On Thu, Nov 14, 2013 at 05:54:10PM +0800, Shaojie Sun wrote:
No, I think it is a bug.
Because I tested the option with NO_HZ_FULL and without NO_HZ_FULL_ALL. It had only little interruptes on CPU0 twd. With same code, I added NO_HZ_FULL_ALL option. It had too many interruptes on CPU0 twd.
If you select:
NO_HZ_FULL=y NO_HZ_FULL_ALL=n
then you need to pass a nohz_full= cpu range in the boot parameter, otherwise it's simply going to behave like NO_HZ_FULL=n
OTOH, if you select NO_HZ_FULL_ALL=y, the "nohz_full=" parameter is not needed and all CPUs will be full dynticks except CPU 0 where you should see more tick than usual because it's handling the timekeeping for every other CPUs. Don't forget to select CONFIG_NO_HZ_FULL_SYSIDLE=y or CPU 0 will never shutdown its tick even if the entire system is idle.