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Date: Mon, 09 Nov 2009 16:26:33 +0100
From: Eric Dumazet <eric.dumazet@...il.com>
To: "David S. Miller" <davem@...emloft.net>
CC: Linux Netdev List <netdev@...r.kernel.org>,
Lucian Adrian Grijincu <lgrijincu@...acom.com>,
Octavian Purdila <opurdila@...acom.com>
Subject: [PATCH net-next-2.6] 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@...il.com>
---
include/linux/udp.h | 6 +++
include/net/udp.h | 3 +
net/ipv4/udp.c | 73 +++++++++++++++++++++++++++++++++++++-----
net/ipv6/udp.c | 14 ++++----
4 files changed, 80 insertions(+), 16 deletions(-)
diff --git a/include/linux/udp.h b/include/linux/udp.h
index 59f0ddf..03f72a2 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h
@@ -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
diff --git a/include/net/udp.h b/include/net/udp.h
index af41850..5348d80 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -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,
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index d73e917..1eaf575 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -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,
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 2915e1d..f4c85b2 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -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,
--
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