test/hotspot/jtreg/gc/epsilon/TestMemoryMXBeans.java

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/**
 * @test TestMemoryMXBeans
 * @key gc
 * @requires vm.gc.Epsilon & !vm.graal.enabled
 * @summary Test JMX memory beans
 * @modules java.base/jdk.internal.misc
 *          java.management
 * @run main/othervm -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC          -Xmx1g TestMemoryMXBeans   -1 1024
 * @run main/othervm -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC -Xms1g   -Xmx1g TestMemoryMXBeans 1024 1024
 * @run main/othervm -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC -Xms128m -Xmx1g TestMemoryMXBeans  128 1024
 */

import java.lang.management.*;
import java.util.*;

public class TestMemoryMXBeans {

    static volatile Object sink;

    public static void main(String[] args) throws Exception {
        if (args.length < 2) {
            throw new IllegalStateException("Should provide expected heap sizes");
        }

        long initSize = 1L * Integer.parseInt(args[0]) * 1024 * 1024;
        long maxSize =  1L * Integer.parseInt(args[1]) * 1024 * 1024;

        testMemoryBean(initSize, maxSize);
        testAllocs();
    }

    public static void testMemoryBean(long initSize, long maxSize) {
        MemoryMXBean memoryMXBean = ManagementFactory.getMemoryMXBean();
        long heapInit = memoryMXBean.getHeapMemoryUsage().getInit();
        long heapMax = memoryMXBean.getHeapMemoryUsage().getMax();
        long nonHeapInit = memoryMXBean.getNonHeapMemoryUsage().getInit();
        long nonHeapMax = memoryMXBean.getNonHeapMemoryUsage().getMax();

        if (initSize > 0 && heapInit != initSize) {
            throw new IllegalStateException("Init heap size is wrong: " + heapInit + " vs " + initSize);
        }
        if (maxSize > 0 && heapMax != maxSize) {
            throw new IllegalStateException("Max heap size is wrong: " + heapMax + " vs " + maxSize);
        }
    }

    public static void testAllocs() throws Exception {
        MemoryMXBean memoryMXBean = ManagementFactory.getMemoryMXBean();

        // Try multiple times, to capture either APIs we call allocate lazily, or the background threads allocating
        int maxTries = 10;
        int tries = 0;

        while (true) {
            // Compute how much we waste during the calls themselves:
            long heapUsed1 = memoryMXBean.getHeapMemoryUsage().getUsed();
            long heapUsed2 = memoryMXBean.getHeapMemoryUsage().getUsed();
            long adj = heapUsed2 - heapUsed1;

            heapUsed1 = memoryMXBean.getHeapMemoryUsage().getUsed();
            sink = new int[1024*1024];
            heapUsed2 = memoryMXBean.getHeapMemoryUsage().getUsed();

            long diff = heapUsed2 - heapUsed1 - adj;
            long min =  8 + 4*1024*1024;
            long max = 16 + 4*1024*1024;
            if ((min <= diff && diff <= max)) {
              // Success
              return;
            }

            if (tries++ > maxTries) {
              throw new IllegalStateException("Allocation did not change used space right: " + diff + " should be in [" + min + ", " + max + "]");
            }

            // Wait and try again
            Thread.sleep(1000);
        }
    }

}