[dpdk-dev] [PATCH v3 1/2] net/i40e: improve performance for scalar Tx

[Feifei Wang]

For i40e scalar Tx path, if implement FAST_FREE_MBUF mode, it means
per-queue all mbufs come from the same mempool and have refcnt = 1.

Thus we can use bulk free of the buffers when mbuf fast free mode is
enabled.

Following are the test results with this patch:

MRR L3FWD Test:
two ports & bi-directional flows & one core
RX API: i40e_recv_pkts_bulk_alloc
TX API: i40e_xmit_pkts_simple
ring_descs_size = 1024;
Ring_I40E_TX_MAX_FREE_SZ = 64;
tx_rs_thresh = I40E_DEFAULT_TX_RSBIT_THRESH = 32;
tx_free_thresh = I40E_DEFAULT_TX_FREE_THRESH = 32;

For scalar path in arm platform with default 'tx_rs_thresh':
In n1sdp, performance is improved by 7.9%;
In thunderx2, performance is improved by 7.6%.

For scalar path in x86 platform with default 'tx_rs_thresh':
performance is improved by 4.7%.

Suggested-by: Ruifeng Wang <ruifeng.wang at arm.com>
Signed-off-by: Feifei Wang <feifei.wang2 at arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang at arm.com>
---
 drivers/net/i40e/i40e_rxtx.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/drivers/net/i40e/i40e_rxtx.c b/drivers/net/i40e/i40e_rxtx.c
index 6c58decece..0d3482a9d2 100644
--- a/drivers/net/i40e/i40e_rxtx.c
+++ b/drivers/net/i40e/i40e_rxtx.c
@@ -1294,22 +1294,40 @@ static __rte_always_inline int
 i40e_tx_free_bufs(struct i40e_tx_queue *txq)
 {
 	struct i40e_tx_entry *txep;
-	uint16_t i;
+	uint16_t tx_rs_thresh = txq->tx_rs_thresh;
+	uint16_t i = 0, j = 0;
+	struct rte_mbuf *free[RTE_I40E_TX_MAX_FREE_BUF_SZ];
+	const uint16_t k = RTE_ALIGN_FLOOR(tx_rs_thresh, RTE_I40E_TX_MAX_FREE_BUF_SZ);
+	const uint16_t m = tx_rs_thresh % RTE_I40E_TX_MAX_FREE_BUF_SZ;
 
 	if ((txq->tx_ring[txq->tx_next_dd].cmd_type_offset_bsz &
 			rte_cpu_to_le_64(I40E_TXD_QW1_DTYPE_MASK)) !=
 			rte_cpu_to_le_64(I40E_TX_DESC_DTYPE_DESC_DONE))
 		return 0;
 
-	txep = &(txq->sw_ring[txq->tx_next_dd - (txq->tx_rs_thresh - 1)]);
+	txep = &txq->sw_ring[txq->tx_next_dd - (tx_rs_thresh - 1)];
 
-	for (i = 0; i < txq->tx_rs_thresh; i++)
+	for (i = 0; i < tx_rs_thresh; i++)
 		rte_prefetch0((txep + i)->mbuf);
 
 	if (txq->offloads & DEV_TX_OFFLOAD_MBUF_FAST_FREE) {
-		for (i = 0; i < txq->tx_rs_thresh; ++i, ++txep) {
-			rte_mempool_put(txep->mbuf->pool, txep->mbuf);
-			txep->mbuf = NULL;
+		if (k) {
+			for (j = 0; j != k; j += RTE_I40E_TX_MAX_FREE_BUF_SZ) {
+				for (i = 0; i < RTE_I40E_TX_MAX_FREE_BUF_SZ; ++i, ++txep) {
+					free[i] = txep->mbuf;
+					txep->mbuf = NULL;
+				}
+				rte_mempool_put_bulk(free[0]->pool, (void **)free,
+						RTE_I40E_TX_MAX_FREE_BUF_SZ);
+			}
+		}
+
+		if (m) {
+			for (i = 0; i < m; ++i, ++txep) {
+				free[i] = txep->mbuf;
+				txep->mbuf = NULL;
+			}
+			rte_mempool_put_bulk(free[0]->pool, (void **)free, m);
 		}
 	} else {
 		for (i = 0; i < txq->tx_rs_thresh; ++i, ++txep) {
-- 
2.25.1