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maxrsessiz.5 (2010 09)

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maxrsessiz(5)
Itanium(R)-based Systems Only
maxrsessiz(5)
(Tunable Kernel Parameters)
NAME
maxrsessiz, maxrsessiz_64bit - maximum size (in bytes) of the RSE stack for any user process on the
Itanium-based platform
VALUES
Default
32 bit default:
0x800000 (8MB)
64 bit default:
0x800000 (8MB)
Allowed values
32 bit minimum:
0x40000
32 bit maximum: 0x17F00000
64 bit minimum: 0x40000
64 bit maximum: 0x40000000
DESCRIPTION
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
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 [SIGSEGV] 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.
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 [SIGSEGV] error.
What Other Tunable Values Should Be Changed at the Same Time?
None.
WARNINGS
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 parame-
ter 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://www.hp.com/go/hpux-core-docs.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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