to allow getting the number of "performance" cores-only

Feature or enhancement

Proposal:

Currently Python provides os.cpu_count() which returns the total number of physical CPU cores.

On macOS M-class machines (and probably other ARM hardware), there are actually two types of CPU cores: performance cores, and efficiency cores.

For many tasks where a user wants to do "1 task per core", it really only makes sense to do 1 task per performance core.

Therefore it'd be sensible to expose this number. On macOS it can be found with the hw.perflevel0.logicalcpu sysctl.

This could be done in one of two ways, a new function, e.g. os.performance_cpu_count(), or as a keyword-argument to os.cpu_count(performance_cores_only=True).

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

首先阅读现有的 os.cpu_count() API 及其特定于平台的实现，然后调查提案中描述的 macOS hw.perflevel0.logicalcpu sysctl。比较在受支持平台上采用新函数和关键字参数的方案，并找出相关测试。当所选 API 能够可靠地提供性能核心数量，并且针对受支持系统具有文档化的行为和测试覆盖时，即视为完成。