IBM Support

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

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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 number

    IV58794

  • Reported component name

    JIT

  • Reported component ID

    620700124

  • Reported release

    260

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2014-04-04

  • Closed date

    2014-04-22

  • Last modified date

    2014-04-22

  • 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



Document information

More support for: Runtimes for Java Technology
Just In Time (JIT) Compiler

Software version: 260

Reference #: IV58794

Modified date: 22 April 2014