You can modify certain kernel parameters to improve system performance and allocate resources more
effectively. The optimum setting for kernel parameters is often determined by a system’s hardware
configuration and the specific mix of applications running on the system. Hewlett-Packard attempts to provide
reasonable default settings, but you can modify these values to improve performance based on your system’s
particular needs.
Before modifying the value of any parameter, be sure you understand the implications of a change. Many kernel
parameters interact with each other, so selecting values should always be done in a balanced manner. Changing
kernel parameters to improper values can lead to data loss, system panics, or other operating anomalies that are
difficult to diagnose.
The table below shows the recommended parameter settings for N- and V-Class servers running under HP-UX
11.0.
Parameter
Name
STRMSGSZ
Default
Setting
0
swapmem_on 1
Recommended Setting
65535
0
vps_ceiling
16
64
shmmax
0x4000000
0x7B000000
nstrpty
calculated
60
maxusers
32
250
maxswapchunk
256
s
16384
maxdsiz
0xF6000000
0x4000000
maxdsiz_64bit 0x40000000 0xF6000000
Description
Maximum number of bytes that can be sent in the data
part of a STREAMS message using the function putmsg
and write. If STRMSGSZ is 0, the maximum data
message size is infinite.
Allows the oversubscription of swap so applications can
run that cannot allocate swap space (for example, when
memory is smaller than swap). swapmem_on is enabled
for 16G servers. However, it appears to take memory
away from the free list if swap is not big enough.
Maximum variable page size should be higher on VClass servers due to a larger cache. This allows up to
64K pages.
Maximum use of shared memory.
Number of STREAMS-based pseudo-terminals.
The maxusers default is too small for large memory
systems. The value of maxusers is used to calculate other
parameters.
Maximum value. The value of maxswapchunks only
needs to be large enough to handle the swap space.
The maxdsiz default is too small for large memory
systems.
The maxdsiz_64bit default is too small for large memory
systems. Be careful, however, when setting the value
larger then memory; otherwise, applications can run into
trouble.
0x005000000
The maxssize default is too small for large memory
systems.
maxssiz_64bit 0x800000
0x5000000
The maxssize_64bit default is too small for large
memory systems.
lotsfree
131072
maxssiz
0x800000
0
Upper bound from which the paging daemon will begin
stealing pages. Must be set by editing the /stand/system
file instead of using SAM.
minfree
desfree
ninode
0
0
calculated
(1818)
8192
32768
8000
Minimal amount of free memory that is tolerable. If free
memory drops below this amount, the system begins
deactivating processes. Must be set by editing the
/stand/system file instead of using SAM.
Desired amount of free memory. This is the lower bound
at which the paging daemon begins stealing pages. Must
be set by editing the /stand/system file instead of using
SAM.
Provides more space for the inode cache—this is good
for NFS or other servers that open or stat many files
frequently. For heavily-loaded NFS servers, set the value
of ninode between 100000 and 200000.