gro: Optimise Ethernet header comparison

This patch optimises the Ethernet header comparison to use 2-byte
and 4-byte xors instead of memcmp.  In order to facilitate this,
the actual comparison is now carried out by the callers of the
shared dev_gro_receive function.

This has a significant impact when receiving 1500B packets through
10GbE.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 9ee344bc6c13..355662aac940 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1117,6 +1117,13 @@ static inline void skb_gro_reset_offset(struct sk_buff *skb)
         NAPI_GRO_CB(skb)->data_offset = 0;
 }
 
+static inline void *skb_gro_mac_header(struct sk_buff *skb)
+{
+        return skb_mac_header(skb) < skb->data ? skb_mac_header(skb) :
+               page_address(skb_shinfo(skb)->frags[0].page) +
+               skb_shinfo(skb)->frags[0].page_offset;
+}
+
 static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev,
                                   unsigned short type,
                                   const void *daddr, const void *saddr,