[dpdk-dev] [PATCH v1] ixgbe: remove vector pmd burst size restriction

[Cunming Liang]

The patch removes the restriction of burst size on a constant 32.

On receive side, the burst size floor now aligns to RTE_IXGBE_DESCS_PER_LOOP power of 2.
According to this rule, the burst size less than 4 still won't receive anything.
(Before this change, the burst size less than 32 can't receive anything.)

On transmit side, the max burst size no longer bind with a constant, however it still
require to check the cross tx_rs_thresh violation.

There's no obvious performance drop found on both recv_pkts_vec
and recv_scattered_pkts_vec on burst size 32.

Signed-off-by: Cunming Liang <cunming.liang at intel.com>
---
 drivers/net/ixgbe/ixgbe_rxtx.c     |  3 ++-
 drivers/net/ixgbe/ixgbe_rxtx.h     |  4 +---
 drivers/net/ixgbe/ixgbe_rxtx_vec.c | 35 ++++++++++++++++-------------------
 3 files changed, 19 insertions(+), 23 deletions(-)

diff --git a/drivers/net/ixgbe/ixgbe_rxtx.c b/drivers/net/ixgbe/ixgbe_rxtx.c
index 3f808b3..dbdb761 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx.c
@@ -4008,7 +4008,8 @@ ixgbe_set_rx_function(struct rte_eth_dev *dev)
 	 */
 	} else if (adapter->rx_vec_allowed) {
 		PMD_INIT_LOG(DEBUG, "Vector rx enabled, please make sure RX "
-				   "burst size no less than 32.");
+				    "burst size no less than 4 (port=%d).",
+			     dev->data->port_id);
 
 		dev->rx_pkt_burst = ixgbe_recv_pkts_vec;
 	} else if (adapter->rx_bulk_alloc_allowed) {
diff --git a/drivers/net/ixgbe/ixgbe_rxtx.h b/drivers/net/ixgbe/ixgbe_rxtx.h
index 113682a..eb931fe 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx.h
+++ b/drivers/net/ixgbe/ixgbe_rxtx.h
@@ -47,9 +47,7 @@
 	(uint64_t) ((mb)->buf_physaddr + RTE_PKTMBUF_HEADROOM)
 
 #ifdef RTE_IXGBE_INC_VECTOR
-#define RTE_IXGBE_VPMD_RX_BURST         32
-#define RTE_IXGBE_VPMD_TX_BURST         32
-#define RTE_IXGBE_RXQ_REARM_THRESH      RTE_IXGBE_VPMD_RX_BURST
+#define RTE_IXGBE_RXQ_REARM_THRESH      32
 #define RTE_IXGBE_TX_MAX_FREE_BUF_SZ    64
 #endif
 
diff --git a/drivers/net/ixgbe/ixgbe_rxtx_vec.c b/drivers/net/ixgbe/ixgbe_rxtx_vec.c
index 1c16dec..b72f817 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx_vec.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx_vec.c
@@ -199,13 +199,11 @@ desc_to_olflags_v(__m128i descs[4], struct rte_mbuf **rx_pkts)
 #endif
 
 /*
- * vPMD receive routine, now only accept (nb_pkts == RTE_IXGBE_VPMD_RX_BURST)
- * in one loop
+ * vPMD raw receive routine
  *
  * Notice:
- * - nb_pkts < RTE_IXGBE_VPMD_RX_BURST, just return no packet
- * - nb_pkts > RTE_IXGBE_VPMD_RX_BURST, only scan RTE_IXGBE_VPMD_RX_BURST
- *   numbers of DD bit
+ * - floor align nb_pkts to a RTE_IXGBE_DESC_PER_LOOP power-of-two
+ * - 'nb_pkts < 4' causes 0 packet receiving
  * - don't support ol_flags for rss and csum err
  */
 static inline uint16_t
@@ -240,8 +238,7 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 	__m128i dd_check, eop_check;
 #endif /* RTE_NEXT_ABI */
 
