netdev - [RFC PATCH 1/2] net: Add net_dev_start_xmit trace event, exposing more skb fields

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Message-ID: <1381761660.1626.9.camel@bwh-desktop.uk.level5networks.com>
Date:	Mon, 14 Oct 2013 15:41:00 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	David Miller <davem@...emloft.net>
CC:	<netdev@...r.kernel.org>, <linux-net-drivers@...arflare.com>
Subject: [RFC PATCH 1/2] net: Add net_dev_start_xmit trace event, exposing
 more skb fields

The existing net/net_dev_xmit trace event provides little information
about the skb that has been passed to the driver, and it is not
simple to add more since the skb may already have been freed at
the point the event is emitted.

Add a separate trace event before the skb is passed to the driver,
including most fields that are likely to be interesting for debugging
driver datapath behaviour.

Signed-off-by: Ben Hutchings <bhutchings@...arflare.com>
---
 include/trace/events/net.h | 58 ++++++++++++++++++++++++++++++++++++++++++++++
 net/core/dev.c             |  2 ++
 2 files changed, 60 insertions(+)

diff --git a/include/trace/events/net.h b/include/trace/events/net.h
index f99645d..0b61f2a 100644
--- a/include/trace/events/net.h
+++ b/include/trace/events/net.h
@@ -6,9 +6,67 @@
 
 #include <linux/skbuff.h>
 #include <linux/netdevice.h>
+#include <linux/if_vlan.h>
 #include <linux/ip.h>
 #include <linux/tracepoint.h>
 
+TRACE_EVENT(net_dev_start_xmit,
+
+	TP_PROTO(const struct sk_buff *skb, const struct net_device *dev),
+
+	TP_ARGS(skb, dev),
+
+	TP_STRUCT__entry(
+		__string(	name,			dev->name	)
+		__field(	u16,			queue_mapping	)
+		__field(	const void *,		skbaddr		)
+		__field(	bool,			vlan_tagged	)
+		__field(	u16,			vlan_proto	)
+		__field(	u16,			vlan_tci	)
+		__field(	u16,			protocol	)
+		__field(	u8,			ip_summed	)
+		__field(	unsigned int,		len		)
+		__field(	unsigned int,		data_len	)
+		__field(	int,			network_offset	)
+		__field(	bool,			transport_offset_valid)
+		__field(	int,			transport_offset)
+		__field(	u8,			tx_flags	)
+		__field(	u16,			gso_size	)
+		__field(	u16,			gso_segs	)
+		__field(	u16,			gso_type	)
+	),
+
+	TP_fast_assign(
+		__assign_str(name, dev->name);
+		__entry->queue_mapping = skb->queue_mapping;
+		__entry->skbaddr = skb;
+		__entry->vlan_tagged = vlan_tx_tag_present(skb);
+		__entry->vlan_proto = ntohs(skb->vlan_proto);
+		__entry->vlan_tci = vlan_tx_tag_get(skb);
+		__entry->protocol = ntohs(skb->protocol);
+		__entry->ip_summed = skb->ip_summed;
+		__entry->len = skb->len;
+		__entry->data_len = skb->data_len;
+		__entry->network_offset = skb_network_offset(skb);
+		__entry->transport_offset_valid =
+			skb_transport_header_was_set(skb);
+		__entry->transport_offset = skb_transport_offset(skb);
+		__entry->tx_flags = skb_shinfo(skb)->tx_flags;
+		__entry->gso_size = skb_shinfo(skb)->gso_size;
+		__entry->gso_segs = skb_shinfo(skb)->gso_segs;
+		__entry->gso_type = skb_shinfo(skb)->gso_type;
+	),
+
+	TP_printk("dev=%s queue_mapping=%u skbaddr=%p vlan_tagged=%d vlan_proto=0x%04x vlan_tci=0x%04x protocol=0x%04x ip_summed=%d len=%u data_len=%u network_offset=%d transport_offset_valid=%d transport_offset=%d tx_flags=%d gso_size=%d gso_segs=%d gso_type=%#x",
+		  __get_str(name), __entry->queue_mapping, __entry->skbaddr,
+		  __entry->vlan_tagged, __entry->vlan_proto, __entry->vlan_tci,
+		  __entry->protocol, __entry->ip_summed, __entry->len,
+		  __entry->data_len, 
+		  __entry->network_offset, __entry->transport_offset_valid,
+		  __entry->transport_offset, __entry->tx_flags,
+		  __entry->gso_size, __entry->gso_segs, __entry->gso_type)
+);
+
 TRACE_EVENT(net_dev_xmit,
 
 	TP_PROTO(struct sk_buff *skb,
diff --git a/net/core/dev.c b/net/core/dev.c
index 1b6eadf..e221963 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2602,6 +2602,7 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
 			dev_queue_xmit_nit(skb, dev);
 
 		skb_len = skb->len;
+		trace_net_dev_start_xmit(skb, dev);
 		rc = ops->ndo_start_xmit(skb, dev);
 		trace_net_dev_xmit(skb, rc, dev, skb_len);
 		if (rc == NETDEV_TX_OK)
@@ -2620,6 +2621,7 @@ gso:
 			dev_queue_xmit_nit(nskb, dev);
 
 		skb_len = nskb->len;
+		trace_net_dev_start_xmit(nskb, dev);
 		rc = ops->ndo_start_xmit(nskb, dev);
 		trace_net_dev_xmit(nskb, rc, dev, skb_len);
 		if (unlikely(rc != NETDEV_TX_OK)) {


-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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