skbuff: pass the result of data ksize to __build_skb_around

Avoid to call ksize again in __build_skb_around by passing
the result of data ksize to __build_skb_around

nginx stress test shows this change can reduce ksize cpu usage,
and give a little performance boost

Signed-off-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7c2ab27..74601bb 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -394,8 +394,9 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
 {
        struct kmem_cache *cache;
        struct sk_buff *skb;
-       u8 *data;
+       unsigned int osize;
        bool pfmemalloc;
+       u8 *data;
 
        cache = (flags & SKB_ALLOC_FCLONE)
                ? skbuff_fclone_cache : skbuff_head_cache;
@@ -427,7 +428,8 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
         * Put skb_shared_info exactly at the end of allocated zone,
         * to allow max possible filling before reallocation.
         */
-       size = SKB_WITH_OVERHEAD(ksize(data));
+       osize = ksize(data);
+       size = SKB_WITH_OVERHEAD(osize);
        prefetchw(data + size);
 
        /*
@@ -436,7 +438,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
         * the tail pointer in struct sk_buff!
         */
        memset(skb, 0, offsetof(struct sk_buff, tail));
-       __build_skb_around(skb, data, 0);
+       __build_skb_around(skb, data, osize);
        skb->pfmemalloc = pfmemalloc;
 
        if (flags & SKB_ALLOC_FCLONE) {