virtio/vsock: allocate multiple skbuffs on tx

This adds small optimization for tx path: instead of allocating single
skbuff on every call to transport, allocate multiple skbuff's until
credit space allows, thus trying to send as much as possible data without
return to af_vsock.c.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 957cdc0..8c60fc7 100644 (file)
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -196,7 +196,8 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
        const struct virtio_transport *t_ops;
        struct virtio_vsock_sock *vvs;
        u32 pkt_len = info->pkt_len;
-       struct sk_buff *skb;
+       u32 rest_len;
+       int ret;
 
        info->type = virtio_transport_get_type(sk_vsock(vsk));
 
@@ -216,10 +217,6 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
 
        vvs = vsk->trans;
 
-       /* we can send less than pkt_len bytes */
-       if (pkt_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE)
-               pkt_len = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;
-
        /* virtio_transport_get_credit might return less than pkt_len credit */
        pkt_len = virtio_transport_get_credit(vvs, pkt_len);
 
@@ -227,17 +224,49 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
        if (pkt_len == 0 && info->op == VIRTIO_VSOCK_OP_RW)
                return pkt_len;
 
-       skb = virtio_transport_alloc_skb(info, pkt_len,
-                                        src_cid, src_port,
-                                        dst_cid, dst_port);
-       if (!skb) {
-               virtio_transport_put_credit(vvs, pkt_len);
-               return -ENOMEM;
-       }
+       rest_len = pkt_len;
+
+       do {
+               struct sk_buff *skb;
+               size_t skb_len;
+
+               skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE, rest_len);
+
+               skb = virtio_transport_alloc_skb(info, skb_len,
+                                                src_cid, src_port,
+                                                dst_cid, dst_port);
+               if (!skb) {
+                       ret = -ENOMEM;
+                       break;
+               }
 
-       virtio_transport_inc_tx_pkt(vvs, skb);
+               virtio_transport_inc_tx_pkt(vvs, skb);
 
-       return t_ops->send_pkt(skb);
+               ret = t_ops->send_pkt(skb);
+               if (ret < 0)
+                       break;
+
+               /* Both virtio and vhost 'send_pkt()' returns 'skb_len',
+                * but for reliability use 'ret' instead of 'skb_len'.
+                * Also if partial send happens (e.g. 'ret' != 'skb_len')
+                * somehow, we break this loop, but account such returned
+                * value in 'virtio_transport_put_credit()'.
+                */
+               rest_len -= ret;
+
+               if (WARN_ONCE(ret != skb_len,
+                             "'send_pkt()' returns %i, but %zu expected\n",
+                             ret, skb_len))
+                       break;
+       } while (rest_len);
+
+       virtio_transport_put_credit(vvs, rest_len);
+
+       /* Return number of bytes, if any data has been sent. */
+       if (rest_len != pkt_len)
+               ret = pkt_len - rest_len;
+
+       return ret;
 }
 
 static bool virtio_transport_inc_rx_pkt(struct virtio_vsock_sock *vvs,