skb: Add tracepoints to freeing skb

This patch adds tracepoint to consume_skb and add trace_kfree_skb
before __kfree_skb in skb_free_datagram_locked and net_tx_action.
Combinating with tracepoint on dev_hard_start_xmit, we can check
how long it takes to free transmitted packets. And using it, we can
calculate how many packets driver had at that time. It is useful when
a drop of transmitted packet is a problem.

            sshd-6828  [000] 112689.258154: consume_skb: skbaddr=f2d99bb8

Signed-off-by: Koki Sanagi <sanagi.koki@jp.fujitsu.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Kaneshige Kenji <kaneshige.kenji@jp.fujitsu.com>
Cc: Izumo Taku <izumi.taku@jp.fujitsu.com>
Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Scott Mcmillan <scott.a.mcmillan@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
LKML-Reference: <4C724364.50903@jp.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

4 files changed, 21 insertions, 0 deletions

diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 4b2be6dc76f0..75ce9d500d8e 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -35,6 +35,23 @@ TRACE_EVENT(kfree_skb,
                 __entry->skbaddr, __entry->protocol, __entry->location)
 );
 
+TRACE_EVENT(consume_skb,
+
+        TP_PROTO(struct sk_buff *skb),
+
+        TP_ARGS(skb),
+
+        TP_STRUCT__entry(
+                __field(        void *, skbaddr )
+        ),
+
+        TP_fast_assign(
+                __entry->skbaddr = skb;
+        ),
+
+        TP_printk("skbaddr=%p", __entry->skbaddr)
+);
+
 TRACE_EVENT(skb_copy_datagram_iovec,
 
         TP_PROTO(const struct sk_buff *skb, int len),
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 251997a95483..282806ba7a57 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -243,6 +243,7 @@ void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb)
         unlock_sock_fast(sk, slow);
 
         /* skb is now orphaned, can be freed outside of locked section */
+        trace_kfree_skb(skb, skb_free_datagram_locked);
         __kfree_skb(skb);
 }
 EXPORT_SYMBOL(skb_free_datagram_locked);
diff --git a/net/core/dev.c b/net/core/dev.c
index 5a4fbc7405e2..2308cce48048 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -129,6 +129,7 @@
 #include <linux/random.h>
 #include <trace/events/napi.h>
 #include <trace/events/net.h>
+#include <trace/events/skb.h>
 #include <linux/pci.h>
 
 #include "net-sysfs.h"
@@ -2576,6 +2577,7 @@ static void net_tx_action(struct softirq_action *h)
                         clist = clist->next;
 
                         WARN_ON(atomic_read(&skb->users));
+                        trace_kfree_skb(skb, net_tx_action);
                         __kfree_skb(skb);
                 }
         }
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 3a2513f0d0c3..12e61e351d0e 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -466,6 +466,7 @@ void consume_skb(struct sk_buff *skb)
                 smp_rmb();
         else if (likely(!atomic_dec_and_test(&skb->users)))
                 return;
+        trace_consume_skb(skb);
         __kfree_skb(skb);
 }
 EXPORT_SYMBOL(consume_skb);