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: Jesper Dangaard Brouer <brouer@redhat.com>
Reviewed-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 17 insertions, 16 deletions

diff --git a/include/net/netns/conntrack.h b/include/net/netns/conntrack.h
index c9c0c538b68b..fbcc7fa536dc 100644
--- a/include/net/netns/conntrack.h
+++ b/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