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Subject[PATCH v4 4/5] 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 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.

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

Signed-off-by: Koki Sanagi <sanagi.koki@jp.fujitsu.com>
---
include/trace/events/skb.h | 17 +++++++++++++++++
net/core/datagram.c | 1 +
net/core/dev.c | 2 ++
net/core/skbuff.c | 1 +
4 files changed, 21 insertions(+), 0 deletions(-)
diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 4b2be6d..75ce9d5 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 251997a..282806b 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 c9b026a..48f7977 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"
@@ -2589,6 +2590,7 @@ 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 99ef721..ef4ffa8 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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