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>

2 files changed, 12 insertions, 7 deletions

diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
index 07eeb5b99dce..3438c01bbacf 100644
--- a/net/8021q/vlan_core.c
+++ b/net/8021q/vlan_core.c
@@ -105,9 +105,12 @@ vlan_gro_common(struct napi_struct *napi, struct vlan_group *grp,
                 goto drop;
 
         for (p = napi->gro_list; p; p = p->next) {
-                NAPI_GRO_CB(p)->same_flow =
-                        p->dev == skb->dev && !compare_ether_header(
-                                skb_mac_header(p), skb_gro_mac_header(skb));
+                unsigned long diffs;
+
+                diffs = (unsigned long)p->dev ^ (unsigned long)skb->dev;
+                diffs |= compare_ether_header(skb_mac_header(p),
+                                              skb_gro_mac_header(skb));
+                NAPI_GRO_CB(p)->same_flow = !diffs;
                 NAPI_GRO_CB(p)->flush = 0;
         }
 
diff --git a/net/core/dev.c b/net/core/dev.c
index 859e30ff044a..63bd20a75929 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3169,16 +3169,18 @@ normal:
 }
 EXPORT_SYMBOL(dev_gro_receive);
 
-static gro_result_t
+static inline gro_result_t
 __napi_gro_receive(struct napi_struct *napi, struct sk_buff *skb)
 {
         struct sk_buff *p;
 
         for (p = napi->gro_list; p; p = p->next) {
-                NAPI_GRO_CB(p)->same_flow =
-                        (p->dev == skb->dev) &&
-                        !compare_ether_header(skb_mac_header(p),
+                unsigned long diffs;
+
+                diffs = (unsigned long)p->dev ^ (unsigned long)skb->dev;
+                diffs |= compare_ether_header(skb_mac_header(p),
                                               skb_gro_mac_header(skb));
+                NAPI_GRO_CB(p)->same_flow = !diffs;
                 NAPI_GRO_CB(p)->flush = 0;
         }