pa_maxssiz: pa_maxssiz_32bit, pa_maxssiz_64bit - maximum size (in
bytes) of the stack for a user process running under the PA-RISC emula‐
tor on an Integrity system
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 or
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 or 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 the address space used by the
emulator is both private to the process and not usable for other pur‐
poses 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 pro‐
cesses since the default address space model only provides 1 Gb of pri‐
vate data space. Setting this tunable too high will result in execu‐
tion failure when other allocations (private calls or calls) fail due
to insufficient available address space. If this occurs, revise the
address space model of the failing PA-RISC executable using to allow
more private data virtual address space or lower the tunable.
Who is Expected to Change This Tunable?
Restrictions on Changing
Given that the user memory stack size is not modifiable by this tun‐
able, 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. Rais‐
ing 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 emu‐
lated PA-RISC binary executions. Emulated processes needing larger
stacks will fail stack growth requests (just as lowering or may cause
process termination due to failure to grow stack).
What Other Tunable Values Should Be Changed at the Same Time?
All HP-UX kernel tunable parameters are release specific. This parame‐
ter may be removed or have its meaning changed in future releases of
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 val‐
ues. For information about the effects of installation on tunable val‐
ues, consult the documentation for the kernel software being installed.
For information about optional kernel software that was factory
installed on your system, see at
was developed by HP.
SEE ALSOchatr(1), mmap(2), sbrk(2), maxssiz(5).
Integrity Systems Only Tunable Kernel Parameters pa_maxssiz(5)