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>
diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
index 1cb0f0b..a1f17ab 100644
--- a/include/linux/etherdevice.h
+++ b/include/linux/etherdevice.h
@@ -184,4 +184,25 @@
}
#endif /* __KERNEL__ */
+/**
+ * compare_ether_header - Compare two Ethernet headers
+ * @a: Pointer to Ethernet header
+ * @b: Pointer to Ethernet header
+ *
+ * Compare two ethernet headers, returns 0 if equal.
+ * This assumes that the network header (i.e., IP header) is 4-byte
+ * aligned OR the platform can handle unaligned access. This is the
+ * case for all packets coming into netif_receive_skb or similar
+ * entry points.
+ */
+
+static inline int compare_ether_header(const void *a, const void *b)
+{
+ u32 *a32 = (u32 *)((u8 *)a + 2);
+ u32 *b32 = (u32 *)((u8 *)b + 2);
+
+ return (*(u16 *)a ^ *(u16 *)b) | (a32[0] ^ b32[0]) |
+ (a32[1] ^ b32[1]) | (a32[2] ^ b32[2]);
+}
+
#endif /* _LINUX_ETHERDEVICE_H */