From: Jason Wang <jasowang@redhat.com>
Date: Mon, 13 Nov 2017 11:45:34 +0800
Subject: vhost_net: conditionally enable tx polling
Patch-mainline: v4.15-rc1
Git-commit: feb8892cb441c742d4220cf7ced001e7fa070731
References: bsc#1109837

We always poll tx for socket, this is sub optimal since this will
slightly increase the waitqueue traversing time and more important,
vhost could not benefit from commit 9e641bdcfa4e ("net-tun:
restructure tun_do_read for better sleep/wakeup efficiency") even if
we've stopped rx polling during handle_rx(), tx poll were still left
in the waitqueue.

Pktgen from a remote host to VM over mlx4 on two 2.00GHz Xeon E5-2650
shows 11.7% improvements on rx PPS. (from 1.28Mpps to 1.44Mpps)

Cc: Wei Xu <wexu@redhat.com>
Cc: Matthew Rosato <mjrosato@linux.vnet.ibm.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/vhost/net.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -471,6 +471,7 @@ static void handle_tx(struct vhost_net *
 		goto out;
 
 	vhost_disable_notify(&net->dev, vq);
+	vhost_net_disable_vq(net, vq);
 
 	hdr_size = nvq->vhost_hlen;
 	zcopy = nvq->ubufs;
@@ -555,6 +556,7 @@ static void handle_tx(struct vhost_net *
 					% UIO_MAXIOV;
 			}
 			vhost_discard_vq_desc(vq, 1);
+			vhost_net_enable_vq(net, vq);
 			break;
 		}
 		if (err != len)