| 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() |
| } |