Commit 3d709f69 authored by Ido Schimmel's avatar Ido Schimmel Committed by David S. Miller
Browse files

ipv6: Use hash-threshold instead of modulo-N 



Now that each nexthop stores its region boundary in the multipath hash
function's output space, we can use hash-threshold instead of modulo-N
in multipath selection.

This reduces the number of checks we need to perform during lookup, as
dead and linkdown nexthops are assigned a negative region boundary. In
addition, in contrast to modulo-N, only flows near region boundaries are
affected when a nexthop is added or removed.

Signed-off-by: default avatarIdo Schimmel <idosch@mellanox.com>
Acked-by: default avatarDavid Ahern <dsahern@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7696c06a

net/ipv6/route.c

+13 −23
Original line number Diff line number Diff line
@@ -455,7 +455,6 @@ static struct rt6_info *rt6_multipath_select(struct rt6_info *match, 
					     int strict)

{

	struct rt6_info *sibling, *next_sibling;

	int route_choosen;



	/* We might have already computed the hash for ICMPv6 errors. In such

	 * case it will always be non-zero. Otherwise now is the time to do it.
@@ -463,28 +462,19 @@ static struct rt6_info *rt6_multipath_select(struct rt6_info *match, 
	if (!fl6->mp_hash)

		fl6->mp_hash = rt6_multipath_hash(fl6, NULL);



	route_choosen = fl6->mp_hash % (match->rt6i_nsiblings + 1);

	/* Don't change the route, if route_choosen == 0

	 * (siblings does not include ourself)

	 */

	if (route_choosen)

		list_for_each_entry_safe(sibling, next_sibling,

				&match->rt6i_siblings, rt6i_siblings) {

			route_choosen--;

			if (route_choosen == 0) {

				struct inet6_dev *idev = sibling->rt6i_idev;

	if (fl6->mp_hash <= atomic_read(&match->rt6i_nh_upper_bound))

		return match;



				if (sibling->rt6i_nh_flags & RTNH_F_DEAD)

					break;

				if (sibling->rt6i_nh_flags & RTNH_F_LINKDOWN &&

				    idev->cnf.ignore_routes_with_linkdown)

					break;

	list_for_each_entry_safe(sibling, next_sibling, &match->rt6i_siblings,

				 rt6i_siblings) {

		if (fl6->mp_hash > atomic_read(&sibling->rt6i_nh_upper_bound))

			continue;

		if (rt6_score_route(sibling, oif, strict) < 0)

			break;

		match = sibling;

		break;

	}

		}



	return match;

}

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