[dpdk-dev] [PATCH v3 12/13] ixgbe: Fix perf regression due to moved pool ptr

[Bruce Richardson]

Adjust the fast-path code to fix the regression caused by the pool
pointer moving to the second cache line. This change adjusts the
prefetching and also the way in which the mbufs are freed back to the
mempool.
Note: slow-path e.g. path supporting jumbo frames, is still slower, but
is dealt with by a later commit

Updates in V2:
* fixup checkpatch issue

Updates in V3:
* The variable definitions for freeing mbufs now need to be included
whether or not reference counting is enabled.

Signed-off-by: Bruce Richardson <bruce.richardson at intel.com>
---
 lib/librte_pmd_ixgbe/ixgbe_rxtx.c     |  8 ++-
 lib/librte_pmd_ixgbe/ixgbe_rxtx.h     | 14 +-----
 lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c | 94 +++++++++++++----------------------
 3 files changed, 38 insertions(+), 78 deletions(-)

diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx.c b/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
index 1a46393..d6448a4 100644
--- a/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
+++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
@@ -142,10 +142,6 @@ ixgbe_tx_free_bufs(struct igb_tx_queue *txq)
 	 */
 	txep = &(txq->sw_ring[txq->tx_next_dd - (txq->tx_rs_thresh - 1)]);
 
-	/* prefetch the mbufs that are about to be freed */
-	for (i = 0; i < txq->tx_rs_thresh; ++i)
-		rte_prefetch0((txep + i)->mbuf);
-
 	/* free buffers one at a time */
 	if ((txq->txq_flags & (uint32_t)ETH_TXQ_FLAGS_NOREFCOUNT) != 0) {
 		for (i = 0; i < txq->tx_rs_thresh; ++i, ++txep) {
@@ -186,6 +182,7 @@ tx4(volatile union ixgbe_adv_tx_desc *txdp, struct rte_mbuf **pkts)
 				((uint32_t)DCMD_DTYP_FLAGS | pkt_len);
 		txdp->read.olinfo_status =
 				(pkt_len << IXGBE_ADVTXD_PAYLEN_SHIFT);
+		rte_prefetch0(&(*pkts)->pool);
 	}
 }
 
@@ -205,6 +202,7 @@ tx1(volatile union ixgbe_adv_tx_desc *txdp, struct rte_mbuf **pkts)
 			((uint32_t)DCMD_DTYP_FLAGS | pkt_len);
 	txdp->read.olinfo_status =
 			(pkt_len << IXGBE_ADVTXD_PAYLEN_SHIFT);
+	rte_prefetch0(&(*pkts)->pool);
 }
 
 /*
@@ -1875,7 +1873,7 @@ ixgbe_dev_tx_queue_setup(struct rte_eth_dev *dev,
 		PMD_INIT_LOG(INFO, "Using simple tx code path\n");
 #ifdef RTE_IXGBE_INC_VECTOR
 		if (txq->tx_rs_thresh <= RTE_IXGBE_TX_MAX_FREE_BUF_SZ &&
-		    ixgbe_txq_vec_setup(txq, socket_id) == 0) {
+		    ixgbe_txq_vec_setup(txq) == 0) {
 			PMD_INIT_LOG(INFO, "Vector tx enabled.\n");
 			dev->tx_pkt_burst = ixgbe_xmit_pkts_vec;
 		}
diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx.h b/lib/librte_pmd_ixgbe/ixgbe_rxtx.h
index e92a864..a97fddb 100644
--- a/lib/librte_pmd_ixgbe/ixgbe_rxtx.h
+++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx.h
@@ -96,14 +96,6 @@ struct igb_tx_entry_v {
 };
 
 /**
- * continuous entry sequence, gather by the same mempool
- */
-struct igb_tx_entry_seq {
-	const struct rte_mempool* pool;
-	uint32_t same_pool;
-};
-
-/**
  * Structure associated with each RX queue.
  */
 struct igb_rx_queue {
@@ -190,10 +182,6 @@ struct igb_tx_queue {
 	volatile union ixgbe_adv_tx_desc *tx_ring;
 	uint64_t            tx_ring_phys_addr; /**< TX ring DMA address. */
 	struct igb_tx_entry *sw_ring;      /**< virtual address of SW ring. */
-#ifdef RTE_IXGBE_INC_VECTOR
-	/** continuous tx entry sequence within the same mempool */
-	struct igb_tx_entry_seq *sw_ring_seq;
-#endif
 	volatile uint32_t   *tdt_reg_addr; /**< Address of TDT register. */
 	uint16_t            nb_tx_desc;    /**< number of TX descriptors. */
 	uint16_t            tx_tail;       /**< current value of TDT reg. */
@@ -258,7 +246,7 @@ struct ixgbe_txq_ops {
 #ifdef RTE_IXGBE_INC_VECTOR
 uint16_t ixgbe_recv_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t nb_pkts);
 uint16_t ixgbe_xmit_pkts_vec(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts);
-int ixgbe_txq_vec_setup(struct igb_tx_queue *txq, unsigned int socket_id);
+int ixgbe_txq_vec_setup(struct igb_tx_queue *txq);
 int ixgbe_rxq_vec_setup(struct igb_rx_queue *rxq);
 int ixgbe_rx_vec_condition_check(struct rte_eth_dev *dev);
 #endif
diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c b/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c
index d53e239..9869b8b 100644
--- a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c
+++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c
@@ -342,14 +342,11 @@ static inline int __attribute__((always_inline))
 ixgbe_tx_free_bufs(struct igb_tx_queue *txq)
 {
 	struct igb_tx_entry_v *txep;
-	struct igb_tx_entry_seq *txsp;
 	uint32_t status;
-	uint32_t n, k;
-#ifdef RTE_MBUF_REFCNT
+	uint32_t n;
 	uint32_t i;
 	int nb_free = 0;
 	struct rte_mbuf *m, *free[RTE_IXGBE_TX_MAX_FREE_BUF_SZ];
-#endif
 
