package sysinfo // import "github.com/docker/docker/pkg/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() }