-	if (unlikely(nb_pkts < RTE_IXGBE_VPMD_RX_BURST))
-		return 0;
+	nb_pkts = RTE_ALIGN_FLOOR(nb_pkts, RTE_IXGBE_DESCS_PER_LOOP);
 
 	/* Just the act of getting into the function from the application is
 	 * going to cost about 7 cycles */
@@ -310,7 +307,7 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 	 * D. fill info. from desc to mbuf
 	 */
 #endif /* RTE_NEXT_ABI */
-	for (pos = 0, nb_pkts_recd = 0; pos < RTE_IXGBE_VPMD_RX_BURST;
+	for (pos = 0, nb_pkts_recd = 0; pos < nb_pkts;
 			pos += RTE_IXGBE_DESCS_PER_LOOP,
 			rxdp += RTE_IXGBE_DESCS_PER_LOOP) {
 		__m128i descs[RTE_IXGBE_DESCS_PER_LOOP];
@@ -450,13 +447,11 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 }
 
 /*
- * vPMD receive routine, now only accept (nb_pkts == RTE_IXGBE_VPMD_RX_BURST)
- * in one loop
+ * vPMD receive routine
  *
  * Notice:
- * - nb_pkts < RTE_IXGBE_VPMD_RX_BURST, just return no packet
- * - nb_pkts > RTE_IXGBE_VPMD_RX_BURST, only scan RTE_IXGBE_VPMD_RX_BURST
- *   numbers of DD bit
+ * - floor align nb_pkts to a RTE_IXGBE_DESC_PER_LOOP power-of-two
+ * - 'nb_pkts < 4' causes 0 packet receiving
  * - don't support ol_flags for rss and csum err
  */
 uint16_t
@@ -470,12 +465,11 @@ static inline uint16_t
 reassemble_packets(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_bufs,
 		uint16_t nb_bufs, uint8_t *split_flags)
 {
-	struct rte_mbuf *pkts[RTE_IXGBE_VPMD_RX_BURST]; /*finished pkts*/
+	struct rte_mbuf *pkts[nb_bufs]; /*finished pkts*/
 	struct rte_mbuf *start = rxq->pkt_first_seg;
 	struct rte_mbuf *end =  rxq->pkt_last_seg;
 	unsigned pkt_idx, buf_idx;
 
-
 	for (buf_idx = 0, pkt_idx = 0; buf_idx < nb_bufs; buf_idx++) {
 		if (end != NULL) {
 			/* processing a split packet */
@@ -535,14 +529,17 @@ reassemble_packets(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_bufs,
  *
  * Notice:
  * - don't support ol_flags for rss and csum err
- * - now only accept (nb_pkts == RTE_IXGBE_VPMD_RX_BURST)
+ * - will floor align nb_pkts to a RTE_IXGBE_DESC_PER_LOOP power-of-two
+ * - 'nb_pkts < 4' causes 0 packet receiving
  */
 uint16_t
 ixgbe_recv_scattered_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts,
 		uint16_t nb_pkts)
 {
 	struct ixgbe_rx_queue *rxq = rx_queue;
-	uint8_t split_flags[RTE_IXGBE_VPMD_RX_BURST] = {0};
+	uint8_t split_flags[nb_pkts];
+
+	memset(split_flags, 0, nb_pkts);
 
 	/* get some new buffers */
 	uint16_t nb_bufs = _recv_raw_pkts_vec(rxq, rx_pkts, nb_pkts,
@@ -667,8 +664,8 @@ ixgbe_xmit_pkts_vec(void *tx_queue, struct rte_mbuf **tx_pkts,
 	uint64_t rs = IXGBE_ADVTXD_DCMD_RS|DCMD_DTYP_FLAGS;
 	int i;
 
-	if (unlikely(nb_pkts > RTE_IXGBE_VPMD_TX_BURST))
-		nb_pkts = RTE_IXGBE_VPMD_TX_BURST;
+	/* cross rx_thresh boundary is not allowed */
+	nb_pkts = RTE_MIN(nb_pkts, txq->tx_rs_thresh);
 
 	if (txq->nb_tx_free < txq->tx_free_thresh)
 		ixgbe_tx_free_bufs(txq);
-- 
2.4.3