gro: __napi_gro_receive() optimizations
compare_ether_header() can have a special implementation on 64 bit
arches if CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is defined.
__napi_gro_receive() and vlan_gro_common() can avoid a conditional
branch to perform device match.
On x86_64, __napi_gro_receive() has now 38 instructions instead of 53
As gcc-4.4.3 still choose to not inline it, add inline keyword to this
performance critical function.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: 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 2308fbb..fb6aa60 100644
--- a/include/linux/etherdevice.h
+++ b/include/linux/etherdevice.h
@@ -237,13 +237,29 @@
* entry points.
*/
-static inline int compare_ether_header(const void *a, const void *b)
+static inline unsigned long compare_ether_header(const void *a, const void *b)
{
+#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
+ unsigned long fold;
+
+ /*
+ * We want to compare 14 bytes:
+ * [a0 ... a13] ^ [b0 ... b13]
+ * Use two long XOR, ORed together, with an overlap of two bytes.
+ * [a0 a1 a2 a3 a4 a5 a6 a7 ] ^ [b0 b1 b2 b3 b4 b5 b6 b7 ] |
+ * [a6 a7 a8 a9 a10 a11 a12 a13] ^ [b6 b7 b8 b9 b10 b11 b12 b13]
+ * This means the [a6 a7] ^ [b6 b7] part is done two times.
+ */
+ fold = *(unsigned long *)a ^ *(unsigned long *)b;
+ fold |= *(unsigned long *)(a + 6) ^ *(unsigned long *)(b + 6);
+ return fold;
+#else
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
}
#endif /* _LINUX_ETHERDEVICE_H */