[dpdk-dev] [PATCH 3/5] net/mlx5: use buffer address for LKEY search

[Yongseok Koh <yskoh@mellanox.com>]

When searching LKEY, if search key is mempool pointer, the 2nd cacheline
has to be accessed and it even requires to check whether a buffer is
indirect per every search. Instead, using address for search key can reduce
cycles taken. And caching the last hit entry is beneficial as well.

Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
---
 drivers/net/mlx5/mlx5_mr.c   |  2 ++
 drivers/net/mlx5/mlx5_rxtx.c | 37 ++++++++++++++++++++-----------------
 drivers/net/mlx5/mlx5_rxtx.h |  3 +++
 3 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_mr.c b/drivers/net/mlx5/mlx5_mr.c
index 0a3638460..f2484cb06 100644
--- a/drivers/net/mlx5/mlx5_mr.c
+++ b/drivers/net/mlx5/mlx5_mr.c
@@ -207,6 +207,8 @@ txq_mp2mr_reg(struct txq *txq, struct rte_mempool *mp, unsigned int idx)
 			 sizeof(txq_ctrl->txq.mp2mr[0])));
 	}
 	/* Store the new entry. */
+	txq_ctrl->txq.mp2mr[idx].start = (uintptr_t)mr->addr;
+	txq_ctrl->txq.mp2mr[idx].end = (uintptr_t)mr->addr + mr->length;
 	txq_ctrl->txq.mp2mr[idx].mp = mp;
 	txq_ctrl->txq.mp2mr[idx].mr = mr;
 	txq_ctrl->txq.mp2mr[idx].lkey = htonl(mr->lkey);
diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index d81d630f7..5cc38ccb7 100644
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -77,7 +77,7 @@ static __rte_always_inline void
 txq_complete(struct txq *txq);
 
 static __rte_always_inline uint32_t
-txq_mp2mr(struct txq *txq, struct rte_mempool *mp);
+txq_mb2mr(struct txq *txq, struct rte_mbuf *mb);
 
 static __rte_always_inline void
 mlx5_tx_dbrec(struct txq *txq, volatile struct mlx5_wqe *wqe);
@@ -355,7 +355,7 @@ txq_mb2mp(struct rte_mbuf *buf)
 }
 
 /**
- * Get Memory Region (MR) <-> Memory Pool (MP) association from txq->mp2mr[].
+ * Get Memory Region (MR) <-> rte_mbuf association from txq->mp2mr[].
  * Add MP to txq->mp2mr[] if it's not registered yet. If mp2mr[] is full,
  * remove an entry first.
  *
@@ -368,27 +368,30 @@ txq_mb2mp(struct rte_mbuf *buf)
  *   mr->lkey on success, (uint32_t)-1 on failure.
  */
 static inline uint32_t
-txq_mp2mr(struct txq *txq, struct rte_mempool *mp)
+txq_mb2mr(struct txq *txq, struct rte_mbuf *mb)
 {
-	unsigned int i;
-	uint32_t lkey = (uint32_t)-1;
+	uint16_t i = txq->mr_cache_idx;
+	uintptr_t addr = rte_pktmbuf_mtod(mb, uintptr_t);
 
+	assert(i < RTE_DIM(txq->mp2mr));
+	if (likely(txq->mp2mr[i].start <= addr && txq->mp2mr[i].end >= addr))
+		return txq->mp2mr[i].lkey;
 	for (i = 0; (i != RTE_DIM(txq->mp2mr)); ++i) {
 		if (unlikely(txq->mp2mr[i].mp == NULL)) {
 			/* Unknown MP, add a new MR for it. */
 			break;
 		}
-		if (txq->mp2mr[i].mp == mp) {
+		if (txq->mp2mr[i].start <= addr &&
+		    txq->mp2mr[i].end >= addr) {
 			assert(txq->mp2mr[i].lkey != (uint32_t)-1);
 			assert(htonl(txq->mp2mr[i].mr->lkey) ==
 			       txq->mp2mr[i].lkey);
-			lkey = txq->mp2mr[i].lkey;
-			break;
+			txq->mr_cache_idx = i;
+			return txq->mp2mr[i].lkey;
 		}
 	}
-	if (unlikely(lkey == (uint32_t)-1))
-		lkey = txq_mp2mr_reg(txq, mp, i);
-	return lkey;
+	txq->mr_cache_idx = 0;
+	return txq_mp2mr_reg(txq, txq_mb2mp(mb), i);
 }
 
