[dpdk-dev] [PATCH] net/sfc: remove unnecessary mbuf initialization on Rx path

[Andrew Rybchenko <arybchenko@solarflare.com>]

mbuf next is equal to NULL, nb_segs and reference counter are equal to 1
when mbuf is obtained from mempool.

Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
---
Depends on http://dpdk.org/ml/archives/dev/2017-March/059693.html

 drivers/net/sfc/sfc_ef10_rx.c | 18 +++++++++---------
 drivers/net/sfc/sfc_rx.c      |  6 +++---
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/net/sfc/sfc_ef10_rx.c b/drivers/net/sfc/sfc_ef10_rx.c
index 2a3bf89..1484bab 100644
--- a/drivers/net/sfc/sfc_ef10_rx.c
+++ b/drivers/net/sfc/sfc_ef10_rx.c
@@ -386,9 +386,8 @@ sfc_ef10_rx_process_event(struct sfc_ef10_rxq *rxq, efx_qword_t rx_ev,
 
 	*rx_pkts++ = m;
 
-	*(uint64_t *)(&m->rearm_data) = rxq->rearm_data;
-	/* rearm_data rewrites ol_flags which is updated below */
-	rte_compiler_barrier();
+	RTE_BUILD_BUG_ON(sizeof(m->rearm_data[0]) != sizeof(rxq->rearm_data));
+	m->rearm_data[0] = rxq->rearm_data;
 
 	/* Classify packet based on Rx event */
 	sfc_ef10_rx_ev_to_offloads(rxq, rx_ev, m);
@@ -412,7 +411,7 @@ sfc_ef10_rx_process_event(struct sfc_ef10_rxq *rxq, efx_qword_t rx_ev,
 	rte_pktmbuf_data_len(m) = pkt_len;
 	rte_pktmbuf_pkt_len(m) = pkt_len;
 
-	m->next = NULL;
+	SFC_ASSERT(m->next == NULL);
 
 	/* Remember mbuf to copy offload flags and packet type from */
 	m0 = m;
@@ -426,9 +425,9 @@ sfc_ef10_rx_process_event(struct sfc_ef10_rxq *rxq, efx_qword_t rx_ev,
 		if (ready > rxq->prepared)
 			*rx_pkts++ = m;
 
-		*(uint64_t *)(&m->rearm_data) = rxq->rearm_data;
-		/* rearm_data rewrites ol_flags which is updated below */
-		rte_compiler_barrier();
+		RTE_BUILD_BUG_ON(sizeof(m->rearm_data[0]) !=
+				 sizeof(rxq->rearm_data));
+		m->rearm_data[0] = rxq->rearm_data;
 
 		/* Event-dependent information is the same */
 		m->ol_flags = m0->ol_flags;
@@ -449,7 +448,7 @@ sfc_ef10_rx_process_event(struct sfc_ef10_rxq *rxq, efx_qword_t rx_ev,
 		rte_pktmbuf_data_len(m) = pkt_len;
 		rte_pktmbuf_pkt_len(m) = pkt_len;
 
-		m->next = NULL;
+		SFC_ASSERT(m->next == NULL);
 	}
 
 	return n_rx_pkts;
@@ -560,7 +559,8 @@ sfc_ef10_mk_mbuf_rearm_data(uint16_t port_id, uint16_t prefix_size)
 
 	/* rearm_data covers structure members filled in above */
 	rte_compiler_barrier();
-	return *(uint64_t *)(&m.rearm_data);
+	RTE_BUILD_BUG_ON(sizeof(m.rearm_data[0]) != sizeof(uint64_t));
+	return m.rearm_data[0];
 }
 
 static sfc_dp_rx_qcreate_t sfc_ef10_rx_qcreate;
diff --git a/drivers/net/sfc/sfc_rx.c b/drivers/net/sfc/sfc_rx.c
index 56130b2..ddf9217 100644
--- a/drivers/net/sfc/sfc_rx.c
+++ b/drivers/net/sfc/sfc_rx.c
@@ -122,10 +122,10 @@ sfc_efx_rx_qrefill(struct sfc_efx_rxq *rxq)
 			rxd = &rxq->sw_desc[id];
 			rxd->mbuf = m;
 
-			rte_mbuf_refcnt_set(m, 1);
+			SFC_ASSERT(rte_mbuf_refcnt_read(m) == 1);
 			m->data_off = RTE_PKTMBUF_HEADROOM;
-			m->next = NULL;
-			m->nb_segs = 1;
+			SFC_ASSERT(m->next == NULL);
+			SFC_ASSERT(m->nb_segs == 1);
 			m->port = port_id;
 
 			addr[i] = rte_pktmbuf_mtophys(m);
-- 
2.7.4