[RFC PATCH 0/2] netdev: Add tracepoint to network/driver interface

[RFC PATCH 0/2] netdev: Add tracepoint to network/driver interface

[Koki Sanagi]

These patches add tracepoints to network/driver interface.

These tracepoints are helpful to investigate whether a packet passes or not.
For example, when Heart Beat is disconnected, that information is helpful
to investigate the cause is whether driver/device side or not.

An output is below.

   sshd-2443  [001] 68238.415621: netdev_start_xmit: dev=eth3 skbaddr=f3db5138 len=114
<idle>-0     [001] 68238.417058: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=52
<idle>-0     [001] 68238.704363: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=100
   sshd-2443  [001] 68238.705459: netdev_start_xmit: dev=eth3 skbaddr=f3db5138 len=114
<idle>-0     [001] 68238.706891: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=52
<idle>-0     [001] 68238.878736: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=100
   sshd-2443  [001] 68238.880361: netdev_start_xmit: dev=eth3 skbaddr=f3db5138 len=114

As other use case I have, we can get throughput per interface with some sort of
perf scripts. I plan to create it.

Thanks
Koki Sanagi

[RFC PATCH 1/2] netdev: Add tracepoint to dev_hard_start_xmit

[Koki Sanagi]

This patch adds tracepoint to dev_hard_start_xmit.
It notices that xmit packet passes network/driver interface.
An output is below.

   sshd-2443  [001] 68238.415621: netdev_start_xmit: dev=eth3 skbaddr=f3db5138 len=114
   sshd-2443  [001] 68238.705459: netdev_start_xmit: dev=eth3 skbaddr=f3db5138 len=114
   sshd-2443  [001] 68238.880361: netdev_start_xmit: dev=eth3 skbaddr=f3db5138 len=114

Signed-off-by: Koki Sanagi <sanagi.koki@jp.fujitsu.com>
---
  include/trace/events/skb.h |   28 ++++++++++++++++++++++++++++
  net/core/dev.c             |    3 +++
  2 files changed, 31 insertions(+), 0 deletions(-)

diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 4b2be6d..425a062 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -9,6 +9,34 @@
  #include <linux/tracepoint.h>
  
  /*
+ *  netdev_start_xmit - invoked when skb is passed to the driver
+ *  @skb:		pointer to struct sk_buff
+ *  @dev:		pointer to struct net_device
+ */
+TRACE_EVENT(netdev_start_xmit,
+
+	TP_PROTO(struct sk_buff *skb,
+		 struct net_device *dev),
+
+	TP_ARGS(skb, dev),
+
+	TP_STRUCT__entry(
+		__field(	const void *, 	skbaddr		)
+		__field(	unsigned int, 	len		)
+		__string(	name, 		dev->name	)
+       ),
+
+	TP_fast_assign(
+		__entry->skbaddr = skb;
+		__entry->len = skb->len;
+		__assign_str(name, dev->name);
+	),
+
+	TP_printk("dev=%s skbaddr=%p len=%u",
+		__get_str(name), __entry->skbaddr, __entry->len)
+);
+
+/*
   * Tracepoint for free an sk_buff:
   */
  TRACE_EVENT(kfree_skb,
diff --git a/net/core/dev.c b/net/core/dev.c
index 2a9b7dd..4667a96 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -129,6 +129,7 @@
  #include <linux/jhash.h>
  #include <linux/random.h>
  #include <trace/events/napi.h>
+#include <trace/events/skb.h>
  #include <linux/pci.h>
  
  #include "net-sysfs.h"
@@ -1903,6 +1904,7 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
  		if (dev->priv_flags & IFF_XMIT_DST_RELEASE)
  			skb_dst_drop(skb);
  
+		trace_netdev_start_xmit(skb, dev);
  		rc = ops->ndo_start_xmit(skb, dev);
  		if (rc == NETDEV_TX_OK)
  			txq_trans_update(txq);
@@ -1937,6 +1939,7 @@ gso:
  		if (dev->priv_flags & IFF_XMIT_DST_RELEASE)
  			skb_dst_drop(nskb);
  
+		trace_netdev_start_xmit(nskb, dev);
  		rc = ops->ndo_start_xmit(nskb, dev);
  		if (unlikely(rc != NETDEV_TX_OK)) {
  			if (rc & ~NETDEV_TX_MASK)

[RFC PATCH 2/2] netdev: Add tracepoint to netif_receive_skb

[Koki Sanagi]

This patch adds tracepoint to netif_receive_skb.
It notices that receive packet passes network/driver interface.
An output is below.

