intr_strobe_ics_pct(5)                               intr_strobe_ics_pct(5)
                          Tunable Kernel Parameters



 NAME    [Toc]    [Back]
      intr_strobe_ics_pct - limit for the percent of time a processor is
      allowed to spend in interrupt context

 VALUES    [Toc]    [Back]
    Failsafe
      100

    Default    [Toc]    [Back]
      100

    Allowed values    [Toc]    [Back]
      80 - 100

      Setting intr_strobe_ics_pct to 100 will switch the feature off.

    Recommended values    [Toc]    [Back]
      100

 DESCRIPTION    [Toc]    [Back]
      intr_strobe_ics_pct specifies the system limit for the percent of time
      a processor is allowed to spend in interrupt context.  When the
      tunable is set to a value less than 100, the kernel does not allow I/O
      interrupts to consume the processor time beyond the set limit and
      hence the threads and other low priority interrupts get time to
      execute.  This is important when the system is under a heavy I/O
      interrupt load and some threads, like heartbeat timer in service guard
      environment, need to run within a limited time delay.

      In the normal working of the system, value of the tunable
      intr_strobe_ics_pct should be 100.

      If intr_strobe_ics_pct is set to less than 100, a message like the
      following may be seen in the message buffer.

           An interrupt context threshold of #% was exceeded on processor #
           within the last 5 minutes. The current value is #.

      The message buffer can be read via dmesg or syslog.  This message
      indicates that the percent of time spent on the processor had crossed
      the specified limit, and corrective action had been taken.

    Who Is Expected to Change This Tunable?
      Only HP Field engineers should change the value of this tunable.

    Restrictions on Changing    [Toc]    [Back]
      Changes to this tunable take effect immediately.

    When Should the Value of This Tunable Be Lowered?
      The value should be lowered only when heavy I/O interrupt load is
      causing a time critical process to timeout.



 Hewlett-Packard Company            - 1 -      HP-UX 11i Version 2: Sep 2004






 intr_strobe_ics_pct(5)                               intr_strobe_ics_pct(5)
                          Tunable Kernel Parameters



    What are the Side Effects of Lowering the Value?
      Reducing the value of the tunable would give the thread context more
      time to execute.  However, the overall system throughput may decrease.

    What Other Tunable Values Should Be Changed at the Same Time?
      This tunable is independent of other tunables.

 WARNINGS    [Toc]    [Back]
      All HP-UX kernel tunable parameters are release specific.  This
      parameter may be removed or have its meaning changed in future
      releases of HP-UX.

      Installation of optional kernel software, from HP or other vendors,
      may cause changes to tunable parameter values.  After installation,
      some tunable parameters may no longer be at the default or recommended
      values.  For information about the effects of installation on tunable
      values, consult the documentation for the kernel software being
      installed. For information about optional kernel software that was
      factory installed on your system, see HP-UX Release Notes at
      http://docs.hp.com.

 AUTHOR    [Toc]    [Back]
      intr_strobe_ics_pct was developed by HP.

 SEE ALSO    [Toc]    [Back]
      kctune(1M), kcweb(1M).


 Hewlett-Packard Company            - 2 -      HP-UX 11i Version 2: Sep 2004