From: dlg <dlg@openbsd.org>
Date: Mon, 18 Mar 2024 06:05:23 +0000 (+0000)
Subject: use high bits from the mbuf flowid to pick a port to transmit on.
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=a717bb6c38096e149136b0eef90a30d50895e9d8;p=openbsd

use high bits from the mbuf flowid to pick a port to transmit on.

a port here is a physical interface used by an aggr.

this leaves the low bits for a physical interface to use to pick a
tx ring. without this, aggr used low bits for port selection, which
takes bits away from the ring selection, which can lead to uneven
distribution of packets over tx rings.

ive been running this in production for well over a year now.
---

diff --git a/sys/net/if_aggr.c b/sys/net/if_aggr.c
index 748b3c9224f..21a6cc06800 100644
--- a/sys/net/if_aggr.c
+++ b/sys/net/if_aggr.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_aggr.c,v 1.43 2024/03/04 04:44:12 dlg Exp $ */
+/*	$OpenBSD: if_aggr.c,v 1.44 2024/03/18 06:05:23 dlg Exp $ */
 
 /*
  * Copyright (c) 2019 The University of Queensland
@@ -299,7 +299,10 @@ static const char *lacp_mux_event_names[] = {
  * aggr interface
  */
 
-#define AGGR_MAX_PORTS		32
+#define AGGR_PORT_BITS		5
+#define AGGR_FLOWID_SHIFT	(16 - AGGR_PORT_BITS)
+
+#define AGGR_MAX_PORTS		(1 << AGGR_PORT_BITS)
 #define AGGR_MAX_SLOW_PKTS	(AGGR_MAX_PORTS * 3)
 
 struct aggr_multiaddr {
@@ -660,7 +663,7 @@ aggr_transmit(struct aggr_softc *sc, const struct aggr_map *map, struct mbuf *m)
 #endif
 
 	if (ISSET(m->m_pkthdr.csum_flags, M_FLOWID))
-		flow = m->m_pkthdr.ph_flowid;
+		flow = m->m_pkthdr.ph_flowid >> AGGR_FLOWID_SHIFT;
 
 	ifp0 = map->m_ifp0s[flow % AGGR_MAX_PORTS];