skbuff: remove unused dma_head & dma_maps fields
Alexander Duyck [Tue, 23 Mar 2010 20:40:50 +0000 (20:40 +0000)]
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 <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

index 03f816a..124f90c 100644 (file)
@@ -190,9 +190,6 @@ struct skb_shared_info {
        atomic_t        dataref;
        unsigned short  nr_frags;
        unsigned short  gso_size;
-#ifdef CONFIG_HAS_DMA
-       dma_addr_t      dma_head;
-#endif
        /* 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];
-#ifdef CONFIG_HAS_DMA
-       dma_addr_t      dma_maps[MAX_SKB_FRAGS];
-#endif
        /* Intermediate layers must ensure that destructor_arg
         * remains valid until skb destructor */
        void *          destructor_arg;