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Commit 8804b272 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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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: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b3d05147

net/ipv4/tcp_input.c

+2 −2
Original line number Diff line number Diff line
@@ -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 &&