[dpdk-dev] [PATCH v2 14/15] net/enic: cap Rx packet processing to end of desc ring

[John Daley <johndale@cisco.com>]

In the default Rx handler stop processing packets at the end of
the completion ring so that wrapping doesn't have to be checked
in the inner while loop.

Also, check the color bit in the completion without using a conditional.

Signed-off-by: John Daley <johndale@cisco.com>
Reviewed-by: Hyong Youb Kim <hyonkim@cisco.com>
---
 drivers/net/enic/enic_rxtx.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/drivers/net/enic/enic_rxtx.c b/drivers/net/enic/enic_rxtx.c
index e0f93dd5e..7ae03f31b 100644
--- a/drivers/net/enic/enic_rxtx.c
+++ b/drivers/net/enic/enic_rxtx.c
@@ -310,7 +310,7 @@ enic_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
 	struct vnic_rq *rq;
 	struct enic *enic = vnic_dev_priv(sop_rq->vdev);
 	uint16_t cq_idx;
-	uint16_t rq_idx;
+	uint16_t rq_idx, max_rx;
 	uint16_t rq_num;
 	struct rte_mbuf *nmb, *rxmb;
 	uint16_t nb_rx = 0;
@@ -325,19 +325,23 @@ enic_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
 	cq = &enic->cq[enic_cq_rq(enic, sop_rq->index)];
 	cq_idx = cq->to_clean;		/* index of cqd, rqd, mbuf_table */
 	cqd_ptr = (struct cq_desc *)(cq->ring.descs) + cq_idx;
+	color = cq->last_color;
 
 	data_rq = &enic->rq[sop_rq->data_queue_idx];
 
-	while (nb_rx < nb_pkts) {
+	/* Receive until the end of the ring, at most. */
+	max_rx = RTE_MIN(nb_pkts, cq->ring.desc_count - cq_idx);
+
+	while (max_rx) {
 		volatile struct rq_enet_desc *rqd_ptr;
 		struct cq_desc cqd;
 		uint8_t packet_error;
 		uint16_t ciflags;
 
+		max_rx--;
+
 		/* Check for pkts available */
-		color = (cqd_ptr->type_color >> CQ_DESC_COLOR_SHIFT)
-			& CQ_DESC_COLOR_MASK;
-		if (color == cq->last_color)
+		if ((cqd_ptr->type_color & CQ_DESC_COLOR_MASK_NOSHIFT) == color)
 			break;
 
 		/* Get the cq descriptor and extract rq info from it */
@@ -361,13 +365,7 @@ enic_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
 		/* Get the mbuf to return and replace with one just allocated */
 		rxmb = rq->mbuf_ring[rq_idx];
 		rq->mbuf_ring[rq_idx] = nmb;
-
-		/* Increment cqd, rqd, mbuf_table index */
 		cq_idx++;
-		if (unlikely(cq_idx == cq->ring.desc_count)) {
-			cq_idx = 0;
-			cq->last_color = cq->last_color ? 0 : 1;
-		}
 
 		/* Prefetch next mbuf & desc while processing current one */
 		cqd_ptr = (struct cq_desc *)(cq->ring.descs) + cq_idx;
@@ -419,6 +417,7 @@ enic_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
 		first_seg->packet_type =
 			enic_cq_rx_flags_to_pkt_type(&cqd, tnl);
 		enic_cq_rx_to_pkt_flags(&cqd, first_seg);
+
 		/* Wipe the outer types set by enic_cq_rx_flags_to_pkt_type() */
 		if (tnl) {
 			first_seg->packet_type &= ~(RTE_PTYPE_L3_MASK |
@@ -438,6 +437,10 @@ enic_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
 		/* store the mbuf address into the next entry of the array */
 		rx_pkts[nb_rx++] = first_seg;
 	}
+	if (unlikely(cq_idx == cq->ring.desc_count)) {
+		cq_idx = 0;
+		cq->last_color ^= CQ_DESC_COLOR_MASK_NOSHIFT;
+	}
 
 	sop_rq->pkt_first_seg = first_seg;
 	sop_rq->pkt_last_seg = last_seg;
-- 
2.16.2