IV15424: JAVA JIT PERFORMANCE ISSUE AFTER LOADING CLASS

APAR status

• Closed as program error.

Error description

• Error Message: Performance degradation can occur when a large
  number of JIT compiled methods are invalidated by loading a new
  class. In severe cases, the degradation can appear to cause the
  application to hang. System monitoring tools or profilers may
  reveal that a lot of CPU time is consumed by the JIT compiler
  run-time code.
  .
  Stack Trace: Profiling may show significant time spent in
  TR_RuntimeAssumption::isAssumingMethod(void*)
  .
  

Local fix

• This issue can be worked around with
  -Xjit:disableInvariantArgumentPreexistence
  This may degrade application performance to some extent.
  

Problem summary

• The problem occurs if:
  1) an application runs for a long time and compiles many methods
  which call a given class,
  2) a second class is loaded which invalidates the previously
  compiled methods, usually by providing an alternative
  implementation of an interface.
  The required clean-up of meta-data associated with the
  invalidated methods may cause a significant pause in application
  processing.
  

Problem conclusion

• This defect will be fixed in:
  6.0.0 SR11
  6.0.1 SR4
  7.0.0 SR3
  .
  The JIT compiler run-time code has been updated to search for
  and update compiled method meta data in a more efficient manner.
  

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

• R600 PSY

     UP