Locality-Optimized Resource Alignment for Superdome 2

5
vPars
The virtualization model of vPars is particularly well-suited to LORA. The first version of the T1335DC
product tailored for Superdome 2, version A.05.07, contains many optimizations to gain additional
benefit from local memory.
Each virtual partition should be configured with ⅞
ths
local memory and ⅛
th
ILM. Since the underlying
nPartition has this memory ratio, it is straightforward to reflect the same ratio in the virtual partitions.
It is important that the processor and memory resources assigned to each virtual partition span the
minimal number of localities. If a virtual partition must span multiple localities, then the processor and
memory resources should be distributed symmetrically across those localities.
Aligning I/O resources with the processors and memory is helpful, but it is a second-order effect, as
the system is usually able to perform useful work while waiting for I/O operations to complete. The
I/O resources on the blades can be grouped together to exploit locality. The I/O resources on I/O
Expansion Enclosures are all the same distance away from the blades.
HP recommends that virtual partitions configured with ⅞
ths
local memory be operated in LORA mode.
This can be achieved most easily by leaving the numa_mode kernel tunable parameter at its default
value. For virtual partitions containing exactly one locality, there is no difference between interleaved
memory and local memory. For such a partition, there is no difference between SMP mode and
LORA mode.
The appendix
Configuring vPars for LORA explains these points in more detail.
Integrity Virtual Machines
The nPartition containing the Integrity Virtual Machines host should be configured with ⅞
ths
local
memory and ⅛
th
ILM. The guest instances operate in a Uniform Memory Architecture environment, so
it is neither necessary nor possible to configure local memory in the guest instances. The Integrity
Virtual Machines host will allocate resources to the guest instances to gain the greatest possible
benefit from memory local to the processors.
The binding of virtual resources to physical resources in Integrity Virtual Machines is flexible and fluid,
yet there are still opportunities to gain performance advantage through resource alignment. HP
recommends deploying Integrity Virtual Machines with LORA.
LORA system administration
For the most part, managing a system in LORA mode is identical to managing it in SMP mode.
Suggestions for adapting to unusual workload profiles are in the
Advanced Tuning appendix.
Server Tunables product in the Tune-N-Tools bundle
We recommend using the Server Tunables product in the Tune-N-Tools bundle with LORA to improve
application performance. This product was introduced with Update 3 and is also available on the
web in the HP ‘software depot’:
http://h20392.www2.hp.com/portal/swdepot/displayProductInfo.do?productNumber=Tune-N-Tools
loratune command
The loratune command is valuable in LORA mode. The command can be used to restore good
resource alignment if it has been disturbed by an event such as terminating a major application or
completing a backup.