commit a2d7ec58ac09f30ab726f216827f7c7095b2a98f
author Eric Dumazet <eric.dumazet@gmail.com> Fri Nov 18 17:32:46 2011 +0000
committer David S. Miller <davem@davemloft.net> Mon Nov 21 16:38:08 2011 -0500
tree 1b733090406abc18c42308e84703dcb703e15125
parent 9205fd9ccab8ef51ad771c1917eed7b2f2225d45

netfilter: use jump_label for nf_hooks

On configs where CONFIG_JUMP_LABEL=y, we can replace in fast path a
load/compare/conditional jump by a single jump with no dcache reference.

Jump target is modified as soon as nf_hooks[pf][hook] switches from
empty state to non empty states. jump_label state is kept outside of
nf_hooks array so has no cost on cpu caches.

This patch removes the test on CONFIG_NETFILTER_DEBUG : No need to call
nf_hook_slow() at all if nf_hooks[pf][hook] is empty, this didnt give
useful information, but slowed down things a lot.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Patrick McHardy <kaber@trash.net>
CC: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/core.c

diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index afca6c7..4aa0f4b 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -54,6 +54,12 @@
 
 struct list_head nf_hooks[NFPROTO_NUMPROTO][NF_MAX_HOOKS] __read_mostly;
 EXPORT_SYMBOL(nf_hooks);
+
+#if defined(CONFIG_JUMP_LABEL)
+struct jump_label_key nf_hooks_needed[NFPROTO_NUMPROTO][NF_MAX_HOOKS];
+EXPORT_SYMBOL(nf_hooks_needed);
+#endif
+
 static DEFINE_MUTEX(nf_hook_mutex);
 
 int nf_register_hook(struct nf_hook_ops *reg)
@@ -70,6 +76,9 @@
 	}
 	list_add_rcu(&reg->list, elem->list.prev);
 	mutex_unlock(&nf_hook_mutex);
+#if defined(CONFIG_JUMP_LABEL)
+	jump_label_inc(&nf_hooks_needed[reg->pf][reg->hooknum]);
+#endif
 	return 0;
 }
 EXPORT_SYMBOL(nf_register_hook);
@@ -79,7 +88,9 @@
 	mutex_lock(&nf_hook_mutex);
 	list_del_rcu(&reg->list);
 	mutex_unlock(&nf_hook_mutex);
-
+#if defined(CONFIG_JUMP_LABEL)
+	jump_label_dec(&nf_hooks_needed[reg->pf][reg->hooknum]);
+#endif
 	synchronize_net();
 }
 EXPORT_SYMBOL(nf_unregister_hook);