[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>

1 files changed, 55 insertions, 34 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 7c717907896d..368e4c825ff1 100644
--- 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,