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ipv4: take rt_uncached_lock only if needed

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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>
This commit is contained in:
Eric Dumazet 2012-08-24 05:40:47 +00:00 • committed by David S. Miller
parent a0dfb2634e
commit 78df76a065
1 changed files with 1 additions and 1 deletions
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2
net/ipv4/route.c
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@ -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);