Adjusting kernel virtual segments for large mappings
The ZBM_LGMAP_PERCENT tunable can be used to
control the percentage of the kpgseg (segkvn)
kernel virtual segment reserved for most large mappings,
but DRV_SEGKMEM_BYTES is the preferred tunable when setting aside
kernel virtual memory for large driver mappings.
Note that ZBM_LGMAP_PERCENT effectively replaces
PSE_VMEMSIZE as a way to reserve kernel virtual
space for large mappings.
However, ZBM_LGMAP_PERCENT does not use PSE mappings, and
does not require that the PSE driver be configured in.
The ZBM_LGMAP_PERCENT tunable, in conjunction with
SEGKMEM_BYTES, can be used to satisfy large requirements
for kernel virtual space originating from
When you know the specific amount of space
you need, increase SEGKMEM_BYTES by that quantity (in bytes).
When used in conjunction with SEGKVN_BYTES, the
ZBM_LGMAP_PERCENT tunable can be used to provide contiguous
kernel virtual space for loadable modules.
When you know the specific amount of space you
need, increase SEGKVN_BYTES by that quantity (in bytes).
In order to obtain the best overall system performance, you want
to keep ZBM_LGMAP_PERCENT as small as possible, but still
large enough to obtain the kernel virtual space you need.
In order to estimate a new value for ZBM_LGMAP_PERCENT, you
need to obtain the actual value for the size of segkmem.
You can do this using
As root, issue the commands:
dumpfile = /dev/mem, namelist = /stand/unix, outfile = stdout
Engine: 0 Procslot: 56 Lwpslot: 0
> od segkmem_size
In this example, the size for segkmem is 0x2600000 bytes
DRV_SEGKMEM_BYTES specifies the quantity of kernel virtual memory
which will be put aside for large driver mappings, especially those
Typically, this parameter is incremented by driver package installation
scripts rather than by the administrator.
DRV_SEGKMEM_BYTES is the preferred tunable when setting aside
kernel virtual memory for large driver mappings, but
if you need to control the percentage of kernel virtual segments reserved
for large mappings other than large device memory areas, use
Configuring the Dedicated Memory feature
Adjusting stack overflow parameters
© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 22 April 2004