IV26401: REDUCED PERFORMANCE AFTER HEAVY CLASS RE-LOADING

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APAR status

  • Closed as program error.

Error description

  • After very extensive class-reloading, an application may
    demonstrate reduced performance.
    
    If run with -Xjit:verbose={compile*},vlog=jit.log the log will
    contain "CACHE FULL" messages.
    

Local fix

  • There is no completely effective work-around for this issue, but
    it is possible that using the following options to increase the
    size of each code cache and to allow for more memory to be used
    for code cache space will extend the time before performance is
    affected.
    
    Use 32MB code cache segments:
    -Xcodecache32m
    
    Allow up to 256MB of total code cache space:
    -Xjit:codetotal=262144
    
    Note that the -Xjit:codetotal option is not supported for use
    except at the direction of IBM Support in the course of Problem
    Resolution and Diagnosis.
    

Problem summary

  • The problem occurs when an extreme amount of Java code needs to
    be compiled by the JIT in order to maintain application
    performance. Typically this can only happen when a frame-work is
    used which continually generates new classes, uses them briefly
    and then unloads them.
    

Problem conclusion

  • This defect will be fixed in:
    5.0.0 SR15
    .
    An option has been added to the JIT to cause it to try harder to
    re-use memory from compiled classes which have been unloaded
    from the VM. Since this option is likely to be needed only in
    very special cases and may have a negative effect under more
    normal cases, it is not turned on by default. To enable the new
    behaviour the following option is required on the java command
    line:
    -Xjit:enableClearCodeCacheFullFlag
    

Temporary fix

Comments

APAR Information

  • APAR number

    IV26401

  • 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

    2012-08-17

  • Closed date

    2012-10-24

  • Last modified date

    2013-02-12

  • 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

    JAVA 5 JIT

  • Fixed component ID

    620500124

Applicable component levels

  • R500 PSY

       UP



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Document information


More support for:

Runtimes for Java Technology
Just In Time (JIT) Compiler

Software version:

5.0

Reference #:

IV26401

Modified date:

2013-02-12

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