Re: [PATCH net-next 07/15] net/mlx5e: reduce rep rxq depth to 256 for ECPF

[Michal Swiatkowski]

On Sun, Feb 09, 2025 at 12:17:08PM +0200, Tariq Toukan wrote:
> From: William Tu <witu@xxxxxxxxxx>
> 
> By experiments, a single queue representor netdev consumes kernel
> memory around 2.8MB, and 1.8MB out of the 2.8MB is due to page
> pool for the RXQ. Scaling to a thousand representors consumes 2.8GB,
> which becomes a memory pressure issue for embedded devices such as
> BlueField-2 16GB / BlueField-3 32GB memory.
> 
> Since representor netdevs mostly handles miss traffic, and ideally,
> most of the traffic will be offloaded, reduce the default non-uplink
> rep netdev's RXQ default depth from 1024 to 256 if mdev is ecpf eswitch
> manager. This saves around 1MB of memory per regular RQ,
> (1024 - 256) * 2KB, allocated from page pool.
> 
> With rxq depth of 256, the netlink page pool tool reports
> $./tools/net/ynl/cli.py --spec Documentation/netlink/specs/netdev.yaml \
> 	 --dump page-pool-get
>  {'id': 277,
>   'ifindex': 9,
>   'inflight': 128,
>   'inflight-mem': 786432,
>   'napi-id': 775}]
> 
> This is due to mtu 1500 + headroom consumes half pages, so 256 rxq
> entries consumes around 128 pages (thus create a page pool with
> size 128), shown above at inflight.
> 
> Note that each netdev has multiple types of RQs, including
> Regular RQ, XSK, PTP, Drop, Trap RQ. Since non-uplink representor
> only supports regular rq, this patch only changes the regular RQ's
> default depth.
> 
> Signed-off-by: William Tu <witu@xxxxxxxxxx>
> Reviewed-by: Bodong Wang <bodong@xxxxxxxxxx>
> Reviewed-by: Saeed Mahameed <saeedm@xxxxxxxxxx>
> Signed-off-by: Tariq Toukan <tariqt@xxxxxxxxxx>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/en_rep.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rep.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rep.c
> index fdff9fd8a89e..da399adc8854 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_rep.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rep.c
> @@ -65,6 +65,7 @@
>  #define MLX5E_REP_PARAMS_DEF_LOG_SQ_SIZE \
>  	max(0x7, MLX5E_PARAMS_MINIMUM_LOG_SQ_SIZE)
>  #define MLX5E_REP_PARAMS_DEF_NUM_CHANNELS 1
> +#define MLX5E_REP_PARAMS_DEF_LOG_RQ_SIZE 0x8
>  
>  static const char mlx5e_rep_driver_name[] = "mlx5e_rep";
>  
> @@ -855,6 +856,8 @@ static void mlx5e_build_rep_params(struct net_device *netdev)
>  
>  	/* RQ */
>  	mlx5e_build_rq_params(mdev, params);
> +	if (!mlx5e_is_uplink_rep(priv) && mlx5_core_is_ecpf(mdev))
> +		params->log_rq_mtu_frames = MLX5E_REP_PARAMS_DEF_LOG_RQ_SIZE;
>  
>  	/* If netdev is already registered (e.g. move from nic profile to uplink,
>  	 * RTNL lock must be held before triggering netdev notifiers.

Thanks for detailed commit message.

Reviewed-by: Michal Swiatkowski <michal.swiatkowski@xxxxxxxxxxxxxxx>

> -- 
> 2.45.0