[NET]: Implement SKB fast cloning.

Protocols that make extensive use of SKB cloning,
for example TCP, eat at least 2 allocations per
packet sent as a result.

To cut the kmalloc() count in half, we implement
a pre-allocation scheme wherein we allocate
2 sk_buff objects in advance, then use a simple
reference count to free up the memory at the
correct time.

Based upon an initial patch by Thomas Graf and
suggestions from Herbert Xu.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 8d92ab562aed..75b68116682a 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1582,7 +1582,7 @@ void tcp_send_fin(struct sock *sk)
         } else {
                 /* Socket is locked, keep trying until memory is available. */
                 for (;;) {
-                        skb = alloc_skb(MAX_TCP_HEADER, GFP_KERNEL);
+                        skb = alloc_skb_fclone(MAX_TCP_HEADER, GFP_KERNEL);
                         if (skb)
                                 break;
                         yield();
@@ -1804,7 +1804,7 @@ int tcp_connect(struct sock *sk)
 
         tcp_connect_init(sk);
 
-        buff = alloc_skb(MAX_TCP_HEADER + 15, sk->sk_allocation);
+        buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation);
         if (unlikely(buff == NULL))
                 return -ENOBUFS;