1 /*

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     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

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     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  *

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    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

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    23 

    24 /*

    25  * @test TestGreyReclaimedHumongousObjects.java

    26  * @bug 8069367

    27  * @requires vm.gc.G1

    28  * @summary Test handling of marked but unscanned reclaimed humongous objects.

    29  * @key gc

    30  * @modules jdk.management

    31  * @run main/othervm -XX:+UseG1GC -Xss32m -Xmx128m -XX:G1HeapRegionSize=1m

    32  *      -XX:+UnlockExperimentalVMOptions

    33  *          -XX:+G1EagerReclaimHumongousObjects

    34  *          -XX:+G1EagerReclaimHumongousObjectsWithStaleRefs

    35  *      TestGreyReclaimedHumongousObjects 1048576 90

    36  */

    37 

    38 // This test spawns a bunch of threads, each of them rapidly

    39 // allocating large objects and storing them into a circular buffer

    40 // associated with the thread.  The circular buffer results in these

    41 // objects becoming dead in fairly short order.

    42 //

    43 // The situation we're trying to provoke is

    44 //

    45 // (1) A humongous object H is marked and added to the mark stack.

    46 //

    47 // (2) An evacuation pause determines H is no longer live, and

    48 // reclaims it.  This occurs before concurrent marking has gotten

    49 // around to processing the mark stack entry for H.

    50 //

    51 // (3) Concurrent marking processes the mark stack entry for H.  The

    52 // bug is that it would attempt to scan the now dead object.

    53 //

    54 // Unfortunately, this test is *very* sensitive to configuration.

    55 // Among the parameters that affect whether / how often we'll get into

    56 // the desired situation within a reasonable amount of time are:

    57 //

    58 // - THREAD_COUNT: The number of allocating threads.

    59 //

    60 // - OLD_COUNT: The number of objects each thread keeps.

    61 //

    62 // - MAX_MEMORY: The maximum heap size.

    63 //

    64 // - G1HeapRegionSize

    65 //

    66 // - The size of the objects being allocated.

    67 //

    68 // The parameter values specified here:

    69 //

    70 // - THREAD_COUNT = 12

    71 // - OLD_COUNT == 4

    72 // - MAX_MEMORY == 128m

    73 // - G1HeapRegionSize = 1m

    74 // - Object size = 1048576 (2 regions after header overhead and roundup)

    75 //

    76 // seems to work well at provoking the desired state fairly quickly.

    77 // Even relatively small perturbations may change that.  The key

    78 // factors seem to be keeping the heap mostly full of live objects but

    79 // having them become dead fairly quickly.

    80 

    81 import java.util.Date;

    82 import java.util.concurrent.ExecutorService;

    83 import java.util.concurrent.Executors;

    84 import java.util.concurrent.ThreadFactory;

    85 import java.util.concurrent.TimeUnit;

    86 import com.sun.management.HotSpotDiagnosticMXBean;

    87 import java.lang.management.ManagementFactory;

    88 

    89 public class TestGreyReclaimedHumongousObjects {

    90 

    91     static class NamedThreadFactory implements ThreadFactory {

    92        private int threadNum = 0;

    93 

    94        @Override

    95        public Thread newThread(Runnable r) {

    96          return new Thread(r, THREAD_NAME + (threadNum++));

    97        }

    98     }

    99 

   100     static class Runner extends Thread {

   101         private final Date startDate = new Date();

   102         private final int obj_size;

   103         private final Object[] old_garbage;

   104         private int old_index = 0;

   105 

   106         public Runner(int obj_size) {

   107             this.obj_size = obj_size;

   108             old_garbage = new Object[OLD_COUNT];

   109         }

   110 

   111         private void allocate_garbage() {

   112             byte[] garbage = new byte[obj_size];

   113             old_garbage[Math.abs(++old_index % OLD_COUNT)] = garbage;

   114         }

   115 

   116         @Override

   117         public void run() {

   118             try {

   119                 while (!isInterrupted()) {

   120                     allocate_garbage();

   121                     Thread.sleep(0); // Yield, to ensure interruptable.

   122                 }

   123             } catch (InterruptedException e) {

   124                 System.out.println("Aborted after "

   125                                    + (new Date().getTime() - startDate.getTime())

   126                                    + " ms");

   127                 interrupt();

   128             }

   129         }

   130     }

   131 

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

   133         HotSpotDiagnosticMXBean diagnostic =

   134                 ManagementFactory.getPlatformMXBean(HotSpotDiagnosticMXBean.class);

   135 

   136         System.out.println("Max memory= " + MAX_MEMORY + " bytes");

   137 

   138         int obj_size = 0;

   139         long seconds_to_run = 0;

   140         if (args.length != 2) {

   141             throw new RuntimeException("Object size argument must be supplied");

   142         } else {

   143             obj_size = Integer.parseInt(args[0]);

   144             seconds_to_run = Integer.parseInt(args[1]);

   145         }

   146         System.out.println("Objects size= " + obj_size + " bytes");

   147         System.out.println("Seconds to run=" + seconds_to_run);

   148 

   149         int region_size =

   150             Integer.parseInt(diagnostic.getVMOption("G1HeapRegionSize").getValue());

   151         if (obj_size < (region_size / 2)) {

   152             throw new RuntimeException("Object size " + obj_size +

   153                                        " is not humongous with region size " + region_size);

   154         }

   155 

   156         ExecutorService executor =

   157             Executors.newFixedThreadPool(THREAD_COUNT, new NamedThreadFactory());

   158         System.out.println("Starting " + THREAD_COUNT + " threads");

   159 

   160         for (int i = 0; i < THREAD_COUNT; i++) {

   161             executor.execute(new Runner(obj_size));

   162         }

   163 

   164         Thread.sleep(seconds_to_run * 1000);

   165         executor.shutdownNow();

   166 

   167         if (!executor.awaitTermination(10, TimeUnit.SECONDS)) {

   168             System.err.println("Thread pool did not terminate after 10 seconds after shutdown");

   169         }

   170     }

   171 

   172     private static final long MAX_MEMORY = Runtime.getRuntime().maxMemory();

   173     private static final int OLD_COUNT = 4;

   174     private static final int THREAD_COUNT = 12;

   175     private static final String THREAD_NAME = "TestGreyRH-";

   176 }