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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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23
net/core/dev.c
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@ -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;
}