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net: pskb_expand_head() optimization 

Move frags[] at the end of struct skb_shared_info, and make
pskb_expand_head() copy only the used part of it instead of whole array.

This should avoid kmemcheck warnings and speedup pskb_expand_head() as
well, avoiding a lot of cache misses.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2010-07-22 19:09:08 +00:00 committed by David S. Miller
parent c1f79426e2
commit fed66381d6
2 changed files with 3 additions and 2 deletions
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3
include/linux/skbuff.h
View File

@ -202,10 +202,11 @@ struct skb_shared_info {
*/
atomic_t dataref;
skb_frag_t frags[MAX_SKB_FRAGS];
/* Intermediate layers must ensure that destructor_arg
* remains valid until skb destructor */
void * destructor_arg;
/* must be last field, see pskb_expand_head() */
skb_frag_t frags[MAX_SKB_FRAGS];
};
/* We divide dataref into two halves. The higher 16 bits hold references

2
net/core/skbuff.c
View File

@ -817,7 +817,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
memcpy(data + nhead, skb->head, skb->tail - skb->head);
#endif
memcpy(data + size, skb_end_pointer(skb),
sizeof(struct skb_shared_info));
offsetof(struct skb_shared_info, frags[skb_shinfo(skb)->nr_frags]));
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
get_page(skb_shinfo(skb)->frags[i].page);