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soreuseport: TCP/IPv4 implementation

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Allow multiple listener sockets to bind to the same port.

Motivation for soresuseport would be something like a web server
binding to port 80 running with multiple threads, where each thread
might have it's own listener socket.  This could be done as an
alternative to other models: 1) have one listener thread which
dispatches completed connections to workers. 2) accept on a single
listener socket from multiple threads.  In case #1 the listener thread
can easily become the bottleneck with high connection turn-over rate.
In case #2, the proportion of connections accepted per thread tends
to be uneven under high connection load (assuming simple event loop:
while (1) { accept(); process() }, wakeup does not promote fairness
among the sockets.  We have seen the  disproportion to be as high
as 3:1 ratio between thread accepting most connections and the one
accepting the fewest.  With so_reusport the distribution is
uniform.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Tom Herbert
2013-01-22 09:50:24 +00:00
committed by David S. Miller
parent 055dc21a1d
commit da5e36308d
5 changed files with 73 additions and 21 deletions
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28
net/ipv4/inet_hashtables.c
View File

@@ -39,6 +39,7 @@ struct inet_bind_bucket *inet_bind_bucket_create(struct kmem_cache *cachep,
write_pnet(&tb->ib_net, hold_net(net));
tb->port = snum;
tb->fastreuse = 0;
tb->fastreuseport = 0;
tb->num_owners = 0;
INIT_HLIST_HEAD(&tb->owners);
hlist_add_head(&tb->node, &head->chain);
@@ -151,16 +152,16 @@ static inline int compute_score(struct sock *sk, struct net *net,
if (net_eq(sock_net(sk), net) && inet->inet_num == hnum &&
!ipv6_only_sock(sk)) {
__be32 rcv_saddr = inet->inet_rcv_saddr;
score = sk->sk_family == PF_INET ? 1 : 0;
score = sk->sk_family == PF_INET ? 2 : 1;
if (rcv_saddr) {
if (rcv_saddr != daddr)
return -1;
score += 2;
score += 4;
}
if (sk->sk_bound_dev_if) {
if (sk->sk_bound_dev_if != dif)
return -1;
score += 2;
score += 4;
}
}
return score;
@@ -176,6 +177,7 @@ static inline int compute_score(struct sock *sk, struct net *net,
struct sock *__inet_lookup_listener(struct net *net,
struct inet_hashinfo *hashinfo,
const __be32 saddr, __be16 sport,
const __be32 daddr, const unsigned short hnum,
const int dif)
{
@@ -183,17 +185,29 @@ struct sock *__inet_lookup_listener(struct net *net,
struct hlist_nulls_node *node;
unsigned int hash = inet_lhashfn(net, hnum);
struct inet_listen_hashbucket *ilb = &hashinfo->listening_hash[hash];
int score, hiscore;
int score, hiscore, matches = 0, reuseport = 0;
u32 phash = 0;
rcu_read_lock();
begin:
result = NULL;
hiscore = -1;
hiscore = 0;
sk_nulls_for_each_rcu(sk, node, &ilb->head) {
score = compute_score(sk, net, hnum, daddr, dif);
if (score > hiscore) {
result = sk;
hiscore = score;
reuseport = sk->sk_reuseport;
if (reuseport) {
phash = inet_ehashfn(net, daddr, hnum,
saddr, sport);
matches = 1;
}
} else if (score == hiscore && reuseport) {
matches++;
if (((u64)phash * matches) >> 32 == 0)
result = sk;
phash = next_pseudo_random32(phash);
}
}
/*
@@ -501,7 +515,8 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
inet_bind_bucket_for_each(tb, node, &head->chain) {
if (net_eq(ib_net(tb), net) &&
tb->port == port) {
if (tb->fastreuse >= 0)
if (tb->fastreuse >= 0 ||
tb->fastreuseport >= 0)
goto next_port;
WARN_ON(hlist_empty(&tb->owners));
if (!check_established(death_row, sk,
@@ -518,6 +533,7 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
break;
}
tb->fastreuse = -1;
tb->fastreuseport = -1;
goto ok;
next_port: