From: Lars Ellenberg <lars.ellenberg@linbit.com>
Date: Wed, 5 Feb 2014 05:13:53 +0000 (+0100)
Subject: drbd: trigger tcp_push_pending_frames() for PING and PING_ACK
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=123ff122ade4b22961f2c244c44966d52c2a7ca5;p=deliverable%2Flinux.git

drbd: trigger tcp_push_pending_frames() for PING and PING_ACK

This should reduce latency for such in-DRBD-protocol "pings",
and may help reduce spurious disconnect/reconnect cycles due to
 "PingAck did not arrive in time."

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
---

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 8e0813ddf72a..77d34a61bb58 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -662,6 +662,11 @@ static int __send_command(struct drbd_connection *connection, int vnr,
 			    msg_flags);
 	if (data && !err)
 		err = drbd_send_all(connection, sock->socket, data, size, 0);
+	/* DRBD protocol "pings" are latency critical.
+	 * This is supposed to trigger tcp_push_pending_frames() */
+	if (!err && (cmd == P_PING || cmd == P_PING_ACK))
+		drbd_tcp_nodelay(sock->socket);
+
 	return err;
 }