fix buffer allocation for sparse jumbo frames in vhost

A bug was reported where a jumbo packet would stay in vhost
queue forever or until a large enough number of other packets
arrived in the queue too.

This is due to a bug in vhost input node buffer allocation.

The fix is to make sure that vhost always allocates at least
enough buffers for one single big packet. '40' is used to
account for 65kB frames.

Change-Id: I1d293028854165083e30cd798fab9d4140230b78
Signed-off-by: Pierre Pfister <ppfister@cisco.com>
(cherry picked from commit 67700d41169ac37d21c400949a316750eabad969)

diff --git a/src/vnet/devices/virtio/vhost-user.c b/src/vnet/devices/virtio/vhost-user.c
index ca54f11..6b2c898 100644 (file)
--- a/src/vnet/devices/virtio/vhost-user.c
+++ b/src/vnet/devices/virtio/vhost-user.c
@@ -1545,8 +1545,10 @@ vhost_user_if_input (vlib_main_t * vm,
    * per packet. In case packets are bigger, we will just yeld at some point
    * in the loop and come back later. This is not an issue as for big packet,
    * processing cost really comes from the memory copy.
+   * The assumption is that big packets will fit in 40 buffers.
    */
-  if (PREDICT_FALSE (vum->cpus[thread_index].rx_buffers_len < n_left + 1))
+  if (PREDICT_FALSE (vum->cpus[thread_index].rx_buffers_len < n_left + 1 ||
+                    vum->cpus[thread_index].rx_buffers_len < 40))
     {
       u32 curr_len = vum->cpus[thread_index].rx_buffers_len;
       vum->cpus[thread_index].rx_buffers_len +=