1 /*

     2  * Copyright (c) 2014, 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 TestEagerReclaimHumongousRegionsWithRefs

    26  * @bug 8048179

    27  * @summary Test to make sure that eager reclaim of humongous objects that have previously

    28  * been referenced by other old gen regions work. We simply try to fill

    29  * up the heap with humongous objects and create a remembered set entry from an object by

    30  * referencing that we know is in the old gen. After changing this reference, the object

    31  * should still be eagerly reclaimable to avoid Full GC.

    32  * @key gc

    33  * @library /testlibrary

    34  */

    35 

    36 import java.util.regex.Pattern;

    37 import java.util.regex.Matcher;

    38 import java.util.LinkedList;

    39 

    40 import com.oracle.java.testlibrary.OutputAnalyzer;

    41 import com.oracle.java.testlibrary.ProcessTools;

    42 import static com.oracle.java.testlibrary.Asserts.*;

    43 

    44 class RefHolder {

    45   Object ref;

    46 }

    47 

    48 class ReclaimRegionFast {

    49 

    50     public static final int M = 1024*1024;

    51 

    52     public static LinkedList<Object> garbageList = new LinkedList<Object>();

    53 

    54     public static void genGarbage() {

    55         for (int i = 0; i < 32*1024; i++) {

    56             garbageList.add(new int[100]);

    57         }

    58         garbageList.clear();

    59     }

    60 

    61 

    62     // A large object referenced by a static.

    63     static int[] filler = new int[10 * M];

    64 

    65     // Old gen object referencing the large object, generating remembered

    66     // set entries.

    67     static RefHolder fromOld = new RefHolder();

    68 

    69     public static void main(String[] args) {

    70 

    71         int[] large = new int[M];

    72 

    73         Object ref_from_stack = large;

    74 

    75         for (int i = 0; i < 100; i++) {

    76             // A large object that will be reclaimed eagerly.

    77             large = new int[6*M];

    78             fromOld.ref = large;

    79             genGarbage();

    80         }

    81 

    82         // Keep the reference to the first object alive.

    83         System.out.println(ref_from_stack);

    84     }

    85 }

    86 

    87 public class TestEagerReclaimHumongousRegionsWithRefs {

    88 

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

    90         ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(

    91             "-XX:+UseG1GC",

    92             "-Xms128M",

    93             "-Xmx128M",

    94             "-Xmn16M",

    95             "-XX:+PrintGC",

    96             ReclaimRegionFast.class.getName());

    97 

    98         Pattern p = Pattern.compile("Full GC");

    99 

   100         OutputAnalyzer output = new OutputAnalyzer(pb.start());

   101 

   102         int found = 0;

   103         Matcher m = p.matcher(output.getStdout());

   104         while (m.find()) {

   105             found++;

   106         }

   107         System.out.println("Issued " + found + " Full GCs");

   108 

   109         assertLessThan(found, 10, "Found that " + found + " Full GCs were issued. This is larger than the bound. Eager reclaim of objects once referenced from old gen seems to not work at all");

   110         output.shouldHaveExitValue(0);

   111     }

   112 }

   113