[v3,1/2] net/i40e: improve performance for scalar Tx

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

> -----Original Message-----
> From: Feifei Wang <feifei.wang2@arm.com>
> Sent: Wednesday, June 30, 2021 2:41 PM
> To: Xing, Beilei <beilei.xing@intel.com>
> Cc: dev@dpdk.org; nd@arm.com; Feifei Wang <feifei.wang2@arm.com>;
> Ruifeng Wang <ruifeng.wang@arm.com>
> Subject: [PATCH v3 1/2] net/i40e: improve performance for scalar Tx
> 
> 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@arm.com>
> Signed-off-by: Feifei Wang <feifei.wang2@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@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
Acked-by: Beilei Xing <beilei.xing@intel.com>