Eric Dumazet a écrit :
But seeing your disassembly, I can see compare_ether_addr() is not inlined.
This sucks.
/**
* compare_ether_addr - Compare two Ethernet addresses
* @addr1: Pointer to a six-byte array containing the Ethernet address
* @addr2: Pointer other six-byte array containing the Ethernet address
*
* Compare two ethernet addresses, returns 0 if equal
*/
static inline unsigned compare_ether_addr(const u8 *addr1, const u8 *addr2)
{
const u16 *a = (const u16 *) addr1;
const u16 *b = (const u16 *) addr2;
BUILD_BUG_ON(ETH_ALEN != 6);
return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | (a[2] ^ b[2])) != 0;
}
On my machine/compiler, it is inlined, that makes a big difference.
old gcc compiler... OK understood...
c0420750 <eth_type_trans>: /* eth_type_trans total: 14417 0.4101 */
Could you try this patch Ingo ?
Thanks
[PATCH] net: eth_type_trans() should be a leaf function
In old days, eth_type_trans() was a leaf function. It is not anymore the case.
eth_type_trans() is a critical network function, called for each incoming packet.
We should make sure it is not calling functions, especially trivial ones.
1) Adds an __always_inline to compare_ether_addr() : This one was created to be faster
than memcmp(). It really should be faster (and inlined)
2) Hand code skb_put() call in eth_type_trans()
Signed-off-by: Eric Dumazet <dada1@xxxxxxxxxxxxx>
---
include/linux/etherdevice.h | 2 +-
net/ethernet/eth.c | 7 ++++++-
2 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
index 25d62e6..94af6a7 100644
--- a/include/linux/etherdevice.h
+++ b/include/linux/etherdevice.h
@@ -128,7 +128,7 @@ static inline void random_ether_addr(u8 *addr)
*
* Compare two ethernet addresses, returns 0 if equal
*/
-static inline unsigned compare_ether_addr(const u8 *addr1, const u8 *addr2)
+static __always_inline unsigned compare_ether_addr(const u8 *addr1, const u8 *addr2)
{
const u16 *a = (const u16 *) addr1;
const u16 *b = (const u16 *) addr2;
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index b9d85af..30b60b2 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -162,7 +162,12 @@ __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
skb->dev = dev;
skb_reset_mac_header(skb);
- skb_pull(skb, ETH_HLEN);
+ /*
+ * Hand coded skb_pull(skb, ETH_HLEN) to avoid a function call
+ */
+ if (likely(skb->len >= ETH_HLEN))
+ __skb_pull(skb, ETH_HLEN);
+
eth = eth_hdr(skb);
if (is_multicast_ether_addr(eth->h_dest)) {
