GetSafepointCount.java

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/*
 * @test
 * @bug     4858522
 * @summary Basic unit test of HotspotClassLoadingMBean.getSafepointCount()
 * @author  Steve Bohne
 *
 * @run main/othervm -XX:+UsePerfData GetSafepointCount
 */

/*
 * This test is just a sanity check and does not check for the correct value.
 */

import sun.management.*;

public class GetSafepointCount {

    private static HotspotRuntimeMBean mbean =
        (HotspotRuntimeMBean)ManagementFactoryHelper.getHotspotRuntimeMBean();

    private static final long NUM_THREAD_DUMPS = 5;

    // Careful with these values.
    private static final long MIN_VALUE_FOR_PASS = NUM_THREAD_DUMPS;
    private static final long MAX_VALUE_FOR_PASS = Long.MAX_VALUE;

    private static boolean trace = false;

    public static void main(String args[]) throws Exception {
        if (args.length > 0 && args[0].equals("trace")) {
            trace = true;
        }

        // Thread.getAllStackTraces() should cause safepoints.
        // If this test is failing because it doesn't,
        // MIN_VALUE_FOR_PASS should be reset to 0
        for (int i = 0; i < NUM_THREAD_DUMPS; i++) {
            Thread.getAllStackTraces();
        }

        long value = mbean.getSafepointCount();

        if (trace) {
            System.out.println("Safepoint count: " + value);
        }

        if (value < MIN_VALUE_FOR_PASS || value > MAX_VALUE_FOR_PASS) {
            throw new RuntimeException("Safepoint count " +
                                       "illegal value: " + value + " " +
                                       "(MIN = " + MIN_VALUE_FOR_PASS + "; " +
                                       "MAX = " + MAX_VALUE_FOR_PASS + ")");
        }

        for (int i = 0; i < NUM_THREAD_DUMPS; i++) {
            Thread.getAllStackTraces();
        }

        long value2 = mbean.getSafepointCount();

        if (trace) {
            System.out.println("Safepoint count2: " + value2);
        }

        if (value2 <= value) {
            throw new RuntimeException("Safepoint count " +
                                       "did not increase " +
                                       "(value = " + value + "; " +
                                       "value2 = " + value2 + ")");
        }

        System.out.println("Test passed.");
    }
}