linux-kernel - Re: [PATCH net-next] net: bcmgenet: suppress warnings on failed Rx SKB allocations

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Date:   Thu, 23 Apr 2020 16:10:07 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Doug Berger <opendmb@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     bcm-kernel-feedback-list@...adcom.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] net: bcmgenet: suppress warnings on failed Rx
 SKB allocations



On 4/23/2020 4:02 PM, Doug Berger wrote:
> The driver is designed to drop Rx packets and reclaim the buffers
> when an allocation fails, and the network interface needs to safely
> handle this packet loss. Therefore, an allocation failure of Rx
> SKBs is relatively benign.
> 
> However, the output of the warning message occurs with a high
> scheduling priority that can cause excessive jitter/latency for
> other high priority processing.
> 
> This commit suppresses the warning messages to prevent scheduling
> problems while retaining the failure count in the statistics of
> the network interface.
> 
> Signed-off-by: Doug Berger <opendmb@...il.com>

Acked-by: Florian Fainelli <f.fainelli@...il.com>

It seems to me this should be the default behavior for all network
device drivers, but I am fine with this being a driver decision if
people think differently.

> ---
>  drivers/net/ethernet/broadcom/genet/bcmgenet.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> index 20aba79becce..bfeff5585f4b 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> @@ -1617,7 +1617,8 @@ static struct sk_buff *bcmgenet_rx_refill(struct bcmgenet_priv *priv,
>  	dma_addr_t mapping;
>  
>  	/* Allocate a new Rx skb */
> -	skb = netdev_alloc_skb(priv->dev, priv->rx_buf_len + SKB_ALIGNMENT);
> +	skb = __netdev_alloc_skb(priv->dev, priv->rx_buf_len + SKB_ALIGNMENT,
> +				 GFP_ATOMIC | __GFP_NOWARN);
>  	if (!skb) {
>  		priv->mib.alloc_rx_buff_failed++;
>  		netif_err(priv, rx_err, priv->dev,
> 

-- 
Florian