From ca4faf543a33373bed3650812d5f0cd0bd295b1a Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Sat, 2 May 2020 10:37:44 -0400 Subject: SUNRPC: Move xpt_mutex into socket xpo_sendto methods It appears that the RPC/RDMA transport does not need serialization of calls to its xpo_sendto method. Move the mutex into the socket methods that still need that serialization. Tail latencies are unambiguously better with this patch applied. fio randrw 8KB 70/30 on NFSv3, smaller numbers are better: clat percentiles (usec): With xpt_mutex: r | 99.99th=[ 8848] w | 99.99th=[ 9634] Without xpt_mutex: r | 99.99th=[ 8586] w | 99.99th=[ 8979] Serializing the construction of RPC/RDMA transport headers is not really necessary at this point, because the Linux NFS server implementation never changes its credit grant on a connection. If that should change, then svc_rdma_sendto will need to serialize access to the transport's credit grant fields. Reported-by: kbuild test robot [ cel: fix uninitialized variable warning ] Signed-off-by: Chuck Lever --- net/sunrpc/xprtsock.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'net/sunrpc/xprtsock.c') diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c index 845d0be805ec..839c49330785 100644 --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -2548,8 +2548,16 @@ static int bc_sendto(struct rpc_rqst *req) return sent; } -/* - * The send routine. Borrows from svc_send +/** + * bc_send_request - Send a backchannel Call on a TCP socket + * @req: rpc_rqst containing Call message to be sent + * + * xpt_mutex ensures @rqstp's whole message is written to the socket + * without interruption. + * + * Return values: + * %0 if the message was sent successfully + * %ENOTCONN if the message was not sent */ static int bc_send_request(struct rpc_rqst *req) { -- cgit v1.2.3