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[NET]: Reorder some hot fields of struct net_device
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Place them on separate cache lines in SMP to lower memory bouncing
between multiple CPU accessing the device.

     - One part is mostly used on receive path (including
       eth_type_trans()) (poll_list, poll, quota, weight, last_rx,
       dev_addr, broadcast)

     - One part is mostly used on queue transmit path (qdisc)
      (queue_lock, qdisc, qdisc_sleeping, qdisc_list, tx_queue_len)

     - One part is mostly used on xmit path (device)
      (xmit_lock, xmit_lock_owner, priv, hard_start_xmit, trans_start)

'features' is placed outside of these hot points, in a location that
may be shared by all cpus (because mostly read)

name_hlist is moved close to name[IFNAMSIZ] to speedup __dev_get_by_name()

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Eric Dumazet authored and David S. Miller committed Sep 27, 2005
1 parent 2d7ceec commit 9356b8f
Showing 1 changed file with 55 additions and 34 deletions.
89 changes: 55 additions & 34 deletions include/linux/netdevice.h
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Original file line number Diff line number Diff line change
Expand Up @@ -265,6 +265,8 @@ struct net_device
* the interface.
*/
char name[IFNAMSIZ];
/* device name hash chain */
struct hlist_node name_hlist;

/*
* I/O specific fields
Expand Down Expand Up @@ -292,6 +294,21 @@ struct net_device

/* ------- Fields preinitialized in Space.c finish here ------- */

/* Net device features */
unsigned long features;
#define NETIF_F_SG 1 /* Scatter/gather IO. */
#define NETIF_F_IP_CSUM 2 /* Can checksum only TCP/UDP over IPv4. */
#define NETIF_F_NO_CSUM 4 /* Does not require checksum. F.e. loopack. */
#define NETIF_F_HW_CSUM 8 /* Can checksum all the packets. */
#define NETIF_F_HIGHDMA 32 /* Can DMA to high memory. */
#define NETIF_F_FRAGLIST 64 /* Scatter/gather IO. */
#define NETIF_F_HW_VLAN_TX 128 /* Transmit VLAN hw acceleration */
#define NETIF_F_HW_VLAN_RX 256 /* Receive VLAN hw acceleration */
#define NETIF_F_HW_VLAN_FILTER 512 /* Receive filtering on VLAN */
#define NETIF_F_VLAN_CHALLENGED 1024 /* Device cannot handle VLAN packets */
#define NETIF_F_TSO 2048 /* Can offload TCP/IP segmentation */
#define NETIF_F_LLTX 4096 /* LockLess TX */

struct net_device *next_sched;

/* Interface index. Unique device identifier */
Expand All @@ -316,9 +333,6 @@ struct net_device
* will (read: may be cleaned up at will).
*/

/* These may be needed for future network-power-down code. */
unsigned long trans_start; /* Time (in jiffies) of last Tx */
unsigned long last_rx; /* Time of last Rx */

unsigned short flags; /* interface flags (a la BSD) */
unsigned short gflags;
Expand All @@ -328,15 +342,12 @@ struct net_device
unsigned mtu; /* interface MTU value */
unsigned short type; /* interface hardware type */
unsigned short hard_header_len; /* hardware hdr length */
void *priv; /* pointer to private data */

struct net_device *master; /* Pointer to master device of a group,
* which this device is member of.
*/

/* Interface address info. */
unsigned char broadcast[MAX_ADDR_LEN]; /* hw bcast add */
unsigned char dev_addr[MAX_ADDR_LEN]; /* hw address */
unsigned char perm_addr[MAX_ADDR_LEN]; /* permanent hw address */
unsigned char addr_len; /* hardware address length */
unsigned short dev_id; /* for shared network cards */
Expand All @@ -346,8 +357,6 @@ struct net_device
int promiscuity;
int allmulti;

int watchdog_timeo;
struct timer_list watchdog_timer;

