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- // +build linux
- package sysinfo
- import (
- "runtime"
- "syscall"
- "unsafe"
- )
- // 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, _, _ := syscall.RawSyscall(syscall.SYS_GETPID, 0, 0, 0)
- var mask [1024 / 64]uintptr
- _, _, err := syscall.RawSyscall(syscall.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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