tcp: tcp_mark_head_lost() optimization

It will be a bit more expensive to get the head of rtx queue
once rtx queue is converted to an rb-tree.

We can avoid this extra cost in case tp->lost_skb_hint is set.

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

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 90afe41..abc3b1d 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2207,12 +2207,12 @@ static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
        const u32 loss_high = tcp_is_sack(tp) ?  tp->snd_nxt : tp->high_seq;
 
        WARN_ON(packets > tp->packets_out);
-       if (tp->lost_skb_hint) {
-               skb = tp->lost_skb_hint;
-               cnt = tp->lost_cnt_hint;
+       skb = tp->lost_skb_hint;
+       if (skb) {
                /* Head already handled? */
-               if (mark_head && skb != tcp_write_queue_head(sk))
+               if (mark_head && after(TCP_SKB_CB(skb)->seq, tp->snd_una))
                        return;
+               cnt = tp->lost_cnt_hint;
        } else {
                skb = tcp_write_queue_head(sk);
                cnt = 0;