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| author | Benjamin LaHaise <bcrl@kvack.org> | 2006-01-03 14:06:50 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2006-01-03 14:06:50 -0800 |
| commit | 4947d3ef8de7b4f42aed6ea9ba689dc8fb45b5a5 (patch) | |
| tree | a4e77f0271702e4ff34a7a9e0c9598a3807204ee /net/core | |
| parent | 17ba15fb6264f27374bc87f4c3f8519b80289d85 (diff) | |
| download | linux-4947d3ef8de7b4f42aed6ea9ba689dc8fb45b5a5.tar.bz2 | |
[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/core')
| -rw-r--r-- | net/core/skbuff.c | 27 |
1 files changed, 13 insertions, 14 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 83fee37de38e..070f91cfde59 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: |