maxrsessiz(5)          Itanium(R)-Based System Only           maxrsessiz(5)
                          Tunable Kernel Parameters



 NAME    [Toc]    [Back]
      maxrsessiz, maxrsessiz_64bit - maximum size (in bytes) of the RSE
      stack for any user process on the Itanium-based platform

 VALUES    [Toc]    [Back]
    Default
      32 bit default: 0x800000 (8MB)

      64 bit default: 0x800000 (8MB)

    Allowed values    [Toc]    [Back]
      32 bit minimum: 0x40000

      32 bit maximum: 0x17F00000

      64 bit minimum: 0x40000

      64 bit maximum: 0x40000000

 DESCRIPTION    [Toc]    [Back]
      Itanium-based systems utilize a per-process register stack in main
      memory (for more information see the Intel IA-64 Architecture Software
      Developer's Manual, Volume 2, Chapter 6). This stack moves registers
      between the physical registers and main memory and is maintained by
      the Register Stack Engine (RSE).  maxrsessiz determines the size of
      this stack.

    Who is Expected to Change This Tunable?
      Anyone.

    Restrictions on Changing    [Toc]    [Back]
      Changes to this tunable only take effect after a reboot of the system.

    When Should the Value of This Tunable Be Raised?
      maxrsessiz should be raised if user processes are being terminated
      with the error [SIGBUS] due to overflow of the RSE stack.

    What Are the Side Effects of Raising the Value?
      User processes will dedicate more virtual memory to the RSE stack.
      This will result in less virtual memory being available for data
      allocation.

    When Should the Value of This Tunable Be Lowered?
      This tunable should be lowered only if swap space is at a premium on
      the system, since virtual memory for the RSE stack still requires
      matching swap reservation or allocation. Serious consideration should
      be given if maxrsessiz is being lowered below the default as this may
      cause unexpected failures of user applications on RSE stack overflow.

      This tunable is best left unchanged without complete and detailed
      knowledge of the RSE stack usage of the machine workload.



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






 maxrsessiz(5)          Itanium(R)-Based System Only           maxrsessiz(5)
                          Tunable Kernel Parameters



    What Are the Side Effects of Lowering the Value?
      Lowering this tunable will limit the amount of memory available for
      RSE stack usage per process.  This could cause processes with large
      RSE stack requirements to terminate with a [SIGBUS] error.

    What Other Tunable Values Should Be Changed at the Same Time?
      None.

 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]
      maxrsessiz was developed by HP.

 SEE ALSO    [Toc]    [Back]
      maxssiz(5), maxdsiz(5), maxtsiz(5).


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