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authorFrederic Weisbecker <fweisbec@gmail.com>2015-05-27 19:22:08 +0200
committerFrederic Weisbecker <fweisbec@gmail.com>2015-07-29 15:45:00 +0200
commit73738a95d00467812664b7f86ba3052f5faf96d7 (patch)
tree9827c57a6391c154fa87e4d103672e5888c7fa71 /kernel/time
parent594493594373862ed2a7f91d88a5a2670742faa6 (diff)
downloadlinux-73738a95d00467812664b7f86ba3052f5faf96d7.tar.bz2
nohz: Restart nohz full tick from irq exit
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>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/tick-sched.c34
1 files changed, 10 insertions, 24 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index d6c8eff6e7b4..a06cd4af0ff1 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -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);
}
/**