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gro: Optimise length comparison in skb_gro_header 

By caching frag0_len, we can avoid checking both frag0 and the
length separately in skb_gro_header.  This helps as skb_gro_header
is called four times per packet which amounts to a few million
times at 10Gb/s.

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 2009-05-26 18:50:27 +00:00 committed by David S. Miller
parent 30a3ae30c7
commit 7489594cb2
2 changed files with 9 additions and 3 deletions
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7
include/linux/netdevice.h
View File

@ -1011,6 +1011,9 @@ struct napi_gro_cb {
/* Virtual address of skb_shinfo(skb)->frags[0].page + offset. */
void *frag0;
/* Length of frag0. */
unsigned int frag0_len;
/* This indicates where we are processing relative to skb->data. */
int data_offset;
@ -1134,9 +1137,9 @@ static inline void *skb_gro_header(struct sk_buff *skb, unsigned int hlen)
unsigned int offset = skb_gro_offset(skb);
hlen += offset;
if (!NAPI_GRO_CB(skb)->frag0 ||
unlikely(skb_shinfo(skb)->frags[0].size < hlen)) {
if (NAPI_GRO_CB(skb)->frag0_len < hlen) {
NAPI_GRO_CB(skb)->frag0 = NULL;
NAPI_GRO_CB(skb)->frag0_len = 0;
return pskb_may_pull(skb, hlen) ? skb->data + offset : NULL;
}

5
net/core/dev.c
View File

@ -2509,12 +2509,15 @@ void skb_gro_reset_offset(struct sk_buff *skb)
{
NAPI_GRO_CB(skb)->data_offset = 0;
NAPI_GRO_CB(skb)->frag0 = NULL;
NAPI_GRO_CB(skb)->frag0_len = 0;
if (skb->mac_header == skb->tail &&
!PageHighMem(skb_shinfo(skb)->frags[0].page))
!PageHighMem(skb_shinfo(skb)->frags[0].page)) {
NAPI_GRO_CB(skb)->frag0 =
page_address(skb_shinfo(skb)->frags[0].page) +
skb_shinfo(skb)->frags[0].page_offset;
NAPI_GRO_CB(skb)->frag0_len = skb_shinfo(skb)->frags[0].size;
}
}
EXPORT_SYMBOL(skb_gro_reset_offset);