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authorZhenzhong Duan <zhenzhong.duan@oracle.com>2017-10-08 20:55:59 -0700
committerThomas Gleixner <tglx@linutronix.de>2017-10-18 15:29:33 +0200
commitc310ce4dcb9df9b2f1be82caff7dae609fe53f72 (patch)
tree8fa396c14f6322c0c1eec01b7abd28f4cf25d6fc /kernel/time
parentb93ab338f7f0e39321b282d694a52736fdab172b (diff)
downloadlinux-c310ce4dcb9df9b2f1be82caff7dae609fe53f72.tar.bz2
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@oracle.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Anna-Maria Gleixner <anna-maria@linutronix.de> Cc: Joe Jin <joe.jin@oracle.com> Cc: sboyd@codeaurora.org Cc: Srinivas Reddy Eeda <srinivas.eeda@oracle.com> Cc: john.stultz@linaro.org Link: https://lkml.kernel.org/r/7086a857-f90c-4616-bbe8-f7696f21626c@default
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/timer.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 38613ced2324..ee1a88d8afb2 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;