1 /*

     2  * Copyright (c) 2018, 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 import java.lang.instrument.ClassFileTransformer;

    26 import java.lang.instrument.Instrumentation;

    27 import java.lang.instrument.IllegalClassFormatException;

    28 import java.security.ProtectionDomain;

    29 

    30 // This test is sensitive to -Xmx. It must be run with -xmx64m.

    31 // Running with a different -Xmx requires changing the parameters and careful re-testing.

    32 public class HumongousDuringDumpTransformer implements ClassFileTransformer {

    33     public byte[] transform(ClassLoader loader, String name, Class<?> classBeingRedefined,

    34                             ProtectionDomain pd, byte[] buffer) throws IllegalClassFormatException {

    35         if (name.equals("Hello")) {

    36             try {

    37                 makeHumongousRegions();

    38             } catch (Throwable t) {

    39                 array = null;

    40                 humon = null;

    41                 System.out.println("Unexpected error: " + t);

    42                 t.printStackTrace();

    43             }

    44         }

    45         array = null;

    46         return null;

    47     }

    48 

    49     private static Instrumentation savedInstrumentation;

    50 

    51     public static void premain(String agentArguments, Instrumentation instrumentation) {

    52         long xmx = Runtime.getRuntime().maxMemory();

    53         if (xmx < 60 * 1024 * 1024 || xmx > 80 * 1024 * 1024) {

    54             System.out.println("Running with incorrect heap size: " + xmx);

    55             System.exit(1);

    56         }

    57 

    58         System.out.println("ClassFileTransformer.premain() is called");

    59         instrumentation.addTransformer(new HumongousDuringDumpTransformer(), /*canRetransform=*/true);

    60         savedInstrumentation = instrumentation;

    61     }

    62 

    63     public static Instrumentation getInstrumentation() {

    64         return savedInstrumentation;

    65     }

    66 

    67     public static void agentmain(String args, Instrumentation inst) throws Exception {

    68         premain(args, inst);

    69     }

    70 

    71     Object[] array;

    72 

    73     static final int DUMMY_SIZE = 4096 - 16 - 8;

    74     static final int HUMON_SIZE = 4 * 1024 * 1024 - 16 - 8;

    75     static final int SKIP = 13;

    76 

    77     byte humon[] = null;

    78     boolean first = true;

    79 

    80     public synchronized void makeHumongousRegions() {

    81         if (!first) {

    82             return;

    83         }

    84         System.out.println("===============================================================================");

    85         first = false;

    86 

    87         int total = 0;

    88         array = new Object[100000];

    89         System.out.println(array);

    90 

    91         // (1) Allocate about 8MB of old objects.

    92         for (int n=0, i=0; total < 8 * 1024 * 1024; n++) {

    93             // Make enough allocations to cause a GC (for 64MB heap) to create

    94             // old regions.

    95             //

    96             // But don't completely fill up the heap. That would cause OOM and

    97             // may not be handled gracefully inside class transformation!

    98             Object x = new byte[DUMMY_SIZE];

    99             if ((n  % SKIP) == 0) {

   100                 array[i++] = x;

   101                 total += DUMMY_SIZE;

   102             }

   103         }

   104 

   105         System.gc();

   106 

   107         // (2) Now allocate a humongous array. It will sit above the 8MB of old regions.

   108         humon = new byte[HUMON_SIZE];

   109         array = null;

   110         System.gc();

   111     }

   112 }