[PATCH v2 04/18] sunrpc: Move trace_svc_xprt_dequeue()

[Chuck Lever <chuck.lever@oracle.com>]

Reduce the amount of noise generated by trace_svc_xprt_dequeue by
moving it to the end of svc_get_next_xprt. This generates exactly
one trace event when a ready xprt is found, rather than spurious
events when there is no work to do. The empty events contain no
information that can't be obtained simply by tracing function calls
to svc_xprt_dequeue.

A small additional benefit is simplification of the svc_xprt_event
trace class, which no longer has to handle the case when the @xprt
parameter is NULL.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/trace/events/sunrpc.h |   16 +++++-----------
 net/sunrpc/svc_xprt.c         |    5 +----
 2 files changed, 6 insertions(+), 15 deletions(-)

diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
index a231444..9bba307 100644
--- a/include/trace/events/sunrpc.h
+++ b/include/trace/events/sunrpc.h
@@ -634,24 +634,18 @@
 	TP_STRUCT__entry(
 		__field(struct svc_xprt *, xprt)
 		__field(unsigned long, flags)
-		__dynamic_array(unsigned char, addr, xprt != NULL ?
-			xprt->xpt_remotelen : 0)
+		__dynamic_array(unsigned char, addr, xprt->xpt_remotelen)
 	),
 
 	TP_fast_assign(
 		__entry->xprt = xprt;
-		if (xprt) {
-			memcpy(__get_dynamic_array(addr),
-					&xprt->xpt_remote,
-					xprt->xpt_remotelen);
-			__entry->flags = xprt->xpt_flags;
-		} else
-			__entry->flags = 0;
+		__entry->flags = xprt->xpt_flags;
+		memcpy(__get_dynamic_array(addr),
+		       &xprt->xpt_remote, xprt->xpt_remotelen);
 	),
 
 	TP_printk("xprt=0x%p addr=%pIScp flags=%s", __entry->xprt,
-		__get_dynamic_array_len(addr) != 0 ?
-			(struct sockaddr *)__get_dynamic_array(addr) : NULL,
+		(struct sockaddr *)__get_dynamic_array(addr),
 		show_svc_xprt_flags(__entry->flags))
 );
 
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index 4e3b4c5..71f4718 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -454,13 +454,9 @@ static struct svc_xprt *svc_xprt_dequeue(struct svc_pool *pool)
 					struct svc_xprt, xpt_ready);
 		list_del_init(&xprt->xpt_ready);
 		svc_xprt_get(xprt);
-
-		dprintk("svc: transport %p dequeued, inuse=%d\n",
-			xprt, kref_read(&xprt->xpt_ref));
 	}
 	spin_unlock_bh(&pool->sp_lock);
 out:
-	trace_svc_xprt_dequeue(xprt);
 	return xprt;
 }
 
@@ -734,6 +730,7 @@ static struct svc_xprt *svc_get_next_xprt(struct svc_rqst *rqstp, long timeout)
 		rqstp->rq_chandle.thread_wait = 5*HZ;
 	else
 		rqstp->rq_chandle.thread_wait = 1*HZ;
+	trace_svc_xprt_dequeue(rqstp->rq_xprt);
 	return rqstp->rq_xprt;
 }