tick/sched: Optimize tick_do_update_jiffies64() further

Now that it's clear that there is always one tick to account, simplify the
calculations some more.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.565663056@linutronix.de

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index ca9191c..306adeb 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -55,7 +55,7 @@ static ktime_t last_jiffies_update;
  */
 static void tick_do_update_jiffies64(ktime_t now)
 {
-       unsigned long ticks = 0;
+       unsigned long ticks = 1;
        ktime_t delta;
 
        /*
@@ -93,20 +93,21 @@ static void tick_do_update_jiffies64(ktime_t now)
 
        write_seqcount_begin(&jiffies_seq);
 
-       last_jiffies_update = ktime_add(last_jiffies_update, tick_period);
-
        delta = ktime_sub(now, tick_next_period);
        if (unlikely(delta >= tick_period)) {
                /* Slow path for long idle sleep times */
                s64 incr = ktime_to_ns(tick_period);
 
-               ticks = ktime_divns(delta, incr);
+               ticks += ktime_divns(delta, incr);
 
                last_jiffies_update = ktime_add_ns(last_jiffies_update,
                                                   incr * ticks);
+       } else {
+               last_jiffies_update = ktime_add(last_jiffies_update,
+                                               tick_period);
        }
 
-       do_timer(++ticks);
+       do_timer(ticks);
 
        /*
         * Keep the tick_next_period variable up to date.  WRITE_ONCE()