netdev - Re: [PATCH 6/8] net: mv643xx_eth: Limit the TSO segments and adjust stop/wake thresholds

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Date:	Fri, 30 May 2014 15:08:39 -0300
From:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org, David Miller <davem@...emloft.net>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Gregory Clement <gregory.clement@...e-electrons.com>,
	Lior Amsalem <alior@...vell.com>,
	Tawfik Bayouk <tawfik@...vell.com>, fugang.duan@...escale.com,
	Willy Tarreau <w@....eu>
Subject: Re: [PATCH 6/8] net: mv643xx_eth: Limit the TSO segments and adjust
 stop/wake thresholds

Hi Eric,

On 30 May 10:21 AM, Eric Dumazet wrote:
> On Fri, 2014-05-30 at 13:40 -0300, Ezequiel Garcia wrote:
> >  
> > -static int txq_submit_skb(struct tx_queue *txq, struct sk_buff *skb)
> > +static int txq_submit_skb(struct tx_queue *txq, struct sk_buff *skb,
> > +			  struct net_device *dev)
> >  {
> >  	struct mv643xx_eth_private *mp = txq_to_mp(txq);
> >  	int nr_frags = skb_shinfo(skb)->nr_frags;
> > @@ -910,11 +918,15 @@ static int txq_submit_skb(struct tx_queue *txq, struct sk_buff *skb)
> >  	cmd_sts = 0;
> >  	l4i_chk = 0;
> >  
> > +	if (txq->tx_ring_size - txq->tx_desc_count < MAX_SKB_FRAGS + 1) {
> 
> I am not sure I understand this part.
> 
> You have one skb here, so why are you using MAX_SKB_FRAGS ?
> 

This check was moved around, so I'm blindly carrying it over.
You meant that I can directly use skb_shinfo(skb)->nr_frags, right?

> > +		if (net_ratelimit())
> > +			netdev_err(dev, "tx queue full?!\n");
> > +		return -EBUSY;
> > +	}
> > +
> 
> Also it looks like this part will become dead after the following
> patch...
> 

Indeed, I've kept it just for consistency. I had to return some error value
and EBUSY seems the most appropriate. Do you think I should change this?

Thanks for the feedback,
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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