[PATCH v4 6/8] net/mlx4: separate Tx segment cases

[Matan Azrad <matan@mellanox.com>]

Optimize single segment case by processing it in different block which
prevents checks, calculations and barriers relevant only for multi
segment case.

Call a dedicated function for handling multi segments case.

Signed-off-by: Matan Azrad <matan@mellanox.com>
Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
---
 drivers/net/mlx4/mlx4_rxtx.c | 236 +++++++++++++++++++++++++++----------------
 1 file changed, 151 insertions(+), 85 deletions(-)

diff --git a/drivers/net/mlx4/mlx4_rxtx.c b/drivers/net/mlx4/mlx4_rxtx.c
index 0a6cbf1..176000f 100644
--- a/drivers/net/mlx4/mlx4_rxtx.c
+++ b/drivers/net/mlx4/mlx4_rxtx.c
@@ -62,6 +62,9 @@
 #include "mlx4_rxtx.h"
 #include "mlx4_utils.h"
 
+#define WQE_ONE_DATA_SEG_SIZE \
+	(sizeof(struct mlx4_wqe_ctrl_seg) + sizeof(struct mlx4_wqe_data_seg))
+
 /**
  * Pointer-value pair structure used in tx_post_send for saving the first
  * DWORD (32 byte) of a TXBB.
@@ -141,21 +144,18 @@ struct pv {
  *   0 on success, -1 on failure.
  */
 static int
-mlx4_txq_complete(struct txq *txq)
+mlx4_txq_complete(struct txq *txq, const unsigned int elts_n,
+				  struct mlx4_sq *sq)
 {
 	unsigned int elts_comp = txq->elts_comp;
 	unsigned int elts_tail = txq->elts_tail;
-	const unsigned int elts_n = txq->elts_n;
 	struct mlx4_cq *cq = &txq->mcq;
-	struct mlx4_sq *sq = &txq->msq;
 	struct mlx4_cqe *cqe;
 	uint32_t cons_index = cq->cons_index;
 	uint16_t new_index;
 	uint16_t nr_txbbs = 0;
 	int pkts = 0;
 
-	if (unlikely(elts_comp == 0))
-		return 0;
 	/*
 	 * Traverse over all CQ entries reported and handle each WQ entry
 	 * reported by them.
@@ -238,6 +238,119 @@ struct pv {
 	return buf->pool;
 }
 
