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netfilter: reduce size of hook entry point locations

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struct net contains:

struct nf_hook_entries __rcu *hooks[NFPROTO_NUMPROTO][NF_MAX_HOOKS];

which store the hook entry point locations for the various protocol
families and the hooks.

Using array results in compact c code when doing accesses, i.e.
  x = rcu_dereference(net->nf.hooks[pf][hook]);

but its also wasting a lot of memory, as most families are
not used.

So split the array into those families that are used, which
are only 5 (instead of 13).  In most cases, the 'pf' argument is
constant, i.e. gcc removes switch statement.

struct net before:
 /* size: 5184, cachelines: 81, members: 46 */
after:
 /* size: 4672, cachelines: 73, members: 46 */

Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>
This commit is contained in:
Florian Westphal 2017-12-03 00:58:47 +01:00 • committed by Pablo Neira Ayuso
commit b0f38338ae
5 changed files with 77 additions and 14 deletions
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2
net/bridge/br_netfilter_hooks.c
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@ -991,7 +991,7 @@ int br_nf_hook_thresh(unsigned int hook, struct net *net,
unsigned int i;
int ret;
e = rcu_dereference(net->nf.hooks[NFPROTO_BRIDGE][hook]);
e = rcu_dereference(net->nf.hooks_bridge[hook]);
if (!e)
return okfn(net, sk, skb);