IZ80868: JAVA JIT: HANG WHEN ATTEMPTING TO START A GC CYCLE

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You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error description

  • Error Message: The Java application hangs when a GC cycle
    starts. CPU utilization will be low but one thread will be
    executing endlessly in JIT compiled code. All other threads will
    have stopped, waiting for the GC cycle to complete.
    .
    Stack Trace: N/A
    .
    For this problem to occur, there must be a long running or
    endless loop in the Java code, e.g. a thread is waiting for work
    but there is no work to be processed so it endlessly loops
    checking the work queue without giving up the CPU by sleeping.
    In the case where this problem is occurring in a long running
    loop, the symptom could be seen as a long GC pause time rather
    then a out right hang.
    

Local fix

  • The problem can be avoid by using the following Java command
    line argument:
    .
    -Xjit:disableRedundantAsyncCheckRemoval
    .
    Using this option will have a slight impact on the performance
    of the Java application but in most cases the cost will only be
    a few percent.
    

Problem summary

  • The JIT would fail to generate code to check for a pending GC
    cycle within an irregular loop structure. An irregular loop
    could be written into the Java code or could be the result of a
    JIT transformation. If the irregular loop was long running or
    never ending then the GC cycle would be held up for quite some
    time.
    

Problem conclusion

  • This defect will be fixed in:
    5.0.0 SR12
    6.0.0 SR9
    .
    The JIT was modified to eliminate this problem.
    .
    To obtain the fix:
    Install build 20100622 or later
    

Temporary fix

Comments

APAR Information

  • APAR number

    IZ80868

  • Reported component name

    JAVA 5 JIT

  • Reported component ID

    620500124

  • Reported release

    500

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2010-07-23

  • Closed date

    2010-07-30

  • Last modified date

    2011-12-22

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

    IZ80884

Fix information

  • Fixed component name

    JAVA 5 JIT

  • Fixed component ID

    620500124

Applicable component levels

  • R500 PSN

       UP



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Document information


More support for:

Runtimes for Java Technology
Just In Time (JIT) Compiler

Software version:

5.0

Reference #:

IZ80868

Modified date:

2011-12-22

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