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