I beleive that's the intended behaviour. We always put cpus that are not
balanced into null sched domains. This was done since day one (ie when
cpuisol= option was introduced) and cpusets just followed the same convention.
I think the idea is that we want to make balancer a noop on those processors.
We could change cpusets code to create a root sched domain for each cpu I
guess. But can we maybe scale cpupri some other way ?