net: reorder struct netns_ct for better cache-line usage

Reorder struct netns_ct so that atomic_t "count" changes don't
slowdown users of read mostly fields.

This is based on Eric Dumazet's proposed patch:
 "netfilter: conntrack: remove the central spinlock"
 http://thread.gmane.org/gmane.linux.network/268758/focus=47306

The tricky part of cache-aligning this structure, that it is getting
inlined in struct net (include/net/net_namespace.h), thus changes to
other netns_xxx structures affects our alignment.

Eric's original patch contained an ambiguity on 32-bit regarding
alignment in struct net.  This patch also takes 32-bit into account,
and in case of changed (struct net) alignment sysctl_xxx entries have
been ordered according to how often they are accessed.
Signed-off-by: NJesper Dangaard Brouer <brouer@redhat.com>
Reviewed-by: NJiri Benc <jbenc@redhat.com>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

include/net/netns/conntrack.h

@@ -65,6 +65,23 @@ struct nf_ip_net {
 struct netns_ct {
 	atomic_t		count;
 	unsigned int		expect_count;
+#ifdef CONFIG_SYSCTL
+	struct ctl_table_header	*sysctl_header;
+	struct ctl_table_header	*acct_sysctl_header;
+	struct ctl_table_header	*tstamp_sysctl_header;
+	struct ctl_table_header	*event_sysctl_header;
+	struct ctl_table_header	*helper_sysctl_header;
+#endif
+	char			*slabname;
+	unsigned int		sysctl_log_invalid; /* Log invalid packets */
+	unsigned int		sysctl_events_retry_timeout;
+	int			sysctl_events;
+	int			sysctl_acct;
+	int			sysctl_auto_assign_helper;
+	bool			auto_assign_helper_warned;
+	int			sysctl_tstamp;
+	int			sysctl_checksum;
+
 	unsigned int		htable_size;
 	struct kmem_cache	*nf_conntrack_cachep;
 	struct hlist_nulls_head	*hash;
@@ -75,14 +92,6 @@ struct netns_ct {
 	struct ip_conntrack_stat __percpu *stat;
 	struct nf_ct_event_notifier __rcu *nf_conntrack_event_cb;
 	struct nf_exp_event_notifier __rcu *nf_expect_event_cb;
-	int			sysctl_events;
-	unsigned int		sysctl_events_retry_timeout;
-	int			sysctl_acct;
-	int			sysctl_tstamp;
-	int			sysctl_checksum;
-	unsigned int		sysctl_log_invalid; /* Log invalid packets */
-	int			sysctl_auto_assign_helper;
-	bool			auto_assign_helper_warned;
 	struct nf_ip_net	nf_ct_proto;
 #if defined(CONFIG_NF_CONNTRACK_LABELS)
 	unsigned int		labels_used;
@@ -92,13 +101,5 @@ struct netns_ct {
 	struct hlist_head	*nat_bysource;
 	unsigned int		nat_htable_size;
 #endif
-#ifdef CONFIG_SYSCTL
-	struct ctl_table_header	*sysctl_header;
-	struct ctl_table_header	*acct_sysctl_header;
-	struct ctl_table_header	*tstamp_sysctl_header;
-	struct ctl_table_header	*event_sysctl_header;
-	struct ctl_table_header	*helper_sysctl_header;
-#endif
-	char			*slabname;
 };
 #endif