IV88941: JIT COMPILER TAKES FAR TOO LONG TO COMPILE A METHOD

APAR status

• Closed as program error.

Error description

• Error Message: The symptoms of this APAR are sustained high CPU
  usage by a JIT compilation thread, and potentially the JVM
  hanging on shutdown. Additionally, a JIT verbose log will show a
  compile request for a method that never completes even after a
  long period of time, or takes far too long to complete.
  .
  Stack Trace: The stack backtrace of the JIT compiler thread
  using sustained high CPU may look like this:
  fixUpTree() // likely many frames of this
  TR_EliminateDeadTrees::process()
  .
  

Local fix

• This problem can be avoided using the Java command line option
  -Xjit:disableDeadTreeElimination
  Note that this may affect performance. This can be limited by
  only applying the option to the method(s) experiencing the
  problem.
  

Problem summary

• Certain patterns of Java bytecodes can cause the JIT
  optimization Dead Tree Elimination to get stuck iterating over
  the same trees in an exponential walk, causing the optimization
  and compilation to run for a very long time and give the
  appearance of being stuck in an infinite loop. This causes the
  JIT compilation thread compiling the method to sustain high CPU
  usage and potentially prevent JVM shutdown.
  

Problem conclusion

• Checks have been added to the Dead Tree Elimination optimization
  to prevent the JIT compiler from getting stuck iterating over
  the same trees in an exponential walk.
  .
  This APAR will be fixed in the following Java Releases:
     7 R1 SR4 FP20  (7.1.4.20)
     7    SR10 FP20 (7.0.10.20)
     6 R1 SR8 FP60  (6.1.8.60)
     8    SR5 FP6   (8.0.5.6)
  .
  Contact your IBM Product's Service Team for these Service
  Refreshes and Fix Packs.
  For those running stand-alone, information about the available
  Service Refreshes and Fix Packs can be found at:
             https://www.ibm.com/developerworks/java/jdk/
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels

• R130 PSY

     UP

• R260 PSY

     UP