Re: [PATCH net-next] net: pktgen: packet bursting via skb->xmit_more

[Eric Dumazet <eric.dumazet@gmail.com>]

On Tue, 2014-09-30 at 17:03 -0700, Alexei Starovoitov wrote:
...

>  static void pktgen_xmit(struct pktgen_dev *pkt_dev)
>  {
> +	unsigned int burst = ACCESS_ONCE(pkt_dev->burst), burst_cnt;
>  	struct net_device *odev = pkt_dev->odev;
>  	struct netdev_queue *txq;
> +	bool more;
>  	int ret;
>  
>  	/* If device is offline, then don't send */
> @@ -3347,8 +3363,14 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
>  		pkt_dev->last_ok = 0;
>  		goto unlock;
>  	}
> -	atomic_inc(&(pkt_dev->skb->users));
> -	ret = netdev_start_xmit(pkt_dev->skb, odev, txq, false);
> +	atomic_add(burst, &pkt_dev->skb->users);
> +
> +	burst_cnt = 0;
> +

It seems you dont really need @burst_cnt or @more in this function.

xmit_more:
	ret = netdev_start_xmit(pkt_dev->skb, odev, txq, --burst > 0);

> +xmit_more:
> +	more = ++burst_cnt < burst;
> +
> +	ret = netdev_start_xmit(pkt_dev->skb, odev, txq, more);
>  
>  	switch (ret) {
>  	case NETDEV_TX_OK:
> @@ -3356,6 +3378,8 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
>  		pkt_dev->sofar++;
>  		pkt_dev->seq_num++;
>  		pkt_dev->tx_bytes += pkt_dev->last_pkt_size;
> +		if (more && !netif_xmit_frozen_or_drv_stopped(txq))
> +			goto xmit_more;

	if (burst > 0 && !netif_xmit_frozen_or_drv_stopped(txq))
		goto xmit_more

>  		break;
>  	case NET_XMIT_DROP:
>  	case NET_XMIT_CN:
> @@ -3374,6 +3398,9 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
>  		atomic_dec(&(pkt_dev->skb->users));
>  		pkt_dev->last_ok = 0;
>  	}
> +
> +	if (unlikely(burst - burst_cnt > 0))
> +		atomic_sub(burst - burst_cnt, &pkt_dev->skb->users);

	if (unlikely(burst))
		atomic_sub(burst, &pkt_dev->skb->users);

>  unlock:
>  	HARD_TX_UNLOCK(odev, txq);
>  
> @@ -3572,6 +3599,7 @@ static int pktgen_add_device(struct pktgen_thread *t, const char *ifname)
>  	pkt_dev->svlan_p = 0;
>  	pkt_dev->svlan_cfi = 0;
>  	pkt_dev->svlan_id = 0xffff;
> +	pkt_dev->burst = 1;
>  	pkt_dev->node = -1;
>  
>  	err = pktgen_setup_dev(t->net, pkt_dev, ifname);