我有一个关于获得给定JNI块的CPU利用率的问题.我在底层的C JNI本机方法中进行了一些密集的CPU计算.我正在优化这个计算,并希望根据不同的输入进行基准测试.我需要一些关于如何测量这个的指导.我到目前为止考虑的替代方案是

>使用JMX ThreadMXBean来测量调用JNI方法调用的当前线程的系统CPU使用率.但是,我不确定JNI代码是否在调用线程上下文中执行.当线程产生更多线程时会发生什么？
>使用JMX OperatingSystemMXBean获取整个JVM的CPU使用率.理想情况下,这不是我想要的,因为JVM中可能存在可能调整基准测试的并行执行.
>使用getrusage(..)进行外部测量.我想知道的是它与使用OperatingSystemMXBean有何不同.

解决方法:

您可以使用ThreadMXBean从所有正在运行的线程获取cpu使用情况统计信息.在下面的示例中,计算每个线程的CPU使用率：

private int sampleTime = 10000;
private ThreadMXBean threadMxBean = ManagementFactory.getThreadMXBean();
private RuntimeMXBean runtimeMxBean = ManagementFactory.getRuntimeMXBean();
private OperatingSystemMXBean osMxBean = ManagementFactory.getOperatingSystemMXBean();
private Map<Long, Long> threadInitialCPU = new HashMap<Long, Long>();
private Map<Long, Float> threadCPUUsage = new HashMap<Long, Float>();
private long initialUptime = runtimeMxBean.getUptime();

ThreadInfo[] threadInfos = threadMxBean.dumpAllThreads(false, false);
for (ThreadInfo info : threadInfos) {
    threadInitialCPU.put(info.getThreadId(), threadMxBean.getThreadCpuTime(info.getThreadId()));
}

try {Thread.sleep(sampleTime);} catch (InterruptedException e) {}

long upTime = runtimeMxBean.getUptime();

Map<Long, Long> threadCurrentCPU = new HashMap<Long, Long>();
ThreadInfo[] threadInfos = threadMxBean.dumpAllThreads(false, false);
for (ThreadInfo info : threadInfos) {
    threadCurrentCPU.put(info.getThreadId(), threadMxBean.getThreadCpuTime(info.getThreadId()));
}

// CPU over all processes
//int nrCPUs = osMxBean.getAvailableProcessors();
// total CPU: CPU % can be more than 100% (devided over multiple cpus)
long nrCPUs = 1;
// elapsedTime is in ms.
long elapsedTime = (upTime - initialUptime);
for (ThreadInfo info : threadInfos) {
    // elapsedCpu is in ns
    Long initialCPU = threadInitialCPU.get(info.getThreadId());
    if (initialCPU != null) {
        long elapsedCpu = threadCurrentCPU.get(info.getThreadId()) - initialCPU;
        float cpuUsage = elapsedCpu / (elapsedTime * 1000000F * nrCPUs);
        threadCPUUsage.put(info.getThreadId(), cpuUsage);
    }
}

// threadCPUUsage contains cpu % per thread
System.out.println(threadCPUUsage);
// You can use osMxBean.getThreadInfo(theadId) to get information on every thread reported in threadCPUUsage and analyze the most CPU intentive threads