[10-STABLE, 11-CURRENT] something wrong between cam and eventtimer or geom and eventtimer

[Oliver Pinter]

Hi all!

The machine is a Haswell machine, the disc performance was very poor
(20-30MByte/sec).
When I change the kern.eventtimer.idletick from 0 to 1, the normal
performance restored back to normal (70-90MByte/sec).

The default eventtimer was LAPIC.

On other machine Q9300, this was fully reproducible.