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: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 31 insertions, 1 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7a10f0894152..7645df1bada0 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -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));
 
-        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)) {
                 skb_reserve(skb, NET_SKB_PAD);
                 skb->dev = dev;