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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: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2016-04-13 22:05:40 -07:00 committed by David S. Miller
parent b3d051477c
commit 8804b2722d
1 changed files with 2 additions and 2 deletions
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4
net/ipv4/tcp_input.c
View File

@ -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 &&