[ofa-general] Re: [PATCH 2/9 Rev3] [core] Add skb_blist & hard_start_xmit_batch

[Evgeniy Polyakov]

Hi Krishna.

On Wed, Aug 08, 2007 at 03:01:35PM +0530, Krishna Kumar (krkumar2 at in.ibm.com) wrote:
> +int dev_change_tx_batch_skb(struct net_device *dev, unsigned long new_batch_skb)
> +{
> +	int ret = 0;
> +	struct sk_buff_head *blist;
> +
> +	if (!dev->hard_start_xmit_batch) {
> +		/* Driver doesn't support batching skb API */
> +		ret = -ENOTSUPP;
> +		goto out;
> +	}
> +
> +	/* Handle invalid argument */
> +	if (new_batch_skb < 0) {
> +		ret = -EINVAL;
> +		goto out;
> +	}

It is unsigned, how can it be less than zero?

And actually you use it just like a binary flag (casted to/from u32 in
the code, btw), so why not using ethtool_value directly here?

> +	/* Check if new value is same as the current */
> +	if (!!dev->skb_blist == !!new_batch_skb)
> +		goto out;
> +
> +	if (new_batch_skb &&
> +	    (blist = kmalloc(sizeof *blist, GFP_KERNEL)) == NULL) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +
> +	spin_lock(&dev->queue_lock);
> +	if (new_batch_skb) {
> +		skb_queue_head_init(blist);
> +		dev->skb_blist = blist;
> +	} else
> +		free_batching(dev);
> +	spin_unlock(&dev->queue_lock);

This needs bh lock too, since blist is accessed by qdisc_restart.

> +int dev_add_skb_to_blist(struct sk_buff *skb, struct net_device *dev)
> +{
> +	if (!list_empty(&ptype_all))
> +		dev_queue_xmit_nit(skb, dev);
> +
> +	if (netif_needs_gso(dev, skb)) {
> +		if (unlikely(dev_gso_segment(skb))) {
> +			kfree(skb);
> +			return 0;
> +		}
> +
> +		if (skb->next) {
> +			int count = 0;
> +
> +			do {
> +				struct sk_buff *nskb = skb->next;
> +
> +				skb->next = nskb->next;
> +				__skb_queue_tail(dev->skb_blist, nskb);
> +				count++;
> +			} while (skb->next);

Is it possible to move list without iterating over each entry?


-- 
	Evgeniy Polyakov