tcp: remove false sharing in tcp_rcv_state_process() (8804b272) · Commits · 戴 / test

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 <edumazet@google.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -5796,8 +5796,6 @@ int tcp_rcv_state_process(struct sock sk, struct sk_buff skb)
	int queued = 0;		int queued = 0;
	bool acceptable;		bool acceptable;

	tp->rx_opt.saw_tstamp = 0;

	switch (sk->sk_state) {		switch (sk->sk_state) {
	case TCP_CLOSE:		case TCP_CLOSE:
	goto discard;		goto discard;
	@@ -5838,6 +5836,7 @@ int tcp_rcv_state_process(struct sock sk, struct sk_buff skb)
	goto discard;		goto discard;

	case TCP_SYN_SENT:		case TCP_SYN_SENT:
			tp->rx_opt.saw_tstamp = 0;
	queued = tcp_rcv_synsent_state_process(sk, skb, th);		queued = tcp_rcv_synsent_state_process(sk, skb, th);
	if (queued >= 0)		if (queued >= 0)
	return queued;		return queued;
	@@ -5849,6 +5848,7 @@ int tcp_rcv_state_process(struct sock sk, struct sk_buff skb)
	return 0;		return 0;
	}		}

			tp->rx_opt.saw_tstamp = 0;
	req = tp->fastopen_rsk;		req = tp->fastopen_rsk;
	if (req) {		if (req) {
	WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&		WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&

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