Commit 39b02d6d authored by Vladimir Oltean's avatar Vladimir Oltean Committed by David S. Miller
Browse files

net/sched: taprio: don't segment unnecessarily 



Improve commit 497cc002 ("taprio: Handle short intervals and large
packets") to only perform segmentation when skb->len exceeds what
taprio_dequeue() expects.

In practice, this will make the biggest difference when a traffic class
gate is always open in the schedule. This is because the max_frm_len
will be U32_MAX, and such large skb->len values as Kurt reported will be
sent just fine unsegmented.

What I don't seem to know how to handle is how to make sure that the
segmented skbs themselves are smaller than the maximum frame size given
by the current queueMaxSDU[tc]. Nonetheless, we still need to drop
those, otherwise the Qdisc will hang.

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 2d5e8071

net/sched/sch_taprio.c

+20 −11
Original line number Diff line number Diff line
@@ -566,9 +566,6 @@ static int taprio_enqueue_one(struct sk_buff *skb, struct Qdisc *sch, 
			return qdisc_drop(skb, sch, to_free);

	}



	if (taprio_skb_exceeds_queue_max_sdu(sch, skb))

		return qdisc_drop(skb, sch, to_free);



	qdisc_qstats_backlog_inc(sch, skb);

	sch->q.qlen++;
@@ -593,7 +590,14 @@ static int taprio_enqueue_segmented(struct sk_buff *skb, struct Qdisc *sch, 
		qdisc_skb_cb(segs)->pkt_len = segs->len;

		slen += segs->len;



		/* FIXME: we should be segmenting to a smaller size

		 * rather than dropping these

		 */

		if (taprio_skb_exceeds_queue_max_sdu(sch, segs))

			ret = qdisc_drop(segs, sch, to_free);

		else

			ret = taprio_enqueue_one(segs, sch, child, to_free);



		if (ret != NET_XMIT_SUCCESS) {

			if (net_xmit_drop_count(ret))

				qdisc_qstats_drop(sch);
@@ -625,13 +629,18 @@ static int taprio_enqueue(struct sk_buff *skb, struct Qdisc *sch, 
	if (unlikely(!child))

		return qdisc_drop(skb, sch, to_free);



	/* Large packets might not be transmitted when the transmission duration

	 * exceeds any configured interval. Therefore, segment the skb into

	 * smaller chunks. Drivers with full offload are expected to handle

	 * this in hardware.

	if (taprio_skb_exceeds_queue_max_sdu(sch, skb)) {

		/* Large packets might not be transmitted when the transmission

		 * duration exceeds any configured interval. Therefore, segment

		 * the skb into smaller chunks. Drivers with full offload are

		 * expected to handle this in hardware.

		 */

		if (skb_is_gso(skb))

		return taprio_enqueue_segmented(skb, sch, child, to_free);

			return taprio_enqueue_segmented(skb, sch, child,

							to_free);



		return qdisc_drop(skb, sch, to_free);

	}



	return taprio_enqueue_one(skb, sch, child, to_free);

}