target/linux/generic/backport-4.9/024-6-tcp-tcp_mtu_probe-is-likely-to-exit-early.patch

   1 From 12a59abc22d6664f7d3944f625ceefee92de8820 Mon Sep 17 00:00:00 2001
   2 From: Eric Dumazet <edumazet@google.com>
   3 Date: Sat, 3 Dec 2016 11:14:55 -0800
   4 Subject: [PATCH 06/10] tcp: tcp_mtu_probe() is likely to exit early
   5
   6 Adding a likely() in tcp_mtu_probe() moves its code which used to
   7 be inlined in front of tcp_write_xmit()
   8
   9 We still have a cache line miss to access icsk->icsk_mtup.enabled,
  10 we will probably have to reorganize fields to help data locality.
  11
  12 Signed-off-by: Eric Dumazet <edumazet@google.com>
  13 Signed-off-by: David S. Miller <davem@davemloft.net>
  14 ---
  15  net/ipv4/tcp_output.c | 18 +++++++++---------
  16  1 file changed, 9 insertions(+), 9 deletions(-)
  17
  18 --- a/net/ipv4/tcp_output.c
  19 +++ b/net/ipv4/tcp_output.c
  20 @@ -1948,26 +1948,26 @@ static bool tcp_can_coalesce_send_queue_
  21   */
  22  static int tcp_mtu_probe(struct sock *sk)
  23  {
  24 -       struct tcp_sock *tp = tcp_sk(sk);
  25         struct inet_connection_sock *icsk = inet_csk(sk);
  26 +       struct tcp_sock *tp = tcp_sk(sk);
  27         struct sk_buff *skb, *nskb, *next;
  28         struct net *net = sock_net(sk);
  29 -       int len;
  30         int probe_size;
  31         int size_needed;
  32 -       int copy;
  33 +       int copy, len;
  34         int mss_now;
  35         int interval;
  36
  37         /* Not currently probing/verifying,
  38          * not in recovery,
  39          * have enough cwnd, and
  40 -        * not SACKing (the variable headers throw things off) */
  41 -       if (!icsk->icsk_mtup.enabled ||
  42 -           icsk->icsk_mtup.probe_size ||
  43 -           inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
  44 -           tp->snd_cwnd < 11 ||
  45 -           tp->rx_opt.num_sacks || tp->rx_opt.dsack)
  46 +        * not SACKing (the variable headers throw things off)
  47 +        */
  48 +       if (likely(!icsk->icsk_mtup.enabled ||
  49 +                  icsk->icsk_mtup.probe_size ||
  50 +                  inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
  51 +                  tp->snd_cwnd < 11 ||
  52 +                  tp->rx_opt.num_sacks || tp->rx_opt.dsack))
  53                 return -1;
  54
  55         /* Use binary search for probe_size between tcp_mss_base,