HP Integrity Virtual Machines Installation, Configuration, and Administration Version A.03.50

This feature limits the types of software you can run on a VM Host system. If the VM Host system
supports an additional workload beyond the virtual machines, the large pages tend to fragment
and performance of the newly started virtual machine might degrade.
Dynamic memory increases the possibility of VM Host memory becoming fragmented. The
current implementation of dynamic memory releases portions of the memory allocated to a
virtual machine. These operations must be performed in large contiguous chunks; otherwise,
the act of reducing the size of a virtual machine fragments the VM Host memory allocated to it.
This potential fragmentation is prevented by the software, which reduces a virtual machine's
size in multiples of a minimum chunk size of 64 MB of physically contiguous memory. For more
information, see Section 9.6.3.3 (page 136) and Section 9.6.3.5 (page 137).
9.6.3.3 Guest Resource Considerations
During normal operation of a system that has a workload running on it, the large pages might
become fragmented over time. This is true on the VM Host as well as a virtual machine running
the HP-UX operating system. If the virtual machine's memory is fragmented, the dynamic memory
subsystem is unable to reduce the size of guest. This is due to the minimum chunk size used for
the reduction. If dynamic memory cannot remove at least 64 MB of physically contiguous guest
memory, no reduction in size takes place.
9.6.3.4 Specify Sufficient Guest Memory
If you set the value of ram_dyn_target_start too small, the guest operating system might
hang or crash while booting. In this case, the guest does not have access to a sufficient amount
of memory. As a rule, do not decrease the memory allocated to an HP-UX guest by more than
75% of its allocated memory size. Do not reduce the memory of a virtual machines configured
with 2 GB of memory by more than 50%.
If the guest crashes while booting on the VM Host , use the hpvmmodify command to increase
the value of the ram_dyn_target_start parameter. For example, to increase the memory size
for the guest named compass1, enter the following command on the VM Host:
# hpvmmodify -P compass1 -x ram_dyn_target_start = new memory size
After you set this parameter, reboot the guest.
If the guest hangs, on the VM Host, use the hpvmstatus command to check the memory statistics
on the guest. For example:
# hpvmstatus -V -P compass1
.
.
.
[Dynamic Memory Information]
Type : driver
Minimum memory : 1222 MB
Target memory : 2103 MB
Maximum memory : 6144 MB
Current memory : 2103 MB
Comfortable minimum : 2167 MB
Boot memory : 6135 MB
Free memory : 0 MB
Available memory : 286 MB
Memory pressure : 100
Memory chunksize : 65536 KB
Driver Mode(s) : STARTED ENABLED
.
.
.
An indication of this problem is a small or zero amount of free memory and a large memory
pressure value (100). If these indicators are present, use the hpvmmodify command on the VM
Host to increase the memory size of the guest. The guest should then boot normally.
136 Managing Guests