CPUSET

Each cpuset is a contiguous, non-overlapping range of CPUs.
Not defining any cpuset creates a "default" cpuset, containing
all CPUs, important for backward compatibility.  All NICs are
assigned to this cpuset if no other is defined.

It is possible to have CPUs not assigned to any cpuset, they
are then unused by irqd.

Each NIC may be assigned to exactly one cpuset, in case no cpuset
is assigned irqd does not balance the NIC interrupts.
NOTE: problematic, because the unbalanced IRQs may break proper
balancing.  Goal is therefore to assign all NICs to some cpuset.

General format for cpusets:

  //  first eight CPUs for the network path
  cpuset "network" 0 8  {
  };

