Calc proc cpu usage

main.go

package main

import (
	"fmt"
	"os"
	"strconv"
	"time"

	linuxproc "github.com/c9s/goprocinfo/linux"
)

func getCPUInfo() (*linuxproc.CPUInfo, error) {
	return linuxproc.ReadCPUInfo("/proc/cpuinfo")
}

func readProcessStat(pid uint64) (*linuxproc.ProcessStat, error) {
	return linuxproc.ReadProcessStat(fmt.Sprintf("/proc/%v/stat", pid))
}

func getCPUWorkTime() uint64 {
	ps, _ := linuxproc.ReadStat("/proc/stat")
	return ps.CPUStatAll.User + ps.CPUStatAll.Nice + ps.CPUStatAll.System + ps.CPUStatAll.IRQ + ps.CPUStatAll.SoftIRQ + ps.CPUStatAll.Steal + ps.CPUStatAll.Idle + ps.CPUStatAll.IOWait
}

func getProcWorkTime(pid uint64) uint64 {
	s, _ := readProcessStat(pid)
	return s.Stime + s.Utime + uint64(s.Cstime) + uint64(s.Cutime)
}

func main() {
	if len(os.Args) < 2 {
		fmt.Printf("need PID, e.g. try \"%s $(pgrep mysqld)\"\n", os.Args[0])
		os.Exit(1)
	}
	var pid uint64
	pid, _ = strconv.ParseUint(os.Args[1], 10, 64)
	captureInterval := time.Duration(5) * time.Second

	cpuinfo, _ := getCPUInfo()
	mul := float64(cpuinfo.NumCPU()) * 100

	prevProcCPUsage := getProcWorkTime(pid)
	prevCPUsage := getCPUWorkTime()

	for {
		currentCPUsage := getCPUWorkTime()
		currentProcCPUsage := getProcWorkTime(pid)

		fmt.Println(mul * float64(currentProcCPUsage-prevProcCPUsage) / float64(currentCPUsage-prevCPUsage+1))

		prevProcCPUsage = currentProcCPUsage
		prevCPUsage = currentCPUsage

		time.Sleep(captureInterval)
	}
}