+static int
+mlx4_tx_burst_segs(struct rte_mbuf *buf, struct txq *txq,
+			       struct mlx4_wqe_ctrl_seg **pctrl)
+{
+	int wqe_real_size;
+	int nr_txbbs;
+	struct pv *pv = (struct pv *)txq->bounce_buf;
+	struct mlx4_sq *sq = &txq->msq;
+	uint32_t head_idx = sq->head & sq->txbb_cnt_mask;
+	struct mlx4_wqe_ctrl_seg *ctrl;
+	struct mlx4_wqe_data_seg *dseg;
+	struct rte_mbuf *sbuf;
+	uint32_t lkey;
+	uintptr_t addr;
+	uint32_t byte_count;
+	int pv_counter = 0;
+
+	/* Calculate the needed work queue entry size for this packet. */
+	wqe_real_size = sizeof(struct mlx4_wqe_ctrl_seg) +
+		buf->nb_segs * sizeof(struct mlx4_wqe_data_seg);
+	nr_txbbs = MLX4_SIZE_TO_TXBBS(wqe_real_size);
+	/*
+	 * Check that there is room for this WQE in the send queue and that
+	 * the WQE size is legal.
+	 */
+	if (((sq->head - sq->tail) + nr_txbbs +
+				sq->headroom_txbbs) >= sq->txbb_cnt ||
+			nr_txbbs > MLX4_MAX_WQE_TXBBS) {
+		return -1;
+	}
+	/* Get the control and data entries of the WQE. */
+	ctrl = (struct mlx4_wqe_ctrl_seg *)mlx4_get_send_wqe(sq, head_idx);
+	dseg = (struct mlx4_wqe_data_seg *)((uintptr_t)ctrl +
+			sizeof(struct mlx4_wqe_ctrl_seg));
+	*pctrl = ctrl;
+	/* Fill the data segments with buffer information. */
+	for (sbuf = buf; sbuf != NULL; sbuf = sbuf->next, dseg++) {
+		addr = rte_pktmbuf_mtod(sbuf, uintptr_t);
+		rte_prefetch0((volatile void *)addr);
+		/* Handle WQE wraparound. */
+		if (dseg >= (struct mlx4_wqe_data_seg *)sq->eob)
+			dseg = (struct mlx4_wqe_data_seg *)sq->buf;
+		dseg->addr = rte_cpu_to_be_64(addr);
+		/* Memory region key (big endian) for this memory pool. */
+		lkey = mlx4_txq_mp2mr(txq, mlx4_txq_mb2mp(sbuf));
+		dseg->lkey = rte_cpu_to_be_32(lkey);
+#ifndef NDEBUG
+		/* Calculate the needed work queue entry size for this packet */
+		if (unlikely(dseg->lkey == rte_cpu_to_be_32((uint32_t)-1))) {
+			/* MR does not exist. */
+			DEBUG("%p: unable to get MP <-> MR association",
+					(void *)txq);
+			/*
+			 * Restamp entry in case of failure.
+			 * Make sure that size is written correctly
+			 * Note that we give ownership to the SW, not the HW.
+			 */
+			wqe_real_size = sizeof(struct mlx4_wqe_ctrl_seg) +
+				buf->nb_segs * sizeof(struct mlx4_wqe_data_seg);
+			ctrl->fence_size = (wqe_real_size >> 4) & 0x3f;
+			mlx4_txq_stamp_freed_wqe(sq, head_idx,
+					(sq->head & sq->txbb_cnt) ? 0 : 1);
+			return -1;
+		}
+#endif /* NDEBUG */
+		if (likely(sbuf->data_len)) {
+			byte_count = rte_cpu_to_be_32(sbuf->data_len);
+		} else {
+			/*
+			 * Zero length segment is treated as inline segment
+			 * with zero data.
+			 */
+			byte_count = RTE_BE32(0x80000000);
+		}
+		/*
+		 * If the data segment is not at the beginning of a
+		 * Tx basic block (TXBB) then write the byte count,
+		 * else postpone the writing to just before updating the
+		 * control segment.
+		 */
+		if ((uintptr_t)dseg & (uintptr_t)(MLX4_TXBB_SIZE - 1)) {
+			/*
+			 * Need a barrier here before writing the byte_count
+			 * fields to make sure that all the data is visible
+			 * before the byte_count field is set.
+			 * Otherwise, if the segment begins a new cacheline,
+			 * the HCA prefetcher could grab the 64-byte chunk and
+			 * get a valid (!= 0xffffffff) byte count but stale
+			 * data, and end up sending the wrong data.
+			 */
+			rte_io_wmb();
+			dseg->byte_count = byte_count;
+		} else {
+			/*
+			 * This data segment starts at the beginning of a new
+			 * TXBB, so we need to postpone its byte_count writing
+			 * for later.
+			 */
+			pv[pv_counter].dseg = dseg;
+			pv[pv_counter++].val = byte_count;
+		}
+	}
+	/* Write the first DWORD of each TXBB save earlier. */
+	if (pv_counter) {
+		/* Need a barrier here before writing the byte_count. */
+		rte_io_wmb();
+		for (--pv_counter; pv_counter  >= 0; pv_counter--)
+			pv[pv_counter].dseg->byte_count = pv[pv_counter].val;
+	}
+	/* Fill the control parameters for this packet. */
+	ctrl->fence_size = (wqe_real_size >> 4) & 0x3f;
+	return nr_txbbs;
+}
 /**
  * DPDK callback for Tx.
  *
@@ -261,10 +374,11 @@ struct pv {
 	unsigned int i;
 	unsigned int max;
 	struct mlx4_sq *sq = &txq->msq;
-	struct pv *pv = (struct pv *)txq->bounce_buf;
+	int nr_txbbs;
 
