IV78208: PERFORMANCE REGRESSION DUE TO FAILED COMPILATION

APAR status

• Closed as program error.

Error description

• Error Message: Some applications showed a 10-30% regression
  compared with earlier Java releases. Verbose log shows
  compilationExcessiveComplexity failure on some of the hottest
  methods.
  .
  Stack Trace: N/A
  .
  This regression is possible on all platforms (X86, Power, System
  z), mostly on power and z
  

Local fix

• This issue can be worked around using the
  -Xjit:acceptHugeMethods option. Note this would increase the
  memory usage of the Java program as larger methods would be
  compiled. The option can be applied to individual methods if
  preferred.
  

Problem summary

• The compilations of some hottest methods with nested loops
  failed and the Java program ends up running with less optimized
  version of these methods. This happens because an incorrect loop
  related optimization creates too many loops and the number of
  loops exceeds the limit for some compiled methods.
  

Problem conclusion

• The loop related optimization in JIT has been fixed so that the
  number of loops created for the hottest methods won't exceed the
  limit.
  .
  This APAR will be fixed in the following Java Releases:
   8 SR2 (8.0.2.0)
  .
  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:

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels

• R130 PSY

     UP