Commit a42d71e3 authored by Toke Høiland-Jørgensen's avatar Toke Høiland-Jørgensen Committed by Jakub Kicinski
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net_sched: sch_cake: Add drop reasons 



Add three qdisc-specific drop reasons and use them in sch_cake:

 1) SKB_DROP_REASON_QDISC_OVERLIMIT
    Whenever the total queue limit for a qdisc instance is exceeded
    and a packet is dropped to make room.

 2) SKB_DROP_REASON_QDISC_CONGESTED
    Whenever a packet is dropped by the qdisc AQM algorithm because
    congestion is detected.

 3) SKB_DROP_REASON_CAKE_FLOOD
    Whenever a packet is dropped by the flood protection part of the
    CAKE AQM algorithm (BLUE).

Also use the existing SKB_DROP_REASON_QUEUE_PURGE in cake_clear_tin().

Reasons show up as:

perf record -a -e skb:kfree_skb sleep 1; perf script

          iperf3     665 [005]   848.656964: skb:kfree_skb: skbaddr=0xffff98168a333500 rx_sk=(nil) protocol=34525 location=__dev_queue_xmit+0x10f0 reason: QDISC_OVERLIMIT
         swapper       0 [001]   909.166055: skb:kfree_skb: skbaddr=0xffff98168280cee0 rx_sk=(nil) protocol=34525 location=cake_dequeue+0x5ef reason: QDISC_CONGESTED

Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarJamal Hadi Salim <jhs@mojatatu.com>
Acked-by: default avatarDave Taht <dave.taht@gmail.com>
Signed-off-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Link: https://patch.msgid.link/20241211-cake-drop-reason-v2-1-920afadf4d1b@redhat.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 5098462f

include/net/dropreason-core.h

+18 −0
Original line number Diff line number Diff line
@@ -58,6 +58,9 @@ 
	FN(TC_EGRESS)			\

	FN(SECURITY_HOOK)		\

	FN(QDISC_DROP)			\

	FN(QDISC_OVERLIMIT)		\

	FN(QDISC_CONGESTED)		\

	FN(CAKE_FLOOD)			\

	FN(FQ_BAND_LIMIT)		\

	FN(FQ_HORIZON_LIMIT)		\

	FN(FQ_FLOW_LIMIT)		\
@@ -314,6 +317,21 @@ enum skb_drop_reason { 
	 * failed to enqueue to current qdisc)

	 */

	SKB_DROP_REASON_QDISC_DROP,

	/**

	 * @SKB_DROP_REASON_QDISC_OVERLIMIT: dropped by qdisc when a qdisc

	 * instance exceeds its total buffer size limit.

	 */

	SKB_DROP_REASON_QDISC_OVERLIMIT,

	/**

	 * @SKB_DROP_REASON_QDISC_CONGESTED: dropped by a qdisc AQM algorithm

	 * due to congestion.

	 */

	SKB_DROP_REASON_QDISC_CONGESTED,

	/**

	 * @SKB_DROP_REASON_CAKE_FLOOD: dropped by the flood protection part of

	 * CAKE qdisc AQM algorithm (BLUE).

	 */

	SKB_DROP_REASON_CAKE_FLOOD,

	/**

	 * @SKB_DROP_REASON_FQ_BAND_LIMIT: dropped by fq qdisc when per band

	 * limit is reached.

net/sched/sch_cake.c

+23 −20
Original line number Diff line number Diff line
@@ -484,13 +484,14 @@ static bool cobalt_queue_empty(struct cobalt_vars *vars, 
/* Call this with a freshly dequeued packet for possible congestion marking.

 * Returns true as an instruction to drop the packet, false for delivery.