 	assert(txq->elts_comp_cd != 0);
-	mlx4_txq_complete(txq);
+	if (likely(txq->elts_comp != 0))
+		mlx4_txq_complete(txq, elts_n, sq);
 	max = (elts_n - (elts_head - txq->elts_tail));
 	if (max > elts_n)
 		max -= elts_n;
@@ -283,7 +397,6 @@ struct pv {
 		uint32_t owner_opcode = MLX4_OPCODE_SEND;
 		struct mlx4_wqe_ctrl_seg *ctrl;
 		struct mlx4_wqe_data_seg *dseg;
-		struct rte_mbuf *sbuf;
 		union {
 			uint32_t flags;
 			uint16_t flags16[2];
@@ -291,10 +404,6 @@ struct pv {
 		uint32_t head_idx = sq->head & sq->txbb_cnt_mask;
 		uint32_t lkey;
 		uintptr_t addr;
-		uint32_t byte_count;
-		int wqe_real_size;
-		int nr_txbbs;
-		int pv_counter = 0;
 
 		/* Clean up old buffer. */
 		if (likely(elt->buf != NULL)) {
@@ -313,38 +422,29 @@ struct pv {
 			} while (tmp != NULL);
 		}
 		RTE_MBUF_PREFETCH_TO_FREE(elt_next->buf);
-		/*
-		 * Calculate the needed work queue entry size
-		 * for this packet.
-		 */
-		wqe_real_size = sizeof(struct mlx4_wqe_ctrl_seg) +
-				buf->nb_segs * sizeof(struct mlx4_wqe_data_seg);
-		nr_txbbs = MLX4_SIZE_TO_TXBBS(wqe_real_size);
-		/*
-		 * Check that there is room for this WQE in the send
-		 * queue and that the WQE size is legal.
-		 */
-		if (((sq->head - sq->tail) + nr_txbbs +
-		     sq->headroom_txbbs) >= sq->txbb_cnt ||
-		    nr_txbbs > MLX4_MAX_WQE_TXBBS) {
-			elt->buf = NULL;
-			break;
-		}
-		/* Get the control and data entries of the WQE. */
-		ctrl = (struct mlx4_wqe_ctrl_seg *)
-				mlx4_get_send_wqe(sq, head_idx);
-		dseg = (struct mlx4_wqe_data_seg *)((uintptr_t)ctrl +
-				sizeof(struct mlx4_wqe_ctrl_seg));
-		/* Fill the data segments with buffer information. */
-		for (sbuf = buf; sbuf != NULL; sbuf = sbuf->next, dseg++) {
-			addr = rte_pktmbuf_mtod(sbuf, uintptr_t);
+		if (buf->nb_segs == 1) {
+			/*
+			 * Check that there is room for this WQE in the send
+			 * queue and that the WQE size is legal
+			 */
+			if (((sq->head - sq->tail) + 1 + sq->headroom_txbbs) >=
+			     sq->txbb_cnt || 1 > MLX4_MAX_WQE_TXBBS) {
+				elt->buf = NULL;
+				break;
+			}
+			/* Get the control and data entries of the WQE. */
+			ctrl = (struct mlx4_wqe_ctrl_seg *)
+					mlx4_get_send_wqe(sq, head_idx);
+			dseg = (struct mlx4_wqe_data_seg *)((uintptr_t)ctrl +
+					sizeof(struct mlx4_wqe_ctrl_seg));
+			addr = rte_pktmbuf_mtod(buf, uintptr_t);
 			rte_prefetch0((volatile void *)addr);
 			/* Handle WQE wraparound. */
 			if (dseg >= (struct mlx4_wqe_data_seg *)sq->eob)
 				dseg = (struct mlx4_wqe_data_seg *)sq->buf;
 			dseg->addr = rte_cpu_to_be_64(addr);
 			/* Memory region key (big endian). */
-			lkey = mlx4_txq_mp2mr(txq, mlx4_txq_mb2mp(sbuf));
