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, 1 insertions, 1 deletions

diff --git a/sys/netinet/netdump/netdump_client.c b/sys/netinet/netdump/netdump_client.c
index c6174b9c1fec..a662fa86e9c7 100644
--- a/sys/netinet/netdump/netdump_client.c
+++ b/sys/netinet/netdump/netdump_client.c
@@ -1069,7 +1069,7 @@ netdump_configure(struct netdump_conf *conf, struct thread *td)
 		return (EINVAL);
 	}
 	IFNET_RLOCK_NOSLEEP();
-	TAILQ_FOREACH(ifp, &V_ifnet, if_link) {
+	CK_STAILQ_FOREACH(ifp, &V_ifnet, if_link) {
 		if (strcmp(ifp->if_xname, conf->ndc_iface) == 0)
 			break;
 	}