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PI63856: THREAD POOL REUSES THREADS INSTEAD OF DISPATCHING TO NEW THREADS

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You can track all active APARs for this component.

 

APAR status

  • Closed as program error.

Error description

  • In some cases, the thread pool is waiting for worker threads to
    complete their work and reusing them, rather than dispatching
    to an idle thread, leading to performance delays.  There is no
    stack or anything for the problem, and the "failures" caused by
    the issue are specific to the customer's testcase.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:  Users of IBM WebSphere Application Server   *
    *                  experiencing latency in thread pool         *
    *                  dispatch times                              *
    ****************************************************************
    * PROBLEM DESCRIPTION: Threads handling work items are not     *
    *                      dispatched as quickly as you may        *
    *                      expect                                  *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    The WebSphere Application Server thread pool utilizes a thread
    pool to dispatch work items to worker threads.  The work items
    are placed on a bufffer from which they are pulled by the
    pool.  In some cases, particularly when a large number of work
    items are dispatched at once, the mechanism used to lock
    buffer slots may acquire the locks in an inefficient order,
    leading to slight delays in dispatch of new threads (or reuse
    of existing threads when a new thread should be created).
    Note that this issue has only been observed on AIX, and the
    latency was only detected in rare cases, within a strict test
    scenario requiring 100ms response times; this is not a
    pervasive performance issue.
    

Problem conclusion

  • An optional, optimized version of the buffer locking mechanism
    was added to the thread pool infrastructure.  To enabled it,
    add "-Dcom.ibm.websphere.threadpool.alternateBufferLock=true"
    as a generic JVM argument on the server process.
    
    The fix for this APAR is currently targeted for inclusion in
    fix packs 8.5.5.12 and 9.0.0.4.  Please refer to the
    Recommended Updates page for delivery information:
    http://www.ibm.com/support/docview.wss?rs=180&uid=swg27004980
    

Temporary fix

Comments

APAR Information

  • APAR number

    PI63856

  • Reported component name

    WEBSPHERE APP S

  • Reported component ID

    5724J0800

  • Reported release

    850

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2016-06-09

  • Closed date

    2016-12-22

  • Last modified date

    2017-04-12

  • 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

    WEBSPHERE APP S

  • Fixed component ID

    5724J0800

Applicable component levels

  • R850 PSY

       UP

  • R900 PSY

       UP

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Document Information

Modified date:
15 October 2021