Subject: Re: [RFC PATCH v3 3/5] netdev: add tracepoints to netdev layer

From: Koki Sanagi <[email-masked]>
Date: Wed, 21 Jul 2010 16:01:19 +0900

(2010/07/20 20:41), Neil Horman wrote:
> On Tue, Jul 20, 2010 at 09:47:59AM +0900, Koki Sanagi wrote:
>> This patch adds tracepoint to dev_queue_xmit, dev_hard_start_xmit and
>> netif_receive_skb. These tracepoints help you to monitor network driver's
>> input/output.
>>
>>             sshd-4445  [001] 241367.066046: net_dev_queue: dev=eth3 skbaddr=dd6b2538 len=114
>>             sshd-4445  [001] 241367.066047: net_dev_xmit: dev=eth3 skbaddr=dd6b2538 len=114 rc=0
>>           <idle>-0     [001] 241367.067472: net_dev_receive: dev=eth3 skbaddr=f5e59000 len=52
>>
>> Signed-off-by: Koki Sanagi <[email-masked]>
>> ---
>>  include/trace/events/net.h |   75 ++++++++++++++++++++++++++++++++++++++++++++
>>  net/core/dev.c             |    5 +++
>>  net/core/net-traces.c      |    1 +
>>  3 files changed, 81 insertions(+), 0 deletions(-)
>>
>> diff --git a/include/trace/events/net.h b/include/trace/events/net.h
>> new file mode 100644
>> index 0000000..8a21361
>> --- /dev/null
>> +++ b/include/trace/events/net.h
>> @@ -0,0 +1,75 @@
>> +#undef TRACE_SYSTEM
>> +#define TRACE_SYSTEM net
>> +
>> +#if !defined(_TRACE_NET_H) || defined(TRACE_HEADER_MULTI_READ)
>> +#define _TRACE_NET_H
>> +
>> +#include <linux/skbuff.h>
>> +#include <linux/netdevice.h>
>> +#include <linux/ip.h>
>> +#include <linux/tracepoint.h>
>> +
>> +TRACE_EVENT(net_dev_xmit,
>> +
>> +	TP_PROTO(struct sk_buff *skb,
>> +		 int rc),
>> +
>> +	TP_ARGS(skb, rc),
>> +
>> +	TP_STRUCT__entry(
>> +		__field(	void *,		skbaddr		)
>> +		__field(	unsigned int,	len		)
>> +		__field(	int,		rc		)
>> +		__string(	name,		skb->dev->name	)
>> +	),
>> +
>> +	TP_fast_assign(
>> +		__entry->skbaddr = skb;
>> +		__entry->len = skb->len;
>> +		__entry->rc = rc;
>> +		__assign_str(name, skb->dev->name);
>> +	),
>> +
>> +	TP_printk("dev=%s skbaddr=%p len=%u rc=%d",
>> +		__get_str(name), __entry->skbaddr, __entry->len, __entry->rc)
>> +);
>> +
>> +DECLARE_EVENT_CLASS(net_dev_template,
>> +
>> +	TP_PROTO(struct sk_buff *skb),
>> +
>> +	TP_ARGS(skb),
>> +
>> +	TP_STRUCT__entry(
>> +		__field(	void *,		skbaddr		)
>> +		__field(	unsigned int,	len		)
>> +		__string(	name,		skb->dev->name	)
>> +	),
>> +
>> +	TP_fast_assign(
>> +		__entry->skbaddr = skb;
>> +		__entry->len = skb->len;
>> +		__assign_str(name, skb->dev->name);
>> +	),
>> +
>> +	TP_printk("dev=%s skbaddr=%p len=%u",
>> +		__get_str(name), __entry->skbaddr, __entry->len)
>> +)
>> +
>> +DEFINE_EVENT(net_dev_template, net_dev_queue,
>> +
>> +	TP_PROTO(struct sk_buff *skb),
>> +
>> +	TP_ARGS(skb)
>> +);
>> +
>> +DEFINE_EVENT(net_dev_template, net_dev_receive,
>> +
>> +	TP_PROTO(struct sk_buff *skb),
>> +
>> +	TP_ARGS(skb)
>> +);
>> +#endif /* _TRACE_NET_H */
>> +
>> +/* This part must be outside protection */
>> +#include <trace/define_trace.h>
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index 93b8929..4acfec6 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -130,6 +130,7 @@
>>  #include <linux/jhash.h>
>>  #include <linux/random.h>
>>  #include <trace/events/napi.h>
>> +#include <trace/events/net.h>
>>  #include <linux/pci.h>
>>  
>>  #include "net-sysfs.h"
>> @@ -1955,6 +1956,7 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
>>  		}
>>  
>>  		rc = ops->ndo_start_xmit(skb, dev);
>> +		trace_net_dev_xmit(skb, rc);
>>  		if (rc == NETDEV_TX_OK)
>>  			txq_trans_update(txq);
>>  		return rc;
>> @@ -1975,6 +1977,7 @@ gso:
>>  			skb_dst_drop(nskb);
>>  
>>  		rc = ops->ndo_start_xmit(nskb, dev);
>> +		trace_net_dev_xmit(nskb, rc);
>>  		if (unlikely(rc != NETDEV_TX_OK)) {
>>  			if (rc & ~NETDEV_TX_MASK)
>>  				goto out_kfree_gso_skb;
>> @@ -2165,6 +2168,7 @@ int dev_queue_xmit(struct sk_buff *skb)
>>  #ifdef CONFIG_NET_CLS_ACT
>>  	skb->tc_verd = SET_TC_AT(skb->tc_verd, AT_EGRESS);
>>  #endif
>> +	trace_net_dev_queue(skb);
>>  	if (q->enqueue) {
>>  		rc = __dev_xmit_skb(skb, q, dev, txq);
>>  		goto out;
>> @@ -2939,6 +2943,7 @@ int netif_receive_skb(struct sk_buff *skb)
>>  	if (netdev_tstamp_prequeue)
>>  		net_timestamp_check(skb);
>>  
>> +	trace_net_dev_receive(skb);
> 
> I imagine for completeness you'll want to make a call to this in netif_rx and
> netif_rx_ni as well.
> 
It might be better to add tracepoint to netif_rx to determine a time between
netif_rx and netif_receive_skb.

Thanks,
Koki Sanagi.