[PATCH v1] net/memif: remove extra mbuf refcnt update in zero copy Tx

[Liangxing Wang]

The refcnt update of stored mbufs in memif driver is redundant since
those mbufs are only freed in eth_memif_tx_zc(). No other place
can free those stored mbufs quietly. So remove the redundant mbuf
refcnt update in dpdk memif driver to avoid extra heavy cost.
Performance of dpdk memif zero copy tx is improved with this change.

Signed-off-by: Liangxing Wang <liangxing.wang at arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang at arm.com>
---
 drivers/net/memif/rte_eth_memif.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/net/memif/rte_eth_memif.c b/drivers/net/memif/rte_eth_memif.c
index 7cc8c0da91..962d390b90 100644
--- a/drivers/net/memif/rte_eth_memif.c
+++ b/drivers/net/memif/rte_eth_memif.c
@@ -265,8 +265,6 @@ memif_free_stored_mbufs(struct pmd_process_private *proc_private, struct memif_q
 	cur_tail = __atomic_load_n(&ring->tail, __ATOMIC_ACQUIRE);
 	while (mq->last_tail != cur_tail) {
 		RTE_MBUF_PREFETCH_TO_FREE(mq->buffers[(mq->last_tail + 1) & mask]);
-		/* Decrement refcnt and free mbuf. (current segment) */
-		rte_mbuf_refcnt_update(mq->buffers[mq->last_tail & mask], -1);
 		rte_pktmbuf_free_seg(mq->buffers[mq->last_tail & mask]);
 		mq->last_tail++;
 	}
@@ -825,10 +823,6 @@ memif_tx_one_zc(struct pmd_process_private *proc_private, struct memif_queue *mq
 next_in_chain:
 	/* store pointer to mbuf to free it later */
 	mq->buffers[slot & mask] = mbuf;
-	/* Increment refcnt to make sure the buffer is not freed before server
-	 * receives it. (current segment)
-	 */
-	rte_mbuf_refcnt_update(mbuf, 1);
 	/* populate descriptor */
 	d0 = &ring->desc[slot & mask];
 	d0->length = rte_pktmbuf_data_len(mbuf);
-- 
2.25.1