Calculate the CPU usage properly using the Java Management API on Windows machine

Question

I want to implement a test program which calculates the CPU Usage using the Java Management API properly. The result should be the artihmetic mean over all processors and their cores. The problem on a windows machine is that the standard methods

ManagementFactory.getOperatingSystemMXBean().

(a) getSystemLoadAverage()
(b) getProcessCpuLoad()
(c) getSystemCpuLoad()

deliver too often the value -1.00 which means that the cpu usage could not be calculated. The standard methods work fine on linux, but not on windows. I also searched for the solution in this forum. I found in this forum some approaches to solve this problem, but none of them are helpful for me. For, example the code below always calculates 16 % on my machine which is not realistically.

public synchronized double getCpuUsage() {
    double cpuPercent = 0.0;

    for (int i = 0; i < 30; i++) {
        long start = System.nanoTime();
        int cpuCount = getOperatingSystemMxBean().getAvailableProcessors();
        Random random = new Random(start);
        int seed = Math.abs(random.nextInt());
        int primes = 10000;
        long startCpuTime = ManagementFactory.getThreadMXBean().getCurrentThreadCpuTime();
        start = System.nanoTime();
        while (primes != 0) {
            if (isPrime(seed))
            {
                primes--;
            }
            seed++;
        } 

        cpuPercent = calcCpu(startCpuTime, start, cpuCount);

        try {
            Thread.sleep(1000);
        }
        catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    return cpuPercent;
}

static boolean isPrime(int n) {
    // 2 is the smallest prime
    if (n <= 2)
    {
        return n == 2;
    }

    // even numbers other than 2 are not prime
    if (n % 2 == 0) {
        return false;
    }

    //check odd divisory from 3
    // to the square root of n
    for (int i = 3, end = (int)Math.sqrt(n); i <= end; i += 2) {
        if (n % i == 0)  {
            return false;
        }
    }

    return true;
}

public static int calcCpu(long cpuStartTime, long elapsedStartTime, int cpuCount) {
    long end = System.nanoTime();
    long totalAvailCpuTime = cpuCount * (end - elapsedStartTime);
    long totalUsedCpuTime = ManagementFactory.getThreadMXBean().getCurrentThreadCpuTime() - cpuStartTime;
    float per = ((float)totalUsedCpuTime*100) / (float)totalAvailCpuTime;
    //log (per);
    return (int)per;
}

private OperatingSystemMXBean getOperatingSystemMxBean() {
    return (OperatingSystemMXBean) ManagementFactory.getOperatingSystemMXBean();
}

Do you know a proper solution for this problem?

You would want to include real links to other SO questions you consulted already. And maybe you would need some JNI interface into some real Windows system calls here. — GhostCat, Sep 15 '17 at 14:09
Link to other Cpu Usage question: https://stackoverflow.com/questions/47177/how-do-i-monitor-the-computers-cpu-memory-and-disk-usage-in-java — user2969510, Sep 15 '17 at 14:15
By A) identifying suitable system interfaces to then B) do research on JNI. Dont expect other people to do your work. — GhostCat, Sep 15 '17 at 14:16
Maybe you can run some powershell scripts instead. But life is what it is - not necessarily what we *need* or want. — GhostCat, Sep 15 '17 at 15:42

score 0 · Answer 1 · answered Jun 07 '18 at 14:36

0

I solved the problem in the windows machine by using the library oshi. On Solaris and Linux I continue using the Java Management API.

answered Jun 07 '18 at 14:36

user2969510

21
5

Calculate the CPU usage properly using the Java Management API on Windows machine

1 Answers1