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 748b3c9..21a6cc0 100644 (file)
--- 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];