From f4a775d14489a801a5b8b0540e23ab82e2703091 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 22 Sep 2014 16:29:32 -0700 Subject: net: introduce __skb_header_release() While profiling TCP stack, I noticed one useless atomic operation in tcp_sendmsg(), caused by skb_header_release(). It turns out all current skb_header_release() users have a fresh skb, that no other user can see, so we can avoid one atomic operation. Introduce __skb_header_release() to clearly document this. This gave me a 1.5 % improvement on TCP_RR workload. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/skbuff.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'include/linux/skbuff.h') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index f1bfa3781c75..8eaa62400fca 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1083,6 +1083,7 @@ static inline int skb_header_cloned(const struct sk_buff *skb) * Drop a reference to the header part of the buffer. This is done * by acquiring a payload reference. You must not read from the header * part of skb->data after this. + * Note : Check if you can use __skb_header_release() instead. */ static inline void skb_header_release(struct sk_buff *skb) { @@ -1091,6 +1092,20 @@ static inline void skb_header_release(struct sk_buff *skb) atomic_add(1 << SKB_DATAREF_SHIFT, &skb_shinfo(skb)->dataref); } +/** + * __skb_header_release - release reference to header + * @skb: buffer to operate on + * + * Variant of skb_header_release() assuming skb is private to caller. + * We can avoid one atomic operation. + */ +static inline void __skb_header_release(struct sk_buff *skb) +{ + skb->nohdr = 1; + atomic_set(&skb_shinfo(skb)->dataref, 1 + (1 << SKB_DATAREF_SHIFT)); +} + + /** * skb_shared - is the buffer shared * @skb: buffer to check -- cgit v1.2.3-55-g7522