/*

 * Copyright (c) 2018, Google and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package MyPackage;

/**

 * @test

 * @summary Verifies the JVMTI Heap Monitor sampling interval average.

 * @build Frame HeapMonitor

 * @compile HeapMonitorStatIntervalTest.java

 * @requires vm.compMode != "Xcomp"

 * @run main/othervm/native -agentlib:HeapMonitorTest MyPackage.HeapMonitorStatIntervalTest

 */

public class HeapMonitorStatIntervalTest {

  private native static double getAverageInterval();

  private static boolean testIntervalOnce(int interval, boolean throwIfFailure) {

    HeapMonitor.resetEventStorage();

    HeapMonitor.setSamplingInterval(interval);

    HeapMonitor.enableSamplingEvents();

    int allocationTotal = 10 * 1024 * 1024;

    int allocationIterations = 10;

    double actualCount = 0;

    for (int i = 0; i < allocationIterations; i++) {

      HeapMonitor.resetEventStorage();

      HeapMonitor.allocateSize(allocationTotal);

      actualCount += HeapMonitor.getEventStorageElementCount();

    }

    HeapMonitor.disableSamplingEvents();

    double expectedCount = allocationTotal * allocationIterations / interval;

    double error = Math.abs(actualCount - expectedCount);

    double errorPercentage = error / expectedCount * 100;

    boolean success = (errorPercentage < 10.0);

    if (!success && throwIfFailure) {

      throw new RuntimeException("Interval average over 10% for interval " + interval + " -> "

          + actualCount + ", " + expectedCount);

    }

    return success;

  }

  private static void testInterval(int interval) {

    // Test the interval twice, it can happen that the test is "unlucky" and the interval just goes above

    // the 10% mark. So try again to squash flakiness.

    // Flakiness is due to the fact that this test is dependent on the sampling interval, which is a

    // statistical geometric variable around the sampling interval. This means that the test could be

    // unlucky and not achieve the mean average fast enough for the test case.

    if (!testIntervalOnce(interval, false)) {

      testIntervalOnce(interval, true);

    }

  }

  public static void main(String[] args) {

    int[] tab = {1024, 8192};

    for (int intervalIdx = 0; intervalIdx < tab.length; intervalIdx++) {

      testInterval(tab[intervalIdx]);

    }

  }

}