From 1580ab63fc9a03593072cc5656167a75c4f1d173 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 11 Feb 2016 16:28:49 -0800 Subject: [PATCH] tcp/dccp: better use of ephemeral ports in connect() In commit 07f4c90062f8 ("tcp/dccp: try to not exhaust ip_local_port_range in connect()"), I added a very simple heuristic, so that we got better chances to use even ports, and allow bind() users to have more available slots. It gave nice results, but with more than 200,000 TCP sessions on a typical server, the ~30,000 ephemeral ports are still a rare resource. I chose to go a step further, by looking at all even ports, and if none was available, fallback to odd ports. The companion patch does the same in bind(), but in opposite way. I've seen exec times of up to 30ms on busy servers, so I no longer disable BH for the whole traversal, but only for each hash bucket. I also call cond_resched() to be gentle to other tasks. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/inet_hashtables.c | 182 ++++++++++++++++++------------------- 1 file changed, 91 insertions(+), 91 deletions(-) diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c index c0f9942de924..bc68eced0105 100644 --- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -565,106 +565,106 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row, struct sock *, __u16, struct inet_timewait_sock **)) { struct inet_hashinfo *hinfo = death_row->hashinfo; - const unsigned short snum = inet_sk(sk)->inet_num; + struct inet_timewait_sock *tw = NULL; struct inet_bind_hashbucket *head; - struct inet_bind_bucket *tb; - int ret; + int port = inet_sk(sk)->inet_num; struct net *net = sock_net(sk); + struct inet_bind_bucket *tb; + u32 remaining, offset; + int ret, i, low, high; + static u32 hint; - if (!snum) { - int i, remaining, low, high, port; - static u32 hint; - u32 offset = hint + port_offset; - struct inet_timewait_sock *tw = NULL; - - inet_get_local_port_range(net, &low, &high); - remaining = (high - low) + 1; - - /* By starting with offset being an even number, - * we tend to leave about 50% of ports for other uses, - * like bind(0). - */ - offset &= ~1; - - local_bh_disable(); - for (i = 0; i < remaining; i++) { - port = low + (i + offset) % remaining; - if (inet_is_local_reserved_port(net, port)) - continue; - head = &hinfo->bhash[inet_bhashfn(net, port, - hinfo->bhash_size)]; - spin_lock(&head->lock); - - /* Does not bother with rcv_saddr checks, - * because the established check is already - * unique enough. - */ - inet_bind_bucket_for_each(tb, &head->chain) { - if (net_eq(ib_net(tb), net) && - tb->port == port) { - if (tb->fastreuse >= 0 || - tb->fastreuseport >= 0) - goto next_port; - WARN_ON(hlist_empty(&tb->owners)); - if (!check_established(death_row, sk, - port, &tw)) - goto ok; - goto next_port; - } - } - - tb = inet_bind_bucket_create(hinfo->bind_bucket_cachep, - net, head, port); - if (!tb) { - spin_unlock(&head->lock); - break; - } - tb->fastreuse = -1; - tb->fastreuseport = -1; - goto ok; - - next_port: - spin_unlock(&head->lock); + if (port) { + head = &hinfo->bhash[inet_bhashfn(net, port, + hinfo->bhash_size)]; + tb = inet_csk(sk)->icsk_bind_hash; + spin_lock_bh(&head->lock); + if (sk_head(&tb->owners) == sk && !sk->sk_bind_node.next) { + inet_ehash_nolisten(sk, NULL); + spin_unlock_bh(&head->lock); + return 0; } - local_bh_enable(); - - return -EADDRNOTAVAIL; - -ok: - hint += (i + 2) & ~1; - - /* Head lock still held and bh's disabled */ - inet_bind_hash(sk, tb, port); - if (sk_unhashed(sk)) { - inet_sk(sk)->inet_sport = htons(port); - inet_ehash_nolisten(sk, (struct sock *)tw); - } - if (tw) - inet_twsk_bind_unhash(tw, hinfo); - spin_unlock(&head->lock); - - if (tw) - inet_twsk_deschedule_put(tw); - - ret = 0; - goto out; - } - - head = &hinfo->bhash[inet_bhashfn(net, snum, hinfo->bhash_size)]; - tb = inet_csk(sk)->icsk_bind_hash; - spin_lock_bh(&head->lock); - if (sk_head(&tb->owners) == sk && !sk->sk_bind_node.next) { - inet_ehash_nolisten(sk, NULL); - spin_unlock_bh(&head->lock); - return 0; - } else { spin_unlock(&head->lock); /* No definite answer... Walk to established hash table */ - ret = check_established(death_row, sk, snum, NULL); -out: + ret = check_established(death_row, sk, port, NULL); local_bh_enable(); return ret; } + + inet_get_local_port_range(net, &low, &high); + high++; /* [32768, 60999] -> [32768, 61000[ */ + remaining = high - low; + if (likely(remaining > 1)) + remaining &= ~1U; + + offset = (hint + port_offset) % remaining; + /* In first pass we try ports of @low parity. + * inet_csk_get_port() does the opposite choice. + */ + offset &= ~1U; +other_parity_scan: + port = low + offset; + for (i = 0; i < remaining; i += 2, port += 2) { + if (unlikely(port >= high)) + port -= remaining; + if (inet_is_local_reserved_port(net, port)) + continue; + head = &hinfo->bhash[inet_bhashfn(net, port, + hinfo->bhash_size)]; + spin_lock_bh(&head->lock); + + /* Does not bother with rcv_saddr checks, because + * the established check is already unique enough. + */ + inet_bind_bucket_for_each(tb, &head->chain) { + if (net_eq(ib_net(tb), net) && tb->port == port) { + if (tb->fastreuse >= 0 || + tb->fastreuseport >= 0) + goto next_port; + WARN_ON(hlist_empty(&tb->owners)); + if (!check_established(death_row, sk, + port, &tw)) + goto ok; + goto next_port; + } + } + + tb = inet_bind_bucket_create(hinfo->bind_bucket_cachep, + net, head, port); + if (!tb) { + spin_unlock_bh(&head->lock); + return -ENOMEM; + } + tb->fastreuse = -1; + tb->fastreuseport = -1; + goto ok; +next_port: + spin_unlock_bh(&head->lock); + cond_resched(); + } + + offset++; + if ((offset & 1) && remaining > 1) + goto other_parity_scan; + + return -EADDRNOTAVAIL; + +ok: + hint += i + 2; + + /* Head lock still held and bh's disabled */ + inet_bind_hash(sk, tb, port); + if (sk_unhashed(sk)) { + inet_sk(sk)->inet_sport = htons(port); + inet_ehash_nolisten(sk, (struct sock *)tw); + } + if (tw) + inet_twsk_bind_unhash(tw, hinfo); + spin_unlock(&head->lock); + if (tw) + inet_twsk_deschedule_put(tw); + local_bh_enable(); + return 0; } /*