For i40e vector Tx path, if tx_offload is set as FAST_FREE_MBUF mode,
no mbuf fast free operations are executed. To fix this, add mbuf fast
free mode for vector Tx path.

Furthermore, for i40e vector Tx path, if implement FAST_FREE_MBUF mode,
it means per-queue all mbufs come from the same mempool and have
refcnt = 1. Thus we can use bulk free of the buffers when mbuf fast free
mode is enabled.

For vector path in arm platform:
In n1sdp, performance is improved by 18.4%;
In thunderx2, performance is improved by 23%.

For vector path in x86 platform:
No performance changes.

Suggested-by: Ruifeng Wang <redacted>
Signed-off-by: Feifei Wang <redacted>
Reviewed-by: Ruifeng Wang <redacted>
---
 drivers/net/i40e/i40e_rxtx_vec_common.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/net/i40e/i40e_rxtx_vec_common.h b/drivers/net/i40e/i40e_rxtx_vec_common.h
index 16fcf0aec6..f52ed98d62 100644
--- a/drivers/net/i40e/i40e_rxtx_vec_common.h
+++ b/drivers/net/i40e/i40e_rxtx_vec_common.h

@@ -99,6 +99,16 @@ i40e_tx_free_bufs(struct i40e_tx_queue *txq)
 	  * tx_next_dd - (tx_rs_thresh-1)
 	  */
 	txep = &txq->sw_ring[txq->tx_next_dd - (n - 1)];
+
+	if (txq->offloads & DEV_TX_OFFLOAD_MBUF_FAST_FREE) {
+		for (i = 0; i < n; i++) {
+			free[i] = txep[i].mbuf;
+			txep[i].mbuf = NULL;
+		}
+		rte_mempool_put_bulk(free[0]->pool, (void **)free, n);
+		goto done;
+	}
+
 	m = rte_pktmbuf_prefree_seg(txep[0].mbuf);
 	if (likely(m != NULL)) {
 		free[0] = m;

@@ -126,6 +136,7 @@ i40e_tx_free_bufs(struct i40e_tx_queue *txq)
 		}
 	}
 
+done:
 	/* buffers were freed, update counters */
 	txq->nb_tx_free = (uint16_t)(txq->nb_tx_free + txq->tx_rs_thresh);
 	txq->tx_next_dd = (uint16_t)(txq->tx_next_dd + txq->tx_rs_thresh);

-- 
2.25.1