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gro: Optimise Ethernet header comparison

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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>
This commit is contained in:
Herbert Xu 2009-02-08 18:00:37 +00:00 committed by David S. Miller
parent 4ae5544f9a
commit aa4b9f533e
4 changed files with 33 additions and 22 deletions
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21
include/linux/etherdevice.h
View File

@ -184,4 +184,25 @@ static inline unsigned compare_ether_addr_64bits(const u8 addr1[6+2],
}
#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 */

7
include/linux/netdevice.h
View File

@ -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,

4
net/8021q/vlan_core.c
View File

@ -85,7 +85,9 @@ static int 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;
NAPI_GRO_CB(p)->same_flow =
p->dev == skb->dev && !compare_ether_header(
skb_mac_header(p), skb_gro_mac_header(skb));
NAPI_GRO_CB(p)->flush = 0;
}

23
net/core/dev.c
View File

@ -215,13 +215,6 @@ static inline struct hlist_head *dev_index_hash(struct net *net, int ifindex)
return &net->dev_index_head[ifindex & ((1 << NETDEV_HASHBITS) - 1)];
}
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;
}
/* Device list insertion */
static int list_netdevice(struct net_device *dev)
{
@ -2415,29 +2408,16 @@ int dev_gro_receive(struct napi_struct *napi, struct sk_buff *skb)
rcu_read_lock();
list_for_each_entry_rcu(ptype, head, list) {
struct sk_buff *p;
void *mac;
if (ptype->type != type || ptype->dev || !ptype->gro_receive)
continue;
skb_set_network_header(skb, skb_gro_offset(skb));
mac = skb_gro_mac_header(skb);
mac_len = skb->network_header - skb->mac_header;
skb->mac_len = mac_len;
NAPI_GRO_CB(skb)->same_flow = 0;
NAPI_GRO_CB(skb)->flush = 0;
NAPI_GRO_CB(skb)->free = 0;
for (p = napi->gro_list; p; p = p->next) {
if (!NAPI_GRO_CB(p)->same_flow)
continue;
if (p->mac_len != mac_len ||
memcmp(skb_mac_header(p), mac, mac_len))
NAPI_GRO_CB(p)->same_flow = 0;
}
pp = ptype->gro_receive(&napi->gro_list, skb);
break;
}
@ -2492,7 +2472,8 @@ static int __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 = 1;
NAPI_GRO_CB(p)->same_flow = !compare_ether_header(
skb_mac_header(p), skb_gro_mac_header(skb));
NAPI_GRO_CB(p)->flush = 0;
}