Commit d2ad689d authored by Vladimir Oltean's avatar Vladimir Oltean Committed by David S. Miller
Browse files

net/sched: taprio: calculate budgets per traffic class 



Currently taprio assumes that the budget for a traffic class expires at
the end of the current interval as if the next interval contains a "gate
close" event for this traffic class.

This is, however, an unfounded assumption. Allow schedule entry
intervals to be fused together for a particular traffic class by
calculating the budget until the gate *actually* closes.

This means we need to keep budgets per traffic class, and we also need
to update the budget consumption procedure.

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 e5517551

net/sched/sch_taprio.c

+46 −8
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ struct sched_entry { 
	 * respective traffic class gate closes

	 */

	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
@@ -51,7 +52,6 @@ struct sched_entry { 
	 */

	ktime_t end_time;

	ktime_t next_txtime;

	atomic_t budget;

	int index;

	u32 gate_mask;

	u32 interval;
@@ -563,11 +563,48 @@ static struct sk_buff *taprio_peek(struct Qdisc *sch) 
	return NULL;

}



static void taprio_set_budget(struct taprio_sched *q, struct sched_entry *entry)

static void taprio_set_budgets(struct taprio_sched *q,

			       struct sched_gate_list *sched,

			       struct sched_entry *entry)

{

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

	int num_tc = netdev_get_num_tc(dev);

	int tc, budget;



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

		/* Traffic classes which never close have infinite budget */

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

			budget = INT_MAX;

		else

			budget = div64_u64((u64)entry->gate_duration[tc] * PSEC_PER_NSEC,

					   atomic64_read(&q->picos_per_byte));



		atomic_set(&entry->budget[tc], budget);

	}

}



/* When an skb is sent, it consumes from the budget of all traffic classes */

static int taprio_update_budgets(struct sched_entry *entry, size_t len,

				 int tc_consumed, int num_tc)

{

	atomic_set(&entry->budget,

		   div64_u64((u64)entry->interval * PSEC_PER_NSEC,

			     atomic64_read(&q->picos_per_byte)));

	int tc, budget, new_budget = 0;



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

		budget = atomic_read(&entry->budget[tc]);

		/* Don't consume from infinite budget */

		if (budget == INT_MAX) {

			if (tc == tc_consumed)

				new_budget = budget;

			continue;

		}



		if (tc == tc_consumed)

			new_budget = atomic_sub_return(len, &entry->budget[tc]);

		else

			atomic_sub(len, &entry->budget[tc]);

	}



	return new_budget;

}



static struct sk_buff *taprio_dequeue_from_txq(struct Qdisc *sch, int txq,
@@ -577,6 +614,7 @@ static struct sk_buff *taprio_dequeue_from_txq(struct Qdisc *sch, int txq, 
	struct taprio_sched *q = qdisc_priv(sch);

	struct net_device *dev = qdisc_dev(sch);

	struct Qdisc *child = q->qdiscs[txq];

	int num_tc = netdev_get_num_tc(dev);

	struct sk_buff *skb;

	ktime_t guard;

	int prio;
@@ -611,7 +649,7 @@ static struct sk_buff *taprio_dequeue_from_txq(struct Qdisc *sch, int txq, 


	/* ... and no budget. */

	if (gate_mask != TAPRIO_ALL_GATES_OPEN &&

	    atomic_sub_return(len, &entry->budget) < 0)

	    taprio_update_budgets(entry, len, tc, num_tc) < 0)

		return NULL;



skip_peek_checks:
@@ -832,7 +870,7 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer) 
	}



	next->end_time = end_time;

	taprio_set_budget(q, next);

	taprio_set_budgets(q, oper, next);



first_run:

	rcu_assign_pointer(q->current_entry, next);
@@ -1091,7 +1129,7 @@ static void setup_first_end_time(struct taprio_sched *q, 
	sched->cycle_end_time = ktime_add_ns(base, cycle);



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

	taprio_set_budget(q, first);

	taprio_set_budgets(q, sched, first);

	rcu_assign_pointer(q->current_entry, NULL);

}