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Subject[PATCH 1/2] sched/nohz: add debugfs control over sched_tick_max_deferment
Date
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 <fweisbec@gmail.com>
Signed-off-by: Kevin Hilman <khilman@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 5ac63c9..4b1fe3e 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);
#endif

notrace unsigned long get_parent_ip(unsigned long addr)
--
1.8.3


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