pa_maxssiz(5)          Itanium(R)-based System Only           pa_maxssiz(5)
                          Tunable Kernel Parameters



 NAME    [Toc]    [Back]
      pa_maxssiz_32bit, pa_maxssiz_64bit - maximum size (in bytes) of the
      stack for a user process running under the PA-RISC emulator on
      Itanium-based system

 VALUES    [Toc]    [Back]
    Default
      32 bit default: 0x04FC6000 (79Mb)

      64 bit default: 0x20000000 (512Mb)

    Allowed values    [Toc]    [Back]
      32 bit minimum: 0x04FC6000 (79Mb)

      32 bit maximum: 0x1BF00000 (447Mb)

      64 bit minimum: 0x20000000 (512Mb)

      64 bit maximum: 0x60000000 (1.5Gb)

 DESCRIPTION    [Toc]    [Back]
      User programs on HP-UX systems are composed of five discrete segments
      of virtual memory: text (or code), data, stack, shared, and I/O.

      PA-RISC binaries running under Itanium-based system using the PA-RISC
      emulator have their stack segment size (which includes both the memory
      stack and the RSE stack) determined by pa_maxssiz_32bit or
      pa_maxssiz_64bit.

      The emulated stack from the process perspective is the same as the
      stack if the process were executed on a PA-RISC machine without the
      emulator.  The actual (non-emulated) process stack (both memory and
      RSE) for an emulated process are of a non-configurable size and are
      used solely for the internal use of the emulator for a PA-RISC process
      on Itanium-based system.  This tunable therefore represents the
      required value of maxssiz or maxssiz_64bit on a corresponding PA-RISC
      machine to execute the emulated process plus working space for the
      emulator itself.

      As with the stack address space sized by maxssiz, the address space
      used by the emulator is both private to the process and not usable for
      other purposes regardless of whether the emulator stack grows to
      encompass the full range or not. As a consequence, the tunable value
      may be viewed as an amount of process data address space which will be
      unavailable to this PA-RISC process. Caution is advised especially for
      32 bit processes since the default address space model only provides 1
      Gb of private data space. Setting this tunable too high will result in
      execution failure when other allocations (private mmap() calls or
      sbrk() calls) fail due to insufficient available address space. If
      this occurs, revise the address space model of the failing PA-RISC
      executable using chatr to allow more private data virtual address



 Hewlett-Packard Company            - 1 -   HP-UX 11i Version 2: August 2003






 pa_maxssiz(5)          Itanium(R)-based System Only           pa_maxssiz(5)
                          Tunable Kernel Parameters



      space or lower the tunable.

    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.

      Given that the user memory stack size is not modifiable by this
      tunable, it is expected that detailed knowledge of the PA-RISC
      emulator memory usage is needed before modifying this tunable.

    When Should the Value of This Tunable Be Raised?
      This tunable should be raised if the PA-RISC emulator on Itanium-based
      system requires additional space for stack emulation.

    What Are the Side Effects of Raising the Value?
      The PA-RISC emulator will use more of the virtual address space for
      stack, leaving less virtual address space for data allocations.
      Raising the value too high will result in application failure when
      data allocations fail due to insufficient virtual address space.

      Since it may not be known which processes are based off of PA-RISC
      binaries and which off Itanium-based binaries, arbitrary raising of
      this tunable is discouraged.

    When Should the Value of This Tunable Be Lowered?
      This tunable should only be lowered if the workload for the PA-RISC
      emulator is known on the system, more space than is needed is
      currently used for stack emulation, and swap space (either reserved or
      allocated) is at a premium on the system.

    What Are the Side Effects of Lowering the Value?
      Lowering this tunable will decrease the available stack space for
      emulated PA-RISC binary executions. Emulated processes needing larger
      stacks will fail stack growth requests (just as lowering maxssiz or
      maxssiz_64bit may cause process termination due to failure to grow
      stack).

    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.

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





 Hewlett-Packard Company            - 2 -   HP-UX 11i Version 2: August 2003






 pa_maxssiz(5)          Itanium(R)-based System Only           pa_maxssiz(5)
                          Tunable Kernel Parameters



 SEE ALSO    [Toc]    [Back]
      chatr(1), maxssiz(5), mmap(2), sbrk(2)


 Hewlett-Packard Company            - 3 -   HP-UX 11i Version 2: August 2003