From 3b24d854cb35383c30642116e5992fd619bdc9bc Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 1 Apr 2016 08:52:17 -0700 Subject: tcp/dccp: do not touch listener sk_refcnt under synflood When a SYNFLOOD targets a non SO_REUSEPORT listener, multiple cpus contend on sk->sk_refcnt and sk->sk_wmem_alloc changes. By letting listeners use SOCK_RCU_FREE infrastructure, we can relax TCP_LISTEN lookup rules and avoid touching sk_refcnt Note that we still use SLAB_DESTROY_BY_RCU rules for other sockets, only listeners are impacted by this change. Peak performance under SYNFLOOD is increased by ~33% : On my test machine, I could process 3.2 Mpps instead of 2.4 Mpps Most consuming functions are now skb_set_owner_w() and sock_wfree() contending on sk->sk_wmem_alloc when cooking SYNACK and freeing them. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv6/inet6_hashtables.c | 56 ++++++++++++--------------------------------- 1 file changed, 15 insertions(+), 41 deletions(-) (limited to 'net/ipv6/inet6_hashtables.c') diff --git a/net/ipv6/inet6_hashtables.c b/net/ipv6/inet6_hashtables.c index e6ef6ce1ed74..607da088344d 100644 --- a/net/ipv6/inet6_hashtables.c +++ b/net/ipv6/inet6_hashtables.c @@ -120,6 +120,7 @@ static inline int compute_score(struct sock *sk, struct net *net, return score; } +/* called with rcu_read_lock() */ struct sock *inet6_lookup_listener(struct net *net, struct inet_hashinfo *hashinfo, struct sk_buff *skb, int doff, @@ -127,38 +128,27 @@ struct sock *inet6_lookup_listener(struct net *net, const __be16 sport, const struct in6_addr *daddr, const unsigned short hnum, const int dif) { - struct sock *sk; - const struct hlist_nulls_node *node; - struct sock *result; - int score, hiscore, matches = 0, reuseport = 0; - bool select_ok = true; - u32 phash = 0; unsigned int hash = inet_lhashfn(net, hnum); struct inet_listen_hashbucket *ilb = &hashinfo->listening_hash[hash]; + int score, hiscore = 0, matches = 0, reuseport = 0; + struct sock *sk, *result = NULL; + u32 phash = 0; -begin: - result = NULL; - hiscore = 0; - sk_nulls_for_each(sk, node, &ilb->head) { + sk_for_each(sk, &ilb->head) { score = compute_score(sk, net, hnum, daddr, dif); if (score > hiscore) { hiscore = score; - result = sk; - reuseport = sk->sk_reuseport; if (reuseport) { phash = inet6_ehashfn(net, daddr, hnum, saddr, sport); - if (select_ok) { - struct sock *sk2; - sk2 = reuseport_select_sock(sk, phash, - skb, doff); - if (sk2) { - result = sk2; - goto found; - } - } + result = reuseport_select_sock(sk, phash, + skb, doff); + if (result) + return result; matches = 1; } + result = sk; + reuseport = sk->sk_reuseport; } else if (score == hiscore && reuseport) { matches++; if (reciprocal_scale(phash, matches) == 0) @@ -166,24 +156,6 @@ begin: phash = next_pseudo_random32(phash); } } - /* - * if the nulls value we got at the end of this lookup is - * not the expected one, we must restart lookup. - * We probably met an item that was moved to another chain. - */ - if (get_nulls_value(node) != hash + LISTENING_NULLS_BASE) - goto begin; - if (result) { -found: - if (unlikely(!atomic_inc_not_zero(&result->sk_refcnt))) - result = NULL; - else if (unlikely(compute_score(result, net, hnum, daddr, - dif) < hiscore)) { - sock_put(result); - select_ok = false; - goto begin; - } - } return result; } EXPORT_SYMBOL_GPL(inet6_lookup_listener); @@ -195,10 +167,12 @@ struct sock *inet6_lookup(struct net *net, struct inet_hashinfo *hashinfo, const int dif) { struct sock *sk; + bool refcounted; sk = __inet6_lookup(net, hashinfo, skb, doff, saddr, sport, daddr, - ntohs(dport), dif); - + ntohs(dport), dif, &refcounted); + if (sk && !refcounted && !atomic_inc_not_zero(&sk->sk_refcnt)) + sk = NULL; return sk; } EXPORT_SYMBOL_GPL(inet6_lookup); -- cgit