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SubjectRe: nohz: Warn if the machine can not perform nohz_full

> Gitweb: http://git.kernel.org/linus/;a=commit;h=e12d0271774fea9fddf1e2a7952a0bffb2ee8e8b
> Commit: e12d0271774fea9fddf1e2a7952a0bffb2ee8e8b
> Parent: 7d132055814ef17a6c7b69f342244c410a5e000f
> Author: Steven Rostedt <rostedt@goodmis.org>
> AuthorDate: Fri May 10 17:12:28 2013 -0400
> Committer: Frederic Weisbecker <fweisbec@gmail.com>
> CommitDate: Thu Jun 20 01:15:51 2013 +0200
>
> nohz: Warn if the machine can not perform nohz_full
>
> If the user configures NO_HZ_FULL and defines nohz_full=XXX on the
> kernel command line, or enables NO_HZ_FULL_ALL, but nohz fails
> due to the machine having a unstable clock, warn about it.
>
> We do not want users thinking that they are getting the benefit
> of nohz when their machine can not support it.
> ---
> kernel/time/tick-sched.c | 5 +++++
> 1 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> index f420813..d87d22c 100644
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -178,6 +178,11 @@ static bool can_stop_full_tick(void)
> */
> if (!sched_clock_stable) {
> trace_tick_stop(0, "unstable sched clock\n");
> + /*
> + * Don't allow the user to think they can get
> + * full NO_HZ with this machine.
> + */
> + WARN_ONCE(1, "NO_HZ FULL will not work with unstable sched clock");
> return false;

So I guess you guys never want this to be enabled on distro kernels ?
If that's the case, can you add something to that effect in Kconfig ?

Dave



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