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 <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 06a8feb..512dc7d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3179,7 +3179,7 @@
skb_shinfo(nskb)->frag_list = p;
skb_shinfo(nskb)->gso_size = pinfo->gso_size;
pinfo->gso_size = 0;
- skb_header_release(p);
+ __skb_header_release(p);
NAPI_GRO_CB(nskb)->last = p;
nskb->data_len += p->len;
@@ -3211,7 +3211,7 @@
else
NAPI_GRO_CB(p)->last->next = skb;
NAPI_GRO_CB(p)->last = skb;
- skb_header_release(skb);
+ __skb_header_release(skb);
lp = p;
done: