For the threads scheduler, it makes sense to have NumCPU available.
For all other schedulers, the number of available CPUs is practically
limited to one by the scheduler (even though the system might have more
CPUs).
This is not a scheduler in the runtime, instead every goroutine is
mapped to a single OS thread - meaning 1:1 scheduling.
While this may not perform well (or at all) for large numbers of
threads, it greatly simplifies many things in the runtime. For example,
blocking syscalls can be called directly instead of having to use epoll
or similar. Also, we don't need to do anything special to call C code -
the default stack is all we need.
Ayke van Laethem