Check whether space are enough before burst enqueue operation. If more
space is needed, will try to cleanup used descriptors for space on
demand. It can give more chances to free used descriptors, thus will
help RFC2544 performance.

Signed-off-by: Marvin Liu <yong....@intel.com>
---
 drivers/net/virtio/virtio_rxtx.c | 73 +++++++++++++++++++++++---------
 1 file changed, 54 insertions(+), 19 deletions(-)

diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index d3ca36831..842b600c3 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -2152,6 +2152,22 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf 
**tx_pkts, uint16_t nb_pkts)
        return nb_tx;
 }
 
+static __rte_always_inline int
+virtio_xmit_try_cleanup_inorder(struct virtqueue *vq, uint16_t need)
+{
+       uint16_t nb_used, nb_clean, nb_descs;
+       struct virtio_hw *hw = vq->hw;
+
+       nb_descs = vq->vq_free_cnt + need;
+       nb_used = VIRTQUEUE_NUSED(vq);
+       virtio_rmb(hw->weak_barriers);
+       nb_clean = RTE_MIN(need, (int)nb_used);
+
+       virtio_xmit_cleanup_inorder(vq, nb_clean);
+
+       return (nb_descs - vq->vq_free_cnt);
+}
+
 uint16_t
 virtio_xmit_pkts_inorder(void *tx_queue,
                        struct rte_mbuf **tx_pkts,
@@ -2161,8 +2177,9 @@ virtio_xmit_pkts_inorder(void *tx_queue,
        struct virtqueue *vq = txvq->vq;
        struct virtio_hw *hw = vq->hw;
        uint16_t hdr_size = hw->vtnet_hdr_size;
-       uint16_t nb_used, nb_avail, nb_tx = 0, nb_inorder_pkts = 0;
+       uint16_t nb_used, nb_tx = 0, nb_inorder_pkts = 0;
        struct rte_mbuf *inorder_pkts[nb_pkts];
+       int need, nb_left;
 
        if (unlikely(hw->started == 0 && tx_pkts != hw->inject_pkts))
                return nb_tx;
@@ -2175,17 +2192,12 @@ virtio_xmit_pkts_inorder(void *tx_queue,
        nb_used = VIRTQUEUE_NUSED(vq);
 
        virtio_rmb(hw->weak_barriers);
-       if (likely(nb_used > vq->vq_nentries - vq->vq_free_thresh))
-               virtio_xmit_cleanup_inorder(vq, nb_used);
-
-       if (unlikely(!vq->vq_free_cnt))
+       if (likely(nb_used > (vq->vq_nentries - vq->vq_free_thresh)))
                virtio_xmit_cleanup_inorder(vq, nb_used);
 
-       nb_avail = RTE_MIN(vq->vq_free_cnt, nb_pkts);
-
-       for (nb_tx = 0; nb_tx < nb_avail; nb_tx++) {
+       for (nb_tx = 0; nb_tx < nb_pkts; nb_tx++) {
                struct rte_mbuf *txm = tx_pkts[nb_tx];
-               int slots, need;
+               int slots;
 
                /* optimize ring usage */
                if ((vtpci_with_feature(hw, VIRTIO_F_ANY_LAYOUT) ||
@@ -2199,11 +2211,25 @@ virtio_xmit_pkts_inorder(void *tx_queue,
                        inorder_pkts[nb_inorder_pkts] = txm;
                        nb_inorder_pkts++;
 
-                       virtio_update_packet_stats(&txvq->stats, txm);
                        continue;
                }
 
                if (nb_inorder_pkts) {
+                       need = nb_inorder_pkts - vq->vq_free_cnt;
+
+                       if (unlikely(need > 0)) {
+                               nb_left = virtio_xmit_try_cleanup_inorder(vq,
+                                                                       need);
+
+                               if (unlikely(nb_left > 0)) {
+                                       PMD_TX_LOG(ERR,
+                                               "No free tx descriptors to "
+                                               "transmit");
+                                       nb_inorder_pkts = vq->vq_free_cnt;
+                                       break;
+                               }
+                       }
+
                        virtqueue_enqueue_xmit_inorder(txvq, inorder_pkts,
                                                        nb_inorder_pkts);
                        nb_inorder_pkts = 0;
@@ -2212,15 +2238,9 @@ virtio_xmit_pkts_inorder(void *tx_queue,
                slots = txm->nb_segs + 1;
                need = slots - vq->vq_free_cnt;
                if (unlikely(need > 0)) {
-                       nb_used = VIRTQUEUE_NUSED(vq);
-                       virtio_rmb(hw->weak_barriers);
-                       need = RTE_MIN(need, (int)nb_used);
-
-                       virtio_xmit_cleanup_inorder(vq, need);
+                       nb_left = virtio_xmit_try_cleanup_inorder(vq, slots);
 
-                       need = slots - vq->vq_free_cnt;
-
-                       if (unlikely(need > 0)) {
+                       if (unlikely(nb_left > 0)) {
                                PMD_TX_LOG(ERR,
                                        "No free tx descriptors to transmit");
                                break;
@@ -2233,9 +2253,24 @@ virtio_xmit_pkts_inorder(void *tx_queue,
        }
 
        /* Transmit all inorder packets */
-       if (nb_inorder_pkts)
+       if (nb_inorder_pkts) {
+               need = nb_inorder_pkts - vq->vq_free_cnt;
+
+               if (unlikely(need > 0)) {
+                       nb_left = virtio_xmit_try_cleanup_inorder(vq,
+                                                                 need);
+
+                       if (unlikely(nb_left > 0)) {
+                               PMD_TX_LOG(ERR,
+                                       "No free tx descriptors to transmit");
+                               nb_inorder_pkts = vq->vq_free_cnt;
+                               nb_tx -= nb_left;
+                       }
+               }
+
                virtqueue_enqueue_xmit_inorder(txvq, inorder_pkts,
                                                nb_inorder_pkts);
+       }
 
        txvq->stats.packets += nb_tx;
 
-- 
2.17.1

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