[dpdk-dev] [PATCH 1/2] net/mlx5: replace memory barrier type
Nélio Laranjeiro
nelio.laranjeiro at 6wind.com
Wed Aug 23 13:39:08 CEST 2017
On Mon, Aug 21, 2017 at 10:47:01AM +0300, Sagi Grimberg wrote:
> From: Shahaf Shuler <shahafs at mellanox.com>
>
> The reason for the requirement of a barrier between the txq writes
> and the doorbell record writes is to avoid a case where the device
> reads the doorbell record's new value before the txq writes are flushed
> to memory.
>
> The current use of rte_wmb is not necessary, and can be replaced by
> rte_compiler_barrier as it acts as a write memory barrier.
> More details on this type of barrier can be found on [1]
>
> Replacing the rte_wmb is also expected to improve the throughput.
>
> [1] https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html
>
> Signed-off-by: Shahaf Shuler <shahafs at mellanox.com>
> Signed-off-by: Yongseok Koh <yskoh at mellanox.com>
> Signed-off-by: Alexander Solganik <solganik at gmail.com>
> Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
> ---
> drivers/net/mlx5/mlx5_rxtx.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/mlx5/mlx5_rxtx.h b/drivers/net/mlx5/mlx5_rxtx.h
> index 7de1d10863e5..59b9ff24fb82 100644
> --- a/drivers/net/mlx5/mlx5_rxtx.h
> +++ b/drivers/net/mlx5/mlx5_rxtx.h
> @@ -602,7 +602,7 @@ mlx5_tx_dbrec(struct txq *txq, volatile struct mlx5_wqe *wqe)
> uint64_t *dst = (uint64_t *)((uintptr_t)txq->bf_reg);
> volatile uint64_t *src = ((volatile uint64_t *)wqe);
>
> - rte_wmb();
> + rte_compiler_barrier();
> *txq->qp_db = htonl(txq->wqe_ci);
> /* Ensure ordering between DB record and BF copy. */
> rte_wmb();
> --
> 2.7.4
Acked-by: Nelio Laranjeiro <nelio.laranjeiro at 6wind.com>
--
Nélio Laranjeiro
6WIND
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