timers: Forward the wheel clock whenever possible
The wheel clock is stale when a CPU goes into a long idle sleep. This has the
side effect that timers which are queued end up in the outer wheel levels.
That results in coarser granularity.
To solve this, we keep track of the idle state and forward the wheel clock
whenever possible.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.512039360@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 69abc7b..5d81f9a 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -700,6 +700,12 @@
delta = next_tick - basemono;
if (delta <= (u64)TICK_NSEC) {
tick.tv64 = 0;
+
+ /*
+ * Tell the timer code that the base is not idle, i.e. undo
+ * the effect of get_next_timer_interrupt():
+ */
+ timer_clear_idle();
/*
* We've not stopped the tick yet, and there's a timer in the
* next period, so no point in stopping it either, bail.
@@ -809,6 +815,12 @@
tick_do_update_jiffies64(now);
cpu_load_update_nohz_stop();
+ /*
+ * Clear the timer idle flag, so we avoid IPIs on remote queueing and
+ * the clock forward checks in the enqueue path:
+ */
+ timer_clear_idle();
+
calc_load_exit_idle();
touch_softlockup_watchdog_sched();
/*
