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Commit a1c7fff7 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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net: netdev_alloc_skb() use build_skb() 



netdev_alloc_skb() is used by networks driver in their RX path to
allocate an skb to receive an incoming frame.

With recent skb->head_frag infrastructure, it makes sense to change
netdev_alloc_skb() to use build_skb() and a frag allocator.

This permits a zero copy splice(socket->pipe), and better GRO or TCP
coalescing.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1de5a71c

net/core/skbuff.c

+31 −1
Original line number Diff line number Diff line
@@ -293,6 +293,12 @@ struct sk_buff *build_skb(void *data, unsigned int frag_size) 
}

EXPORT_SYMBOL(build_skb);



struct netdev_alloc_cache {

	struct page *page;

	unsigned int offset;

};

static DEFINE_PER_CPU(struct netdev_alloc_cache, netdev_alloc_cache);



/**

 *	__netdev_alloc_skb - allocate an skbuff for rx on a specific device

 *	@dev: network device to receive on
@@ -310,8 +316,32 @@ struct sk_buff *__netdev_alloc_skb(struct net_device *dev, 
		unsigned int length, gfp_t gfp_mask)

{

	struct sk_buff *skb;

	unsigned int fragsz = SKB_DATA_ALIGN(length + NET_SKB_PAD) +

			      SKB_DATA_ALIGN(sizeof(struct skb_shared_info));



	if (fragsz <= PAGE_SIZE && !(gfp_mask & __GFP_WAIT)) {

		struct netdev_alloc_cache *nc;

		void *data = NULL;



		nc = &get_cpu_var(netdev_alloc_cache);

		if (!nc->page) {

refill:			nc->page = alloc_page(gfp_mask);

			nc->offset = 0;

		}

		if (likely(nc->page)) {

			if (nc->offset + fragsz > PAGE_SIZE) {

				put_page(nc->page);

				goto refill;

			}

			data = page_address(nc->page) + nc->offset;

			nc->offset += fragsz;

			get_page(nc->page);

		}

		put_cpu_var(netdev_alloc_cache);

		skb = data ? build_skb(data, fragsz) : NULL;

	} else {

		skb = __alloc_skb(length + NET_SKB_PAD, gfp_mask, 0, NUMA_NO_NODE);

	}

	if (likely(skb)) {

		skb_reserve(skb, NET_SKB_PAD);

		skb->dev = dev;