From: Martin KaFai Lau Date: Fri, 24 Jul 2015 16:57:43 +0000 (-0700) Subject: ipv6: Avoid rt6_probe() taking writer lock in the fast path X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=8d6c31bf574177c8de48dd1387d96e1ec3a8b8bc;p=linux-beck.git 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 Cc: Hannes Frederic Sowa CC: Julian Anastasov CC: YOSHIFUJI Hideaki Signed-off-by: David S. Miller --- diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 0ef52623fc77..54fccf0d705d 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -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