SUNRPC: Add trace points to observe transport congestion control

To help debug problems with RPC/RDMA credit management, replace
dprintk() call sites in the transport send lock paths with trace
events.

Similar trace points are defined for the non-congestion paths.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

2 files changed, 106 insertions, 9 deletions

diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
index ffa3c51dbb1a..378233fe5ac7 100644
--- a/include/trace/events/sunrpc.h
+++ b/include/trace/events/sunrpc.h
@@ -777,6 +777,99 @@ TRACE_EVENT(xprt_ping,
 			__get_str(addr), __get_str(port), __entry->status)
 );
 
+DECLARE_EVENT_CLASS(xprt_writelock_event,
+	TP_PROTO(
+		const struct rpc_xprt *xprt, const struct rpc_task *task
+	),
+
+	TP_ARGS(xprt, task),
+
+	TP_STRUCT__entry(
+		__field(unsigned int, task_id)
+		__field(unsigned int, client_id)
+		__field(unsigned int, snd_task_id)
+	),
+
+	TP_fast_assign(
+		if (task) {
+			__entry->task_id = task->tk_pid;
+			__entry->client_id = task->tk_client ?
+					     task->tk_client->cl_clid : -1;
+		} else {
+			__entry->task_id = -1;
+			__entry->client_id = -1;
+		}
+		__entry->snd_task_id = xprt->snd_task ?
+					xprt->snd_task->tk_pid : -1;
+	),
+
+	TP_printk("task:%u@%u snd_task:%u",
+			__entry->task_id, __entry->client_id,
+			__entry->snd_task_id)
+);
+
+#define DEFINE_WRITELOCK_EVENT(name) \
+	DEFINE_EVENT(xprt_writelock_event, xprt_##name, \
+			TP_PROTO( \
+				const struct rpc_xprt *xprt, \
+				const struct rpc_task *task \
+			), \
+			TP_ARGS(xprt, task))
+
+DEFINE_WRITELOCK_EVENT(reserve_xprt);
+DEFINE_WRITELOCK_EVENT(release_xprt);
+
+DECLARE_EVENT_CLASS(xprt_cong_event,
+	TP_PROTO(
+		const struct rpc_xprt *xprt, const struct rpc_task *task
+	),
+
+	TP_ARGS(xprt, task),
+
+	TP_STRUCT__entry(
+		__field(unsigned int, task_id)
+		__field(unsigned int, client_id)
+		__field(unsigned int, snd_task_id)
+		__field(unsigned long, cong)
+		__field(unsigned long, cwnd)
+		__field(bool, wait)
+	),
+
+	TP_fast_assign(
+		if (task) {
+			__entry->task_id = task->tk_pid;
+			__entry->client_id = task->tk_client ?
+					     task->tk_client->cl_clid : -1;
+		} else {
+			__entry->task_id = -1;
+			__entry->client_id = -1;
+		}
+		__entry->snd_task_id = xprt->snd_task ?
+					xprt->snd_task->tk_pid : -1;
+		__entry->cong = xprt->cong;
+		__entry->cwnd = xprt->cwnd;
+		__entry->wait = test_bit(XPRT_CWND_WAIT, &xprt->state);
+	),
+
+	TP_printk("task:%u@%u snd_task:%u cong=%lu cwnd=%lu%s",
+			__entry->task_id, __entry->client_id,
+			__entry->snd_task_id, __entry->cong, __entry->cwnd,
+			__entry->wait ? " (wait)" : "")
+);
+
+#define DEFINE_CONG_EVENT(name) \
+	DEFINE_EVENT(xprt_cong_event, xprt_##name, \
+			TP_PROTO( \
+				const struct rpc_xprt *xprt, \
+				const struct rpc_task *task \
+			), \
+			TP_ARGS(xprt, task))
+
+DEFINE_CONG_EVENT(reserve_cong);
+DEFINE_CONG_EVENT(release_cong);
+DEFINE_CONG_EVENT(get_cong);
+DEFINE_CONG_EVENT(put_cong);
+
 TRACE_EVENT(xs_stream_read_data,
 	TP_PROTO(struct rpc_xprt *xprt, ssize_t err, size_t total),
 
