From dca0aaf8472f15836a68bbed8a0ef9ea39e783aa Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 17 Aug 2016 07:48:36 -0700 Subject: [PATCH] tcp: defer sacked assignment While chasing tcp_xmit_retransmit_queue() kasan issue, I found that we could avoid reading sacked field of skb that we wont send, possibly removing one cache line miss. Very minor change in slow path, but why not ? ;) Signed-off-by: Eric Dumazet Acked-by: Neal Cardwell Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index bdaef7fd6e47..8b45794eb6b2 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2776,7 +2776,7 @@ void tcp_xmit_retransmit_queue(struct sock *sk) max_segs = tcp_tso_autosize(sk, tcp_current_mss(sk)); tcp_for_write_queue_from(skb, sk) { - __u8 sacked = TCP_SKB_CB(skb)->sacked; + __u8 sacked; int segs; if (skb == tcp_send_head(sk)) @@ -2788,6 +2788,7 @@ void tcp_xmit_retransmit_queue(struct sock *sk) segs = tp->snd_cwnd - tcp_packets_in_flight(tp); if (segs <= 0) return; + sacked = TCP_SKB_CB(skb)->sacked; /* In case tcp_shift_skb_data() have aggregated large skbs, * we need to make sure not sending too bigs TSO packets */ -- 2.20.1