Hi, Ruifeng
Could we go further and implement loop inside the conditional?
Like this:
if (mlx5_mr_btree_len(&rxq->mr_ctrl.cache_bh) > 1) {
for (i = 0; i < n; ++i) {
void *buf_addr = elts[i]->buf_addr;
wq[i].addr = rte_cpu_to_be_64((uintptr_t)buf_addr +
RTE_PKTMBUF_HEADROOM);
wq[i].lkey = mlx5_rx_mb2mr(rxq, elts[i]);
}
} else {
for (i = 0; i < n; ++i) {
void *buf_addr = elts[i]->buf_addr;
wq[i].addr = rte_cpu_to_be_64((uintptr_t)buf_addr +
RTE_PKTMBUF_HEADROOM);
}
}
What do you think?
Also, we should check the performance on other archs is not affected.
With best regards,
Slava
> -----Original Message-----
> From: Ruifeng Wang <ruifeng.w...@arm.com>
> Sent: Tuesday, June 1, 2021 11:31
> To: Raslan Darawsheh <rasl...@nvidia.com>; Matan Azrad
> <ma...@nvidia.com>; Shahaf Shuler <shah...@nvidia.com>; Slava Ovsiienko
> <viachesl...@nvidia.com>
> Cc: dev@dpdk.org; jer...@marvell.com; n...@arm.com;
> honnappa.nagaraha...@arm.com; Ruifeng Wang <ruifeng.w...@arm.com>
> Subject: [PATCH 2/2] net/mlx5: reduce unnecessary memory access
>
> MR btree len is a constant during Rx replenish.
> Moved retrieve of the value out of loop to reduce data loads.
> Slight performance uplift was measured on N1SDP.
>
> Signed-off-by: Ruifeng Wang <ruifeng.w...@arm.com>
> ---
> drivers/net/mlx5/mlx5_rxtx_vec.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/mlx5/mlx5_rxtx_vec.c
> b/drivers/net/mlx5/mlx5_rxtx_vec.c
> index d5af2d91ff..fc7e2a7f41 100644
> --- a/drivers/net/mlx5/mlx5_rxtx_vec.c
> +++ b/drivers/net/mlx5/mlx5_rxtx_vec.c
> @@ -95,6 +95,7 @@ mlx5_rx_replenish_bulk_mbuf(struct mlx5_rxq_data
> *rxq)
> volatile struct mlx5_wqe_data_seg *wq =
> &((volatile struct mlx5_wqe_data_seg *)rxq->wqes)[elts_idx];
> unsigned int i;
> + uint16_t btree_len;
>
> if (n >= rxq->rq_repl_thresh) {
> MLX5_ASSERT(n >=
> MLX5_VPMD_RXQ_RPLNSH_THRESH(q_n));
> @@ -106,6 +107,8 @@ mlx5_rx_replenish_bulk_mbuf(struct mlx5_rxq_data
> *rxq)
> rxq->stats.rx_nombuf += n;
> return;
> }
> +
> + btree_len = mlx5_mr_btree_len(&rxq->mr_ctrl.cache_bh);
> for (i = 0; i < n; ++i) {
> void *buf_addr;
>
> @@ -119,8 +122,7 @@ mlx5_rx_replenish_bulk_mbuf(struct mlx5_rxq_data
> *rxq)
> wq[i].addr = rte_cpu_to_be_64((uintptr_t)buf_addr +
>
> RTE_PKTMBUF_HEADROOM);
> /* If there's a single MR, no need to replace LKey. */
> - if (unlikely(mlx5_mr_btree_len(&rxq-
> >mr_ctrl.cache_bh)
> - > 1))
> + if (unlikely(btree_len > 1))
> wq[i].lkey = mlx5_rx_mb2mr(rxq, elts[i]);
> }
> rxq->rq_ci += n;
> --
> 2.25.1
