[PATCH 5/7] Traffic control using high-resolution timer issue

[Erez Geva]

  - Add new schedule function for Qdisc watchdog.
    The function avoids reprogram if watchdog already expire
    before new expire.

  - Use new schedule function in ETF.

  - Add ETF range value to kernel configuration.
    as the value is characteristic to Hardware.

Signed-off-by: Erez Geva <erez.geva.ext@xxxxxxxxxxx>
---
 include/net/pkt_sched.h |  2 ++
 net/sched/Kconfig       |  8 ++++++++
 net/sched/sch_api.c     | 33 +++++++++++++++++++++++++++++++++
 net/sched/sch_etf.c     | 10 ++++++++--
 4 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index ac8c890a2657..4306c2773778 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -78,6 +78,8 @@ void qdisc_watchdog_init(struct qdisc_watchdog *wd, struct Qdisc *qdisc);
 
 void qdisc_watchdog_schedule_range_ns(struct qdisc_watchdog *wd, u64 expires,
 				      u64 delta_ns);
+void qdisc_watchdog_schedule_soon_ns(struct qdisc_watchdog *wd, u64 expires,
+				     u64 delta_ns);
 
 static inline void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd,
 					      u64 expires)
diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index a3b37d88800e..0f5261ee9e1b 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -195,6 +195,14 @@ config NET_SCH_ETF
 	  To compile this code as a module, choose M here: the
 	  module will be called sch_etf.
 
+config NET_SCH_ETF_TIMER_RANGE
+	int "ETF Watchdog time range delta in nano seconds"
+	depends on NET_SCH_ETF
+	default 5000
+	help
+	  Specify the time range delta for ETF watchdog
+	  Default is 5 microsecond
+
 config NET_SCH_TAPRIO
 	tristate "Time Aware Priority (taprio) Scheduler"
 	help
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index ebf59ca1faab..80bd09555f5e 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -645,6 +645,39 @@ void qdisc_watchdog_schedule_range_ns(struct qdisc_watchdog *wd, u64 expires,
 }
 EXPORT_SYMBOL(qdisc_watchdog_schedule_range_ns);
 
+void qdisc_watchdog_schedule_soon_ns(struct qdisc_watchdog *wd, u64 expires,
+				     u64 delta_ns)
+{
+	if (test_bit(__QDISC_STATE_DEACTIVATED,
+		     &qdisc_root_sleeping(wd->qdisc)->state))
+		return;
+
+	if (wd->last_expires == expires)
+		return;
+
+	/**
+	 * If expires is in [0, now + delta_ns],
+	 * do not program it.
+	 */
+	if (expires <= ktime_to_ns(hrtimer_cb_get_time(&wd->timer)) + delta_ns)
+		return;
+
+	/**
+	 * If timer is already set in [0, expires + delta_ns],
+	 * do not reprogram it.
+	 */
+	if (hrtimer_is_queued(&wd->timer) &&
+	    wd->last_expires <= expires + delta_ns)
+		return;
+
+	wd->last_expires = expires;
+	hrtimer_start_range_ns(&wd->timer,
+			       ns_to_ktime(expires),
+			       delta_ns,
+			       HRTIMER_MODE_ABS_PINNED);
+}
+EXPORT_SYMBOL(qdisc_watchdog_schedule_soon_ns);
+
 void qdisc_watchdog_cancel(struct qdisc_watchdog *wd)
 {
 	hrtimer_cancel(&wd->timer);
diff --git a/net/sched/sch_etf.c b/net/sched/sch_etf.c
index c48f91075b5c..48b2868c4672 100644
--- a/net/sched/sch_etf.c
+++ b/net/sched/sch_etf.c
@@ -20,6 +20,11 @@
 #include <net/pkt_sched.h>
 #include <net/sock.h>
 
+#ifdef CONFIG_NET_SCH_ETF_TIMER_RANGE
+#define NET_SCH_ETF_TIMER_RANGE CONFIG_NET_SCH_ETF_TIMER_RANGE
+#else
+#define NET_SCH_ETF_TIMER_RANGE (5 * NSEC_PER_USEC)
+#endif
 #define DEADLINE_MODE_IS_ON(x) ((x)->flags & TC_ETF_DEADLINE_MODE_ON)
 #define OFFLOAD_IS_ON(x) ((x)->flags & TC_ETF_OFFLOAD_ON)
 #define SKIP_SOCK_CHECK_IS_SET(x) ((x)->flags & TC_ETF_SKIP_SOCK_CHECK)
@@ -128,8 +133,9 @@ static void reset_watchdog(struct Qdisc *sch)
 		return;
 	}
 
-	next = ktime_sub_ns(skb->tstamp, q->delta);
-	qdisc_watchdog_schedule_ns(&q->watchdog, ktime_to_ns(next));
+	next = ktime_sub_ns(skb->tstamp, q->delta + NET_SCH_ETF_TIMER_RANGE);
+	qdisc_watchdog_schedule_soon_ns(&q->watchdog, ktime_to_ns(next),
+					NET_SCH_ETF_TIMER_RANGE);
 }
 
 static void report_sock_error(struct sk_buff *skb, u32 err, u8 code)
-- 
2.20.1