net_sched: add qdisc_watchdog_schedule_range_ns()

Some packet schedulers might want to add a slack
when programming hrtimers. This can reduce number
of interrupts and increase batch sizes and thus
give good xmit_more savings.

This commit adds qdisc_watchdog_schedule_range_ns()
helper, with an extra delta_ns parameter.

Legacy qdisc_watchdog_schedule_n() becomes an inline
passing a zero slack.

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

include/net/pkt_sched.h

@@ -75,7 +75,15 @@ struct qdisc_watchdog {
 void qdisc_watchdog_init_clockid(struct qdisc_watchdog *wd, struct Qdisc *qdisc,
 				 clockid_t clockid);
 void qdisc_watchdog_init(struct qdisc_watchdog *wd, struct Qdisc *qdisc);
-void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd, u64 expires);
+
+void qdisc_watchdog_schedule_range_ns(struct qdisc_watchdog *wd, u64 expires,
+				      u64 delta_ns);
+
+static inline void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd,
+					      u64 expires)
+{
+	return qdisc_watchdog_schedule_range_ns(wd, expires, 0ULL);
+}
 
 static inline void qdisc_watchdog_schedule(struct qdisc_watchdog *wd,
 					   psched_time_t expires)

net/sched/sch_api.c

@@ -618,7 +618,8 @@ void qdisc_watchdog_init(struct qdisc_watchdog *wd, struct Qdisc *qdisc)
 }
 EXPORT_SYMBOL(qdisc_watchdog_init);
 
-void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd, u64 expires)
+void qdisc_watchdog_schedule_range_ns(struct qdisc_watchdog *wd, u64 expires,
+				      u64 delta_ns)
 {
 	if (test_bit(__QDISC_STATE_DEACTIVATED,
 		     &qdisc_root_sleeping(wd->qdisc)->state))
@@ -628,11 +629,12 @@ void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd, u64 expires)
 		return;
 
 	wd->last_expires = expires;
-	hrtimer_start(&wd->timer,
+	hrtimer_start_range_ns(&wd->timer,
-		      ns_to_ktime(expires),
+			       ns_to_ktime(expires),
-		      HRTIMER_MODE_ABS_PINNED);
+			       delta_ns,
+			       HRTIMER_MODE_ABS_PINNED);
 }
-EXPORT_SYMBOL(qdisc_watchdog_schedule_ns);
+EXPORT_SYMBOL(qdisc_watchdog_schedule_range_ns);
 
 void qdisc_watchdog_cancel(struct qdisc_watchdog *wd)
 {