vhost_net: conditionally enable tx polling

jasowang · davem330 · commit feb8892cb441 · 2017-11-15T13:50:58.000+09:00
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 9e641bd ("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>
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
@@ -471,6 +471,7 @@ static void handle_tx(struct vhost_net *net)
 		goto out;
 
 	vhost_disable_notify(&net->dev, vq);
+	vhost_net_disable_vq(net, vq);
 
 	hdr_size = nvq->vhost_hlen;
 	zcopy = nvq->ubufs;
@@ -556,6 +557,7 @@ static void handle_tx(struct vhost_net *net)
 					% UIO_MAXIOV;
 			}
 			vhost_discard_vq_desc(vq, 1);
+			vhost_net_enable_vq(net, vq);
 			break;
 		}
 		if (err != len)

Original file line number	Diff line number	Diff line change
`@@ -471,6 +471,7 @@ static void handle_tx(struct vhost_net *net)`
`471`	`471`	`goto out;`
`472`	`472`
`473`	`473`	`vhost_disable_notify(&net->dev, vq);`
	`474`	`+ vhost_net_disable_vq(net, vq);`
`474`	`475`
`475`	`476`	`hdr_size = nvq->vhost_hlen;`
`476`	`477`	`zcopy = nvq->ubufs;`
`@@ -556,6 +557,7 @@ static void handle_tx(struct vhost_net *net)`
`556`	`557`	`% UIO_MAXIOV;`
`557`	`558`	`}`
`558`	`559`	`vhost_discard_vq_desc(vq, 1);`
	`560`	`+ vhost_net_enable_vq(net, vq);`
`559`	`561`	`break;`
`560`	`562`	`}`
`561`	`563`	`if (err != len)`