net/virtio: add Rx free threshold setting

Introduce free threshold setting in Rx queue, its default value is 32.
Limit the threshold size to multiple of four as only vectorized packed
Rx function will utilize it. Virtio driver will rearm Rx queue when
more than rx_free_thresh descs were dequeued.

Signed-off-by: Marvin Liu <yong.liu@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index 0604105..94ba7a3 100644 (file)
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -936,6 +936,7 @@ virtio_dev_rx_queue_setup(struct rte_eth_dev *dev,
        struct virtio_hw *hw = dev->data->dev_private;
        struct virtqueue *vq = hw->vqs[vtpci_queue_idx];
        struct virtnet_rx *rxvq;
+       uint16_t rx_free_thresh;
 
        PMD_INIT_FUNC_TRACE();
 
@@ -944,6 +945,28 @@ virtio_dev_rx_queue_setup(struct rte_eth_dev *dev,
                return -EINVAL;
        }
 
+       rx_free_thresh = rx_conf->rx_free_thresh;
+       if (rx_free_thresh == 0)
+               rx_free_thresh =
+                       RTE_MIN(vq->vq_nentries / 4, DEFAULT_RX_FREE_THRESH);
+
+       if (rx_free_thresh & 0x3) {
+               RTE_LOG(ERR, PMD, "rx_free_thresh must be multiples of four."
+                       " (rx_free_thresh=%u port=%u queue=%u)\n",
+                       rx_free_thresh, dev->data->port_id, queue_idx);
+               return -EINVAL;
+       }
+
+       if (rx_free_thresh >= vq->vq_nentries) {
+               RTE_LOG(ERR, PMD, "rx_free_thresh must be less than the "
+                       "number of RX entries (%u)."
+                       " (rx_free_thresh=%u port=%u queue=%u)\n",
+                       vq->vq_nentries,
+                       rx_free_thresh, dev->data->port_id, queue_idx);
+               return -EINVAL;
+       }
+       vq->vq_free_thresh = rx_free_thresh;
+
        if (nb_desc == 0 || nb_desc > vq->vq_nentries)
                nb_desc = vq->vq_nentries;
        vq->vq_free_cnt = RTE_MIN(vq->vq_free_cnt, nb_desc);

diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
index e3d38b5..011a67a 100644 (file)
--- a/drivers/net/virtio/virtqueue.h
+++ b/drivers/net/virtio/virtqueue.h
@@ -18,6 +18,8 @@
 
 struct rte_mbuf;
 
+#define DEFAULT_RX_FREE_THRESH 32
+
 /*
  * Per virtio_ring.h in Linux.
  *     For virtio_pci on SMP, we don't need to order with respect to MMIO