ipv4: udp: optimize unicast RX path
authorEric Dumazet <eric.dumazet@gmail.com>
Sun, 8 Nov 2009 10:18:11 +0000 (10:18 +0000)
committerDavid S. Miller <davem@davemloft.net>
Mon, 9 Nov 2009 04:53:07 +0000 (20:53 -0800)
We first locate the (local port) hash chain head
If few sockets are in this chain, we proceed with previous lookup algo.

If too many sockets are listed, we take a look at the secondary
(port, address) hash chain we added in previous patch.

We choose the shortest chain and proceed with a RCU lookup on the elected chain.

But, if we chose (port, address) chain, and fail to find a socket on given address,
 we must try another lookup on (port, INADDR_ANY) chain to find socket not bound
to a particular IP.

-> No extra cost for typical setups, where the first lookup will probabbly
be performed.

RCU lookups everywhere, we dont acquire spinlock.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/ipv4/udp.c

index 5f04216f35ce1ffa0a7313fd936661d00a915737..dd7f3d20989a8fa9625b16a797d4232a364b0127 100644 (file)
@@ -298,6 +298,91 @@ static inline int compute_score(struct sock *sk, struct net *net, __be32 saddr,
        return score;
 }
 
+/*
+ * In this second variant, we check (daddr, dport) matches (inet_rcv_sadd, inet_num)
+ */
+#define SCORE2_MAX (1 + 2 + 2 + 2)
+static inline int compute_score2(struct sock *sk, struct net *net,
+                                __be32 saddr, __be16 sport,
+                                __be32 daddr, unsigned int hnum, int dif)
+{
+       int score = -1;
+
+       if (net_eq(sock_net(sk), net) && !ipv6_only_sock(sk)) {
+               struct inet_sock *inet = inet_sk(sk);
+
+               if (inet->inet_rcv_saddr != daddr)
+                       return -1;
+               if (inet->inet_num != hnum)
+                       return -1;
+
+               score = (sk->sk_family == PF_INET ? 1 : 0);
+               if (inet->inet_daddr) {
+                       if (inet->inet_daddr != saddr)
+                               return -1;
+                       score += 2;
+               }
+               if (inet->inet_dport) {
+                       if (inet->inet_dport != sport)
+                               return -1;
+                       score += 2;
+               }
+               if (sk->sk_bound_dev_if) {
+                       if (sk->sk_bound_dev_if != dif)
+                               return -1;
+                       score += 2;
+               }
+       }
+       return score;
+}
+
+#define udp_portaddr_for_each_entry_rcu(__sk, node, list) \
+       hlist_nulls_for_each_entry_rcu(__sk, node, list, __sk_common.skc_portaddr_node)
+
+/* called with read_rcu_lock() */
+static struct sock *udp4_lib_lookup2(struct net *net,
+               __be32 saddr, __be16 sport,
+               __be32 daddr, unsigned int hnum, int dif,
+               struct udp_hslot *hslot2, unsigned int slot2)
+{
+       struct sock *sk, *result;
+       struct hlist_nulls_node *node;
+       int score, badness;
+
+begin:
+       result = NULL;
+       badness = -1;
+       udp_portaddr_for_each_entry_rcu(sk, node, &hslot2->head) {
+               score = compute_score2(sk, net, saddr, sport,
+                                     daddr, hnum, dif);
+               if (score > badness) {
+                       result = sk;
+                       badness = score;
+                       if (score == SCORE2_MAX)
+                               goto exact_match;
+               }
+       }
+       /*
+        * 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) != slot2)
+               goto begin;
+
+       if (result) {
+exact_match:
+               if (unlikely(!atomic_inc_not_zero(&result->sk_refcnt)))
+                       result = NULL;
+               else if (unlikely(compute_score2(result, net, saddr, sport,
+                                 daddr, hnum, dif) < badness)) {
+                       sock_put(result);
+                       goto begin;
+               }
+       }
+       return result;
+}
+
 /* UDP is nearly always wildcards out the wazoo, it makes no sense to try
  * harder than this. -DaveM
  */
@@ -308,11 +393,35 @@ static struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr,
        struct sock *sk, *result;
        struct hlist_nulls_node *node;
        unsigned short hnum = ntohs(dport);
-       unsigned int hash = udp_hashfn(net, hnum, udptable->mask);
-       struct udp_hslot *hslot = &udptable->hash[hash];
+       unsigned int hash2, slot2, slot = udp_hashfn(net, hnum, udptable->mask);
+       struct udp_hslot *hslot2, *hslot = &udptable->hash[slot];
        int score, badness;
 
        rcu_read_lock();
+       if (hslot->count > 10) {
+               hash2 = udp4_portaddr_hash(net, daddr, hnum);
+               slot2 = hash2 & udptable->mask;
+               hslot2 = &udptable->hash2[slot2];
+               if (hslot->count < hslot2->count)
+                       goto begin;
+
+               result = udp4_lib_lookup2(net, saddr, sport,
+                                         daddr, hnum, dif,
+                                         hslot2, slot2);
+               if (!result) {
+                       hash2 = udp4_portaddr_hash(net, INADDR_ANY, hnum);
+                       slot2 = hash2 & udptable->mask;
+                       hslot2 = &udptable->hash2[slot2];
+                       if (hslot->count < hslot2->count)
+                               goto begin;
+
+                       result = udp4_lib_lookup2(net, INADDR_ANY, sport,
+                                                 daddr, hnum, dif,
+                                                 hslot2, slot2);
+               }
+               rcu_read_unlock();
+               return result;
+       }
 begin:
        result = NULL;
        badness = -1;
@@ -329,7 +438,7 @@ begin:
         * 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)
+       if (get_nulls_value(node) != slot)
                goto begin;
 
        if (result) {