clockevents: Remove the per cpu tick skew

Historically, Linux has tried to make the regular timer tick on the
various CPUs not happen at the same time, to avoid contention on
xtime_lock.

Nowadays, with the tickless kernel, this contention no longer happens
since time keeping and updating are done differently. In addition,
this skew is actually hurting power consumption in a measurable way on
many-core systems.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
LKML-Reference: <20100727210210.58d3118c@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 813993b..74644cc 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -780,7 +780,6 @@ void tick_setup_sched_timer(void)
 {
        struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
        ktime_t now = ktime_get();
-       u64 offset;
 
        /*
         * Emulate tick processing via per-CPU hrtimers:
@@ -790,10 +789,6 @@ void tick_setup_sched_timer(void)
 
        /* Get the next period (per cpu) */
        hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
-       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);