Commit 70713ddd authored by Qitao Xu's avatar Qitao Xu Committed by David S. Miller
Browse files

net_sched: introduce tracepoint trace_qdisc_enqueue() 



Tracepoint trace_qdisc_enqueue() is introduced to trace skb at
the entrance of TC layer on TX side. This is similar to
trace_qdisc_dequeue():

1. For both we only trace successful cases. The failure cases
   can be traced via trace_kfree_skb().

2. They are called at entrance or exit of TC layer, not for each
   ->enqueue() or ->dequeue(). This is intentional, because
   we want to make trace_qdisc_enqueue() symmetric to
   trace_qdisc_dequeue(), which is easier to use.

The return value of qdisc_enqueue() is not interesting here,
we have Qdisc's drop packets in ->dequeue(), it is impossible to
trace them even if we have the return value, the only way to trace
them is tracing kfree_skb().

We only add information we need to trace ring buffer. If any other
information is needed, it is easy to extend it without breaking ABI,
see commit 3dd344ea ("net: tracepoint: exposing sk_family in all
tcp:tracepoints").

Reviewed-by: default avatarCong Wang <cong.wang@bytedance.com>
Signed-off-by: default avatarQitao Xu <qitao.xu@bytedance.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 851f36e4

include/trace/events/qdisc.h

+26 −0
Original line number Diff line number Diff line
@@ -46,6 +46,32 @@ TRACE_EVENT(qdisc_dequeue, 
		  __entry->txq_state, __entry->packets, __entry->skbaddr )

);



TRACE_EVENT(qdisc_enqueue,



	TP_PROTO(struct Qdisc *qdisc, const struct netdev_queue *txq, struct sk_buff *skb),



	TP_ARGS(qdisc, txq, skb),



	TP_STRUCT__entry(

		__field(struct Qdisc *, qdisc)

		__field(void *,	skbaddr)

		__field(int, ifindex)

		__field(u32, handle)

		__field(u32, parent)

	),



	TP_fast_assign(

		__entry->qdisc = qdisc;

		__entry->skbaddr = skb;

		__entry->ifindex = txq->dev ? txq->dev->ifindex : 0;

		__entry->handle	 = qdisc->handle;

		__entry->parent	 = qdisc->parent;

	),



	TP_printk("enqueue ifindex=%d qdisc handle=0x%X parent=0x%X skbaddr=%px",

		  __entry->ifindex, __entry->handle, __entry->parent, __entry->skbaddr)

);



TRACE_EVENT(qdisc_reset,



	TP_PROTO(struct Qdisc *q),

net/core/dev.c

+16 −4
Original line number Diff line number Diff line
@@ -131,6 +131,7 @@ 
#include <trace/events/napi.h>

#include <trace/events/net.h>

#include <trace/events/skb.h>

#include <trace/events/qdisc.h>

#include <linux/inetdevice.h>

#include <linux/cpu_rmap.h>

#include <linux/static_key.h>
@@ -3844,6 +3845,18 @@ static void qdisc_pkt_len_init(struct sk_buff *skb) 
	}

}



static int dev_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *q,

			     struct sk_buff **to_free,

			     struct netdev_queue *txq)

{

	int rc;



	rc = q->enqueue(skb, q, to_free) & NET_XMIT_MASK;

	if (rc == NET_XMIT_SUCCESS)

		trace_qdisc_enqueue(q, txq, skb);

	return rc;

}



static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,

				 struct net_device *dev,

				 struct netdev_queue *txq)
@@ -3862,8 +3875,7 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q, 
			 * of q->seqlock to protect from racing with requeuing.

			 */

			if (unlikely(!nolock_qdisc_is_empty(q))) {

				rc = q->enqueue(skb, q, &to_free) &

					NET_XMIT_MASK;

				rc = dev_qdisc_enqueue(skb, q, &to_free, txq);

				__qdisc_run(q);

				qdisc_run_end(q);
@@ -3879,7 +3891,7 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q, 
			return NET_XMIT_SUCCESS;

		}



		rc = q->enqueue(skb, q, &to_free) & NET_XMIT_MASK;

		rc = dev_qdisc_enqueue(skb, q, &to_free, txq);

		qdisc_run(q);



no_lock_out:
@@ -3923,7 +3935,7 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q, 
		qdisc_run_end(q);

		rc = NET_XMIT_SUCCESS;

	} else {

		rc = q->enqueue(skb, q, &to_free) & NET_XMIT_MASK;

		rc = dev_qdisc_enqueue(skb, q, &to_free, txq);

		if (qdisc_run_begin(q)) {

			if (unlikely(contended)) {

				spin_unlock(&q->busylock);