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

From: Thomas Gleixner
Date: Fri Jun 24 2016 - 10:34:27 EST


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 <tglx@xxxxxxxxxxxxx>
---
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);
}