IV16006: DELAY IN APPLICATION PROCESSING

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APAR status

  • Closed as program error.

Error description

  • Error Message: The application may appear to pause for several
    seconds/minutes. Profiling data indicates that time is being
    spent in the JIT compiler. A JIT vlog will show a large number
    of synchronous compiles during the period when application
    processing is delayed. A verbose GC log is also likely to show a
    number of long GC periods.
    .
    Stack Trace: N/A
    .
    The problem occurs when a large number of JIT compiled methods
    are invalidated at the same time, causing the compiler to enter
    an extended period of recompilation. The subsequent clean-up of
    meta-data results in the secondary issue of extended GC periods.
    

Local fix

  • This is an unusual performance issue which so far has only been
    seen when a class is loaded into the VM after an extended period
    during which many methods were compiled. The new class provided
    a second implementation of another method that was called from
    each of the compiled methods, invalidating an optimisation and
    requiring all the methods to be recompiled. This scenario can be
    avoided with the following command line option:
    -Xjit:disableInvariantArgumentPreexistence
    This may causes a slight loss of performance (in the 1% range).
    

Problem summary

  • When large numbers of methods need to be recompiled the total
    compilation time can be excessive and interfere with application
    processing.
    

Problem conclusion

  • This defect will be fixed in:
    6.0.0 SR11
    6.0.1 SR2
    7.0.0 SR1
    .
    The JIT has been modified to detect the case where a large
    number of methods need to be recompiled in a short space of time
    and to optimise this case so that the compilation is done more
    quickly.
    A new option has been added to set the threshold for the new
    behaviour:
    -Xjit:queuedInvReqThresholdToDowngradeOptLevel=NNN
    

Temporary fix

Comments

APAR Information

  • APAR number

    IV16006

  • Reported component name

    JIT

  • Reported component ID

    620700124

  • Reported release

    600

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-02-28

  • Closed date

    2012-03-10

  • Last modified date

    2012-06-01

  • 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



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Document information


More support for:

Runtimes for Java Technology
Just In Time (JIT) Compiler

Software version:

6.0

Reference #:

IV16006

Modified date:

2012-06-01

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