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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>
This commit is contained in:
Eric Dumazet 2010-10-14 05:56:18 +00:00 committed by David S. Miller
parent c60ce4e265
commit 8e602ce298
2 changed files with 15 additions and 11 deletions
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17
include/net/net_namespace.h
View File

@ -41,6 +41,8 @@ struct net {
* 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 net {
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 @@ struct net {
/* 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 net {
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
};

9
include/net/netns/xfrm.h
View File

@ -43,10 +43,6 @@ struct netns_xfrm {
unsigned int policy_count[XFRM_POLICY_MAX * 2];
struct work_struct policy_hash_work;
struct dst_ops xfrm4_dst_ops;
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
struct dst_ops xfrm6_dst_ops;
#endif
struct sock *nlsk;
struct sock *nlsk_stash;
@ -58,6 +54,11 @@ struct netns_xfrm {
#ifdef CONFIG_SYSCTL
struct ctl_table_header *sysctl_hdr;
#endif
struct dst_ops xfrm4_dst_ops;
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
struct dst_ops xfrm6_dst_ops;
#endif
};
#endif