On Tue, Dec 17, 2013 at 01:23:07PM -0800, Kevin Hilman wrote:
> Allow debugfs override of sched_tick_max_deferment in order to ease
> finding/fixing the remaining issues with full nohz.
>
> The value to be written is in jiffies, and -1 means the max deferment
> is disabled (scheduler_tick_max_deferment() returns KTIME_MAX.)
>
> Cc: Frederic Weisbecker <fweis...@gmail.com>
> Signed-off-by: Kevin Hilman <khil...@linaro.org>
> ---
> kernel/sched/core.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 5ac63c9a995a..4b1fe3e69fe4 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2175,6 +2175,8 @@ void scheduler_tick(void)
> }
>
> #ifdef CONFIG_NO_HZ_FULL
> +static u32 sched_tick_max_deferment = HZ;
> +
> /**
> * scheduler_tick_max_deferment
> *
> @@ -2193,13 +2195,25 @@ u64 scheduler_tick_max_deferment(void)
> struct rq *rq = this_rq();
> unsigned long next, now = ACCESS_ONCE(jiffies);
>
> - next = rq->last_sched_tick + HZ;
> + if (sched_tick_max_deferment == -1)
> + return KTIME_MAX;
> +
> + next = rq->last_sched_tick + sched_tick_max_deferment;
>
> if (time_before_eq(next, now))
> return 0;
>
> return jiffies_to_usecs(next - now) * NSEC_PER_USEC;
> }
> +
> +static __init int sched_nohz_full_init_debug(void)
> +{
> + debugfs_create_u32("sched_tick_max_deferment", 0644, NULL,
> + &sched_tick_max_deferment);
> +
> + return 0;
> +}
> +late_initcall(sched_nohz_full_init_debug);
If the goal is mostly to turn off sched_tick_max_deferment (set to -1), we
should
perhaps make it a boolean sched feature (see kernel/sched/features.h) as it's a
pretty
well consolidated interface.
> #endif
>
> notrace unsigned long get_parent_ip(unsigned long addr)
> --
> 1.8.3
>
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