 	/* check DD bit on threshold descriptor */
 	status = txq->tx_ring[txq->tx_next_dd].wb.status;
@@ -364,23 +361,38 @@ ixgbe_tx_free_bufs(struct igb_tx_queue *txq)
 	 */
 	txep = &((struct igb_tx_entry_v *)txq->sw_ring)[txq->tx_next_dd -
 			(n - 1)];
-	txsp = &txq->sw_ring_seq[txq->tx_next_dd - (n - 1)];
-
-	while (n > 0) {
-		k = RTE_MIN(n, txsp[n-1].same_pool);
 #ifdef RTE_MBUF_REFCNT
-		for (i = 0; i < k; i++) {
-			m = __rte_pktmbuf_prefree_seg((txep+n-k+i)->mbuf);
-			if (m != NULL)
-				free[nb_free++] = m;
-		}
-		rte_mempool_put_bulk((void *)txsp[n-1].pool,
-				(void **)free, nb_free);
+	m = __rte_pktmbuf_prefree_seg(txep[0].mbuf);
 #else
-		rte_mempool_put_bulk((void *)txsp[n-1].pool,
-				(void **)(txep+n-k), k);
+	m = txep[0].mbuf;
 #endif
-		n -= k;
+	if (likely(m != NULL)) {
+		free[0] = m;
+		nb_free = 1;
+		for (i = 1; i < n; i++) {
+#ifdef RTE_MBUF_REFCNT
+			m = __rte_pktmbuf_prefree_seg(txep[i].mbuf);
+#else
+			m = txep[i]->mbuf;
+#endif
+			if (likely(m != NULL)) {
+				if (likely(m->pool == free[0]->pool))
+					free[nb_free++] = m;
+				else {
+					rte_mempool_put_bulk(free[0]->pool,
+							(void *)free, nb_free);
+					free[0] = m;
+					nb_free = 1;
+				}
+			}
+		}
+		rte_mempool_put_bulk(free[0]->pool, (void **)free, nb_free);
+	} else {
+		for (i = 1; i < n; i++) {
+			m = __rte_pktmbuf_prefree_seg(txep[i].mbuf);
+			if (m != NULL)
+				rte_mempool_put(m->pool, m);
+		}
 	}
 
 	/* buffers were freed, update counters */
@@ -394,19 +406,11 @@ ixgbe_tx_free_bufs(struct igb_tx_queue *txq)
 
 static inline void __attribute__((always_inline))
 tx_backlog_entry(struct igb_tx_entry_v *txep,
-		 struct igb_tx_entry_seq *txsp,
 		 struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 {
 	int i;
-	for (i = 0; i < (int)nb_pkts; ++i) {
+	for (i = 0; i < (int)nb_pkts; ++i)
 		txep[i].mbuf = tx_pkts[i];
-		/* check and update sequence number */
-		txsp[i].pool = tx_pkts[i]->pool;
-		if (txsp[i-1].pool == tx_pkts[i]->pool)
-			txsp[i].same_pool = txsp[i-1].same_pool + 1;
-		else
-			txsp[i].same_pool = 1;
-	}
 }
 
 uint16_t
@@ -416,7 +420,6 @@ ixgbe_xmit_pkts_vec(void *tx_queue, struct rte_mbuf **tx_pkts,
 	struct igb_tx_queue *txq = (struct igb_tx_queue *)tx_queue;
 	volatile union ixgbe_adv_tx_desc *txdp;
 	struct igb_tx_entry_v *txep;
-	struct igb_tx_entry_seq *txsp;
 	uint16_t n, nb_commit, tx_id;
 	uint64_t flags = DCMD_DTYP_FLAGS;
 	uint64_t rs = IXGBE_ADVTXD_DCMD_RS|DCMD_DTYP_FLAGS;
@@ -435,14 +438,13 @@ ixgbe_xmit_pkts_vec(void *tx_queue, struct rte_mbuf **tx_pkts,
 	tx_id = txq->tx_tail;
 	txdp = &txq->tx_ring[tx_id];
 	txep = &((struct igb_tx_entry_v *)txq->sw_ring)[tx_id];
-	txsp = &txq->sw_ring_seq[tx_id];
 
