How can I write CPU usage on screen?

This returns 0 on 1st frame and 100 on every other. is there other way to get CPU usage in script?

using UnityEngine; using System.Collections; using System.Diagnostics;

public class PerformanceCheck : MonoBehaviour { System.Diagnostics.PerformanceCounter cpuCounter;

 void Start()
 {
     System.Diagnostics.PerformanceCounterCategory.Exists("PerformanceCounter");

     cpuCounter = new PerformanceCounter("Processor", "% Processor Time", Process.GetCurrentProcess().ProcessName);

     /*cpuCounter.CategoryName = "Processor";
     cpuCounter.CounterName = "% Processor Time";
     cpuCounter.InstanceName = "_Total";*/
 }

 void OnGUI()
 {
     GUI.Label(new Rect(10, 10, 100, 20), "CPU: " + getCurrentCpuUsage());
 }

 public string getCurrentCpuUsage()
 {
     return cpuCounter.NextValue() + "%";
 }

}