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Subject[143/156] skbuff: remove unused dma_head & dma_maps fields
2.6.33-stable review patch.  If anyone has any objections, please let us know.


From: Alexander Duyck <>

[ Upstream commit 03e6d819c2cb2cc8ce5642669a0a7c72336ee7a2 ]

The dma map fields in the skb_shared_info structure no longer has any users
and can be dropped since it is making the skb_shared_info unecessarily larger.

Running slabtop show that we were using 4K slabs for the skb->head on x86_64 w/
an allocation size of 1522. It turns out that the dma_head and dma_maps array
made skb_shared large enough that we had crossed over the 2k boundary with
standard frames and as such we were using 4k blocks of memory for all skbs.

Signed-off-by: Alexander Duyck <>
Signed-off-by: Jeff Kirsher <>
Acked-by: Eric Dumazet <>
Signed-off-by: David S. Miller <>
Signed-off-by: Greg Kroah-Hartman <>

include/linux/skbuff.h | 6 ------
1 file changed, 6 deletions(-)

--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -190,9 +190,6 @@ struct skb_shared_info {
atomic_t dataref;
unsigned short nr_frags;
unsigned short gso_size;
- dma_addr_t dma_head;
/* Warning: this field is not always filled in (UFO)! */
unsigned short gso_segs;
unsigned short gso_type;
@@ -201,9 +198,6 @@ struct skb_shared_info {
struct sk_buff *frag_list;
struct skb_shared_hwtstamps hwtstamps;
skb_frag_t frags[MAX_SKB_FRAGS];
- dma_addr_t dma_maps[MAX_SKB_FRAGS];
/* Intermediate layers must ensure that destructor_arg
* remains valid until skb destructor */
void * destructor_arg;

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