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udp: bind() optimisation 

UDP bind() can be O(N^2) in some pathological cases.

Thanks to secondary hash tables, we can make it O(N)

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 2009-11-09 05:26:33 +00:00 committed by David S. Miller
parent 0ab365f463
commit 30fff9231f
4 changed files with 80 additions and 16 deletions
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6
include/linux/udp.h
View File

@ -88,6 +88,12 @@ static inline struct udp_sock *udp_sk(const struct sock *sk)
return (struct udp_sock *)sk;
}
#define udp_portaddr_for_each_entry(__sk, node, list) \
hlist_nulls_for_each_entry(__sk, node, list, __sk_common.skc_portaddr_node)
#define udp_portaddr_for_each_entry_rcu(__sk, node, list) \
hlist_nulls_for_each_entry_rcu(__sk, node, list, __sk_common.skc_portaddr_node)
#define IS_UDPLITE(__sk) (udp_sk(__sk)->pcflag)
#endif

3
include/net/udp.h
View File

@ -158,7 +158,8 @@ static inline void udp_lib_close(struct sock *sk, long timeout)
}
extern int udp_lib_get_port(struct sock *sk, unsigned short snum,
int (*)(const struct sock*,const struct sock*));
int (*)(const struct sock *,const struct sock *),
unsigned int hash2_nulladdr);
/* net/ipv4/udp.c */
extern int udp_get_port(struct sock *sk, unsigned short snum,

73
net/ipv4/udp.c
View File

@ -152,16 +152,49 @@ static int udp_lib_lport_inuse(struct net *net, __u16 num,
return 0;
}
/*
* Note: we still hold spinlock of primary hash chain, so no other writer
* can insert/delete a socket with local_port == num
*/
static int udp_lib_lport_inuse2(struct net *net, __u16 num,
struct udp_hslot *hslot2,
struct sock *sk,
int (*saddr_comp)(const struct sock *sk1,
const struct sock *sk2))
{
struct sock *sk2;
struct hlist_nulls_node *node;
int res = 0;
spin_lock(&hslot2->lock);
udp_portaddr_for_each_entry(sk2, node, &hslot2->head)
if (net_eq(sock_net(sk2), net) &&
sk2 != sk &&
(udp_sk(sk2)->udp_port_hash == num) &&
(!sk2->sk_reuse || !sk->sk_reuse) &&
(!sk2->sk_bound_dev_if || !sk->sk_bound_dev_if
|| sk2->sk_bound_dev_if == sk->sk_bound_dev_if) &&
(*saddr_comp)(sk, sk2)) {
res = 1;
break;
}
spin_unlock(&hslot2->lock);
return res;
}
/**
* udp_lib_get_port - UDP/-Lite port lookup for IPv4 and IPv6
*
* @sk: socket struct in question
* @snum: port number to look up
* @saddr_comp: AF-dependent comparison of bound local IP addresses
* @hash2_nulladdr: AF-dependant hash value in secondary hash chains,
* with NULL address
*/
int udp_lib_get_port(struct sock *sk, unsigned short snum,
int (*saddr_comp)(const struct sock *sk1,
const struct sock *sk2))
const struct sock *sk2),
unsigned int hash2_nulladdr)
{
struct udp_hslot *hslot, *hslot2;
struct udp_table *udptable = sk->sk_prot->h.udp_table;
@ -210,6 +243,30 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
} else {
hslot = udp_hashslot(udptable, net, snum);
spin_lock_bh(&hslot->lock);
if (hslot->count > 10) {
int exist;
unsigned int slot2 = udp_sk(sk)->udp_portaddr_hash ^ snum;
slot2 &= udptable->mask;
hash2_nulladdr &= udptable->mask;
hslot2 = udp_hashslot2(udptable, slot2);
if (hslot->count < hslot2->count)
goto scan_primary_hash;
exist = udp_lib_lport_inuse2(net, snum, hslot2,
sk, saddr_comp);
if (!exist && (hash2_nulladdr != slot2)) {
hslot2 = udp_hashslot2(udptable, hash2_nulladdr);
exist = udp_lib_lport_inuse2(net, snum, hslot2,
sk, saddr_comp);
}
if (exist)
goto fail_unlock;
else
goto found;
}
scan_primary_hash:
if (udp_lib_lport_inuse(net, snum, hslot, NULL, sk,
saddr_comp, 0))
goto fail_unlock;
@ -255,12 +312,14 @@ static unsigned int udp4_portaddr_hash(struct net *net, __be32 saddr,
int udp_v4_get_port(struct sock *sk, unsigned short snum)
{
unsigned int hash2_nulladdr =
udp4_portaddr_hash(sock_net(sk), INADDR_ANY, snum);
unsigned int hash2_partial =
udp4_portaddr_hash(sock_net(sk), inet_sk(sk)->inet_rcv_saddr, 0);
/* precompute partial secondary hash */
udp_sk(sk)->udp_portaddr_hash =
udp4_portaddr_hash(sock_net(sk),
inet_sk(sk)->inet_rcv_saddr,
0);
return udp_lib_get_port(sk, snum, ipv4_rcv_saddr_equal);
udp_sk(sk)->udp_portaddr_hash = hash2_partial;
return udp_lib_get_port(sk, snum, ipv4_rcv_saddr_equal, hash2_nulladdr);
}
static inline int compute_score(struct sock *sk, struct net *net, __be32 saddr,
@ -336,8 +395,6 @@ static inline int compute_score2(struct sock *sk, struct net *net,
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,

14
net/ipv6/udp.c
View File

@ -100,12 +100,14 @@ static unsigned int udp6_portaddr_hash(struct net *net,
int udp_v6_get_port(struct sock *sk, unsigned short snum)
{
unsigned int hash2_nulladdr =
udp6_portaddr_hash(sock_net(sk), &in6addr_any, snum);
unsigned int hash2_partial =
udp6_portaddr_hash(sock_net(sk), &inet6_sk(sk)->rcv_saddr, 0);
/* precompute partial secondary hash */
udp_sk(sk)->udp_portaddr_hash =
udp6_portaddr_hash(sock_net(sk),
&inet6_sk(sk)->rcv_saddr,
0);
return udp_lib_get_port(sk, snum, ipv6_rcv_saddr_equal);
udp_sk(sk)->udp_portaddr_hash = hash2_partial;
return udp_lib_get_port(sk, snum, ipv6_rcv_saddr_equal, hash2_nulladdr);
}
static inline int compute_score(struct sock *sk, struct net *net,
@ -181,8 +183,6 @@ static inline int compute_score2(struct sock *sk, struct net *net,
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 *udp6_lib_lookup2(struct net *net,