 */

static bool cobalt_should_drop(struct cobalt_vars *vars,

static enum skb_drop_reason cobalt_should_drop(struct cobalt_vars *vars,

					       struct cobalt_params *p,

					       ktime_t now,

					       struct sk_buff *skb,

					       u32 bulk_flows)

{

	bool next_due, over_target, drop = false;

	enum skb_drop_reason reason = SKB_NOT_DROPPED_YET;

	bool next_due, over_target;

	ktime_t schedule;

	u64 sojourn;
@@ -533,7 +534,8 @@ static bool cobalt_should_drop(struct cobalt_vars *vars, 


	if (next_due && vars->dropping) {

		/* Use ECN mark if possible, otherwise drop */

		drop = !(vars->ecn_marked = INET_ECN_set_ce(skb));

		if (!(vars->ecn_marked = INET_ECN_set_ce(skb)))

			reason = SKB_DROP_REASON_QDISC_CONGESTED;



		vars->count++;

		if (!vars->count)
@@ -556,16 +558,17 @@ static bool cobalt_should_drop(struct cobalt_vars *vars, 
	}



	/* Simple BLUE implementation.  Lack of ECN is deliberate. */

	if (vars->p_drop)

		drop |= (get_random_u32() < vars->p_drop);

	if (vars->p_drop && reason == SKB_NOT_DROPPED_YET &&

	    get_random_u32() < vars->p_drop)

		reason = SKB_DROP_REASON_CAKE_FLOOD;



	/* Overload the drop_next field as an activity timeout */

	if (!vars->count)

		vars->drop_next = ktime_add_ns(now, p->interval);

	else if (ktime_to_ns(schedule) > 0 && !drop)

	else if (ktime_to_ns(schedule) > 0 && reason == SKB_NOT_DROPPED_YET)

		vars->drop_next = now;



	return drop;

	return reason;

}



static bool cake_update_flowkeys(struct flow_keys *keys,
@@ -1528,12 +1531,11 @@ static unsigned int cake_drop(struct Qdisc *sch, struct sk_buff **to_free) 


	flow->dropped++;

	b->tin_dropped++;

	sch->qstats.drops++;



	if (q->rate_flags & CAKE_FLAG_INGRESS)

		cake_advance_shaper(q, b, skb, now, true);



	__qdisc_drop(skb, to_free);

	qdisc_drop_reason(skb, sch, to_free, SKB_DROP_REASON_QDISC_OVERLIMIT);

	sch->q.qlen--;

	qdisc_tree_reduce_backlog(sch, 1, len);
@@ -1926,7 +1928,7 @@ static void cake_clear_tin(struct Qdisc *sch, u16 tin) 
	q->cur_tin = tin;

	for (q->cur_flow = 0; q->cur_flow < CAKE_QUEUES; q->cur_flow++)

		while (!!(skb = cake_dequeue_one(sch)))

			kfree_skb(skb);

			kfree_skb_reason(skb, SKB_DROP_REASON_QUEUE_PURGE);

}



static struct sk_buff *cake_dequeue(struct Qdisc *sch)
@@ -1934,6 +1936,7 @@ static struct sk_buff *cake_dequeue(struct Qdisc *sch) 
	struct cake_sched_data *q = qdisc_priv(sch);

	struct cake_tin_data *b = &q->tins[q->cur_tin];

	struct cake_host *srchost, *dsthost;

	enum skb_drop_reason reason;

	ktime_t now = ktime_get();

	struct cake_flow *flow;

	struct list_head *head;
@@ -2143,12 +2146,12 @@ static struct sk_buff *cake_dequeue(struct Qdisc *sch) 
			goto begin;

		}



		/* Last packet in queue may be marked, shouldn't be dropped */

		if (!cobalt_should_drop(&flow->cvars, &b->cparams, now, skb,

		reason = cobalt_should_drop(&flow->cvars, &b->cparams, now, skb,

					    (b->bulk_flow_count *

					     !!(q->rate_flags &

					    CAKE_FLAG_INGRESS))) ||

		    !flow->head)

						CAKE_FLAG_INGRESS)));

		/* Last packet in queue may be marked, shouldn't be dropped */

		if (reason == SKB_NOT_DROPPED_YET || !flow->head)

			break;



		/* drop this packet, get another one */
@@ -2162,7 +2165,7 @@ static struct sk_buff *cake_dequeue(struct Qdisc *sch) 
		b->tin_dropped++;

		qdisc_tree_reduce_backlog(sch, 1, qdisc_pkt_len(skb));

		qdisc_qstats_drop(sch);

		kfree_skb(skb);

		kfree_skb_reason(skb, reason);

		if (q->rate_flags & CAKE_FLAG_INGRESS)

			goto retry;

	}