[UDP]: UDP can use sk_hash to speedup lookups

In a prior patch, I introduced a sk_hash field (__sk_common.skc_hash)  to let
tcp lookups use one cache line per unmatched entry instead of two.

We can also use sk_hash to speedup UDP part as well. We store in sk_hash the
hnum value, and use sk->sk_hash (same cache line than 'next' pointer),
instead of inet->num (different cache line)

Note : We still have a false sharing problem for SMP machines, because
sock_hold(sock) dirties the cache line containing the 'next' pointer. Not
counting the udp_hash_lock rwlock. (did someone mentioned RCU ? :) )

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index dbe2748db1e9..ccf2f4d196be 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -71,7 +71,7 @@ static struct sock *__udp6_lib_lookup(struct in6_addr *saddr, __be16 sport,
         sk_for_each(sk, node, &udptable[hnum & (UDP_HTABLE_SIZE - 1)]) {
                 struct inet_sock *inet = inet_sk(sk);
 
-                if (inet->num == hnum && sk->sk_family == PF_INET6) {
+                if (sk->sk_hash == hnum && sk->sk_family == PF_INET6) {
                         struct ipv6_pinfo *np = inet6_sk(sk);
                         int score = 0;
                         if (inet->dport) {
@@ -309,7 +309,7 @@ static struct sock *udp_v6_mcast_next(struct sock *sk,
         sk_for_each_from(s, node) {
                 struct inet_sock *inet = inet_sk(s);
 
-                if (inet->num == num && s->sk_family == PF_INET6) {
+                if (s->sk_hash == num && s->sk_family == PF_INET6) {
                         struct ipv6_pinfo *np = inet6_sk(s);
                         if (inet->dport) {
                                 if (inet->dport != rmt_port)