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Subject[PATCH 5/6] sched/nohz: Remove the 1 Hz tick code
Date
Now that the 1Hz tick is offloaded to workqueues, we can safely remove
the residual code that used to handle it locally.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
---
include/linux/sched/nohz.h | 4 ----
kernel/sched/core.c | 29 -----------------------------
kernel/sched/idle_task.c | 1 -
kernel/sched/sched.h | 11 +----------
kernel/time/tick-sched.c | 6 ------
5 files changed, 1 insertion(+), 50 deletions(-)

diff --git a/include/linux/sched/nohz.h b/include/linux/sched/nohz.h
index 3d3a97d..0942172 100644
--- a/include/linux/sched/nohz.h
+++ b/include/linux/sched/nohz.h
@@ -37,8 +37,4 @@ extern void wake_up_nohz_cpu(int cpu);
static inline void wake_up_nohz_cpu(int cpu) { }
#endif

-#ifdef CONFIG_NO_HZ_FULL
-extern u64 scheduler_tick_max_deferment(void);
-#endif
-
#endif /* _LINUX_SCHED_NOHZ_H */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5c0e8b6..5aeecf2 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3091,35 +3091,9 @@ void scheduler_tick(void)
rq->idle_balance = idle_cpu(cpu);
trigger_load_balance(rq);
#endif
- rq_last_tick_reset(rq);
}

#ifdef CONFIG_NO_HZ_FULL
-/**
- * scheduler_tick_max_deferment
- *
- * Keep at least one tick per second when a single
- * active task is running because the scheduler doesn't
- * yet completely support full dynticks environment.
- *
- * This makes sure that uptime, CFS vruntime, load
- * balancing, etc... continue to move forward, even
- * with a very low granularity.
- *
- * Return: Maximum deferment in nanoseconds.
- */
-u64 scheduler_tick_max_deferment(void)
-{
- struct rq *rq = this_rq();
- unsigned long next, now = READ_ONCE(jiffies);
-
- next = rq->last_sched_tick + HZ;
-
- if (time_before_eq(next, now))
- return 0;
-
- return jiffies_to_nsecs(next - now);
-}

struct tick_work {
int cpu;
@@ -6108,9 +6082,6 @@ void __init sched_init(void)
rq->last_load_update_tick = jiffies;
rq->nohz_flags = 0;
#endif
-#ifdef CONFIG_NO_HZ_FULL
- rq->last_sched_tick = 0;
-#endif
#endif /* CONFIG_SMP */
hrtick_rq_init(rq);
atomic_set(&rq->nr_iowait, 0);
diff --git a/kernel/sched/idle_task.c b/kernel/sched/idle_task.c
index d518664..a64fc92 100644
--- a/kernel/sched/idle_task.c
+++ b/kernel/sched/idle_task.c
@@ -48,7 +48,6 @@ dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)

static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
{
- rq_last_tick_reset(rq);
}

static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index c1c7c78..dc6c8b5 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -727,9 +727,7 @@ struct rq {
#endif /* CONFIG_SMP */
unsigned long nohz_flags;
#endif /* CONFIG_NO_HZ_COMMON */
-#ifdef CONFIG_NO_HZ_FULL
- unsigned long last_sched_tick;
-#endif
+
/* capture load from *all* tasks on this cpu: */
struct load_weight load;
unsigned long nr_load_updates;
@@ -1626,13 +1624,6 @@ static inline void sub_nr_running(struct rq *rq, unsigned count)
sched_update_tick_dependency(rq);
}

-static inline void rq_last_tick_reset(struct rq *rq)
-{
-#ifdef CONFIG_NO_HZ_FULL
- rq->last_sched_tick = jiffies;
-#endif
-}
-
extern void update_rq_clock(struct rq *rq);

extern void activate_task(struct rq *rq, struct task_struct *p, int flags);
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index b517485..0c615a0 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -748,12 +748,6 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
delta = KTIME_MAX;
}

-#ifdef CONFIG_NO_HZ_FULL
- /* Limit the tick delta to the maximum scheduler deferment */
- if (!ts->inidle)
- delta = min(delta, scheduler_tick_max_deferment());
-#endif
-
/* Calculate the next expiry time */
if (delta < (KTIME_MAX - basemono))
expires = basemono + delta;
--
2.7.4
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