[dpdk-dev] [PATCH 2/2] net/virtio: on demand cleanup when doing in order xmit

[Marvin Liu]

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

Signed-off-by: Marvin Liu <yong.liu at 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 5d4ed524e..550b0aa62 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -317,7 +317,7 @@ virtio_xmit_cleanup(struct virtqueue *vq, uint16_t num)
 }
 
 /* Cleanup from completed inorder transmits. */
-static void
+static __rte_always_inline void
 virtio_xmit_cleanup_inorder(struct virtqueue *vq, uint16_t num)
 {
 	uint16_t i, idx = vq->vq_used_cons_idx;
@@ -2152,6 +2152,21 @@ 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;
+	struct virtio_hw *hw = vq->hw;
+
+	nb_used = VIRTQUEUE_NUSED(vq);
+	virtio_rmb(hw->weak_barriers);
+	need = RTE_MIN(need, (int)nb_used);
+
+	virtio_xmit_cleanup_inorder(vq, need);
+
+	return (need - vq->vq_free_cnt);
+}
+
 uint16_t
 virtio_xmit_pkts_inorder(void *tx_queue,
 			struct rte_mbuf **tx_pkts,
@@ -2161,8 +2176,9 @@ 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 +2191,12 @@ 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) ||
@@ -2203,6 +2214,22 @@ virtio_xmit_pkts_inorder(void *tx_queue,
 		}
 
 		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;
@@ -2211,15 +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);
+			nb_left = virtio_xmit_try_cleanup_inorder(vq, need);
 
-			virtio_xmit_cleanup_inorder(vq, need);
-
-			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;
@@ -2232,9 +2253,23 @@ 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