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net: netdev_alloc_skb() use build_skb()

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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: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-05-17 07:34:16 +00:00 committed by David S. Miller
parent 1de5a71c3e
commit a1c7fff7e1
1 changed files with 31 additions and 1 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

32
net/core/skbuff.c
View file

@ -293,6 +293,12 @@ struct sk_buff *build_skb(void *data, unsigned int frag_size)
} }
EXPORT_SYMBOL(build_skb); 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 * __netdev_alloc_skb - allocate an skbuff for rx on a specific device
* @dev: network device to receive on * @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) unsigned int length, gfp_t gfp_mask)
{ {
struct sk_buff *skb; struct sk_buff *skb;
unsigned int fragsz = SKB_DATA_ALIGN(length + NET_SKB_PAD) +
SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
skb = __alloc_skb(length + NET_SKB_PAD, gfp_mask, 0, NUMA_NO_NODE); 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)) { if (likely(skb)) {
skb_reserve(skb, NET_SKB_PAD); skb_reserve(skb, NET_SKB_PAD);
skb->dev = dev; skb->dev = dev;