Expose CPU power consumption (AMD ZenX processors) via REST-API

cpupower.go

package main

import (
	"encoding/binary"
	"fmt"
	"net/http"
	"os"
	"sync"
	"time"
)

var (
	pwr = 0.0
	mut = sync.RWMutex{}
)

const (
	pwrMultiplier = 1.52588e-05
)

func main() {
	f, _ := os.OpenFile("/dev/cpu/0/msr", os.O_RDONLY, os.ModeDevice)
	defer f.Close()
	f.Seek(0xC001029B, 0)

	go read(f)

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		mut.RLock()
		fmt.Fprintf(w, "%.2f", pwr)
		mut.RUnlock()
	})
	http.ListenAndServe(":9998", nil)
}

func read(f *os.File) float64 {
	var rawa uint64
	var rawb uint64

	for {
		binary.Read(f, binary.LittleEndian, &rawa)
		time.Sleep(1000 * time.Millisecond)
		binary.Read(f, binary.LittleEndian, &rawb)

		mut.Lock()
		pwr = float64(rawb-rawa) * pwrMultiplier
		mut.Unlock()
	}
}