vsock/virtio: reduce credit update messages

In order to reduce the number of credit update messages,
we send them only when the space available seen by the
transmitter is less than VIRTIO_VSOCK_MAX_PKT_BUF_SIZE.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index 7d97390..49fc9d2 100644 (file)
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -41,6 +41,7 @@ struct virtio_vsock_sock {
 
        /* Protected by rx_lock */
        u32 fwd_cnt;
+       u32 last_fwd_cnt;
        u32 rx_bytes;
        struct list_head rx_queue;
 };

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 095221f..a85559d 100644 (file)
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -211,6 +211,7 @@ static void virtio_transport_dec_rx_pkt(struct virtio_vsock_sock *vvs,
 void virtio_transport_inc_tx_pkt(struct virtio_vsock_sock *vvs, struct virtio_vsock_pkt *pkt)
 {
        spin_lock_bh(&vvs->tx_lock);
+       vvs->last_fwd_cnt = vvs->fwd_cnt;
        pkt->hdr.fwd_cnt = cpu_to_le32(vvs->fwd_cnt);
        pkt->hdr.buf_alloc = cpu_to_le32(vvs->buf_alloc);
        spin_unlock_bh(&vvs->tx_lock);
@@ -261,6 +262,7 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
        struct virtio_vsock_sock *vvs = vsk->trans;
        struct virtio_vsock_pkt *pkt;
        size_t bytes, total = 0;
+       u32 free_space;
        int err = -EFAULT;
 
        spin_lock_bh(&vvs->rx_lock);
@@ -291,11 +293,19 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
                        virtio_transport_free_pkt(pkt);
                }
        }
+
+       free_space = vvs->buf_alloc - (vvs->fwd_cnt - vvs->last_fwd_cnt);
+
        spin_unlock_bh(&vvs->rx_lock);
 
-       /* Send a credit pkt to peer */
-       virtio_transport_send_credit_update(vsk, VIRTIO_VSOCK_TYPE_STREAM,
-                                           NULL);
+       /* We send a credit update only when the space available seen
+        * by the transmitter is less than VIRTIO_VSOCK_MAX_PKT_BUF_SIZE
+        */
+       if (free_space < VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) {
+               virtio_transport_send_credit_update(vsk,
+                                                   VIRTIO_VSOCK_TYPE_STREAM,
+                                                   NULL);
+       }
 
        return total;