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ipv4: udp: optimize unicast RX path

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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>
This commit is contained in:
Eric Dumazet 2009-11-08 10:18:11 +00:00 committed by David S. Miller
parent 512615b6b8
commit 5051ebd275
1 changed files with 112 additions and 3 deletions
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115
net/ipv4/udp.c
View 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) {