java - 我没有得到百分比 linux java 的 cpu 负载

Question

嗨，我正在尝试获取 CPU 负载，但我得到的每个值超过 100% 不明白我在做什么错......

因为我使用的是 core i3，上面有两个虚拟机和一个虚拟机，所以我正在执行此任务，我的源代码是，

public class PerformanceMonitor {

    static long lastSystemTime      = 0;
        static long lastProcessCpuTime  = 0;
        public static int  availableProcessors = ManagementFactory.getOperatingSystemMXBean().getAvailableProcessors();
      // public static int  availableProcessors = Runtime.getRuntime().availableProcessors();
        public synchronized double getCpuUsage()
        {
            ManagementFactory.getThreadMXBean().setThreadCpuTimeEnabled(true);
            if ( lastSystemTime == 0 )
            {
                baselineCounters();
              //  return ;
            }

            long systemTime     = System.nanoTime();
            long processCpuTime = 0;

            processCpuTime = ManagementFactory.getThreadMXBean().getCurrentThreadCpuTime();
            double cpuUsage = (double) (processCpuTime - lastProcessCpuTime ) / ( systemTime - lastSystemTime )*100.0;

            lastSystemTime     = systemTime;
            lastProcessCpuTime = processCpuTime;

            return cpuUsage / availableProcessors;
        }

        private void baselineCounters()
        {
            lastSystemTime = System.nanoTime();

            lastProcessCpuTime = ManagementFactory.getThreadMXBean().getCurrentThreadCpuTime();
        }



        }

我在我的代码中使用了这个类，

  public static void main(String[] args) {

             monitor = new PerformanceMonitor();
            for(int i=0 ; i<10000 ; i++){
                start();
                double usage = monitor.getCpuUsage();
                if(usage!=0)System.out.println("Current CPU usage in pourcentage : "+usage);
            }
        }

        private static void start() {
            int count=0;
            for(int i=0 ; i<100000 ; i++){
                count=(int) Math.random()*100;
            }
        }
}

我得到这样的输出，

Current CPU usage in pourcentage : 114.32926829268293
Current CPU usage in pourcentage : 48.70208931963182
Current CPU usage in pourcentage : 193.08746862328633
Current CPU usage in pourcentage : 236.85457129322594

希望得到您的建议在此先感谢

Answer 1

我怀疑间隔太短了。 linux 上的 cpu 计数器每秒仅更新 100 次，您可能会在大约 1/100 秒内执行循环，这意味着您会遇到非常大的错误。尝试增加循环的长度，使其达到几秒钟。

---

我延长了测试时间并删除了 /availableProcessors，我得到了这样的数字

Current CPU usage in percentage : 99.95763231535723
Current CPU usage in percentage : 99.94895863534565
Current CPU usage in percentage : 99.40642907762789
Current CPU usage in percentage : 99.96184668521532
Current CPU usage in percentage : 99.89017532820115
Current CPU usage in percentage : 99.91157680329947
Current CPU usage in percentage : 99.96919753553432
Current CPU usage in percentage : 99.94121334997978