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  1. JDK
  2. JDK-8224030

Old Gen usage in MemoryUsage.getCollectionUsage() not updated for young collections

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    Details

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

      Description

      ADDITIONAL SYSTEM INFORMATION :
      Linux 64 bit, Windows 10 64 bit

      A DESCRIPTION OF THE PROBLEM :
      Value returned by java.lang.management.MemoryUsage.getUsed() for eden space usage does not match with the value shown by jcmd <pid> GC.heap_info command. Following code always shows eden space usage as 0.


      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      Following code prints the memory usage on console. Once the program prints memory usage, put it in background and capture the jcmd output using "jcmd <pid> GC.heap_info" command. Compare the eden space usage values between these two approaches.

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      Eden space usage as reported by java.lang.management.MemoryUsage should be close to the value reported by jcmd output.
      ACTUAL -
      Eden space usage reported by java.lang.management.MemoryUsage is always 0.

      ---------- BEGIN SOURCE ----------
      import java.lang.management.ManagementFactory;
      import java.lang.management.MemoryPoolMXBean;
      import java.lang.management.MemoryUsage;
      import java.util.HashSet;

      public class HeapUsageTest {

      public HeapUsageTest()
      {
              System.out.println("Before ");
              printHeapUsage();
              HashSet<String> set = new HashSet<>();
              for (int i = 0; i<10000000; i++) {
                  set.add(String.valueOf(i));
              }
              System.out.println("After");
              printHeapUsage();

      }
          public static void main(String[] args) throws InterruptedException {
           new HeapUsageTest();
              Thread.sleep(1000000);
          }

          private void printHeapUsage() {
              for (MemoryPoolMXBean mpbean :
                   ManagementFactory.getMemoryPoolMXBeans()) {
                  MemoryUsage usage = mpbean.getCollectionUsage();
                  if (usage != null) {
                      long max = usage.getMax();
                      long used = usage.getUsed();
                      System.out.println(mpbean.getName() + " Used " + used + ", Max " + max);
                  }
              }

          }
      }

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

      FREQUENCY : always


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              Assignee:
              tschatzl Thomas Schatzl
              Reporter:
              webbuggrp Webbug Group
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                Created:
                Updated:
                Resolved: