[ltt-dev] [PATCH] add tracepoints to track change in napi states on network receive

[Neil Horman]

On Tue, Dec 02, 2008 at 03:01:50PM -0500, Mathieu Desnoyers wrote:
> * Neil Horman (nhorman at tuxdriver.com) wrote:
> > Hey there-
> > 	I thought it would be handy to track the napi receive state of different
> > network devices using ltt.  This patch adds trace points to indicate when a napi
> > instance has been scheduled, when its serviced and when it completes.
> > 
> 
> Sounds great, see comments below,
<snip>

Hey,
	New patch, with previous comments taken into account.

Patch to track the napi receive stat of different network devices using ltt.
Adds trace points to indicate when a napi instance has been scheduled, when its
serviced and when it completes

Regards
Neil

Signed-off-by: Neil Horman <nhorman at tuxdriver.com>


 include/linux/netdevice.h |    5 +++++
 include/trace/netdevice.h |   30 ++++++++++++++++++++++++++++++
 ltt/probes/net-trace.c    |   22 ++++++++++++++++++++++
 net/core/dev.c            |    7 ++++++-
 4 files changed, 63 insertions(+), 1 deletion(-)


diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 488c56e..7da71eb 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -43,6 +43,9 @@
 
 #include <net/net_namespace.h>
 
+struct napi_struct;
+#include <trace/netdevice.h>
+
 struct vlan_group;
 struct ethtool_ops;
 struct netpoll_info;
@@ -386,6 +389,7 @@ static inline void napi_complete(struct napi_struct *n)
 	local_irq_save(flags);
 	__napi_complete(n);
 	local_irq_restore(flags);
+	trace_napi_complete(n);
 }
 
 /**
@@ -1726,6 +1730,7 @@ static inline int skb_bond_should_drop(struct sk_buff *skb)
 	return 0;
 }
 
+
 #endif /* __KERNEL__ */
 
 #endif	/* _LINUX_DEV_H */
diff --git a/include/trace/netdevice.h b/include/trace/netdevice.h
new file mode 100644
index 0000000..ba48f6c
--- /dev/null
+++ b/include/trace/netdevice.h
@@ -0,0 +1,30 @@
+#ifndef _INCLUDE_NETDEVICE_H_
+#define _INCLUDE_NETDEVICE_H_
+
+#include <linux/netdevice.h>
+
+/* Tracepoints */
+
+/*
+ * Note these first 2 traces are actually in __napi_schedule and net_rx_action
+ * respectively.  The former is in __napi_schedule because it uses at-most-once
+ * logic and placing it in the calling routine (napi_schedule) would produce
+ * countless trace events that were effectively  no-ops.  napi_poll is
+ * implemented in net_rx_action, because thats where we do our polling on
+ * devices.  The last trace point is in napi_complete, right where you would
+ * think it would be.
+ */
+DEFINE_TRACE(napi_schedule,
+	TPPROTO(struct napi_struct *n),
+	TPARGS(n));
+
+DEFINE_TRACE(napi_poll,
+	TPPROTO(struct napi_struct *n),
+	TPARGS(n));
+
+DEFINE_TRACE(napi_complete,
+	TPPROTO(struct napi_struct *n),
+	TPARGS(n));
+
+#endif
+
diff --git a/ltt/probes/net-trace.c b/ltt/probes/net-trace.c
index bac2b21..bd4e621 100644
--- a/ltt/probes/net-trace.c
+++ b/ltt/probes/net-trace.c
@@ -9,6 +9,7 @@
 #include <trace/ipv4.h>
 #include <trace/ipv6.h>
 #include <trace/socket.h>
+#include <trace/netdevice.h>
 
 void probe_net_dev_xmit(struct sk_buff *skb)
 {
@@ -104,6 +105,27 @@ void probe_socket_call(int call, unsigned long a0)
 		"call %d a0 %lu", call, a0);
 }
 
+void probe_napi_schedule(struct napi_struct *n)
+{
+	trace_mark_tp(net_napi_schedule, napi_schedule, probe_napi_schedule,
+		"schedule napi_struct %p name  %s",
+		n, n->dev->name);
+}
+
+void probe_napi_poll(struct napi_struct *n)
+{
+	trace_mark_tp(net_napi_poll, napi_poll, probe_napi_poll,
+		"service napi_struct %p name %s",
+		n, n->dev->name); 
+}
+
+void probe_napi_complete(struct napi_struct *n)
+{
+	trace_mark_tp(net_napi_complete, napi_complete, probe_napi_complete,
+		"complete napi_struct %p name %s",
+		n, n->dev->name);
+}
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Mathieu Desnoyers");
 MODULE_DESCRIPTION("Net Tracepoint Probes");
diff --git a/net/core/dev.c b/net/core/dev.c
index 836fe6e..0c55c0f 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -128,6 +128,7 @@
 #include <linux/jhash.h>
 #include <linux/random.h>
 #include <trace/net.h>
+#include <trace/netdevice.h>
 
 #include "net-sysfs.h"
 
@@ -2329,6 +2330,8 @@ void __napi_schedule(struct napi_struct *n)
 {
 	unsigned long flags;
 
+	trace_napi_poll(n);
+
 	local_irq_save(flags);
 	list_add_tail(&n->poll_list, &__get_cpu_var(softnet_data).poll_list);
 	__raise_softirq_irqoff(NET_RX_SOFTIRQ);
@@ -2380,8 +2383,10 @@ static void net_rx_action(struct softirq_action *h)
 		 * accidently calling ->poll() when NAPI is not scheduled.
 		 */
 		work = 0;
-		if (test_bit(NAPI_STATE_SCHED, &n->state))
+		if (test_bit(NAPI_STATE_SCHED, &n->state)) {
+			trace_napi_poll(n);
 			work = n->poll(n, weight);
+		}
 
 		WARN_ON_ONCE(work > weight);
 
-- 
/****************************************************
 * Neil Horman <nhorman at tuxdriver.com>
 * Software Engineer, Red Hat
 ****************************************************/