Commit 8e602ce2 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c60ce4e2

include/net/net_namespace.h

+10 −7
Original line number Diff line number Diff line
@@ -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

};

include/net/netns/xfrm.h

+5 −4
Original line number Diff line number Diff line
@@ -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

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