1 /*
   2  * Copyright (c) 2011, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 /*
  25  * @test TestFullGCount.java
  26  * @bug 7072527
  27  * @summary CMS: JMM GC counters overcount in some cases
  28  * @modules java.management
  29  * @run main/othervm -Xlog:gc TestFullGCCount
  30  */
  31 import java.util.*;
  32 import java.lang.management.*;
  33 
  34 /*
  35  * Originally for a specific failure in CMS, this test now monitors all
  36  * collectors for double-counting of collections.
  37  */
  38 public class TestFullGCCount {
  39 
  40     static List<GarbageCollectorMXBean> collectors = ManagementFactory.getGarbageCollectorMXBeans();
  41 
  42     public static void main(String[] args) {
  43         int iterations = 20;
  44         boolean failed = false;
  45         String errorMessage = "";
  46         HashMap<String, List> counts = new HashMap<String, List>();
  47 
  48         // Prime the collection of count lists for all collectors.
  49         for (int i = 0; i < collectors.size(); i++) {
  50             GarbageCollectorMXBean collector = collectors.get(i);
  51             counts.put(collector.getName(), new ArrayList<Long>(iterations));
  52         }
  53 
  54         // Perform some gc, record collector counts.
  55         for (int i = 0; i < iterations; i++) {
  56             System.gc();
  57             addCollectionCount(counts, i);
  58         }
  59 
  60         // Check the increments:
  61         //   Old gen collectors should increase by one,
  62         //   New collectors may or may not increase.
  63         //   Any increase >=2 is unexpected.
  64         for (String collector : counts.keySet()) {
  65             System.out.println("Checking: " + collector);
  66 
  67             for (int i = 0; i < iterations - 1; i++) {
  68                 List<Long> theseCounts = counts.get(collector);
  69                 long a = theseCounts.get(i);
  70                 long b = theseCounts.get(i + 1);
  71                 if (b - a >= 2) {
  72                     failed = true;
  73                     errorMessage += "Collector '" + collector + "' has increment " + (b - a) +
  74                                     " at iteration " + i + "\n";
  75                 }
  76             }
  77         }
  78         if (failed) {
  79             System.err.println(errorMessage);
  80             throw new RuntimeException("FAILED: System.gc collections miscounted.");
  81         }
  82         System.out.println("Passed.");
  83     }
  84 
  85     private static void addCollectionCount(HashMap<String, List> counts, int iteration) {
  86         for (int i = 0; i < collectors.size(); i++) {
  87             GarbageCollectorMXBean collector = collectors.get(i);
  88             List thisList = counts.get(collector.getName());
  89             thisList.add(collector.getCollectionCount());
  90         }
  91     }
  92 }