获取Java中的CPU线程使用情况 [英] Obtaining CPU thread usage in Java

问题描述

我有一个关于获取给定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衡量这一点的指导。我到目前为止考虑的替代方案是

I have a question around getting CPU utilization for a given JNI block. I'm making some intensive CPU computation in the underlying C++ JNI native method. I'm in the process of optimizing this computation and want to benchmark it against varying inputs.

I need some guidance on how to go about measuring this. The alternatives I have considered so far are

• 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。当线程生成更多线程时会发生什么？

• Using JMX ThreadMXBean to measure system CPU usage for the current thread that invokes call into JNI method. However, I am not sure if JNI code is executed within the invoking thread context. What happens when the thread spawns more threads?

使用JMX OperatingSystemMXBean 来获取CPU的使用率整个JVM。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。

Using JMX OperatingSystemMXBean to get the CPU usage for the entire JVM. Ideally, this is not want I want as there could be parallel executions in JVM that might tweak the benchmarking.

使用 getrusage进行外部测量（..）。我想知道的是它与使用 OperatingSystemMXBean 有什么不同。

Measure externally using getrusage(..). What I want to know here is that how is it different than using OperatingSystemMXBean.

推荐答案

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：

You can use ThreadMXBean to get cpu usage statistics from all running threads. In the example below the CPU usage per thread is calculated:

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

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