net_sched: do not reprogram a timer about to expire

qdisc_watchdog_schedule_range_ns() can use the newly added slack
and avoid rearming the hrtimer a bit earlier than the current
value. This patch has no effect if delta_ns parameter
is zero.

Note that this means the max slack is potentially doubled.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 83984be..0d99df1 100644 (file)
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -625,8 +625,13 @@ void qdisc_watchdog_schedule_range_ns(struct qdisc_watchdog *wd, u64 expires,
                     &qdisc_root_sleeping(wd->qdisc)->state))
                return;
 
-       if (wd->last_expires == expires)
-               return;
+       if (hrtimer_is_queued(&wd->timer)) {
+               /* If timer is already set in [expires, expires + delta_ns],
+                * do not reprogram it.
+                */
+               if (wd->last_expires - expires <= delta_ns)
+                       return;
+       }
 
        wd->last_expires = expires;
        hrtimer_start_range_ns(&wd->timer,