[NET]: Reorder some hot fields of struct net_device

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>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 7c71790..368e4c8 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -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
@@ -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    */
@@ -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;
@@ -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 */
@@ -346,8 +357,6 @@ struct net_device
        int                     promiscuity;
        int                     allmulti;
 
-       int                     watchdog_timeo;
-       struct timer_list       watchdog_timer;
 
        /* Protocol specific pointers */
        
@@ -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;
 
@@ -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. */
@@ -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,