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 8a45b3ccc313..fcbeb56c82cd 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -205,20 +205,20 @@ int xprt_reserve_xprt(struct rpc_xprt *xprt, struct rpc_task *task)
 
 	if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) {
 		if (task == xprt->snd_task)
-			return 1;
+			goto out_locked;
 		goto out_sleep;
 	}
 	if (test_bit(XPRT_WRITE_SPACE, &xprt->state))
 		goto out_unlock;
 	xprt->snd_task = task;
 
+out_locked:
+	trace_xprt_reserve_xprt(xprt, task);
 	return 1;
 
 out_unlock:
 	xprt_clear_locked(xprt);
 out_sleep:
-	dprintk("RPC: %5u failed to lock transport %p\n",
-			task->tk_pid, xprt);
 	task->tk_status = -EAGAIN;
 	if  (RPC_IS_SOFT(task))
 		rpc_sleep_on_timeout(&xprt->sending, task, NULL,
@@ -269,23 +269,22 @@ int xprt_reserve_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task)
 
 	if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) {
 		if (task == xprt->snd_task)
-			return 1;
+			goto out_locked;
 		goto out_sleep;
 	}
 	if (req == NULL) {
 		xprt->snd_task = task;
-		return 1;
+		goto out_locked;
 	}
 	if (test_bit(XPRT_WRITE_SPACE, &xprt->state))
 		goto out_unlock;
 	if (!xprt_need_congestion_window_wait(xprt)) {
 		xprt->snd_task = task;
-		return 1;
+		goto out_locked;
 	}
 out_unlock:
 	xprt_clear_locked(xprt);
 out_sleep:
-	dprintk("RPC: %5u failed to lock transport %p\n", task->tk_pid, xprt);
 	task->tk_status = -EAGAIN;
 	if (RPC_IS_SOFT(task))
 		rpc_sleep_on_timeout(&xprt->sending, task, NULL,
@@ -293,6 +292,9 @@ out_sleep:
 	else
 		rpc_sleep_on(&xprt->sending, task, NULL);
 	return 0;
+out_locked:
+	trace_xprt_reserve_cong(xprt, task);
+	return 1;
 }
 EXPORT_SYMBOL_GPL(xprt_reserve_xprt_cong);
 
@@ -357,6 +359,7 @@ void xprt_release_xprt(struct rpc_xprt *xprt, struct rpc_task *task)
 		xprt_clear_locked(xprt);
 		__xprt_lock_write_next(xprt);
 	}
+	trace_xprt_release_xprt(xprt, task);
 }
 EXPORT_SYMBOL_GPL(xprt_release_xprt);
 
@@ -374,6 +377,7 @@ void xprt_release_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task)
 		xprt_clear_locked(xprt);
 		__xprt_lock_write_next_cong(xprt);
 	}
+	trace_xprt_release_cong(xprt, task);
 }
 EXPORT_SYMBOL_GPL(xprt_release_xprt_cong);
 
@@ -395,8 +399,7 @@ __xprt_get_cong(struct rpc_xprt *xprt, struct rpc_rqst *req)
 {
 	if (req->rq_cong)
 		return 1;
-	dprintk("RPC: %5u xprt_cwnd_limited cong = %lu cwnd = %lu\n",
-			req->rq_task->tk_pid, xprt->cong, xprt->cwnd);
+	trace_xprt_get_cong(xprt, req->rq_task);
 	if (RPCXPRT_CONGESTED(xprt)) {
 		xprt_set_congestion_window_wait(xprt);
 		return 0;
@@ -418,6 +421,7 @@ __xprt_put_cong(struct rpc_xprt *xprt, struct rpc_rqst *req)
 	req->rq_cong = 0;
 	xprt->cong -= RPC_CWNDSCALE;
 	xprt_test_and_clear_congestion_window_wait(xprt);
+	trace_xprt_put_cong(xprt, req->rq_task);
 	__xprt_lock_write_next_cong(xprt);
 }