[patch V3 20/22] timer: Only wake softirq if necessary

[Thomas Gleixner]

With the wheel forwading in place and with the HZ=1000 4ms folding we can
avoid running the softirq at all.

Signed-off-by: Thomas Gleixner <t...@linutronix.de>
---
 kernel/time/timer.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1599,7 +1599,18 @@ static void run_timer_softirq(struct sof
  */
 void run_local_timers(void)
 {
+       struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
+
        hrtimer_run_queues();
+       /* Raise the softirq only if required. */
+       if (time_before(jiffies, base->clk)) {
+               if (!IS_ENABLED(CONFIG_NO_HZ_COMMON) || !base->nohz_active)
+                       return;
+               /* CPU is awake, so check the deferrable base. */
+               base++;
+               if (time_before(jiffies, base->clk))
+                       return;
+       }
        raise_softirq(TIMER_SOFTIRQ);
 }