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nohz: Restart nohz full tick from irq exit

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Restart the tick when necessary from the irq exit path. It makes nohz
full more flexible, simplify the related IPIs and doesn't bring
significant overhead on irq exit.

In a longer term view, it will allow us to piggyback the nohz kick
on the scheduler IPI in the future instead of sending a dedicated IPI
that often doubles the scheduler IPI on task wakeup. This will require
more changes though including careful review of resched_curr() callers
to include nohz full needs.

Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
This commit is contained in:
Frederic Weisbecker 2015-05-27 19:22:08 +02:00
parent 5944935943
commit 73738a95d0
2 changed files with 10 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/tick.h
View File

@ -147,7 +147,6 @@ static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask)
cpumask_or(mask, mask, tick_nohz_full_mask);
}
extern void __tick_nohz_full_check(void);
extern void tick_nohz_full_kick(void);
extern void tick_nohz_full_kick_cpu(int cpu);
extern void tick_nohz_full_kick_all(void);
@ -156,7 +155,6 @@ extern void __tick_nohz_task_switch(struct task_struct *tsk);
static inline bool tick_nohz_full_enabled(void) { return false; }
static inline bool tick_nohz_full_cpu(int cpu) { return false; }
static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { }
static inline void __tick_nohz_full_check(void) { }
static inline void tick_nohz_full_kick_cpu(int cpu) { }
static inline void tick_nohz_full_kick(void) { }
static inline void tick_nohz_full_kick_all(void) { }
@ -190,12 +188,6 @@ static inline void housekeeping_affine(struct task_struct *t)
#endif
}
static inline void tick_nohz_full_check(void)
{
if (tick_nohz_full_enabled())
__tick_nohz_full_check();
}
static inline void tick_nohz_task_switch(struct task_struct *tsk)
{
if (tick_nohz_full_enabled())

34
kernel/time/tick-sched.c
View File

@ -197,25 +197,9 @@ static bool can_stop_full_tick(void)
return true;
}
static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now);
/*
* Re-evaluate the need for the tick on the current CPU
* and restart it if necessary.
*/
void __tick_nohz_full_check(void)
{
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
if (tick_nohz_full_cpu(smp_processor_id())) {
if (ts->tick_stopped && !can_stop_full_tick())
tick_nohz_restart_sched_tick(ts, ktime_get());
}
}
static void nohz_full_kick_work_func(struct irq_work *work)
{
__tick_nohz_full_check();
/* Empty, the tick restart happens on tick_nohz_irq_exit() */
}
static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
@ -250,7 +234,7 @@ void tick_nohz_full_kick_cpu(int cpu)
static void nohz_full_kick_ipi(void *info)
{
__tick_nohz_full_check();
/* Empty, the tick restart happens on tick_nohz_irq_exit() */
}
/*
@ -703,7 +687,9 @@ out:
return tick;
}
static void tick_nohz_full_stop_tick(struct tick_sched *ts)
static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now);
static void tick_nohz_full_update_tick(struct tick_sched *ts)
{
#ifdef CONFIG_NO_HZ_FULL
int cpu = smp_processor_id();
@ -714,10 +700,10 @@ static void tick_nohz_full_stop_tick(struct tick_sched *ts)
if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
return;
if (!can_stop_full_tick())
return;
tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
if (can_stop_full_tick())
tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
else if (ts->tick_stopped)
tick_nohz_restart_sched_tick(ts, ktime_get());
#endif
}
@ -847,7 +833,7 @@ void tick_nohz_irq_exit(void)
if (ts->inidle)
__tick_nohz_idle_enter(ts);
else
tick_nohz_full_stop_tick(ts);
tick_nohz_full_update_tick(ts);
}
/**