netdev - Re: [PATCH] net/mlx5e: Report rx_discards_phy via rx_missed

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Message-ID: <b3c6601b-9108-49cb-a090-247d2d56e64b@gmail.com>
Date: Wed, 6 Nov 2024 11:56:27 +0200
From: Tariq Toukan <ttoukan.linux@...il.com>
To: Yafang Shao <laoar.shao@...il.com>, saeedm@...dia.com, tariqt@...dia.com,
 leon@...nel.org
Cc: netdev@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [PATCH] net/mlx5e: Report rx_discards_phy via rx_missed_errors



On 06/11/2024 8:40, Yafang Shao wrote:
> We observed a high number of rx_discards_phy events on some servers when
> running `ethtool -S`. However, this important counter is not currently
> reflected in the /proc/net/dev statistics file, making it challenging to
> monitor effectively.
> 
> Since rx_missed_errors represents packets dropped due to buffer exhaustion,
> it makes sense to include rx_discards_phy in this counter to enhance
> monitoring visibility. This change will help administrators track these
> events more effectively through standard interfaces.
> 

Hi,

Thanks for your patch.

It's a matter of interpretation...
The documentation in 
Documentation/ABI/testing/sysfs-class-net-statistics refers to the 
driver for the exact meaning.

rx_discards_phy counts packet drops due to exhaustion of the physical 
port memory (not in the host), this happen way before steering the 
packet to any receive queue.
Today, rx_missed_errors counts SW/host memory buffer exhaustion of the 
receive queues.
I don't think that rx_missed_errors should mix both.

Maybe some other counter can be used for rx_discards_phy, like 
rx_fifo_errors?


> Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> Cc: Saeed Mahameed <saeedm@...dia.com>
> Cc: Tariq Toukan <tariqt@...dia.com>
> Cc: Leon Romanovsky <leon@...nel.org>
> ---
>   drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> index 6f686fabed44..42c1b791a74c 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> @@ -3903,7 +3903,8 @@ mlx5e_get_stats(struct net_device *dev, struct rtnl_link_stats64 *stats)
>   		mlx5e_fold_sw_stats64(priv, stats);
>   	}
>   
> -	stats->rx_missed_errors = priv->stats.qcnt.rx_out_of_buffer;
> +	stats->rx_missed_errors = priv->stats.qcnt.rx_out_of_buffer +
> +				  PPORT_2863_GET(pstats, if_in_discards);
>   
>   	stats->rx_length_errors =
>   		PPORT_802_3_GET(pstats, a_in_range_length_errors) +