netdev - [PATCH net-next 4/7] tcp: tcp_mark_head

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Date:   Thu,  5 Oct 2017 22:21:24 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Neal Cardwell <ncardwell@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 4/7] 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@...gle.com>
---
 net/ipv4/tcp_input.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 90afe41435966fc62ae8cb5799ca4c99995076dc..abc3b1db81f85a7feebda40cebc90c07afcef446 100644
--- 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;
-- 
2.14.2.920.gcf0c67979c-goog