Locality-Optimized Resource Alignment

Figure 6. Allocations after the CPU migration operations

CPU

dog

CPU

elk

fox

CPU

cow

CPU

It is also possible to migrate memory along with the processor cores, but only for the memory that was

specifically designated as floating memory. If 1 GB of memory from cell 2 in the vPars instance cow

had been designated as floating memory, it could be migrated to instance dog with the following pair

of commands:

vparmodify -p cow -d cell:2:mem::1024:floating

vparmodify -p dog -a cell:2:mem::1024:floating

Summary of vPars configuration rules

The rules for configuring vPars for LORA are simple:

• Draw resources for each vPars instance from the minimal number of distinct localities

• If the number of localities is greater than one, balance the resources across those localities

• Do the best you can with I/O devices and with instances created from leftover resources

A minor optimization, and one which also applies for 100% interleaved nPartitions, is to keep the

cores on a socket in the same instance, because they share a common cache. Keeping such cores

working together on the same application can give a small performance benefit, which is worth

realizing if the choice of cores is otherwise arbitrary. Use mpsched -K to identify the cores that

share a common socket. Similarly, mpsched –S shows which cores belong to the same proximity

set, and those should be kept together if the choice of cores is otherwise unconstrained.