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authorBenjamin LaHaise <bcrl@kvack.org>2006-01-03 14:06:50 -0800
committerDavid S. Miller <davem@davemloft.net>2006-01-03 14:06:50 -0800
commit4947d3ef8de7b4f42aed6ea9ba689dc8fb45b5a5 (patch)
treea4e77f0271702e4ff34a7a9e0c9598a3807204ee /net
parent17ba15fb6264f27374bc87f4c3f8519b80289d85 (diff)
[NET]: Speed up __alloc_skb()
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>
Diffstat (limited to 'net')
-rw-r--r--net/core/skbuff.c27
1 files changed, 13 insertions, 14 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 83fee37de38..070f91cfde5 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -135,17 +135,13 @@ void skb_under_panic(struct sk_buff *skb, int sz, void *here)
struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
int fclone)
{
+ struct skb_shared_info *shinfo;
struct sk_buff *skb;
u8 *data;
/* Get the HEAD */
- if (fclone)
- skb = kmem_cache_alloc(skbuff_fclone_cache,
- gfp_mask & ~__GFP_DMA);
- else
- skb = kmem_cache_alloc(skbuff_head_cache,
- gfp_mask & ~__GFP_DMA);
-
+ skb = kmem_cache_alloc(fclone ? skbuff_fclone_cache : skbuff_head_cache,
+ gfp_mask & ~__GFP_DMA);
if (!skb)
goto out;
@@ -162,6 +158,16 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
skb->data = data;
skb->tail = data;
skb->end = data + size;
+ /* make sure we initialize shinfo sequentially */
+ shinfo = skb_shinfo(skb);
+ atomic_set(&shinfo->dataref, 1);
+ shinfo->nr_frags = 0;
+ shinfo->tso_size = 0;
+ shinfo->tso_segs = 0;
+ shinfo->ufo_size = 0;
+ shinfo->ip6_frag_id = 0;
+ shinfo->frag_list = NULL;
+
if (fclone) {
struct sk_buff *child = skb + 1;
atomic_t *fclone_ref = (atomic_t *) (child + 1);
@@ -171,13 +177,6 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
child->fclone = SKB_FCLONE_UNAVAILABLE;
}
- atomic_set(&(skb_shinfo(skb)->dataref), 1);
- skb_shinfo(skb)->nr_frags = 0;
- skb_shinfo(skb)->tso_size = 0;
- skb_shinfo(skb)->tso_segs = 0;
- skb_shinfo(skb)->frag_list = NULL;
- skb_shinfo(skb)->ufo_size = 0;
- skb_shinfo(skb)->ip6_frag_id = 0;
out:
return skb;
nodata: