1 /*
   2  * Copyright (c) 2011, 2016, 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 TestFullGCCount.java
  26  * @bug 7072527
  27  * @summary CMS: JMM GC counters overcount in some cases
  28  * @requires !(vm.gc.ConcMarkSweep & vm.opt.ExplicitGCInvokesConcurrent == true)
  29  * @modules java.management
  30  * @run main/othervm -Xlog:gc TestFullGCCount
  31  */
  32 
  33 import java.lang.management.GarbageCollectorMXBean;
  34 import java.lang.management.ManagementFactory;
  35 import java.util.ArrayList;
  36 import java.util.HashMap;
  37 import java.util.List;
  38 
  39 /*
  40  * Originally for a specific failure in CMS, this test now monitors all
  41  * collectors for double-counting of collections.
  42  */
  43 public class TestFullGCCount {
  44 
  45     static List<GarbageCollectorMXBean> collectors = ManagementFactory.getGarbageCollectorMXBeans();
  46 
  47     public static void main(String[] args) {
  48         int iterations = 20;
  49         boolean failed = false;
  50         String errorMessage = "";
  51         HashMap<String, List> counts = new HashMap<>();
  52 
  53         // Prime the collection of count lists for all collectors.
  54         for (int i = 0; i < collectors.size(); i++) {
  55             GarbageCollectorMXBean collector = collectors.get(i);
  56             counts.put(collector.getName(), new ArrayList<>(iterations));
  57         }
  58 
  59         // Perform some gc, record collector counts.
  60         for (int i = 0; i < iterations; i++) {
  61             System.gc();
  62             addCollectionCount(counts, i);
  63         }
  64 
  65         // Check the increments:
  66         //   Old gen collectors should increase by one,
  67         //   New collectors may or may not increase.
  68         //   Any increase >=2 is unexpected.
  69         for (String collector : counts.keySet()) {
  70             System.out.println("Checking: " + collector);
  71 
  72             for (int i = 0; i < iterations - 1; i++) {
  73                 List<Long> theseCounts = counts.get(collector);
  74                 long a = theseCounts.get(i);
  75                 long b = theseCounts.get(i + 1);
  76                 if (b - a >= 2) {
  77                     failed = true;
  78                     errorMessage += "Collector '" + collector + "' has increment " + (b - a) +
  79                                     " at iteration " + i + "\n";
  80                 }
  81             }
  82         }
  83         if (failed) {
  84             System.err.println(errorMessage);
  85             throw new RuntimeException("FAILED: System.gc collections miscounted.");
  86         }
  87         System.out.println("Passed.");
  88     }
  89 
  90     private static void addCollectionCount(HashMap<String, List> counts, int iteration) {
  91         for (int i = 0; i < collectors.size(); i++) {
  92             GarbageCollectorMXBean collector = collectors.get(i);
  93             List thisList = counts.get(collector.getName());
  94             thisList.add(collector.getCollectionCount());
  95         }
  96     }
  97 }