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  1. JDK
  2. JDK-8025635

SoftReferences are not cleared before metaspace OOME are thrown

    Details

    • Subcomponent:
      gc
    • Introduced In Build:
      b57
    • Resolved In Build:
      b55

      Backports

        Description

        There was a bug reported against JDK8 on the mlvm-dev list.

        The following Groovy program works with 7u40 but sometimes fails with JDK8:
        ---
           println "Started"
           for(int i = 0; i < 100; i++) {
               print "."
               for (int j=0;j<100000;j++) {
                   Container c = new Container()
                   c.run()
               }
           }
           println "\ndone"

        public class Container implements Runnable {
         public Container() {}
         public void run() {
           GroovyShell gs = new GroovyShell()
           Script script = gs.parse("")
           script.run()
         }
        }
        ---

        I ran the test with both JDK7u40 and JDK8 and I see a steady increase of Permgen/Metaspace memory.

        In JDK7u40 this continues until the Permgen is full. At that point a Full GC manages to clear out almost the entire Permgen.

        With JDK8 the memory is just increasing indefinitely, unless we limit the metsapce by fore exmple -XX:MaxMetaspaceSize=86m. At that point we get an metaspace OOME instead.

        My guess was that this is caused by SoftReferences and a JFR recording showed that to be plausible. The test added ~100000 SoftReferences during the 1 minute recording I took.

        I also verified that adding:
        Universe::heap()->collector_policy()->set_should_clear_all_soft_refs(true)
         and triggering a GC, before deciding to throw an OOME clears out the metaspace.

          Activity

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            People

            • Assignee:
              jmasa Jon Masamitsu (Inactive)
              Reporter:
              stefank Stefan Karlsson
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              Dates

              • Created:
                Updated:
                Resolved: