Locality-Optimized Resource Alignment for Superdome 2

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fabric. Using a mixture of even-numbered and odd-numbered blades will still work, but some inter-
blade communication will use slower paths through the interconnect fabric.
Configuring vPars for LORA
A nice thing about Superdome 2 is that all of the vPars configuration commands can be entered
directly to the Onboard Administrator, even if none of the virtual partitions are booted. Of course,
the commands are also available with the same syntax in any of the virtual partitions running in the
nPartition.
Considerations for memory granule size
The memory for virtual partitions can be allocated only in multiples of the memory granule size. The
granule size can be different for interleaved memory and local memory. Default granule sizes are
established when a server complex is shipped from the factory. The defaults can be overridden by
using the parcreate and parmodify commands.
A small granule size permits the greatest flexibility in dividing the memory resources in an nPartition
for assignment to virtual partitions. However, a small granule size may limit the size of contiguous
physical memory objects, which are useful to increase the performance of I/O drivers, and can result
in slightly longer boot times. Also, there is a limit on the total number of granules that can be created.
(In a system with a large amount of physical memory, the requested granule size may be ignored and
substituted with a larger value to keep the total number of granules within the limit.) A large granule
size is more efficient for the virtual memory management subsystem to work with, but it means that the
quantum of memory allocation is large.
Under the LORA configuration guidelines, an nPartition has seven times as much local memory as
interleaved memory. Therefore, it is reasonable if the granule size for local memory is larger than the
granule size for interleaved memory. For example, the local memory granule size could be four times
larger or eight times larger than the interleaved memory granule size. HP recommends configuring
the interleaved memory granule size to its minimum permissible value, 256 MB; and the socket local
memory granule size to something larger, such as1024 MB. This modification can be done with the
command:
parmodify –p 2 –G ilm:256 –G slm:1024
We also recommend omitting interleaved memory altogether for extremely small virtual partitions. For
example, a virtual partition with only 2 GB of memory could be configured with 100% local memory,
instead of trying to give it 256 MB of interleaved memory, which would require a granule size at
least that small.
In the examples that follow, it is assumed that the memory granule sizes have been established so that
the requested memory allocations are an integral multiple of the relevant granule size.
Creating new virtual partitions
In this section, we will assume that an nPartition has already been configured in accordance with the
LORA guidelines and will now be configured for vPars. There are two important sub-cases: dividing
the nPartition into a given number of virtual partitions of equal size, and establishing a set of virtual
partitions each with its own processor and memory requirements.
In either case, the goal of the configuration is to create virtual partitions where the cores and local
memory are drawn from the minimal number of localities.