SUNRPC: Make RTT measurement more precise (Receive) (0b87a46b) · Commits · 戴 / test

Some RPC transports have more overhead in their reply handlers than others. For example, for RPC-over-RDMA: - RPC completion has to wait for memory invalidation, which is not a part of the server/network round trip - Recently a context switch was introduced into the reply handler, which further artificially inflates the measure of RPC RTT To capture just server and network latencies more precisely: when receiving a reply, compute the RTT as soon as the XID is recognized rather than at RPC completion time. Signed-off-by:

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

Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprt.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -826,6 +826,7 @@ static void xprt_connect_status(struct rpc_task *task)
		* @xprt: transport on which the original request was transmitted
		* @xid: RPC XID of incoming reply
		*
		* Caller holds xprt->recv_lock.
		*/
		struct rpc_rqst xprt_lookup_rqst(struct rpc_xprt xprt, __be32 xid)
		{
		@@ -834,6 +835,7 @@ struct rpc_rqst xprt_lookup_rqst(struct rpc_xprt xprt, __be32 xid)
		list_for_each_entry(entry, &xprt->recv, rq_list)
		if (entry->rq_xid == xid) {
		trace_xprt_lookup_rqst(xprt, xid, 0);
		entry->rq_rtt = ktime_sub(ktime_get(), entry->rq_xtime);
		return entry;
		}

		@@ -915,7 +917,7 @@ EXPORT_SYMBOL_GPL(xprt_update_rtt);
		* @task: RPC request that recently completed
		* @copied: actual number of bytes received from the transport
		*
		* Caller holds transport lock.
		* Caller holds xprt->recv_lock.
		*/
		void xprt_complete_rqst(struct rpc_task *task, int copied)
		{
		@@ -927,7 +929,6 @@ void xprt_complete_rqst(struct rpc_task *task, int copied)
		trace_xprt_complete_rqst(xprt, req->rq_xid, copied);

		xprt->stat.recvs++;
		req->rq_rtt = ktime_sub(ktime_get(), req->rq_xtime);

		list_del_init(&req->rq_list);
		req->rq_private_buf.len = copied;

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