a bug on NO_HZ_FULL_ALL
Frederic Weisbecker
fweisbec at gmail.com
Thu Nov 14 06:50:05 EST 2013
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.
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