IV58794: JAVA JIT - EXCESSIVE COMPILATION REQUESTS FOR A SINGLE METHOD.

APAR status

• Closed as program error.

Error description

• Error Message: The JIT verbose log shows several compilation
  requests for the same method, in comes cases the number of
  requests can be in the hundreds of thousands.
  .
  Stack Trace: N/A
  .
  The problem exists, but it has never shown to be a problem for
  any customers. There is a small overheard for handling the
  compilation requests but it seems that the overhead is not
  enough to be noticeable. We fixed this as a precaution more then
  out of any belief that it has any significant effect on
  performance.The problem only exists on x86 and z architectures.
  The PPC architecture is not effected by this issue.The issue
  only effects performance, it is NOT a functional issue.
  

Local fix

• -Xjit:disableEDO
  

Problem summary

• The JIT will queue for compilation any previously compiled
  method that shows a runtime history of taking exception paths.
  We do this so we can try and better optimize the exception
  paths. If for some reason the method is unable to be re-compiled
  in a timely manor (i.e. code cache is full or there is already a
  long compile queue) then each execution of the exception path
  will result in a compilation request.
  

Problem conclusion

• This APAR will be fixed in the following Java Releases:
     7    SR7       (7.0.7.0)
     6 R1 SR8       (6.1.8.0)
     6    SR16      (6.0.16.0)
     7 R1 SR1       (7.1.1.0)
  .
  The JIT was modified such that only one attempt to queue a
  method for compilation will be made one exception paths.
  

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

• R260 PSY

     UP

• R600 PSY

     UP

• R130 PSY

     UP