/boot/grub/grub.conf and added
nohz=off to the command line of the default kernel.
I do not see any difference, kernel is compiled with 1000Hz, but when I test with the following tool: http://www.advenage.com/topics/linux-timer-interrupt-frequency.php
It reports only about 500Hz interrupt frequency.
dmesg | grep nohz only shows the kernel boot command.