tree d7723697219a35e66ae7c1dab9e85832a0d19e11
parent 13bb5180e82349d9fcfa11cd17b3c1e7b558a902
author Eric Dumazet <edumazet@google.com> 1410779991 -0700
committer David S. Miller <davem@davemloft.net> 1410806467 -0400

tcp: use TCP_SKB_CB(skb)->tcp_flags in input path

Input path of TCP do not currently uses TCP_SKB_CB(skb)->tcp_flags,
which is only used in output path.

tcp_recvmsg(), looks at tcp_hdr(skb)->syn for every skb found in receive queue,
and its unfortunate because this bit is located in a cache line right before
the payload.

We can simplify TCP by copying tcp flags into TCP_SKB_CB(skb)->tcp_flags.

This patch does so, and avoids the cache line miss in tcp_recvmsg()

Following patches will
- allow a segment with FIN being coalesced in tcp_try_coalesce()
- simplify tcp_collapse() by not copying the headers.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>