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Subject[PATCH 12/18] drbd: trigger tcp_push_pending_frames() for PING and PING_ACK
Date
From: Lars Ellenberg <lars.ellenberg@linbit.com>

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>
---
drivers/block/drbd/drbd_main.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 8e0813d..77d34a6 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;
}

--
1.9.1


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