From fed66381d65a35198639f564365e61a7f256bf79 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 22 Jul 2010 19:09:08 +0000
Subject: [PATCH] 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>
---
include/linux/skbuff.h | 3 ++-
net/core/skbuff.c | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index f5aa87e1e0c8..d89876b806a0 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -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
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 76d33ca5f037..7da58a25ad92 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -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);
--
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