From 8804b2722dc5d6f9b7ba0a9e812eae9ee5ce95bc Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 13 Apr 2016 22:05:40 -0700 Subject: [PATCH] tcp: remove false sharing in tcp_rcv_state_process() Last known hot point during SYNFLOOD attack is the clearing of rx_opt.saw_tstamp in tcp_rcv_state_process() It is not needed for a listener, so we move it where it matters. Performance while a SYNFLOOD hits a single listener socket went from 5 Mpps to 6 Mpps on my test server (24 cores, 8 NIC RX queues) Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 7ea7034af83f..90e0d9256b74 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5796,8 +5796,6 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) int queued = 0; bool acceptable; - tp->rx_opt.saw_tstamp = 0; - switch (sk->sk_state) { case TCP_CLOSE: goto discard; @@ -5838,6 +5836,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) goto discard; case TCP_SYN_SENT: + tp->rx_opt.saw_tstamp = 0; queued = tcp_rcv_synsent_state_process(sk, skb, th); if (queued >= 0) return queued; @@ -5849,6 +5848,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) return 0; } + tp->rx_opt.saw_tstamp = 0; req = tp->fastopen_rsk; if (req) { WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && -- 2.30.2