/*

 * Copyright (c) 2011, 2016, Oracle 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 * @test TestFullGCCount.java

 * @bug 7072527

 * @summary CMS: JMM GC counters overcount in some cases

 * @modules java.management

 * @run main/othervm -Xlog:gc TestFullGCCount

 */

import java.lang.management.GarbageCollectorMXBean;

import java.lang.management.ManagementFactory;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

/*

 * Originally for a specific failure in CMS, this test now monitors all

 * collectors for double-counting of collections.

 */

public class TestFullGCCount {

    static List<GarbageCollectorMXBean> collectors = ManagementFactory.getGarbageCollectorMXBeans();

    public static void main(String[] args) {

        int iterations = 20;

        boolean failed = false;

        String errorMessage = "";

        HashMap<String, List> counts = new HashMap<>();

        // Prime the collection of count lists for all collectors.

        for (int i = 0; i < collectors.size(); i++) {

            GarbageCollectorMXBean collector = collectors.get(i);

            counts.put(collector.getName(), new ArrayList<>(iterations));

        }

        // Perform some gc, record collector counts.

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

            System.gc();

            addCollectionCount(counts, i);

        }

        // Check the increments:

        //   Old gen collectors should increase by one,

        //   New collectors may or may not increase.

        //   Any increase >=2 is unexpected.

        for (String collector : counts.keySet()) {

            System.out.println("Checking: " + collector);

            for (int i = 0; i < iterations - 1; i++) {

                List<Long> theseCounts = counts.get(collector);

                long a = theseCounts.get(i);

                long b = theseCounts.get(i + 1);

                if (b - a >= 2) {

                    failed = true;

                    errorMessage += "Collector '" + collector + "' has increment " + (b - a) +

                                    " at iteration " + i + "\n";

                }

            }

        }

        if (failed) {

            System.err.println(errorMessage);

            throw new RuntimeException("FAILED: System.gc collections miscounted.");

        }

        System.out.println("Passed.");

    }

    private static void addCollectionCount(HashMap<String, List> counts, int iteration) {

        for (int i = 0; i < collectors.size(); i++) {

            GarbageCollectorMXBean collector = collectors.get(i);

            List thisList = counts.get(collector.getName());

            thisList.add(collector.getCollectionCount());

        }

    }

}