Source: debug.go in package runtime


package runtime

import (
	"runtime/internal/atomic"
	"unsafe"
)

GOMAXPROCS sets the maximum number of CPUs that can be executing simultaneously and returns the previous setting. It defaults to the value of runtime.NumCPU. If n < 1, it does not change the current setting. This call will go away when the scheduler improves.

func GOMAXPROCS(n int) int {
	if GOARCH == "wasm" && n > 1 {
		n = 1 // WebAssembly has no threads yet, so only one CPU is possible.
	}

	lock(&sched.lock)
	ret := int(gomaxprocs)
	unlock(&sched.lock)
	if n <= 0 || n == ret {
		return ret
	}

	stopTheWorldGC("GOMAXPROCS")

newprocs will be processed by startTheWorld

	newprocs = int32(n)

	startTheWorldGC()
	return ret
}

NumCPU returns the number of logical CPUs usable by the current process. The set of available CPUs is checked by querying the operating system at process startup. Changes to operating system CPU allocation after process startup are not reflected.

func NumCPU() int {
	return int(ncpu)
}

NumCgoCall returns the number of cgo calls made by the current process.

func NumCgoCall() int64 {
	var n int64
	for mp := (*m)(atomic.Loadp(unsafe.Pointer(&allm))); mp != nil; mp = mp.alllink {
		n += int64(mp.ncgocall)
	}
	return n
}

NumGoroutine returns the number of goroutines that currently exist.

func NumGoroutine() int {
	return int(gcount())
}

go:linkname debug_modinfo runtime/debug.modinfo

func debug_modinfo() string {
	return modinfo