tick: Add tick skew boot option

[karo-tx-linux.git] / kernel / time / tick-sched.c

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 6a3a5b9ff56176c2951256edf7ef9601a0f49106..4eddbb5ea9c5c7bb94aa035f623aa428d4c7b3b3 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -814,6 +814,8 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
        return HRTIMER_RESTART;
 }
 
+static int sched_skew_tick;
+
 /**
  * tick_setup_sched_timer - setup the tick emulation timer
  */
@@ -831,6 +833,14 @@ void tick_setup_sched_timer(void)
        /* Get the next period (per cpu) */
        hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
 
+       /* Offset the tick to avert xtime_lock contention. */
+       if (sched_skew_tick) {
+               u64 offset = ktime_to_ns(tick_period) >> 1;
+               do_div(offset, num_possible_cpus());
+               offset *= smp_processor_id();
+               hrtimer_add_expires_ns(&ts->sched_timer, offset);
+       }
+
        for (;;) {
                hrtimer_forward(&ts->sched_timer, now, tick_period);
                hrtimer_start_expires(&ts->sched_timer,
@@ -910,3 +920,11 @@ int tick_check_oneshot_change(int allow_nohz)
        tick_nohz_switch_to_nohz();
        return 0;
 }
+
+static int __init skew_tick(char *str)
+{
+       get_option(&str, &sched_skew_tick);
+
+       return 0;
+}
+early_param("skew_tick", skew_tick);