HP-UX Reference (11i v3 07/02) - 5 Miscellaneous Topics (vol 9)

p
pa_maxssiz(5)
Integrity Systems Only
pa_maxssiz(5)
(Tunable Kernel Parameters)
NAME
pa_maxssiz: pa_maxssiz_32bit, pa_maxssiz_64bit - maximum size (in bytes) of the stack for a user process
running under the PA-RISC emulator on an Integrity system
VALUES
Default
32 bit default:
0x04FC6000 (79Mb)
64 bit default: 0x20000000 (512Mb)
Allowed values
32 bit minimum: 0x04FC6000 (79Mb)
32 bit maximum: 0x1BF00000 (447Mb)
64 bit minimum: 0x20000000 (512Mb)
64 bit maximum: 0xA0000000 (2.5Gb)
DESCRIPTION
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 seg-
ment 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 emula-
tor 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 encom-
pass 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 space or lower the tun-
able.
Who is Expected to Change This Tunable?
Anyone.
Restrictions on Changing
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.
342 Hewlett-Packard Company − 1 − HP-UX 11i Version 3: February 2007