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  1. JDK
  2. JDK-8175375

MemoryPoolMXBean.getCollectionUsage() does not works with -XX:+UseG1GC -XX:+ExplicitGCInvokesConcurrent

    Details

    • Subcomponent:
      gc
    • CPU:
      generic
    • OS:
      generic

      Description

      FULL PRODUCT VERSION :
      openjdk version "1.8.0_111"
      OpenJDK Runtime Environment (build 1.8.0_111-8u111-b14-2~bpo8+1-b14)
      OpenJDK 64-Bit Server VM (build 25.111-b14, mixed mode)



      FULL OS VERSION :
      Debian 4.3.0-1-amd64
      Microsoft Windows [version 10.0.14393]

      A DESCRIPTION OF THE PROBLEM :
      When java is started with the options -XX:+UseG1GC -XX:+ExplicitGCInvokesConcurrent, the collection usage for the largest heap (in this case the MBean with object name java.lang:type=MemoryPool,name=G1 Old Gen) returns always 0.
      If only one of this options is set, collection usage returns the expected value.

      THE PROBLEM WAS REPRODUCIBLE WITH -Xint FLAG: Yes

      THE PROBLEM WAS REPRODUCIBLE WITH -server FLAG: Yes

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      1) Compile the Main.java: javac Main.java
      2) Run it with and without GC flags:
           java -XX:+UseG1GC -XX:+ExplicitGCInvokesConcurrent Main
           java -XX:+UseG1GC Main
           java -XX:+ExplicitGCInvokesConcurrent Main

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      When started with -XX:+UseG1GC -XX:+ExplicitGCInvokesConcurrent, MemoryPoolMXBean.getCollectionUsage().getUsed() always returns 0 else it returns the expected value.


      ERROR MESSAGES/STACK TRACES THAT OCCUR :
      root@lanzarote:/tmp# java -XX:+UseG1GC -XX:+ExplicitGCInvokesConcurrent Main
      java.lang:type=MemoryPool,name=G1 Old Gen
      Collection usage = 0, usage = 51,765,344
      Collection usage = 0, usage = 104,388,048
      Collection usage = 0, usage = 156,762,032
      Collection usage = 0, usage = 209,167,296
      Collection usage = 0, usage = 261,638,432

      root@lanzarote:/tmp# java -XX:+UseG1GC Main
      java.lang:type=MemoryPool,name=G1 Old Gen
      Collection usage = 52,720,512, usage = 52,720,512
      Collection usage = 105,256,688, usage = 105,256,688
      Collection usage = 157,685,504, usage = 157,685,504
      Collection usage = 210,114,320, usage = 210,114,320
      Collection usage = 262,543,136, usage = 262,543,136

      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------

      import java.lang.management.ManagementFactory;
      import java.lang.management.MemoryPoolMXBean;
      import java.lang.management.MemoryType;
      import java.util.ArrayList;
      import java.util.List;

      public class Main
      {

      public static void main(String[] args) throws Exception {
      MemoryPoolMXBean tenuredGenPool = null;
      List<byte[]> data = new ArrayList<>();
      // heuristic to find the tenured pool (largest heap) as seen on
      // http://www.javaspecialists.eu/archive/Issue092.html
      for (MemoryPoolMXBean pool : ManagementFactory.getMemoryPoolMXBeans()) {
      if (pool.getType() == MemoryType.HEAP && pool.isUsageThresholdSupported()) {
      tenuredGenPool = pool;
      }
      }
      System.out.println(tenuredGenPool.getObjectName());
      for (int i = 0; i < 5; i++) {
      data.add(new byte[1024 * 1024 * 50]);
      Thread.sleep(100);
      System.gc();
      System.out.println("Collection usage = " + tenuredGenPool.getCollectionUsage().getUsed()
      + ", usage = " + tenuredGenPool.getUsage().getUsed());
      }
      }
      }

      ---------- END SOURCE ----------

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              • Assignee:
                Unassigned
                Reporter:
                webbuggrp Webbug Group
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                Dates

                • Created:
                  Updated: