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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>
This commit is contained in:
Eric Dumazet 2011-11-18 17:32:46 +00:00 committed by David S. Miller
parent 9205fd9cca
commit a2d7ec58ac
2 changed files with 33 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
include/linux/netfilter.h
View File

@ -162,6 +162,24 @@ extern struct ctl_path nf_net_ipv4_netfilter_sysctl_path[];
extern struct list_head nf_hooks[NFPROTO_NUMPROTO][NF_MAX_HOOKS];
#if defined(CONFIG_JUMP_LABEL)
#include <linux/jump_label.h>
extern struct jump_label_key nf_hooks_needed[NFPROTO_NUMPROTO][NF_MAX_HOOKS];
static inline bool nf_hooks_active(u_int8_t pf, unsigned int hook)
{
if (__builtin_constant_p(pf) &&
__builtin_constant_p(hook))
return static_branch(&nf_hooks_needed[pf][hook]);
return !list_empty(&nf_hooks[pf][hook]);
}
#else
static inline bool nf_hooks_active(u_int8_t pf, unsigned int hook)
{
return !list_empty(&nf_hooks[pf][hook]);
}
#endif
int nf_hook_slow(u_int8_t pf, unsigned int hook, struct sk_buff *skb,
struct net_device *indev, struct net_device *outdev,
int (*okfn)(struct sk_buff *), int thresh);
@ -179,11 +197,9 @@ static inline int nf_hook_thresh(u_int8_t pf, unsigned int hook,
struct net_device *outdev,
int (*okfn)(struct sk_buff *), int thresh)
{
#ifndef CONFIG_NETFILTER_DEBUG
if (list_empty(&nf_hooks[pf][hook]))
return 1;
#endif
return nf_hook_slow(pf, hook, skb, indev, outdev, okfn, thresh);
if (nf_hooks_active(pf, hook))
return nf_hook_slow(pf, hook, skb, indev, outdev, okfn, thresh);
return 1;
}
static inline int nf_hook(u_int8_t pf, unsigned int hook, struct sk_buff *skb,

13
net/netfilter/core.c
View File

@ -54,6 +54,12 @@ EXPORT_SYMBOL_GPL(nf_unregister_afinfo);
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 @@ int nf_register_hook(struct nf_hook_ops *reg)
}
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 @@ void nf_unregister_hook(struct nf_hook_ops *reg)
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);