monotonic clock sync tests

monotonic.go

package main

import (
	"fmt"
	"sort"
	"time"
	_ "unsafe"

	"golang.org/x/sys/unix"
)

const (
	sampleSize = 5
	diffNs     = 60 * 1e9
)

var samples = make([]struct {
	ts1   unix.Timespec
	ktime int64
	ts2   unix.Timespec
}, sampleSize)

//go:noescape
//go:linkname getKTime runtime.nanotime
func getKTime() int64

func getSample() {
	for i := range samples {
		unix.ClockGettime(unix.CLOCK_BOOTTIME, &samples[i].ts1)
		samples[i].ktime = getKTime()
		unix.ClockGettime(unix.CLOCK_BOOTTIME, &samples[i].ts2)
	}

	sort.Slice(samples, func(i, j int) bool {
		t1 := samples[i].ts2.Nano() - samples[i].ts1.Nano()
		t2 := samples[j].ts2.Nano() - samples[j].ts1.Nano()
		return t1 < t2
	})

	resync := ""
	diff := samples[0].ktime - samples[0].ts1.Nano()
	if diff < 0 {
		diff = -diff
	}
	if diff > diffNs {
		resync = fmt.Sprintf(" RESYNC: %v", diff/1e9)
	}

	fmt.Printf("t1: %v t2: %v kt: %v t2-t1: %v d: %v%v\n",
		samples[0].ts1.Nano(),
		samples[0].ts2.Nano(),
		samples[0].ktime,
		samples[0].ts2.Nano()-samples[0].ts1.Nano(),
		diff,
		resync,
	)
}

func main() {
	for {
		getSample()
		time.Sleep(3 * time.Second)
	}
}