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From: Koki Sanagi on 19 Jul 2010 20:50
[RFC PATCH v3 4/5] skb: add tracepoints to freeing skb
This patch adds tracepoint to consume_skb, dev_kfree_skb_irq and
skb_free_datagram_locked. Combinating with tracepoint on dev_hard_start_xmit,
we can check how long it takes to free transmited packets. And using it, we can
calculate how many packets driver had at that time. It is useful when a drop of
transmited packet is a problem.

<idle>-0 [001] 241409.218333: consume_skb: skbaddr=dd6b2fb8
<idle>-0 [001] 241409.490555: dev_kfree_skb_irq: skbaddr=f5e29840

udp-recv-302 [001] 515031.206008: skb_free_datagram_locked: skbaddr=f5b1d900


Signed-off-by: Koki Sanagi <sanagi.koki(a)jp.fujitsu.com>
---
include/trace/events/skb.h | 42 ++++++++++++++++++++++++++++++++++++++++++
net/core/datagram.c | 1 +
net/core/dev.c | 2 ++
net/core/skbuff.c | 1 +
4 files changed, 46 insertions(+), 0 deletions(-)

diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 4b2be6d..84c9041 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -35,6 +35,48 @@ TRACE_EVENT(kfree_skb,
__entry->skbaddr, __entry->protocol, __entry->location)
);

+DECLARE_EVENT_CLASS(free_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)
+
+);
+
+DEFINE_EVENT(free_skb, consume_skb,
+
+ TP_PROTO(struct sk_buff *skb),
+
+ TP_ARGS(skb)
+
+);
+
+DEFINE_EVENT(free_skb, dev_kfree_skb_irq,
+
+ TP_PROTO(struct sk_buff *skb),
+
+ TP_ARGS(skb)
+
+);
+
+DEFINE_EVENT(free_skb, skb_free_datagram_locked,
+
+ TP_PROTO(struct sk_buff *skb),
+
+ TP_ARGS(skb)
+
+);
+
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 f5b6f43..1ea32a0 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -231,6 +231,7 @@ void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb)
{
bool slow;

+ trace_skb_free_datagram_locked(skb);
if (likely(atomic_read(&skb->users) == 1))
smp_rmb();
else if (likely(!atomic_dec_and_test(&skb->users)))
diff --git a/net/core/dev.c b/net/core/dev.c
index 4acfec6..d979847 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -131,6 +131,7 @@
#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"
@@ -1581,6 +1582,7 @@ void dev_kfree_skb_irq(struct sk_buff *skb)
struct softnet_data *sd;
unsigned long flags;

+ trace_dev_kfree_skb_irq(skb);
local_irq_save(flags);
sd = &__get_cpu_var(softnet_data);
skb->next = sd->completion_queue;
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 34432b4..a7b4036 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);

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Prev: [RFC PATCH v3 1/5] irq: add tracepoint to softirq_raise
Next: [GIT PULL] Shrinker fixes for XFS for 2.6.36-rc6