From 990edb428c2c85c22ca770330437db7183cbe8b5 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Fri, 24 Jul 2015 09:57:42 -0700 Subject: [PATCH 1/2] ipv6: Re-arrange code in rt6_probe() It is a prep work for the next patch to remove write_lock from rt6_probe(). 1. Reduce the number of if(neigh) check. From 4 to 1. 2. Bring the write_(un)lock() closer to the operations that the lock is protecting. Hopefully, the above make rt6_probe() more readable. Signed-off-by: Martin KaFai Lau Cc: Hannes Frederic Sowa Cc: Julian Anastasov Cc: YOSHIFUJI Hideaki Signed-off-by: David S. Miller --- net/ipv6/route.c | 44 ++++++++++++++++++++------------------------ 1 file changed, 20 insertions(+), 24 deletions(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index c9b2b9fe83fc..0ef52623fc77 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -545,6 +545,7 @@ static void rt6_probe_deferred(struct work_struct *w) static void rt6_probe(struct rt6_info *rt) { + struct __rt6_probe_work *work; struct neighbour *neigh; /* * Okay, this does not seem to be appropriate @@ -559,34 +560,29 @@ 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) { + work = NULL; write_lock(&neigh->lock); - if (neigh->nud_state & NUD_VALID) - goto out; - } - - if (!neigh || - time_after(jiffies, neigh->updated + rt->rt6i_idev->cnf.rtr_probe_interval)) { - struct __rt6_probe_work *work; - - work = kmalloc(sizeof(*work), GFP_ATOMIC); - - if (neigh && work) - __neigh_set_probe_once(neigh); - - if (neigh) - write_unlock(&neigh->lock); - - if (work) { - INIT_WORK(&work->work, rt6_probe_deferred); - work->target = rt->rt6i_gateway; - dev_hold(rt->dst.dev); - work->dev = rt->dst.dev; - schedule_work(&work->work); + if (!(neigh->nud_state & NUD_VALID) && + time_after(jiffies, + neigh->updated + + rt->rt6i_idev->cnf.rtr_probe_interval)) { + work = kmalloc(sizeof(*work), GFP_ATOMIC); + if (work) + __neigh_set_probe_once(neigh); } - } else { -out: write_unlock(&neigh->lock); + } else { + work = kmalloc(sizeof(*work), GFP_ATOMIC); } + + if (work) { + INIT_WORK(&work->work, rt6_probe_deferred); + work->target = rt->rt6i_gateway; + dev_hold(rt->dst.dev); + work->dev = rt->dst.dev; + schedule_work(&work->work); + } + rcu_read_unlock_bh(); } #else From 8d6c31bf574177c8de48dd1387d96e1ec3a8b8bc Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Fri, 24 Jul 2015 09:57:43 -0700 Subject: [PATCH 2/2] 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 --- net/ipv6/route.c | 4 ++++ 1 file changed, 4 insertions(+) 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