(2010/07/20 20:50), Neil Horman wrote:

On Tue, Jul 20, 2010 at 09:49:10AM +0900, Koki Sanagi wrote:

quoted

[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 <redacted>
---
 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)
+
+);
+

Why create these last two tracepoints at all?  dev_kfree_skb_irq will eventually
pass through kfree_skb anyway, getting picked up by the tracepoint there, the
while the latter won't (since it uses __kfree_skb instead), I think that could
be fixed up by add a call to trace_kfree_skb there directly, saving you two
tracepoints.

Neil

I think dev_kfree_skb_irq isn't chased by trace_kfree_skb or trace_consume_skb
completely. Because net_tx_action frees skb by __kfree_skb. So it is better to
add trace_kfree_skb before it. skb_free_datagram_locked is same.

Thanks,
Koki Sanagi.

quoted