 	txq->nb_tx_free = (uint16_t)(txq->nb_tx_free - nb_pkts);
 
 	n = (uint16_t)(txq->nb_tx_desc - tx_id);
 	if (nb_commit >= n) {
 
-		tx_backlog_entry(txep, txsp, tx_pkts, n);
+		tx_backlog_entry(txep, tx_pkts, n);
 
 		for (i = 0; i < n - 1; ++i, ++tx_pkts, ++txdp)
 			vtx1(txdp, *tx_pkts, flags);
@@ -457,10 +459,9 @@ ixgbe_xmit_pkts_vec(void *tx_queue, struct rte_mbuf **tx_pkts,
 		/* avoid reach the end of ring */
 		txdp = &(txq->tx_ring[tx_id]);
 		txep = &(((struct igb_tx_entry_v *)txq->sw_ring)[tx_id]);
-		txsp = &(txq->sw_ring_seq[tx_id]);
 	}
 
-	tx_backlog_entry(txep, txsp, tx_pkts, nb_commit);
+	tx_backlog_entry(txep, tx_pkts, nb_commit);
 
 	vtx(txdp, tx_pkts, nb_commit, flags);
 
@@ -484,7 +485,6 @@ ixgbe_tx_queue_release_mbufs(struct igb_tx_queue *txq)
 {
 	unsigned i;
 	struct igb_tx_entry_v *txe;
-	struct igb_tx_entry_seq *txs;
 	uint16_t nb_free, max_desc;
 
 	if (txq->sw_ring != NULL) {
@@ -502,10 +502,6 @@ ixgbe_tx_queue_release_mbufs(struct igb_tx_queue *txq)
 		for (i = 0; i < txq->nb_tx_desc; i++) {
 			txe = (struct igb_tx_entry_v *)&txq->sw_ring[i];
 			txe->mbuf = NULL;
-
-			txs = &txq->sw_ring_seq[i];
-			txs->pool = NULL;
-			txs->same_pool = 0;
 		}
 	}
 }
@@ -520,11 +516,6 @@ ixgbe_tx_free_swring(struct igb_tx_queue *txq)
 		rte_free((struct igb_rx_entry *)txq->sw_ring - 1);
 		txq->sw_ring = NULL;
 	}
-
-	if (txq->sw_ring_seq != NULL) {
-		rte_free(txq->sw_ring_seq - 1);
-		txq->sw_ring_seq = NULL;
-	}
 }
 
 static void
@@ -533,7 +524,6 @@ ixgbe_reset_tx_queue(struct igb_tx_queue *txq)
 	static const union ixgbe_adv_tx_desc zeroed_desc = { .read = {
 			.buffer_addr = 0} };
 	struct igb_tx_entry_v *txe = (struct igb_tx_entry_v *)txq->sw_ring;
-	struct igb_tx_entry_seq *txs = txq->sw_ring_seq;
 	uint16_t i;
 
 	/* Zero out HW ring memory */
@@ -545,8 +535,6 @@ ixgbe_reset_tx_queue(struct igb_tx_queue *txq)
 		volatile union ixgbe_adv_tx_desc *txd = &txq->tx_ring[i];
 		txd->wb.status = IXGBE_TXD_STAT_DD;
 		txe[i].mbuf = NULL;
-		txs[i].pool = NULL;
-		txs[i].same_pool = 0;
 	}
 
 	txq->tx_next_dd = (uint16_t)(txq->tx_rs_thresh - 1);
@@ -588,28 +576,14 @@ ixgbe_rxq_vec_setup(struct igb_rx_queue *rxq)
 	return 0;
 }
 
-int ixgbe_txq_vec_setup(struct igb_tx_queue *txq,
-			unsigned int socket_id)
+int ixgbe_txq_vec_setup(struct igb_tx_queue *txq)
 {
-	uint16_t nb_desc;
-
 	if (txq->sw_ring == NULL)
 		return -1;
 
-	/* request addtional one entry for continous sequence check */
-	nb_desc = (uint16_t)(txq->nb_tx_desc + 1);
-
-	txq->sw_ring_seq = rte_zmalloc_socket("txq->sw_ring_seq",
-				sizeof(struct igb_tx_entry_seq) * nb_desc,
-				CACHE_LINE_SIZE, socket_id);
-	if (txq->sw_ring_seq == NULL)
-		return -1;
-
-
 	/* leave the first one for overflow */
 	txq->sw_ring = (struct igb_tx_entry *)
 		((struct igb_tx_entry_v *)txq->sw_ring + 1);
-	txq->sw_ring_seq += 1;
 	txq->ops = &vec_txq_ops;
 
 	return 0;
-- 
1.9.3