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tick/sched: Optimize tick_do_update_jiffies64() further

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[ Upstream commit 7a35bf2a6a ]

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
Stable-dep-of: e9523a0d81 ("tick/common: Align tick period with the HZ tick.")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Thomas Gleixner
2020-11-17 14:19:47 +01:00
committed by Greg Kroah-Hartman
parent 93c4300836
commit fdc4876746
1 changed files with 6 additions and 5 deletions
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11
kernel/time/tick-sched.c
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@@ -53,7 +53,7 @@ static ktime_t last_jiffies_update;
*/ */
static void tick_do_update_jiffies64(ktime_t now) static void tick_do_update_jiffies64(ktime_t now)
{ {
unsigned long ticks = 0; unsigned long ticks = 1;
ktime_t delta; ktime_t delta;
/* /*
@@ -91,20 +91,21 @@ static void tick_do_update_jiffies64(ktime_t now)
write_seqcount_begin(&jiffies_seq); write_seqcount_begin(&jiffies_seq);
last_jiffies_update = ktime_add(last_jiffies_update, tick_period);
delta = ktime_sub(now, tick_next_period); delta = ktime_sub(now, tick_next_period);
if (unlikely(delta >= tick_period)) { if (unlikely(delta >= tick_period)) {
/* Slow path for long idle sleep times */ /* Slow path for long idle sleep times */
s64 incr = ktime_to_ns(tick_period); 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, last_jiffies_update = ktime_add_ns(last_jiffies_update,
incr * ticks); 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() * Keep the tick_next_period variable up to date. WRITE_ONCE()