vhost: introduce vhost_exceeds_weight()

We used to have vhost_exceeds_weight() for vhost-net to:

- prevent vhost kthread from hogging the cpu
- balance the time spent between TX and RX

This function could be useful for vsock and scsi as well. So move it
to vhost.c. Device must specify a weight which counts the number of
requests, or it can also specific a byte_weight which counts the
number of bytes that has been processed.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 6 insertions, 16 deletions

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index df51a35cf537..061a06dc12a3 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -604,12 +604,6 @@ static size_t init_iov_iter(struct vhost_virtqueue *vq, struct iov_iter *iter,
 	return iov_iter_count(iter);
 }
 
-static bool vhost_exceeds_weight(int pkts, int total_len)
-{
-	return total_len >= VHOST_NET_WEIGHT ||
-	       pkts >= VHOST_NET_PKT_WEIGHT;
-}
-
 static int get_tx_bufs(struct vhost_net *net,
 		       struct vhost_net_virtqueue *nvq,
 		       struct msghdr *msg,
@@ -845,10 +839,8 @@ done:
 		vq->heads[nvq->done_idx].id = cpu_to_vhost32(vq, head);
 		vq->heads[nvq->done_idx].len = 0;
 		++nvq->done_idx;
-		if (vhost_exceeds_weight(++sent_pkts, total_len)) {
-			vhost_poll_queue(&vq->poll);
+		if (vhost_exceeds_weight(vq, ++sent_pkts, total_len))
 			break;
-		}
 	}
 
 	vhost_tx_batch(net, nvq, sock, &msg);
@@ -951,10 +943,9 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
 		else
 			vhost_zerocopy_signal_used(net, vq);
 		vhost_net_tx_packet(net);
-		if (unlikely(vhost_exceeds_weight(++sent_pkts, total_len))) {
-			vhost_poll_queue(&vq->poll);
+		if (unlikely(vhost_exceeds_weight(vq, ++sent_pkts,
+						  total_len)))
 			break;
-		}
 	}
 }
 
@@ -1239,10 +1230,8 @@ static void handle_rx(struct vhost_net *net)
 			vhost_log_write(vq, vq_log, log, vhost_len,
 					vq->iov, in);
 		total_len += vhost_len;
-		if (unlikely(vhost_exceeds_weight(++recv_pkts, total_len))) {
-			vhost_poll_queue(&vq->poll);
+		if (unlikely(vhost_exceeds_weight(vq, ++recv_pkts, total_len)))
 			goto out;
-		}
 	}
 	if (unlikely(busyloop_intr))
 		vhost_poll_queue(&vq->poll);
@@ -1338,7 +1327,8 @@ static int vhost_net_open(struct inode *inode, struct file *f)
 		vhost_net_buf_init(&n->vqs[i].rxq);
 	}
 	vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX,
-		       UIO_MAXIOV + VHOST_NET_BATCH);
+		       UIO_MAXIOV + VHOST_NET_BATCH,
+		       VHOST_NET_WEIGHT, VHOST_NET_PKT_WEIGHT);
 
 	vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, EPOLLOUT, dev);
 	vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, EPOLLIN, dev);