Commit cd13539b authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: shrinks struct net_device 



commit ab95bfe0 (net: replace hooks in __netif_receive_skb) added
rx_handler at wrong place, between two cache line aligned objects,
creating a big hole (a full cache line)

Move rx_handler and rx_handler_data before rx_queue, filling existing
hole.

Move master field in the cache line(s) used in receive path.

This saves 64 bytes (or L1_CACHE_BYTES), and avoids two possible
cache misses in receive path.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 94767632

include/linux/netdevice.h

+11 −9
Original line number Diff line number Diff line
@@ -918,10 +918,6 @@ struct net_device { 
	unsigned short		needed_headroom;

	unsigned short		needed_tailroom;



	struct net_device	*master; /* Pointer to master device of a group,

					  * which this device is member of.

					  */



	/* Interface address info. */

	unsigned char		perm_addr[MAX_ADDR_LEN]; /* permanent hw address */

	unsigned char		addr_assign_type; /* hw address assignment type */
@@ -951,7 +947,7 @@ struct net_device { 
						   assign before registering */



/*

 * Cache line mostly used on receive path (including eth_type_trans())

 * Cache lines mostly used on receive path (including eth_type_trans())

 */

	unsigned long		last_rx;	/* Time of last Rx

						 * This should not be set in
@@ -961,6 +957,10 @@ struct net_device { 
						 * avoid dirtying this cache line.

						 */



	struct net_device	*master; /* Pointer to master device of a group,

					  * which this device is member of.

					  */



	/* Interface address info used in eth_type_trans() */

	unsigned char		*dev_addr;	/* hw address, (before bcast

						   because most packets are
@@ -980,10 +980,14 @@ struct net_device { 
	unsigned int		num_rx_queues;

#endif



	struct netdev_queue	rx_queue;

	rx_handler_func_t	*rx_handler;

	void			*rx_handler_data;



	struct netdev_queue	rx_queue; /* use two cache lines */



/*

 * Cache lines mostly used on transmit path

 */

	struct netdev_queue	*_tx ____cacheline_aligned_in_smp;



	/* Number of TX queues allocated at alloc_netdev_mq() time  */
@@ -997,9 +1001,7 @@ struct net_device { 


	unsigned long		tx_queue_len;	/* Max frames per queue allowed */

	spinlock_t		tx_global_lock;

/*

 * One part is mostly used on xmit path (device)

 */



	/* These may be needed for future network-power-down code. */



	/*

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