netdev - Re: [PATCH net] sunvnet: set queue mapping when doing packet copies

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Date:	Thu, 29 Jan 2015 10:12:26 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David L Stevens <david.stevens@...cle.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Sowmini Varadhan <sowmini.varadhan@...cle.com>
Subject: Re: [PATCH net] sunvnet: set queue mapping when doing packet copies

On Thu, 2015-01-29 at 11:46 -0500, David L Stevens wrote:
> [resending this since it never appeared on netdev yesterday]
> 
> This patch fixes a bug where vnet_skb_shape() didn't set the already-selected
>  queue mapping when a packet copy was required. This results in using the
>  wrong queue index for stops/starts, hung tx queues and watchdog timeouts
>  under heavy load.
> 
> Signed-off-by: David L Stevens <david.stevens@...cle.com>
> Acked-by: Sowmini Varadhan <sowmini.varadhan@...cle.com>
> ---
>  drivers/net/ethernet/sun/sunvnet.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/net/ethernet/sun/sunvnet.c b/drivers/net/ethernet/sun/sunvnet.c
> index 2b719cc..2b10b85 100644
> --- a/drivers/net/ethernet/sun/sunvnet.c
> +++ b/drivers/net/ethernet/sun/sunvnet.c
> @@ -1123,6 +1123,7 @@ static inline struct sk_buff *vnet_skb_shape(struct sk_buff *skb, int ncookies)
>  			skb_shinfo(nskb)->gso_size = skb_shinfo(skb)->gso_size;
>  			skb_shinfo(nskb)->gso_type = skb_shinfo(skb)->gso_type;
>  		}
> +		nskb->queue_mapping = skb->queue_mapping;
>  		dev_kfree_skb(skb);
>  		skb = nskb;
>  	}

Note that vnet_skb_shape() also drops the skb -> sk assocation.

-> That removes flow control, a single socket can fill TX ring buffer.
TCP Small queue is also disabled.

I would try add before the dev_kfree_skb(skb) :

swap(nskb->sk, skb->sk);
swap(nskb->truesize, skb->truesize);



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