Re: [dpdk-dev] [PATCH v1 1/2] net/i40e: improve performance for scalar Tx

["Xing, Beilei" <beilei.xing@intel.com>]

> -----Original Message-----
> From: Feifei Wang <feifei.wang2@arm.com>
> Sent: Thursday, May 27, 2021 4:17 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 v1 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.
> 
> For scalar path in arm platform:
> In n1sdp, performance is improved by 7.8%; In thunderx2, performance is
> improved by 6.7%.
> 
> For scalar path in x86 platform,
> performance is improved by 6%.
> 
> Suggested-by: Ruifeng Wang <ruifeng.wang@arm.com>
> Signed-off-by: Feifei Wang <feifei.wang2@arm.com>
> ---
>  drivers/net/i40e/i40e_rxtx.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/i40e/i40e_rxtx.c b/drivers/net/i40e/i40e_rxtx.c index
> 6c58decece..fe7b20f750 100644
> --- a/drivers/net/i40e/i40e_rxtx.c
> +++ b/drivers/net/i40e/i40e_rxtx.c
> @@ -1295,6 +1295,7 @@ i40e_tx_free_bufs(struct i40e_tx_queue *txq)  {
>  	struct i40e_tx_entry *txep;
>  	uint16_t i;
> +	struct rte_mbuf *free[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)) !=
> @@ -1308,9 +1309,11 @@ i40e_tx_free_bufs(struct i40e_tx_queue *txq)
> 
>  	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);
> +			free[i] = txep->mbuf;

The tx_rs_thresh can be 'nb_desc - 3', so if tx_rs_thres > RTE_I40E_TX_MAX_FREE_BUF_SZ, there'll be out of bounds, right?

>  			txep->mbuf = NULL;
>  		}
> +		rte_mempool_put_bulk(free[0]->pool, (void **)free,
> +					txq->tx_rs_thresh);
>  	} else {
>  		for (i = 0; i < txq->tx_rs_thresh; ++i, ++txep) {
>  			rte_pktmbuf_free_seg(txep->mbuf);
> --
> 2.25.1