0 Replies Latest reply: Jan 26, 2012 5:24 PM by tourtech RSS

    jmap: "unknown generation type" with CMS

    tourtech
      Hi there

      I've recently been evaluating switching from ParallelOldGC to ConcurrentMarkSweet for tenured generation GC, and have noticed that jmap is no longer able to display a heap breakdown after switching to CMS.
      See the message below: "unknown generation type", followed by all the 0 values. Is this a known bug with jmap.

      I'm running Java 1.6 Update 29 on SPARC. The JVM is 64-bit.
      Before switching to CMS, jmap was successfully able to provide memory breakdowns and didn't display the error "unknown generation type".


      $ /usr/java/bin/jmap -d64 -heap 388
      Attaching to process ID 388, please wait...
      Debugger attached successfully.
      Server compiler detected.
      JVM version is 20.4-b02

      using parallel threads in the new generation.
      using thread-local object allocation.
      Concurrent Mark-Sweep GC

      Heap Configuration:
      MinHeapFreeRatio = 40
      MaxHeapFreeRatio = 70
      MaxHeapSize = 2684354560 (2560.0MB)
      NewSize = 1310720 (1.25MB)
      MaxNewSize = 17592186044415 MB
      OldSize = 5439488 (5.1875MB)
      NewRatio = 2
      SurvivorRatio = 8
      PermSize = 21757952 (20.75MB)
      MaxPermSize = 1073741824 (1024.0MB)

      Heap Usage:
      unknown generation type:
      capacity = 0 (0.0MB)
      used = 0 (0.0MB)
      free = 0 (0.0MB)
      NaN% used
      unknown generation type:
      capacity = 0 (0.0MB)
      used = 0 (0.0MB)
      free = 0 (0.0MB)
      NaN% used
      Perm Generation:
      capacity = 388988928 (370.96875MB)
      used = 269534712 (257.04833221435547MB)
      free = 119454216 (113.92041778564453MB)
      69.29110126239891% used