/* Protocol specific pointers */

Expand All @@ -358,32 +367,62 @@ struct net_device
void *ec_ptr; /* Econet specific data */
void *ax25_ptr; /* AX.25 specific data */

struct list_head poll_list; /* Link to poll list */
/*
* Cache line mostly used on receive path (including eth_type_trans())
*/
struct list_head poll_list ____cacheline_aligned_in_smp;
/* Link to poll list */

int (*poll) (struct net_device *dev, int *quota);
int quota;
int weight;
unsigned long last_rx; /* Time of last Rx */
/* Interface address info used in eth_type_trans() */
unsigned char dev_addr[MAX_ADDR_LEN]; /* hw address, (before bcast
because most packets are unicast) */

unsigned char broadcast[MAX_ADDR_LEN]; /* hw bcast add */

/*
* Cache line mostly used on queue transmit path (qdisc)
*/
/* device queue lock */
spinlock_t queue_lock ____cacheline_aligned_in_smp;
struct Qdisc *qdisc;
struct Qdisc *qdisc_sleeping;
struct Qdisc *qdisc_ingress;
struct list_head qdisc_list;
unsigned long tx_queue_len; /* Max frames per queue allowed */

/* ingress path synchronizer */
spinlock_t ingress_lock;
struct Qdisc *qdisc_ingress;

/*
* One part is mostly used on xmit path (device)
*/
/* hard_start_xmit synchronizer */
spinlock_t xmit_lock;
spinlock_t xmit_lock ____cacheline_aligned_in_smp;
/* cpu id of processor entered to hard_start_xmit or -1,
if nobody entered there.
*/
int xmit_lock_owner;
/* device queue lock */
spinlock_t queue_lock;
void *priv; /* pointer to private data */
int (*hard_start_xmit) (struct sk_buff *skb,
struct net_device *dev);
/* These may be needed for future network-power-down code. */
unsigned long trans_start; /* Time (in jiffies) of last Tx */

int watchdog_timeo; /* used by dev_watchdog() */
struct timer_list watchdog_timer;

/*
* refcnt is a very hot point, so align it on SMP
*/
/* Number of references to this device */
atomic_t refcnt;
atomic_t refcnt ____cacheline_aligned_in_smp;

/* delayed register/unregister */
struct list_head todo_list;
/* device name hash chain */
struct hlist_node name_hlist;
/* device index hash chain */
struct hlist_node index_hlist;

Expand All @@ -396,21 +435,6 @@ struct net_device
NETREG_RELEASED, /* called free_netdev */
} reg_state;

/* Net device features */
unsigned long features;
#define NETIF_F_SG 1 /* Scatter/gather IO. */
#define NETIF_F_IP_CSUM 2 /* Can checksum only TCP/UDP over IPv4. */
#define NETIF_F_NO_CSUM 4 /* Does not require checksum. F.e. loopack. */
#define NETIF_F_HW_CSUM 8 /* Can checksum all the packets. */
#define NETIF_F_HIGHDMA 32 /* Can DMA to high memory. */
#define NETIF_F_FRAGLIST 64 /* Scatter/gather IO. */
#define NETIF_F_HW_VLAN_TX 128 /* Transmit VLAN hw acceleration */
#define NETIF_F_HW_VLAN_RX 256 /* Receive VLAN hw acceleration */
#define NETIF_F_HW_VLAN_FILTER 512 /* Receive filtering on VLAN */
#define NETIF_F_VLAN_CHALLENGED 1024 /* Device cannot handle VLAN packets */
#define NETIF_F_TSO 2048 /* Can offload TCP/IP segmentation */
#define NETIF_F_LLTX 4096 /* LockLess TX */

/* Called after device is detached from network. */
void (*uninit)(struct net_device *dev);
/* Called after last user reference disappears. */
Expand All @@ -419,10 +443,7 @@ struct net_device
/* Pointers to interface service routines. */
int (*open)(struct net_device *dev);
int (*stop)(struct net_device *dev);
int (*hard_start_xmit) (struct sk_buff *skb,
struct net_device *dev);
#define HAVE_NETDEV_POLL
int (*poll) (struct net_device *dev, int *quota);
int (*hard_header) (struct sk_buff *skb,
struct net_device *dev,
unsigned short type,
Expand Down

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