Commit-ID: c310ce4dcb9df9b2f1be82caff7dae609fe53f72
Gitweb: https://git.kernel.org/tip/c310ce4dcb9df9b2f1be82caff7dae609fe53f72
Author: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>
AuthorDate: Sun, 8 Oct 2017 20:55:59 -0700
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Wed, 18 Oct 2017 15:29:33 +0200
timers: Avoid an unnecessary iteration in __run_timers()
If the base clock is behind jiffies in the soft irq expiry code then the
next timer is retrieved by get_next_timer_interrupt() to avoid incrementing
base clock one by one. If the next timer interrupt is past current jiffies
then the base clock is set to jiffies - 1. At the call site this is
incremented and another iteration through the expiry loop is executed which
checks empty hash buckets.
That's a pointless excercise because it's already known that the next timer
is past jiffies.
Set the base clock in that case to jiffies directly so it gets incremented
to jiffies + 1 at the call site resulting in immediate termination of the
expiry loop.
[ tglx: Massaged changelog and added comment to the code ]
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Anna-Maria Gleixner <anna-maria@xxxxxxxxxxxxx>
Cc: Joe Jin <joe.jin@xxxxxxxxxx>
Cc: sboyd@xxxxxxxxxxxxxx
Cc: Srinivas Reddy Eeda <srinivas.eeda@xxxxxxxxxx>
Cc: john.stultz@xxxxxxxxxx
Link: https://lkml.kernel.org/r/7086a857-f90c-4616-bbe8-f7696f21626c@default
---
kernel/time/timer.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 38613ce..ee1a88d 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1560,8 +1560,11 @@ static int collect_expired_timers(struct timer_base *base,
* jiffies, otherwise forward to the next expiry time:
*/
if (time_after(next, jiffies)) {
- /* The call site will increment clock! */
- base->clk = jiffies - 1;
+ /*
+ * The call site will increment base->clk and then
+ * terminate the expiry loop immediately.
+ */
+ base->clk = jiffies;
return 0;
}
base->clk = next;
--
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