virtio: add packet buffering on tx

Type: feature

This patch adds packet buffering on tx for
slow backend which have some jitter/delays
in freeing the vrings.

There are some limitations to the current design:
1) It only works in poll mode.
2) Atleast 1 rx queue of an interface (with buffering
   enabled) should be placed on each worker and main thread.

Signed-off-by: Mohsin Kazmi <sykazmi@cisco.com>
Change-Id: Ib93c350298b228e80426e58ac77f3bbc93b8be27

1 files changed, 13 insertions, 0 deletions

diff --git a/src/vnet/devices/virtio/pci.c b/src/vnet/devices/virtio/pci.c
index df8e2bdaf68..71d813abfd7 100644
--- a/src/vnet/devices/virtio/pci.c
+++ b/src/vnet/devices/virtio/pci.c
@@ -1154,6 +1154,19 @@ virtio_pci_create_if (vlib_main_t * vm, virtio_pci_create_if_args_t * args)
 
   vnet_hw_interface_t *hw = vnet_get_hw_interface (vnm, vif->hw_if_index);
   hw->flags |= VNET_HW_INTERFACE_FLAG_SUPPORTS_INT_MODE;
+
+  if (args->virtio_flags & VIRTIO_FLAG_BUFFERING)
+    {
+      error = virtio_set_packet_buffering (vif, args->buffering_size);
+      if (error)
+	{
+	  args->rv = VNET_API_ERROR_INIT_FAILED;
+	  virtio_log_error (vif,
+			    "error encountered during packet buffering init");
+	  goto error;
+	}
+    }
+
   vnet_hw_interface_set_input_node (vnm, vif->hw_if_index,
 				    virtio_input_node.index);
   u32 i = 0;