ioforw_timeout(5)                                         ioforw_timeout(5)
                          Tunable Kernel Parameters



 NAME    [Toc]    [Back]
      ioforw_timeout - enable timeout in I/O forwarding

 VALUES    [Toc]    [Back]
    Failsafe
      0 (off)

    Default    [Toc]    [Back]
      0 (off)

    Allowed values    [Toc]    [Back]
      0 (off) or 1 (on)

    Recommended values    [Toc]    [Back]
      0 (off)

 DESCRIPTION    [Toc]    [Back]
      With I/O forwarding, the drivers' strategy routine forwards the I/O
      requests to a processor that is configured to handle the I/O
      completion interrupts from the device.  I/O forwarding queues these
      requests in a per processor queue and handles them in a low priority
      interrupt context.  In case of large number of requests, I/O
      forwarding may starve processes scheduled on the processor.

      When the tunable ioforw_timeout is set to 1, I/O forwarding times out
      periodically to let the processes execute.  This is important when the
      system has time sensitive processes that may flag an error condition
      in the system resulting in the generation of unnecessary correction
      triggers.  Since a timeout is introduced in I/O forwarding, there may
      be a loss in I/O throughput.

    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 Tunable Be Turned On?
      This tunable should be turned on if a time critical process times out
      in the presence of heavy I/O.

    What Are the Side Effects of Turning the Tunable On?
      As the timeout is introduced in I/O forwarding request processing, I/O
      throughput of the system may be reduced.

    What Other Tunables 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



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






 ioforw_timeout(5)                                         ioforw_timeout(5)
                          Tunable Kernel Parameters



      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]
      ioforw_timeout was developed by HP.

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


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