linux-kernel - Re: [PATCH net-next 1/3] net/mlx4: Track RX allocation failures in a stat

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Date: Tue, 23 Apr 2024 12:38:50 -1000
From: Joe Damato <jdamato@...tly.com>
To: linux-kernel@...r.kernel.org, netdev@...r.kernel.org, tariqt@...dia.com,
	saeedm@...dia.com
Cc: mkarsten@...terloo.ca, gal@...dia.com, nalramli@...tly.com,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	"open list:MELLANOX MLX4 core VPI driver" <linux-rdma@...r.kernel.org>
Subject: Re: [PATCH net-next 1/3] net/mlx4: Track RX allocation failures in a
 stat

On Tue, Apr 23, 2024 at 07:49:28PM +0000, Joe Damato wrote:
> mlx4_en_alloc_frags currently returns -ENOMEM when mlx4_alloc_page
> fails but does not increment a stat field when this occurs.
> 
> struct mlx4_en_rx_ring has a dropped field which is tabulated in
> mlx4_en_DUMP_ETH_STATS, but never incremented by the driver.
> 
> This change modifies mlx4_en_alloc_frags to increment mlx4_en_rx_ring's
> dropped field for the -ENOMEM case.
> 
> Signed-off-by: Joe Damato <jdamato@...tly.com>
> Tested-by: Martin Karsten <mkarsten@...terloo.ca>
> ---
>  drivers/net/ethernet/mellanox/mlx4/en_port.c | 4 +++-
>  drivers/net/ethernet/mellanox/mlx4/en_rx.c   | 4 +++-
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_port.c b/drivers/net/ethernet/mellanox/mlx4/en_port.c
> index 532997eba698..c4b1062158e1 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_port.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_port.c
> @@ -151,7 +151,7 @@ void mlx4_en_fold_software_stats(struct net_device *dev)
>  {
>  	struct mlx4_en_priv *priv = netdev_priv(dev);
>  	struct mlx4_en_dev *mdev = priv->mdev;
> -	unsigned long packets, bytes;
> +	unsigned long packets, bytes, dropped;

Err, sorry forgot to initialize this to 0 below with the rest of the init.
Will fix this in v2 (and whatever other feedback there is). Apologies on
the error here on my part.

>  	int i;
>  
>  	if (!priv->port_up || mlx4_is_master(mdev->dev))
> @@ -164,9 +164,11 @@ void mlx4_en_fold_software_stats(struct net_device *dev)
>  
>  		packets += READ_ONCE(ring->packets);
>  		bytes   += READ_ONCE(ring->bytes);
> +		dropped += READ_ONCE(ring->dropped);
>  	}
>  	dev->stats.rx_packets = packets;
>  	dev->stats.rx_bytes = bytes;
> +	dev->stats.rx_missed_errors = dropped;
>  
>  	packets = 0;
>  	bytes = 0;
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> index 8328df8645d5..573ae10300c7 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> @@ -82,8 +82,10 @@ static int mlx4_en_alloc_frags(struct mlx4_en_priv *priv,
>  
>  	for (i = 0; i < priv->num_frags; i++, frags++) {
>  		if (!frags->page) {
> -			if (mlx4_alloc_page(priv, frags, gfp))
> +			if (mlx4_alloc_page(priv, frags, gfp)) {
> +				ring->dropped++;
>  				return -ENOMEM;
> +			}
>  			ring->rx_alloc_pages++;
>  		}
>  		rx_desc->data[i].addr = cpu_to_be64(frags->dma +
> -- 
> 2.25.1
>