Commit 8d6c31bf authored Jul 24, 2015 by Martin KaFai Lau Committed by David S. Miller Jul 27, 2015

ipv6: Avoid rt6_probe() taking writer lock in the fast path



The patch checks neigh->nud_state before acquiring the writer lock.
Note that rt6_probe() is only used in CONFIG_IPV6_ROUTER_PREF.

40 udpflood processes and a /64 gateway route are used.
The gateway has NUD_PERMANENT.  Each of them is run for 30s.
At the end, the total number of finished sendto():

Before: 55M
After: 95M

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
CC: Julian Anastasov <ja@ssi.bg>
CC: YOSHIFUJI Hideaki <hideaki.yoshifuji@miraclelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 990edb42

net/ipv6/route.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -560,6 +560,9 @@ static void rt6_probe(struct rt6_info *rt)
		rcu_read_lock_bh();
		neigh = __ipv6_neigh_lookup_noref(rt->dst.dev, &rt->rt6i_gateway);
		if (neigh) {
		if (neigh->nud_state & NUD_VALID)
		goto out;

		work = NULL;
		write_lock(&neigh->lock);
		if (!(neigh->nud_state & NUD_VALID) &&
		@@ -583,6 +586,7 @@ static void rt6_probe(struct rt6_info *rt)
		schedule_work(&work->work);
		}

		out:
		rcu_read_unlock_bh();
		}
		#else

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