 /**
@@ -773,7 +776,7 @@ mlx5_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 			naddr = htonll(addr);
 			*dseg = (rte_v128u32_t){
 				htonl(length),
-				txq_mp2mr(txq, txq_mb2mp(buf)),
+				txq_mb2mr(txq, buf),
 				naddr,
 				naddr >> 32,
 			};
@@ -812,7 +815,7 @@ mlx5_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 		naddr = htonll(rte_pktmbuf_mtod(buf, uintptr_t));
 		*dseg = (rte_v128u32_t){
 			htonl(length),
-			txq_mp2mr(txq, txq_mb2mp(buf)),
+			txq_mb2mr(txq, buf),
 			naddr,
 			naddr >> 32,
 		};
@@ -1054,7 +1057,7 @@ mlx5_tx_burst_mpw(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 			addr = rte_pktmbuf_mtod(buf, uintptr_t);
 			*dseg = (struct mlx5_wqe_data_seg){
 				.byte_count = htonl(DATA_LEN(buf)),
-				.lkey = txq_mp2mr(txq, txq_mb2mp(buf)),
+				.lkey = txq_mb2mr(txq, buf),
 				.addr = htonll(addr),
 			};
 #if defined(MLX5_PMD_SOFT_COUNTERS) || !defined(NDEBUG)
@@ -1300,7 +1303,7 @@ mlx5_tx_burst_mpw_inline(void *dpdk_txq, struct rte_mbuf **pkts,
 				addr = rte_pktmbuf_mtod(buf, uintptr_t);
 				*dseg = (struct mlx5_wqe_data_seg){
 					.byte_count = htonl(DATA_LEN(buf)),
-					.lkey = txq_mp2mr(txq, txq_mb2mp(buf)),
+					.lkey = txq_mb2mr(txq, buf),
 					.addr = htonll(addr),
 				};
 #if defined(MLX5_PMD_SOFT_COUNTERS) || !defined(NDEBUG)
@@ -1607,7 +1610,7 @@ mlx5_tx_burst_empw(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 				addr = rte_pktmbuf_mtod(buf, uintptr_t);
 				*dseg = (struct mlx5_wqe_data_seg){
 					.byte_count = htonl(DATA_LEN(buf)),
-					.lkey = txq_mp2mr(txq, txq_mb2mp(buf)),
+					.lkey = txq_mb2mr(txq, buf),
 					.addr = htonll(addr),
 				};
 #if defined(MLX5_PMD_SOFT_COUNTERS) || !defined(NDEBUG)
@@ -1690,7 +1693,7 @@ mlx5_tx_burst_empw(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 			naddr = htonll(addr);
 			*dseg = (rte_v128u32_t) {
 				htonl(length),
-				txq_mp2mr(txq, txq_mb2mp(buf)),
+				txq_mb2mr(txq, buf),
 				naddr,
 				naddr >> 32,
 			};
diff --git a/drivers/net/mlx5/mlx5_rxtx.h b/drivers/net/mlx5/mlx5_rxtx.h
index f9b738b4e..a86f41abc 100644
--- a/drivers/net/mlx5/mlx5_rxtx.h
+++ b/drivers/net/mlx5/mlx5_rxtx.h
@@ -267,10 +267,13 @@ struct txq {
 	volatile uint32_t *cq_db; /* Completion queue doorbell. */
 	volatile void *bf_reg; /* Blueflame register. */
 	struct {
+		uintptr_t start; /* Start address of MR */
+		uintptr_t end;   /* End address of MR */
 		const struct rte_mempool *mp; /* Cached Memory Pool. */
 		struct ibv_mr *mr; /* Memory Region (for mp). */
 		uint32_t lkey; /* htonl(mr->lkey) */
 	} mp2mr[MLX5_PMD_TX_MP_CACHE]; /* MP to MR translation table. */
+	uint16_t mr_cache_idx; /* Index of last hit entry. */
 	struct rte_mbuf *(*elts)[]; /* TX elements. */
 	struct mlx5_txq_stats stats; /* TX queue counters. */
 } __rte_cache_aligned;
-- 
2.11.0