HP-UX Reference (11i v2 04/09) - 5 Miscellaneous Topics (vol 9)

m
max_mem_window(5) max_mem_window(5)
(Tunable Kernel Parameters)
NAME
max_mem_window - maximum number of group-private 32-bit shared memory configurable by users
VALUES
Default
0
Allowed values
Minimum: 0 shared memory windows
Maximum:
65535 shared memory windows
DESCRIPTION
32-bit processes usually share the global quadrants 3 and 4 for such things as I/O mappings, shared
libraries, shared mapped files, etc. However, you may wish to use quadrant 3 in a more limited sharing
fashion with only a select group of processes. Memory windows allow this functionality.
If this tunable is set to 0, 32-bit programs always use the global Q3 and Q4 for shared memory. If this
tunable is greater than 0 processes in defined groups use a Q3 private to that group, and then the glo-
bally shared Q4 if Q3 is full.
Who is Expected to Change This Tunable?
Anyone.
Restrictions on Changing
Changes to this tunable take effect at the next reboot.
When Should the Value of This Tunable Be Raised?
This tunable should be raised if more group-private Q3 areas are needed by the users of the system. Each
memory window in active use will require approximately 1Mb of kernel memory. Windows no longer in
use will have this memory reclaimed by the system.
What Are the Side Effects of Raising the Value?
A little more memory is used in the kernel.
When Should the Value of This Tunable Be Lowered?
If process groups are not being used, or not being used in the quantity set by the tunable, there is really
no point to having this value higher than what is actually needed.
What Are the Side Effects of Lowering the Value?
The kernel uses a little less memory. If the value is set to
0, no group-private Q3’s are allowed.
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://docs.hp.com.
AUTHOR
max_mem_window was developed by HP.
SEE ALSO
getmemwindow(1M), services.window(4), setmemwindow(1M).
Section 5−−186 Hewlett-Packard Company − 1 − HP-UX 11i Version 2: September 2004