[dpdk-dev] [RFC 4/8] net: don't touch mbuf next or nb segs on Rx

[Olivier Matz <olivier.matz@6wind.com>]

Now that the m->next pointer and m->nb_segs is expected to be set (to
NULL and 1 respectively) after a mempool_get(), we can avoid to write them
in the Rx functions of drivers.

Only some drivers are patched, it's not an exhaustive patch. It gives
the idea to do the same in other drivers.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
---
 drivers/net/i40e/i40e_rxtx_vec_sse.c    | 6 ------
 drivers/net/ixgbe/ixgbe_rxtx.c          | 8 --------
 drivers/net/ixgbe/ixgbe_rxtx_vec_neon.c | 6 ------
 drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c  | 6 ------
 drivers/net/null/rte_eth_null.c         | 2 --
 drivers/net/virtio/virtio_rxtx.c        | 3 ---
 6 files changed, 31 deletions(-)

diff --git a/drivers/net/i40e/i40e_rxtx_vec_sse.c b/drivers/net/i40e/i40e_rxtx_vec_sse.c
index 7c84a41..33bc121 100644
--- a/drivers/net/i40e/i40e_rxtx_vec_sse.c
+++ b/drivers/net/i40e/i40e_rxtx_vec_sse.c
@@ -403,12 +403,6 @@ _recv_raw_pkts_vec(struct i40e_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 			/* store the resulting 32-bit value */
 			*(int *)split_packet = _mm_cvtsi128_si32(eop_bits);
 			split_packet += RTE_I40E_DESCS_PER_LOOP;
-
-			/* zero-out next pointers */
-			rx_pkts[pos]->next = NULL;
-			rx_pkts[pos + 1]->next = NULL;
-			rx_pkts[pos + 2]->next = NULL;
-			rx_pkts[pos + 3]->next = NULL;
 		}
 
 		/* C.3 calc available number of desc */
diff --git a/drivers/net/ixgbe/ixgbe_rxtx.c b/drivers/net/ixgbe/ixgbe_rxtx.c
index dd53cc6..2c9e342 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx.c
@@ -1548,8 +1548,6 @@ ixgbe_rx_alloc_bufs(struct ixgbe_rx_queue *rxq, bool reset_mbuf)
 		/* populate the static rte mbuf fields */
 		mb = rxep[i].mbuf;
 		if (reset_mbuf) {
-			mb->next = NULL;
-			mb->nb_segs = 1;
 			mb->port = rxq->port_id;
 		}
 
@@ -2157,12 +2155,6 @@ ixgbe_recv_pkts_lro(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t nb_pkts,
 			goto next_desc;
 		}
 
-		/*
-		 * This is the last buffer of the received packet - return
-		 * the current cluster to the user.
-		 */
-		rxm->next = NULL;
-
 		/* Initialize the first mbuf of the returned packet */
 		ixgbe_fill_cluster_head_buf(first_seg, &rxd, rxq, staterr);
 
diff --git a/drivers/net/ixgbe/ixgbe_rxtx_vec_neon.c b/drivers/net/ixgbe/ixgbe_rxtx_vec_neon.c
index f96cc85..63f2556 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx_vec_neon.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx_vec_neon.c
@@ -333,12 +333,6 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 			*(int *)split_packet = ~stat & IXGBE_VPMD_DESC_EOP_MASK;
 
 			split_packet += RTE_IXGBE_DESCS_PER_LOOP;
-
-			/* zero-out next pointers */
-			rx_pkts[pos]->next = NULL;
-			rx_pkts[pos + 1]->next = NULL;
-			rx_pkts[pos + 2]->next = NULL;
-			rx_pkts[pos + 3]->next = NULL;
 		}
 
 		rte_prefetch_non_temporal(rxdp + RTE_IXGBE_DESCS_PER_LOOP);
diff --git a/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c b/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
index abbf284..65c5da3 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
@@ -425,12 +425,6 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 			/* store the resulting 32-bit value */
 			*(int *)split_packet = _mm_cvtsi128_si32(eop_bits);
 			split_packet += RTE_IXGBE_DESCS_PER_LOOP;
-
-			/* zero-out next pointers */
-			rx_pkts[pos]->next = NULL;
-			rx_pkts[pos + 1]->next = NULL;
-			rx_pkts[pos + 2]->next = NULL;
-			rx_pkts[pos + 3]->next = NULL;
 		}
 
 		/* C.3 calc available number of desc */
diff --git a/drivers/net/null/rte_eth_null.c b/drivers/net/null/rte_eth_null.c
index 57203e2..7e14da0 100644
--- a/drivers/net/null/rte_eth_null.c
+++ b/drivers/net/null/rte_eth_null.c
@@ -112,8 +112,6 @@ eth_null_rx(void *q, struct rte_mbuf **bufs, uint16_t nb_bufs)
 			break;
 		bufs[i]->data_len = (uint16_t)packet_size;
 		bufs[i]->pkt_len = packet_size;
-		bufs[i]->nb_segs = 1;
-		bufs[i]->next = NULL;
 		bufs[i]->port = h->internals->port_id;
 	}
 
diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index b29565e..111a983 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -761,7 +761,6 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t nb_pkts)
 		rxm->vlan_tci = 0;
 
 		rxm->nb_segs = 1;
-		rxm->next = NULL;
 		rxm->pkt_len = (uint32_t)(len[i] - hdr_size);
 		rxm->data_len = (uint16_t)(len[i] - hdr_size);
 
@@ -888,7 +887,6 @@ virtio_recv_mergeable_pkts(void *rx_queue,
 
 		rxm->data_off = RTE_PKTMBUF_HEADROOM;
 		rxm->nb_segs = seg_num;
-		rxm->next = NULL;
 		rxm->ol_flags = 0;
 		rxm->vlan_tci = 0;
 		rxm->pkt_len = (uint32_t)(len[0] - hdr_size);
@@ -933,7 +931,6 @@ virtio_recv_mergeable_pkts(void *rx_queue,
 				rxm = rcv_pkts[extra_idx];
 
 				rxm->data_off = RTE_PKTMBUF_HEADROOM - hdr_size;
-				rxm->next = NULL;
 				rxm->pkt_len = (uint32_t)(len[extra_idx]);
 				rxm->data_len = (uint16_t)(len[extra_idx]);
 
-- 
2.8.1