UDP: further performance improvements on tx

Cumulative throughput while running 64
  netperf -H $DUT -t UDP_STREAM -- -m 1
on a 2x8x2 SKL went from 1.1Mpps to 2.5Mpps

Single stream throughput increases from 910kpps to 1.18Mpps

Baseline:
https://people.freebsd.org/~mmacy/2018.05.11/udpsender2.svg

- Protect read access to global ifnet list with epoch
https://people.freebsd.org/~mmacy/2018.05.11/udpsender3.svg

- Protect short lived ifaddr references with epoch
https://people.freebsd.org/~mmacy/2018.05.11/udpsender4.svg

- Convert if_afdata read lock path to epoch
https://people.freebsd.org/~mmacy/2018.05.11/udpsender5.svg

A fix for the inpcbhash contention is pending sufficient time
on a canary at LLNW.

Reviewed by:	gallatin
Sponsored by:	Limelight Networks
Differential Revision:	https://reviews.freebsd.org/D15409

1 files changed, 8 insertions, 6 deletions

diff --git a/sys/netinet6/raw_ip6.c b/sys/netinet6/raw_ip6.c
index b8de413593d6..a6811c68c2f4 100644
--- a/sys/netinet6/raw_ip6.c
+++ b/sys/netinet6/raw_ip6.c
@@ -734,23 +734,25 @@ rip6_bind(struct socket *so, struct sockaddr *nam, struct thread *td)
 		return (EINVAL);
 	if ((error = prison_check_ip6(td->td_ucred, &addr->sin6_addr)) != 0)
 		return (error);
-	if (TAILQ_EMPTY(&V_ifnet) || addr->sin6_family != AF_INET6)
+	if (CK_STAILQ_EMPTY(&V_ifnet) || addr->sin6_family != AF_INET6)
 		return (EADDRNOTAVAIL);
 	if ((error = sa6_embedscope(addr, V_ip6_use_defzone)) != 0)
 		return (error);
 
+	NET_EPOCH_ENTER();
 	if (!IN6_IS_ADDR_UNSPECIFIED(&addr->sin6_addr) &&
-	    (ifa = ifa_ifwithaddr((struct sockaddr *)addr)) == NULL)
+	    (ifa = ifa_ifwithaddr((struct sockaddr *)addr)) == NULL) {
+		NET_EPOCH_EXIT();
 		return (EADDRNOTAVAIL);
+	}
 	if (ifa != NULL &&
 	    ((struct in6_ifaddr *)ifa)->ia6_flags &
 	    (IN6_IFF_ANYCAST|IN6_IFF_NOTREADY|
 	     IN6_IFF_DETACHED|IN6_IFF_DEPRECATED)) {
-		ifa_free(ifa);
+		NET_EPOCH_EXIT();
 		return (EADDRNOTAVAIL);
 	}
-	if (ifa != NULL)
-		ifa_free(ifa);
+	NET_EPOCH_EXIT();
 	INP_INFO_WLOCK(&V_ripcbinfo);
 	INP_WLOCK(inp);
 	inp->in6p_laddr = addr->sin6_addr;
@@ -772,7 +774,7 @@ rip6_connect(struct socket *so, struct sockaddr *nam, struct thread *td)
 
 	if (nam->sa_len != sizeof(*addr))
 		return (EINVAL);
-	if (TAILQ_EMPTY(&V_ifnet))
+	if (CK_STAILQ_EMPTY(&V_ifnet))
 		return (EADDRNOTAVAIL);
 	if (addr->sin6_family != AF_INET6)
 		return (EAFNOSUPPORT);