Uneven CPU utilization distribution.

[Юрий Иванов via Unbound-users]

Hi,
My Cache has 8 CPU cores and config set accordingly:
$ cat /etc/unbound/unbound.conf | grep threads
        # number of threads to create. 1 disables threading.
        num-threads: 8

Nevertheless 5-th core always has more than twice load than others:
  1  [|||||||||                 15.5%]
  2  [||||||||||                17.4%]
  3  [||||||||||                17.0%]
  4  [|||||||||||               16.8%]
  5  [|||||||||||||||||||||||   43.0%]
  6  [||||||||                  11.4%]
  7  [||||||||||                16.3%]
  8  [||||||||                  14.5%]

Is there any additional configuration stanzas or this normal behavior?