'High Resolution Timer Support' enabled cause CPU usage increase!

Hi,All:
CPU is MPC8548, kernel version is 2.6.31.6. When I enabled this
option, my application's CPU usage increased, then I disabled this
option, CPU usage dropped to normal level.
I also tested on 2.6.30, the result is same.

-- 
The simplest is not all best but the best is surely the simplest!