NAME
nsysmap, nsysmap64 — number of entries in a kernel dynamic memory allocation map
VALUES
Allowed Values
Any positive value.
DESCRIPTION
Note:
In HP-UX 11i Version 3, these tunables are no longer present. The
system will establish an initial size for the table, and increase
the size as needed. This manual page will be remove in a future
release.
Pre-Release 11i Version 3 Usage
This value sizes the kernel dynamic memory resource map, an array of
address/length pairs that describe the free virtual space in the
kernel's dynamic address space.
This array has historically been statically-sized. That means
certain pathological workloads that fragment the kernel address space
will result in too many entries for the array.
Rather than panicking when this condition occurs, the system throws
away the last entry, which results in "leaked" kernel virtual address
space.
If this overflow happens often enough, the system eventually runs out of
virtual space and will panic with the following message:
kalloc: out of virtual space.
By making the map size tunable, the system can automatically scale the map
size according to the system workload size and avoid this problem.
If the automatic scaling does not work, you can hand-tune to
fit a particular workload.
When the default value is overridden, the kernel may increase
the value beyond the your specification depending on the system size.
There are different tunables for 32- and 64-bit kernel because the
64-bit kernel has more virtual address space.
The
nsysmap
tunable controls 32-bit kernels and the
nsysmap64
tunable controls 64-bit kernels.
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 parameter 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
nsysmap
and
nsysmap64
were developed by HP.
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