Re: [PATCH v2 2/3] net/mlx5: add new devarg for Tx queue consecutive memory

[Stephen Hemminger <stephen@networkplumber.org>]

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Why is this needed? Need some documentation. DPDK needs less not more nerd
knobs

On Mon, Jun 23, 2025, 14:35 Bing Zhao <bingz@nvidia.com> wrote:

> With this commit, a new device argument is introduced to control
> the memory allocation for Tx queues.
>
> By default, 'txq_consec_mem' is 1 to let all the Tx queues use a
> consecutive memory area and a single MR.
>
> Signed-off-by: Bing Zhao <bingz@nvidia.com>
> ---
>  drivers/net/mlx5/mlx5.c | 14 ++++++++++++++
>  drivers/net/mlx5/mlx5.h |  1 +
>  2 files changed, 15 insertions(+)
>
> diff --git a/drivers/net/mlx5/mlx5.c b/drivers/net/mlx5/mlx5.c
> index b4bd43aae2..f5beebd2fd 100644
> --- a/drivers/net/mlx5/mlx5.c
> +++ b/drivers/net/mlx5/mlx5.c
> @@ -185,6 +185,9 @@
>  /* Device parameter to control representor matching in ingress/egress
> flows with HWS. */
>  #define MLX5_REPR_MATCHING_EN "repr_matching_en"
>
> +/* Using consecutive memory address and single MR for all Tx queues. */
> +#define MLX5_TXQ_CONSEC_MEM "txq_consec_mem"
> +
>  /* Shared memory between primary and secondary processes. */
>  struct mlx5_shared_data *mlx5_shared_data;
>
> @@ -1447,6 +1450,8 @@ mlx5_dev_args_check_handler(const char *key, const
> char *val, void *opaque)
>                 config->cnt_svc.cycle_time = tmp;
>         } else if (strcmp(MLX5_REPR_MATCHING_EN, key) == 0) {
>                 config->repr_matching = !!tmp;
> +       } else if (strcmp(MLX5_TXQ_CONSEC_MEM, key) == 0) {
> +               config->txq_consec_mem = !!tmp;
>         }
>         return 0;
>  }
> @@ -1486,6 +1491,7 @@ mlx5_shared_dev_ctx_args_config(struct
> mlx5_dev_ctx_shared *sh,
>                 MLX5_HWS_CNT_SERVICE_CORE,
>                 MLX5_HWS_CNT_CYCLE_TIME,
>                 MLX5_REPR_MATCHING_EN,
> +               MLX5_TXQ_CONSEC_MEM,
>                 NULL,
>         };
>         int ret = 0;
> @@ -1501,6 +1507,7 @@ mlx5_shared_dev_ctx_args_config(struct
> mlx5_dev_ctx_shared *sh,
>         config->cnt_svc.cycle_time = MLX5_CNT_SVC_CYCLE_TIME_DEFAULT;
>         config->cnt_svc.service_core = rte_get_main_lcore();
>         config->repr_matching = 1;
> +       config->txq_consec_mem = 1;
>         if (mkvlist != NULL) {
>                 /* Process parameters. */
>                 ret = mlx5_kvargs_process(mkvlist, params,
> @@ -1584,6 +1591,7 @@ mlx5_shared_dev_ctx_args_config(struct
> mlx5_dev_ctx_shared *sh,
>                 config->allow_duplicate_pattern);
>         DRV_LOG(DEBUG, "\"fdb_def_rule_en\" is %u.", config->fdb_def_rule);
>         DRV_LOG(DEBUG, "\"repr_matching_en\" is %u.",
> config->repr_matching);
> +       DRV_LOG(DEBUG, "\"txq_consec_mem\" is %u.",
> config->txq_consec_mem);
>         return 0;
>  }
>
> @@ -3150,6 +3158,12 @@ mlx5_probe_again_args_validate(struct
> mlx5_common_device *cdev,
>                         sh->ibdev_name);
>                 goto error;
>         }
> +       if (sh->config.txq_consec_mem ^ config->txq_consec_mem) {
> +               DRV_LOG(ERR, "\"txq_consec_mem\" "
> +                       "configuration mismatch for shared %s context.",
> +                       sh->ibdev_name);
> +               goto error;
> +       }
>         mlx5_free(config);
>         return 0;
>  error:
> diff --git a/drivers/net/mlx5/mlx5.h b/drivers/net/mlx5/mlx5.h
> index 5695d0f54a..4e0287cbc0 100644
> --- a/drivers/net/mlx5/mlx5.h
> +++ b/drivers/net/mlx5/mlx5.h
> @@ -393,6 +393,7 @@ struct mlx5_sh_config {
>         /* Allow/Prevent the duplicate rules pattern. */
>         uint32_t fdb_def_rule:1; /* Create FDB default jump rule */
>         uint32_t repr_matching:1; /* Enable implicit vport matching in HWS
> FDB. */
> +       uint32_t txq_consec_mem:1; /**/
>  };
>
>  /* Structure for VF VLAN workaround. */
> --
> 2.34.1
>
>

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