Commit a1e6ad30 authored by Vladimir Oltean's avatar Vladimir Oltean Committed by David S. Miller
Browse files

net/sched: taprio: calculate guard band against actual TC gate close time 



taprio_dequeue_from_txq() looks at the entry->end_time to determine
whether the skb will overrun its traffic class gate, as if at the end of
the schedule entry there surely is a "gate close" event for it. Hint:
maybe there isn't.

For each schedule entry, introduce an array of kernel times which
actually tracks when in the future will there be an *actual* gate close
event for that traffic class, and use that in the guard band overrun
calculation.

Signed-off-by: default avatarVladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: default avatarKurt Kanzenbach <kurt@linutronix.de>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent d2ad689d

net/sched/sch_taprio.c

+34 −6
Original line number Diff line number Diff line
@@ -44,12 +44,12 @@ struct sched_entry { 
	 */

	u64 gate_duration[TC_MAX_QUEUE];

	atomic_t budget[TC_MAX_QUEUE];

	struct list_head list;



	/* The instant that this entry ends and the next one

	 * should open, the qdisc will make some effort so that no

	 * packet leaves after this time.

	/* The qdisc makes some effort so that no packet leaves

	 * after this time

	 */

	ktime_t gate_close_time[TC_MAX_QUEUE];

	struct list_head list;

	/* Used to calculate when to advance the schedule */

	ktime_t end_time;

	ktime_t next_txtime;

	int index;
@@ -148,6 +148,12 @@ static void taprio_calculate_gate_durations(struct taprio_sched *q, 
	}

}



static bool taprio_entry_allows_tx(ktime_t skb_end_time,

				   struct sched_entry *entry, int tc)

{

	return ktime_before(skb_end_time, entry->gate_close_time[tc]);

}



static ktime_t sched_base_time(const struct sched_gate_list *sched)

{

	if (!sched)
@@ -644,7 +650,7 @@ static struct sk_buff *taprio_dequeue_from_txq(struct Qdisc *sch, int txq, 
	 * guard band ...

	 */

	if (gate_mask != TAPRIO_ALL_GATES_OPEN &&

	    ktime_after(guard, entry->end_time))

	    !taprio_entry_allows_tx(guard, entry, tc))

		return NULL;



	/* ... and no budget. */
@@ -820,10 +826,13 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer) 
{

	struct taprio_sched *q = container_of(timer, struct taprio_sched,

					      advance_timer);

	struct net_device *dev = qdisc_dev(q->root);

	struct sched_gate_list *oper, *admin;

	int num_tc = netdev_get_num_tc(dev);

	struct sched_entry *entry, *next;

	struct Qdisc *sch = q->root;

	ktime_t end_time;

	int tc;



	spin_lock(&q->current_entry_lock);

	entry = rcu_dereference_protected(q->current_entry,
@@ -861,6 +870,14 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer) 
	end_time = ktime_add_ns(entry->end_time, next->interval);

	end_time = min_t(ktime_t, end_time, oper->cycle_end_time);



	for (tc = 0; tc < num_tc; tc++) {

		if (next->gate_duration[tc] == oper->cycle_time)

			next->gate_close_time[tc] = KTIME_MAX;

		else

			next->gate_close_time[tc] = ktime_add_ns(entry->end_time,

								 next->gate_duration[tc]);

	}



	if (should_change_schedules(admin, oper, end_time)) {

		/* Set things so the next time this runs, the new

		 * schedule runs.
@@ -1117,8 +1134,11 @@ static int taprio_get_start_time(struct Qdisc *sch, 
static void setup_first_end_time(struct taprio_sched *q,

				 struct sched_gate_list *sched, ktime_t base)

{

	struct net_device *dev = qdisc_dev(q->root);

	int num_tc = netdev_get_num_tc(dev);

	struct sched_entry *first;

	ktime_t cycle;

	int tc;



	first = list_first_entry(&sched->entries,

				 struct sched_entry, list);
@@ -1130,6 +1150,14 @@ static void setup_first_end_time(struct taprio_sched *q, 


	first->end_time = ktime_add_ns(base, first->interval);

	taprio_set_budgets(q, sched, first);



	for (tc = 0; tc < num_tc; tc++) {

		if (first->gate_duration[tc] == sched->cycle_time)

			first->gate_close_time[tc] = KTIME_MAX;

		else

			first->gate_close_time[tc] = ktime_add_ns(base, first->gate_duration[tc]);

	}



	rcu_assign_pointer(q->current_entry, NULL);

}