HP-UX vPars and Integrity VM V6.3 Administrator Guide

3.3 VSP memory
On startup, the HP-UX vPars and Integrity VM product reserves a significant portion of the free
system memory available on the VSP for the vPars and Integrity VM memory pool. This memory
will be used for supporting the memory requirements of various vPars and VM guests on the VSP.
The remaining available memory in the VSP is sufficient for the optimal functioning of the vPars
and Integrity VM guests product on the VSP.
About 92% of free memory available at the vPars and Integrity VM product start time (after HP-UX
has booted up on the VSP) is reserved for the vPars and Integrity VM memory pool. The amount
of memory reserved also depends on the total system memory and the total number of system cores.
To view the allocation of memory, enter the following command:
# hpvmhwmgmt -p memory -l
The /var/opt/hpvm/common/command.log file also has information about the free memory
available when the vPars and Integrity VM memory pool was allocated.
Only 64 MB or larger contiguous chunks of memory are reserved for the vPars and Integrity VM
memory pool. Therefore, the system memory fragmentation at start time affects the amount of
memory that can be reserved for the vPars and Integrity VM memory pool. If vPars and Integrity
VM products are stopped and restarted, it is possible that there are not enough contiguous memory
ranges in the VSP to match the memory, that was reserved for vPars and Integrity VM pool
previously. This can lead to an over-commitment of the memory assigned to the Integrity VM or
vPars.
NOTE: HP strongly recommends that you restart the VSP when restarting the vPars and Integrity
VM product, so that system memory fragmentation impact on vPars and Integrity VM memory pool
size can be minimized.
Memory availability for VSP use can be controlled using the HPVM_MEMORY_OVERHEAD_PERCENT
configuration variable. If this variable is set to an appropriate value in the /etc/rc.config.d/
hpvmconf file, that value is used to determine the amount of memory reserved for vPars and
Integrity VM in the memory pool. For example,
# ch_rc –a HPVM_MEMORY_OVERHEAD_PERCENT='N' /etc/rc.config.d/hpvmconf
If HPVM_MEMORY_OVERHEAD_PERCENT is set to 'N', then (100-N)% of free system memory
available at vPars and Integrity VM product start time (after HP-UX has booted up on the VSP) is
reserved for vPars and Integrity VM memory pool. The default setting is 8.
When determining the percentage, consider the following:
• Amount of memory in the system
• Number of guests
• Memory size of the guests you want to run
The higher the percentage, the less memory is available for guest usage.
NOTE: A VSP restart (or vPars and Integrity VM product restart) is required for this change to
take effect. HP strongly recommends that you do not use this configuration variable to change the
memory available for VSP unless otherwise documented or recommended by HP field personnel.
3.3.1 Memory overhead estimation
VSP requires certain amount of memory for the optimal functioning of the product. Given below is
a rough estimate of the memory overhead required for the VSP.
The vPars and Integrity VM memory pool reserved is roughly about 92% of the system free memory
available at the time of vPars and Integrity VM V6 product startup. The remaining memory is left
out as free memory available for VSP use. This is in addition to the memory taken up by HP-UX to
3.3 VSP memory 39