From e994b2f0fb9229aeff5eea9541320bd7b2ca8714 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 2 Oct 2015 11:43:39 -0700 Subject: [PATCH] tcp: do not lock listener to process SYN packets Everything should now be ready to finally allow SYN packets processing without holding listener lock. Tested: 3.5 Mpps SYNFLOOD. Plenty of cpu cycles available. Next bottleneck is the refcount taken on listener, that could be avoided if we remove SLAB_DESTROY_BY_RCU strict semantic for listeners, and use regular RCU. 13.18% [kernel] [k] __inet_lookup_listener 9.61% [kernel] [k] tcp_conn_request 8.16% [kernel] [k] sha_transform 5.30% [kernel] [k] inet_reqsk_alloc 4.22% [kernel] [k] sock_put 3.74% [kernel] [k] tcp_make_synack 2.88% [kernel] [k] ipt_do_table 2.56% [kernel] [k] memcpy_erms 2.53% [kernel] [k] sock_wfree 2.40% [kernel] [k] tcp_v4_rcv 2.08% [kernel] [k] fib_table_lookup 1.84% [kernel] [k] tcp_openreq_init_rwin Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_ipv4.c | 11 +++++++++-- net/ipv6/tcp_ipv6.c | 11 +++++++++-- 2 files changed, 18 insertions(+), 4 deletions(-) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index ac2ea73e9aafc..34310748a3655 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1355,7 +1355,7 @@ static struct sock *tcp_v4_cookie_check(struct sock *sk, struct sk_buff *skb) } /* The socket must have it's spinlock held when we get - * here. + * here, unless it is a TCP_LISTEN socket. * * We have a potential double-lock case here, so even when * doing backlog processing we use the BH locking scheme. @@ -1619,9 +1619,15 @@ int tcp_v4_rcv(struct sk_buff *skb) if (sk_filter(sk, skb)) goto discard_and_relse; - sk_incoming_cpu_update(sk); skb->dev = NULL; + if (sk->sk_state == TCP_LISTEN) { + ret = tcp_v4_do_rcv(sk, skb); + goto put_and_return; + } + + sk_incoming_cpu_update(sk); + bh_lock_sock_nested(sk); tcp_sk(sk)->segs_in += max_t(u16, 1, skb_shinfo(skb)->gso_segs); ret = 0; @@ -1636,6 +1642,7 @@ int tcp_v4_rcv(struct sk_buff *skb) } bh_unlock_sock(sk); +put_and_return: sock_put(sk); return ret; diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 3d18571811c5e..33334f0c217de 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1161,7 +1161,7 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff * } /* The socket must have it's spinlock held when we get - * here. + * here, unless it is a TCP_LISTEN socket. * * We have a potential double-lock case here, so even when * doing backlog processing we use the BH locking scheme. @@ -1415,9 +1415,15 @@ static int tcp_v6_rcv(struct sk_buff *skb) if (sk_filter(sk, skb)) goto discard_and_relse; - sk_incoming_cpu_update(sk); skb->dev = NULL; + if (sk->sk_state == TCP_LISTEN) { + ret = tcp_v6_do_rcv(sk, skb); + goto put_and_return; + } + + sk_incoming_cpu_update(sk); + bh_lock_sock_nested(sk); tcp_sk(sk)->segs_in += max_t(u16, 1, skb_shinfo(skb)->gso_segs); ret = 0; @@ -1432,6 +1438,7 @@ static int tcp_v6_rcv(struct sk_buff *skb) } bh_unlock_sock(sk); +put_and_return: sock_put(sk); return ret ? -1 : 0;