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SubjectRe: [RFC PATCH v3 4/5] skb: add tracepoints to freeing skb
On Tue, Jul 20, 2010 at 09:49:10AM +0900, Koki Sanagi wrote:
> [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@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)
> +
> +);
> +

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

>


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