Locality-Optimized Resource Alignment for Superdome 2

8
Configuring nPartitions for LORA
This section discusses the case of creating a new LORA nPartition and of converting an existing 100%
interleaved nPartition for use with LORA. This is relevant when virtual partitions will not be used, that
is, the nPartition will be used to run a single instance of HP-UX or will act as the host for Integrity
Virtual Machines.
Memory interleaving is a property of the nPartition and the blades that compose it. All memory in a
Superdome 2 system resides in sets of DIMMs associated with, and controlled by, each of the
processor sockets. None, any, or all of the memory on each blade can be designated as interleaved
memory. If memory is designated to be interleaved, then successive cache lines in the physical
address space are drawn from the various sockets in a round-robin fashion. Memory that is not
interleaved remains as local memory, and successive cache lines are all drawn from a single socket.
Creating a new nPartition for LORA
If a new nPartition is to be created for LORA, it is necessary to configure each base blade in the
nPartition with 87.5% local memory.
The parcreate command is used to create a new nPartition. For example:
parcreate -p 2 -L 87.5% -G ilm:256 -G slm:1024 \
-a blade:1/1:base::: -a blade:1/3:base::: -a blade:1/5:base:::
The creation command did not specify any I/O allocations. The needed I/O could be added with
subsequent commands, for example:
parmodify -p 2 –a io:5/1:y -a io:6/1:y
For Superdome 2, ⅞
ths
local memory is the default configuration, so all systems preconfigured for
nPartitions at the factory will have ⅞
ths
local memory unless otherwise specified.
Converting an existing nPartition for LORA
If an existing fully interleaved nPartition is to be converted for LORA, it is only necessary to configure
each base blade in the nPartition with 87.5% local memory.
The parmodify command is used to change the local memory ratio. For example, for an existing
nPartition composed of three blades in enclosure 1:
parmodify -p 2 -m blade:1/1:base:::87.5% -m blade:1/3:base:::87.5% \
-m blade:1/5:base:::87.5%
It is necessary to reboot the partition for the change to take effect. The man page for the
parmodify(1m) command has the full details.
Helpful hints
Memory performance is better when all the sockets in an nPartition have the same amount of memory
installed. This is good advice for the 100% interleaved case, because the deepest interleave is
possible only when each socket contributes the same amount of memory. Having the same amount of
memory on each socket is even more important for LORA: the memory symmetry promotes balanced
utilization of the processing resources. Asymmetry of local memory can cause a slight degradation in
overall system performance.
To the greatest extent possible, each nPartition should be composed of either even-numbered blades
or odd-numbered blades, because those communicate over the fastest paths through the interconnect