[dpdk-dev] [PATCH v2 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.w...@arm.com>
Signed-off-by: Feifei Wang <feifei.wa...@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.w...@arm.com>
---
 drivers/net/i40e/i40e_rxtx.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/drivers/net/i40e/i40e_rxtx.c b/drivers/net/i40e/i40e_rxtx.c
index 6c58decece..8c72391cde 100644
--- a/drivers/net/i40e/i40e_rxtx.c
+++ b/drivers/net/i40e/i40e_rxtx.c
@@ -1294,7 +1294,11 @@ static __rte_always_inline int
 i40e_tx_free_bufs(struct i40e_tx_queue *txq)
 {
        struct i40e_tx_entry *txep;
-       uint16_t i;
+       int n = txq->tx_rs_thresh;
+       uint16_t i = 0, j = 0;
+       struct rte_mbuf *free[RTE_I40E_TX_MAX_FREE_BUF_SZ];
+       const int32_t k = RTE_ALIGN_FLOOR(n, RTE_I40E_TX_MAX_FREE_BUF_SZ);
+       const int32_t m = n % 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)) !=
@@ -1307,9 +1311,23 @@ i40e_tx_free_bufs(struct i40e_tx_queue *txq)
                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