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Subject: Re: [RFC PATCH v2 4/5] skb: add tracepoints to freeing skb
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Koki Sanagi <sanagi.koki@jp.fujitsu.com>
Cc: linux-kernel@vger.kernel.org, kaneshige.kenji@jp.fujitsu.com,
       izumi.taku@jp.fujitsu.com
In-Reply-To: <4C23FF55.3090604@jp.fujitsu.com>
References: <4C2312A8.9060903@jp.fujitsu.com>
	 <4C23FF55.3090604@jp.fujitsu.com>
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Date: Fri, 25 Jun 2010 06:55:11 +0200
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Le vendredi 25 juin 2010 à 09:59 +0900, Koki Sanagi a écrit :
> This patch adds tracepoint to consume_skb and dev_kfree_skb_irq.
> 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
> 
> Signed-off-by: Koki Sanagi <sanagi.koki@jp.fujitsu.com>
> ---
> include/trace/events/skb.h |   36 ++++++++++++++++++++++++++++++++++++
>  net/core/dev.c             |    2 ++
>  net/core/skbuff.c          |    1 +
>  3 files changed, 39 insertions(+), 0 deletions(-)
> 
> diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
> index 4b2be6d..6ab5b34 100644
> --- a/include/trace/events/skb.h
> +++ b/include/trace/events/skb.h
> @@ -35,6 +35,42 @@ 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(dev_kfree_skb_irq,
> +
> +	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/dev.c b/net/core/dev.c
> index 4b64b21..807b1ca 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"
> @@ -1580,6 +1581,7 @@ 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);
> 


You might add a trace point to skb_free_datagram_locked() too, since it
contains an inlined consume_skb()



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