Locality-Optimized Resource Alignment

Figure 2. Six equal vPars instances configured according to LORA rules

To achieve alignment between processors and memory with the vPars version delivered in Update 3,

it was necessary to specify the cell identifiers for the processors to match the local memory. This had

the drawback of disallowing gWLM to perform processor deletion operations upon the cell local

processors. With the enhancements added in Update 4, gWLM is free to delete any core, and online

processor addition operations will select the cores that give the best possible resource alignment.

The creation commands did not specify any I/O allocations. The needed I/O could be added with

subsequent commands. For example:

vparmodify -p vp5 -a io:1/0/0/2/0.6.0:BOOT -a io:1/0/0/1/0

vparmodify -p vp6 -a io:1/0/4/0/0.6.0:BOOT -a io:1/0/6/1/0

As a general rule, overall system performance is determined by processor to memory alignment, and

is less sensitive to I/O location. Most I/O operations are asynchronous and the operating system and

applications employ a wide variety of latency-hiding techniques to make progress while I/O

operations are pending. If a particular workload were sensitive to processor to I/O alignment, this

can be achieved by specifying I/O location with the create command. For example:

vparcreate -p vp5 -a cpu::4 -a io:3/0/0/2/0.6.0:BOOT -a io:3/0/0/1/0

vparcreate -p vp6 -a cpu::4 -a io:3/0/4/0/0.6.0:BOOT -a io:3/0/6/1/0

It is also possible to specify both local memory and I/O in the vparcreate command, in which case

the processor cores are allocated across the set of localities is spanned by the memory and I/O. The

following command would allocate processor cores preferentially from cells 2 and 3:

vparcreate -p vp5 -a cpu::4 -a mem::4096 -a cell:2:mem::28672

-a io:3/0/0/2/0.6.0:BOOT -a io:3/0/0/1/0