timers: Reduce future __run_timers() latency for first add to empty list
The __run_timers() function currently steps through the list one jiffy at
a time in order to update the timer wheel. However, if the timer wheel
is empty, no adjustment is needed other than updating ->timer_jiffies.
Therefore, just before we add a timer to an empty timer wheel, we should
mark the timer wheel as being up to date. This marking will reduce (and
perhaps eliminate) the jiffy-stepping that a future __run_timers() call
will need to do in response to some future timer posting or migration.
This commit therefore updates ->timer_jiffies for this case.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/timer.c b/kernel/timer.c
index 2b2e235..e539dbf 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -745,6 +745,7 @@
base = lock_timer_base(timer, &flags);
+ (void)catchup_timer_jiffies(base);
ret = detach_if_pending(timer, base, false);
if (!ret && pending_only)
goto out_unlock;
