netns: reorder fields in struct net
In a network bench, I noticed an unfortunate false sharing between
'loopback_dev' and 'count' fields in "struct net".
'count' is written each time a socket is created or destroyed, while
loopback_dev might be often read in routing code.
Move loopback_dev in a read mostly section of "struct net"
Note: struct netns_xfrm is cache line aligned on SMP.
(It contains a "struct dst_ops")
Move it at the end to avoid holes, and reduce sizeof(struct net) by 128
bytes on ia32.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index bd10a79..65af9a0 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -41,6 +41,8 @@
* destroy on demand
*/
#endif
+ spinlock_t rules_mod_lock;
+
struct list_head list; /* list of network namespaces */
struct list_head cleanup_list; /* namespaces on death row */
struct list_head exit_list; /* Use only net_mutex */
@@ -52,7 +54,8 @@
struct ctl_table_set sysctls;
#endif
- struct net_device *loopback_dev; /* The loopback */
+ struct sock *rtnl; /* rtnetlink socket */
+ struct sock *genl_sock;
struct list_head dev_base_head;
struct hlist_head *dev_name_head;
@@ -60,11 +63,9 @@
/* core fib_rules */
struct list_head rules_ops;
- spinlock_t rules_mod_lock;
- struct sock *rtnl; /* rtnetlink socket */
- struct sock *genl_sock;
+ struct net_device *loopback_dev; /* The loopback */
struct netns_core core;
struct netns_mib mib;
struct netns_packet packet;
@@ -84,13 +85,15 @@
struct sock *nfnl;
struct sock *nfnl_stash;
#endif
-#ifdef CONFIG_XFRM
- struct netns_xfrm xfrm;
-#endif
#ifdef CONFIG_WEXT_CORE
struct sk_buff_head wext_nlevents;
#endif
struct net_generic *gen;
+
+ /* Note : following structs are cache line aligned */
+#ifdef CONFIG_XFRM
+ struct netns_xfrm xfrm;
+#endif
};