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// +build linux
package sysinfo
import (
"runtime"
"unsafe"
"golang.org/x/sys/unix"
)
// numCPU queries the system for the count of threads available
// for use to this process.
//
// Issues two syscalls.
// Returns 0 on errors. Use |runtime.NumCPU| in that case.
func numCPU() int {
// Gets the affinity mask for a process: The very one invoking this function.
pid, _, _ := unix.RawSyscall(unix.SYS_GETPID, 0, 0, 0)
var mask [1024 / 64]uintptr
_, _, err := unix.RawSyscall(unix.SYS_SCHED_GETAFFINITY, pid, uintptr(len(mask)*8), uintptr(unsafe.Pointer(&mask[0])))
if err != 0 {
return 0
}
// For every available thread a bit is set in the mask.
ncpu := 0
for _, e := range mask {
if e == 0 {
continue
}
ncpu += int(popcnt(uint64(e)))
}
return ncpu
}
// NumCPU returns the number of CPUs which are currently online
func NumCPU() int {
if ncpu := numCPU(); ncpu > 0 {
return ncpu
}
return runtime.NumCPU()
}
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