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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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13
include/net/inet_hashtables.h
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@@ -81,7 +81,9 @@ struct inet_bind_bucket {
struct net *ib_net;
#endif
unsigned short port;
signed short fastreuse;
signed char fastreuse;
signed char fastreuseport;
kuid_t fastuid;
int num_owners;
struct hlist_node node;
struct hlist_head owners;
@@ -257,15 +259,19 @@ extern void inet_unhash(struct sock *sk);
extern struct sock *__inet_lookup_listener(struct net *net,
struct inet_hashinfo *hashinfo,
const __be32 saddr,
const __be16 sport,
const __be32 daddr,
const unsigned short hnum,
const int dif);
static inline struct sock *inet_lookup_listener(struct net *net,
struct inet_hashinfo *hashinfo,
__be32 saddr, __be16 sport,
__be32 daddr, __be16 dport, int dif)
{
return __inet_lookup_listener(net, hashinfo, daddr, ntohs(dport), dif);
return __inet_lookup_listener(net, hashinfo, saddr, sport,
daddr, ntohs(dport), dif);
}
/* Socket demux engine toys. */
@@ -358,7 +364,8 @@ static inline struct sock *__inet_lookup(struct net *net,
struct sock *sk = __inet_lookup_established(net, hashinfo,
saddr, sport, daddr, hnum, dif);
return sk ? : __inet_lookup_listener(net, hashinfo, daddr, hnum, dif);
return sk ? : __inet_lookup_listener(net, hashinfo, saddr, sport,
daddr, hnum, dif);
}
static inline struct sock *inet_lookup(struct net *net,