+			lkey = mlx4_txq_mp2mr(txq, mlx4_txq_mb2mp(buf));
 			dseg->lkey = rte_cpu_to_be_32(lkey);
 #ifndef NDEBUG
 			if (unlikely(dseg->lkey ==
@@ -358,61 +458,27 @@ struct pv {
 				 * Note that we give ownership to the SW,
 				 * not the HW.
 				 */
-				ctrl->fence_size = (wqe_real_size >> 4) & 0x3f;
+				ctrl->fence_size =
+					(WQE_ONE_DATA_SEG_SIZE >> 4) & 0x3f;
 				mlx4_txq_stamp_freed_wqe(sq, head_idx,
 					     (sq->head & sq->txbb_cnt) ? 0 : 1);
 				elt->buf = NULL;
 				break;
 			}
 #endif /* NDEBUG */
-			if (likely(sbuf->data_len)) {
-				byte_count = rte_cpu_to_be_32(sbuf->data_len);
-			} else {
-				/*
-				 * Zero length segment is treated as inline
-				 * segment with zero data.
-				 */
-				byte_count = RTE_BE32(0x80000000);
-			}
-			/*
-			 * If the data segment is not at the beginning
-			 * of a Tx basic block (TXBB) then write the
-			 * byte count, else postpone the writing to
-			 * just before updating the control segment.
-			 */
-			if ((uintptr_t)dseg & (uintptr_t)(MLX4_TXBB_SIZE - 1)) {
-				/*
-				 * Need a barrier here before writing the
-				 * byte_count fields to make sure that all the
-				 * data is visible before the byte_count field
-				 * is set. otherwise, if the segment begins a
-				 * new cacheline, the HCA prefetcher could grab
-				 * the 64-byte chunk and get a valid
-				 * (!= 0xffffffff) byte count but stale data,
-				 * and end up sending the wrong data.
-				 */
-				rte_io_wmb();
-				dseg->byte_count = byte_count;
-			} else {
-				/*
-				 * This data segment starts at the beginning of
-				 * a new TXBB, so we need to postpone its
-				 * byte_count writing for later.
-				 */
-				pv[pv_counter].dseg = dseg;
-				pv[pv_counter++].val = byte_count;
-			}
-		}
-		/* Write the first DWORD of each TXBB save earlier. */
-		if (pv_counter) {
-			/* Need a barrier before writing the byte_count. */
+			/* Need a barrier here before byte count store. */
 			rte_io_wmb();
-			for (--pv_counter; pv_counter  >= 0; pv_counter--)
-				pv[pv_counter].dseg->byte_count =
-						pv[pv_counter].val;
+			dseg->byte_count = rte_cpu_to_be_32(buf->data_len);
+			/* Fill the control parameters for this packet. */
+			ctrl->fence_size = (WQE_ONE_DATA_SEG_SIZE >> 4) & 0x3f;
+			nr_txbbs = 1;
+		} else {
+			nr_txbbs = mlx4_tx_burst_segs(buf, txq, &ctrl);
+			if (nr_txbbs < 0) {
+				elt->buf = NULL;
+				break;
+			}
 		}
-		/* Fill the control parameters for this packet. */
-		ctrl->fence_size = (wqe_real_size >> 4) & 0x3f;
 		/*
 		 * For raw Ethernet, the SOLICIT flag is used to indicate
 		 * that no ICRC should be calculated.
-- 
1.8.3.1