Commit 78df76a0 authored Aug 24, 2012 by Eric Dumazet Committed by David S. Miller Aug 24, 2012

ipv4: take rt_uncached_lock only if needed



Multicast traffic allocates dst with DST_NOCACHE, but dst is
not inserted into rt_uncached_list.

This slowdown multicast workloads on SMP because rt_uncached_lock is
contended.

Change the test before taking the lock to actually check the dst
was inserted into rt_uncached_list.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent a0dfb263

net/ipv4/route.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1263,7 +1263,7 @@ static void ipv4_dst_destroy(struct dst_entry *dst)
		{
		struct rtable rt = (struct rtable ) dst;

		if (dst->flags & DST_NOCACHE) {
		if (!list_empty(&rt->rt_uncached)) {
		spin_lock_bh(&rt_uncached_lock);
		list_del(&rt->rt_uncached);
		spin_unlock_bh(&rt_uncached_lock);