<idle>-0     [001] 68238.417058: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=52
<idle>-0     [001] 68238.704363: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=100
<idle>-0     [001] 68238.706891: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=52
<idle>-0     [001] 68238.878736: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=100

Signed-off-by: Koki Sanagi <sanagi.koki@jp.fujitsu.com>
---
  include/trace/events/skb.h |   28 ++++++++++++++++++++++++++++
  net/core/dev.c             |    1 +
  2 files changed, 29 insertions(+), 0 deletions(-)

diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 425a062..ca78d49 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -37,6 +37,34 @@ TRACE_EVENT(netdev_start_xmit,
  );
  
  /*
+ * netdev_receive_skb - invoked when skb is received from the driver
+ * @skb:		pointer to struct sk_buff
+ * @dev:		pointer to struct net_device
+ */
+TRACE_EVENT(netdev_receive_skb,
+
+	TP_PROTO(struct sk_buff *skb,
+		 struct net_device *dev),
+
+	TP_ARGS(skb, dev),
+
+	TP_STRUCT__entry(
+		__field(	const void *, 	skbaddr		)
+		__field(	unsigned int, 	len		)
+		__string(	name, 		dev->name	)
+       ),
+
+	TP_fast_assign(
+		__entry->skbaddr = skb;
+		__entry->len = skb->len;
+		__assign_str(name, dev->name);
+	),
+
+	TP_printk("dev=%s skbaddr=%p len=%u",
+		__get_str(name), __entry->skbaddr, __entry->len)
+);
+
+/*
   * Tracepoint for free an sk_buff:
   */
  TRACE_EVENT(kfree_skb,
diff --git a/net/core/dev.c b/net/core/dev.c
index 4667a96..7281286 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2683,6 +2683,7 @@ static int __netif_receive_skb(struct sk_buff *skb)
  
  	__get_cpu_var(netdev_rx_stat).total++;
  
+	trace_netdev_receive_skb(skb, orig_dev);
  	skb_reset_network_header(skb);
  	skb_reset_transport_header(skb);
  	skb->mac_len = skb->network_header - skb->mac_header;

Re: [RFC PATCH 0/2] netdev: Add tracepoint to network/driver interface

[Neil Horman]

On Fri, Apr 09, 2010 at 04:37:53PM +0900, Koki Sanagi wrote:
> These patches add tracepoints to network/driver interface.
> 
> These tracepoints are helpful to investigate whether a packet passes or not.
> For example, when Heart Beat is disconnected, that information is helpful
> to investigate the cause is whether driver/device side or not.
> 
> An output is below.
> 
>   sshd-2443  [001] 68238.415621: netdev_start_xmit: dev=eth3 skbaddr=f3db5138 len=114
> <idle>-0     [001] 68238.417058: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=52
> <idle>-0     [001] 68238.704363: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=100
>   sshd-2443  [001] 68238.705459: netdev_start_xmit: dev=eth3 skbaddr=f3db5138 len=114
> <idle>-0     [001] 68238.706891: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=52
> <idle>-0     [001] 68238.878736: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=100
>   sshd-2443  [001] 68238.880361: netdev_start_xmit: dev=eth3 skbaddr=f3db5138 len=114
> 
> As other use case I have, we can get throughput per interface with some sort of
> perf scripts. I plan to create it.
> 
> Thanks
> Koki Sanagi
> 
You can get a reasonable estimate of per-interface throughput using ethtool or
even ifconfig in a script.  What are the tracepoints needed for that?  Don't get
me wrong, I think these tracepoints could have some potential use thats not
covered by other tools, I just don't see the above as a conclusive reason to add
them.

Regards
Neil

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Re: [RFC PATCH 0/2] netdev: Add tracepoint to network/driver interface

[Koki Sanagi]

(2010/04/09 20:04), Neil Horman wrote:
> On Fri, Apr 09, 2010 at 04:37:53PM +0900, Koki Sanagi wrote:
>> These patches add tracepoints to network/driver interface.
>>
>> These tracepoints are helpful to investigate whether a packet passes or not.
>> For example, when Heart Beat is disconnected, that information is helpful
>> to investigate the cause is whether driver/device side or not.
>>
>> An output is below.
>>
>>    sshd-2443  [001] 68238.415621: netdev_start_xmit: dev=eth3 skbaddr=f3db5138 len=114
>> <idle>-0     [001] 68238.417058: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=52
>> <idle>-0     [001] 68238.704363: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=100
>>    sshd-2443  [001] 68238.705459: netdev_start_xmit: dev=eth3 skbaddr=f3db5138 len=114
>> <idle>-0     [001] 68238.706891: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=52
>> <idle>-0     [001] 68238.878736: netdev_receive_skb: dev=eth3 skbaddr=f3c81540 len=100
>>    sshd-2443  [001] 68238.880361: netdev_start_xmit: dev=eth3 skbaddr=f3db5138 len=114
>>
>> As other use case I have, we can get throughput per interface with some sort of
>> perf scripts. I plan to create it.
>>
>> Thanks
>> Koki Sanagi
>>
> You can get a reasonable estimate of per-interface throughput using ethtool or
> even ifconfig in a script.  What are the tracepoints needed for that?  Don't get
> me wrong, I think these tracepoints could have some potential use thats not
> covered by other tools, I just don't see the above as a conclusive reason to add
> them.

Yeah, a script using ethtool or ifconfig can do same thing. But it must be poll
driven. By contrast this implement using tracepoint is event-driven.
It means that a record leaves on memory certainly whenever kernel crashes.
It is useful to investigate network record from dump.
This is superior to ethtool or ifconfig scripts.