hotspot/test/serviceability/tmtools/jstat/GcTest02.java

/*
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import utils.*;
/*
 * @test
 * @summary Test checks output displayed with jstat -gc.
 *          Test scenario:
 *          tests forces debuggee application eat ~70% of heap and runs jstat.
 *          jstat should show that ~70% of heap is utilized (OC/OU ~= 70%).
 * @requires vm.opt.ExplicitGCInvokesConcurrent != true
 * @modules java.base/jdk.internal.misc
 * @library /test/lib
 * @library ../share
 * @run main/othervm -XX:+UsePerfData -XX:InitialHeapSize=128M -XX:MaxHeapSize=128M -XX:MaxMetaspaceSize=128M GcTest02
 */

public class GcTest02 {

    private final static float targetMemoryUsagePercent = 0.7f;

    public static void main(String[] args) throws Exception {

        // We will be running "jstat -gc" tool
        JstatGcTool jstatGcTool = new JstatGcTool(ProcessHandle.current().getPid());

        // Run once and get the  results asserting that they are reasonable
        JstatGcResults measurement1 = jstatGcTool.measure();
        measurement1.assertConsistency();

        GcProvoker gcProvoker = new GcProvoker();

        // Eat metaspace and heap then run the tool again and get the results  asserting that they are reasonable
        gcProvoker.allocateAvailableMetaspaceAndHeap(targetMemoryUsagePercent);
        // Collect garbage. Also updates VM statistics
        System.gc();
        JstatGcResults measurement2 = jstatGcTool.measure();
        measurement2.assertConsistency();

        // Assert that space has been utilized acordingly
        JstatResults.assertSpaceUtilization(measurement2, targetMemoryUsagePercent);
    }
}