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IJ17056: PROBLEMS WITH HPRS ON Z

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APAR status

  • Closed as program error.

Error description

  • Error Message: Different symptoms are possible. These includes
    crashes/abends/assertion/unexpected exceptions errors in the VM,
    GC, and JIT compiled code. Detailed analysis is needed to
    identify this problem.
    .
    Stack Trace: N/A
    .
    These problems can only occur on IBM Z platforms. The likelihood
    of hitting an HPR problem seems to have significantly increased
    around Java 8 SR5 FP20.
    

Local fix

  • It's possible to emulate the effect of this change to the JVM by
    using the following java command line options.
    -Xjit:disableHighWordRA,disableHPRSpill,disableHPRUpgrade
    These options will prevent the JIT from using HPR registers
    and therefore cause the JIT to behave much like the JIT does
    after the changes were applied to the JVM as part of this APAR.
    Using these options may have a minor effect on performance (but
    no more so then what would be seen after upgrading to a JVM that
    has this APAR included).
    

Problem summary

  • The JIT compiler uses halfword general purpose registers (HPRs)
    as part of its generated code. Recent optimizations have exposed
    problematic scenarios around the existing HPR exploitation.
    While this exploitation once provided a performance benefit,
    newer hardware has negated this difference.
    

Problem conclusion

  • The JIT compiler's use of HPRs has been deprecated.
    .
    This APAR will be fixed in the following Java Releases:
       8    SR5 FP31  (8.0.5.31)
    .
    Contact your IBM Product's Service Team for these Service
    Refreshes and Fix Packs.
    For those running stand-alone, information about the available
    Service Refreshes and Fix Packs can be found at:
               https://www.ibm.com/developerworks/java/jdk/
    

Temporary fix

Comments

APAR Information

  • APAR number

    IJ17056

  • Reported component name

    JIT

  • Reported component ID

    620700124

  • Reported release

    130

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2019-06-19

  • Closed date

    2020-02-14

  • Last modified date

    2020-02-14

  • 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

[{"Business Unit":{"code":"BU048","label":"IBM Software"},"Product":{"code":"SSC9HBA","label":"Just In Time (JIT) Compiler"},"Component":"","ARM Category":[],"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"130","Edition":"","Line of Business":{"code":"","label":""}}]

Document Information

Modified date:
27 March 2020