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[NET]: Speed up __alloc_skb()

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From: Benjamin LaHaise <bcrl@kvack.org>

In __alloc_skb(), the use of skb_shinfo() which casts a u8 * to the 
shared info structure results in gcc being forced to do a reload of the 
pointer since it has no information on possible aliasing.  Fix this by 
using a pointer to refer to skb_shared_info.

By initializing skb_shared_info sequentially, the write combining buffers 
can reduce the number of memory transactions to a single write.  Reorder 
the initialization in __alloc_skb() to match the structure definition.  
There is also an alignment issue on 64 bit systems with skb_shared_info 
by converting nr_frags to a short everything packs up nicely.

Also, pass the slab cache pointer according to the fclone flag instead 
of using two almost identical function calls.

This raises bw_unix performance up to a peak of 707KB/s when combined 
with the spinlock patch.  It should help other networking protocols, too.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Benjamin LaHaise 2006-01-03 14:06:50 -08:00 • committed by David S. Miller
parent 17ba15fb62
commit 4947d3ef8d
2 changed files with 14 additions and 15 deletions
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2
include/linux/skbuff.h
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@ -133,7 +133,7 @@ struct skb_frag_struct {
*/
struct skb_shared_info {
atomic_t dataref;
unsigned int nr_frags;
unsigned short nr_frags;
unsigned short tso_size;
unsigned short tso_segs;
unsigned short ufo_size;