Why does RHEL7 show 2 LOC interrupts per second for nohz_full cpus?

Issue

• Why does RHEL7 show 2 LOC interrupts per second for nohz_full cpus?

[root@rhel7 ~]# taskset -c 12 sha1sum /dev/zero &
[1] 4438
[root@rhel7 ~]# perf stat -e irq_vectors:local_timer_entry -e irq_vectors:local_timer_exit -e context-switches -C 12 sleep 20

 Performance counter stats for 'CPU(s) 12':

                40      irq_vectors:local_timer_entry
                40      irq_vectors:local_timer_exit
                 0      context-switches

      20.000894842 seconds time elapsed