From 3ab5aee7fe840b5b1b35a8d1ac11c3de5281e611 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 16 Nov 2008 19:40:17 -0800 Subject: net: Convert TCP & DCCP hash tables to use RCU / hlist_nulls RCU was added to UDP lookups, using a fast infrastructure : - sockets kmem_cache use SLAB_DESTROY_BY_RCU and dont pay the price of call_rcu() at freeing time. - hlist_nulls permits to use few memory barriers. This patch uses same infrastructure for TCP/DCCP established and timewait sockets. Thanks to SLAB_DESTROY_BY_RCU, no slowdown for applications using short lived TCP connections. A followup patch, converting rwlocks to spinlocks will even speedup this case. __inet_lookup_established() is pretty fast now we dont have to dirty a contended cache line (read_lock/read_unlock) Only established and timewait hashtable are converted to RCU (bind table and listen table are still using traditional locking) Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/inet_hashtables.c | 78 ++++++++++++++++++++++++++++++++-------------- 1 file changed, 55 insertions(+), 23 deletions(-) (limited to 'net/ipv4/inet_hashtables.c') diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c index be41ebbec4e..fd269cfef0e 100644 --- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -223,35 +223,65 @@ struct sock * __inet_lookup_established(struct net *net, INET_ADDR_COOKIE(acookie, saddr, daddr) const __portpair ports = INET_COMBINED_PORTS(sport, hnum); struct sock *sk; - const struct hlist_node *node; + const struct hlist_nulls_node *node; /* Optimize here for direct hit, only listening connections can * have wildcards anyways. */ unsigned int hash = inet_ehashfn(net, daddr, hnum, saddr, sport); - struct inet_ehash_bucket *head = inet_ehash_bucket(hashinfo, hash); - rwlock_t *lock = inet_ehash_lockp(hashinfo, hash); + unsigned int slot = hash & (hashinfo->ehash_size - 1); + struct inet_ehash_bucket *head = &hashinfo->ehash[slot]; - prefetch(head->chain.first); - read_lock(lock); - sk_for_each(sk, node, &head->chain) { + rcu_read_lock(); +begin: + sk_nulls_for_each_rcu(sk, node, &head->chain) { if (INET_MATCH(sk, net, hash, acookie, - saddr, daddr, ports, dif)) - goto hit; /* You sunk my battleship! */ + saddr, daddr, ports, dif)) { + if (unlikely(!atomic_inc_not_zero(&sk->sk_refcnt))) + goto begintw; + if (unlikely(!INET_MATCH(sk, net, hash, acookie, + saddr, daddr, ports, dif))) { + sock_put(sk); + goto begin; + } + goto out; + } } + /* + * 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) != slot) + goto begin; +begintw: /* Must check for a TIME_WAIT'er before going to listener hash. */ - sk_for_each(sk, node, &head->twchain) { + sk_nulls_for_each_rcu(sk, node, &head->twchain) { if (INET_TW_MATCH(sk, net, hash, acookie, - saddr, daddr, ports, dif)) - goto hit; + saddr, daddr, ports, dif)) { + if (unlikely(!atomic_inc_not_zero(&sk->sk_refcnt))) { + sk = NULL; + goto out; + } + if (unlikely(!INET_TW_MATCH(sk, net, hash, acookie, + saddr, daddr, ports, dif))) { + sock_put(sk); + goto begintw; + } + goto out; + } } + /* + * 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) != slot) + goto begintw; sk = NULL; out: - read_unlock(lock); + rcu_read_unlock(); return sk; -hit: - sock_hold(sk); - goto out; } EXPORT_SYMBOL_GPL(__inet_lookup_established); @@ -272,14 +302,14 @@ static int __inet_check_established(struct inet_timewait_death_row *death_row, struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash); rwlock_t *lock = inet_ehash_lockp(hinfo, hash); struct sock *sk2; - const struct hlist_node *node; + const struct hlist_nulls_node *node; struct inet_timewait_sock *tw; prefetch(head->chain.first); write_lock(lock); /* Check TIME-WAIT sockets first. */ - sk_for_each(sk2, node, &head->twchain) { + sk_nulls_for_each(sk2, node, &head->twchain) { tw = inet_twsk(sk2); if (INET_TW_MATCH(sk2, net, hash, acookie, @@ -293,7 +323,7 @@ static int __inet_check_established(struct inet_timewait_death_row *death_row, tw = NULL; /* And established part... */ - sk_for_each(sk2, node, &head->chain) { + sk_nulls_for_each(sk2, node, &head->chain) { if (INET_MATCH(sk2, net, hash, acookie, saddr, daddr, ports, dif)) goto not_unique; @@ -306,7 +336,7 @@ unique: inet->sport = htons(lport); sk->sk_hash = hash; WARN_ON(!sk_unhashed(sk)); - __sk_add_node(sk, &head->chain); + __sk_nulls_add_node_rcu(sk, &head->chain); sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1); write_unlock(lock); @@ -338,7 +368,7 @@ static inline u32 inet_sk_port_offset(const struct sock *sk) void __inet_hash_nolisten(struct sock *sk) { struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo; - struct hlist_head *list; + struct hlist_nulls_head *list; rwlock_t *lock; struct inet_ehash_bucket *head; @@ -350,7 +380,7 @@ void __inet_hash_nolisten(struct sock *sk) lock = inet_ehash_lockp(hashinfo, sk->sk_hash); write_lock(lock); - __sk_add_node(sk, list); + __sk_nulls_add_node_rcu(sk, list); sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1); write_unlock(lock); } @@ -400,13 +430,15 @@ void inet_unhash(struct sock *sk) local_bh_disable(); inet_listen_wlock(hashinfo); lock = &hashinfo->lhash_lock; + if (__sk_del_node_init(sk)) + sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); } else { lock = inet_ehash_lockp(hashinfo, sk->sk_hash); write_lock_bh(lock); + if (__sk_nulls_del_node_init_rcu(sk)) + sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); } - if (__sk_del_node_init(sk)) - sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); write_unlock_bh(lock); out: if (sk->sk_state == TCP_LISTEN) -- cgit v1.2.3