netdev - Re: [PATCH] net: bcmgenet: fix throughtput regression with TSO autosizing

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Date:	Thu, 26 Feb 2015 09:27:35 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jaedon Shin <jaedon.shin@...il.com>
Cc:	Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH] net: bcmgenet: fix throughtput regression with TSO
 autosizing

On Thu, 2015-02-26 at 20:05 +0900, Jaedon Shin wrote:
> This patch prevents the performance degradation of xmit after
> 605ad7f ("tcp: refine TSO autosizing").
> 
> Signed-off-by: Jaedon Shin <jaedon.shin@...il.com>
> ---
>  drivers/net/ethernet/broadcom/genet/bcmgenet.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> index ff83c46b..87eeff0 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> @@ -1310,6 +1310,9 @@ static netdev_tx_t bcmgenet_xmit(struct sk_buff *skb, struct net_device *dev)
>  out:
>  	spin_unlock_irqrestore(&ring->lock, flags);
>  
> +	if (index != DESC_INDEX)
> +		skb_orphan(skb);
> +

Hmpff...

Can you elaborate on the regression ?

Is it because NIC delays TX completion irq or something ?

bcmgenet_poll() only drains TX packets on ring16 (DESC_INDEC)

Other tx completions seem to run from hard irq context (bcmgenet_isr1())

Your patch seems to imply a bug in hard irq signaling/handling.


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