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authorChuck Lever <chuck.lever@oracle.com>2018-03-05 23:13:02 +0300
committerAnna Schumaker <Anna.Schumaker@Netapp.com>2018-04-10 23:06:22 +0300
commit0b87a46b437c1629bc7d79f3c5a0ba3608c37544 (patch)
treeacfa846d81e0fe929df5a85fef988dfa7a4d8324 /net/sunrpc/xprt.c
parentecd465ee88bb6648c06c82b1abae6ec28cf5fccb (diff)
downloadlinux-0b87a46b437c1629bc7d79f3c5a0ba3608c37544.tar.xz
SUNRPC: Make RTT measurement more precise (Receive)
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>
Diffstat (limited to 'net/sunrpc/xprt.c')
-rw-r--r--net/sunrpc/xprt.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 13fbb4849188..cb7784c5b741 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -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;