Re: [patch 37/44] xen: add virtual network device driver

+struct netfront_info {
+	struct list_head list;
+	struct net_device *netdev;
+
+	struct net_device_stats stats;

There is now a net_device_stats element inside net_device on
2.6.21 or later.

+
+	struct xen_netif_tx_front_ring tx;
+	struct xen_netif_rx_front_ring rx;
+
+	spinlock_t   tx_lock;
+	spinlock_t   rx_lock;

It might be a performance advantage to reorder/align these
structure elements to put transmit hot elements together, and
put tx and rx on different cache lines?

+	unsigned int evtchn;
+
+	/* Receive-ring batched refills. */
+#define RX_MIN_TARGET 8
+#define RX_DFL_MIN_TARGET 64
+#define RX_MAX_TARGET min_t(int, NET_RX_RING_SIZE, 256)
+	unsigned rx_min_target, rx_max_target, rx_target;
+	struct sk_buff_head rx_batch;
+
+	struct timer_list rx_refill_timer;
+
+	/*
+	 * {tx,rx}_skbs store outstanding skbuffs. Free tx_skb entries
+	 * are linked from tx_skb_freelist through skb_entry.link.
+	 *
+	 *  NB. Freelist index entries are always going to be less than
+	 *  PAGE_OFFSET, whereas pointers to skbs will always be equal or
+	 *  greater than PAGE_OFFSET: we use this property to distinguish
+	 *  them.
+	 */
+	union skb_entry {
+		struct sk_buff *skb;
+		unsigned link;
+	} tx_skbs[NET_TX_RING_SIZE];
+	grant_ref_t gref_tx_head;
+	grant_ref_t grant_tx_ref[NET_TX_RING_SIZE];
+	unsigned tx_skb_freelist;
+
+	struct sk_buff *rx_skbs[NET_RX_RING_SIZE];
+	grant_ref_t gref_rx_head;
+	grant_ref_t grant_rx_ref[NET_RX_RING_SIZE];
+
+	struct xenbus_device *xbdev;
+	int tx_ring_ref;
+	int rx_ring_ref;
+
+	unsigned long rx_pfn_array[NET_RX_RING_SIZE];
+	struct multicall_entry rx_mcl[NET_RX_RING_SIZE+1];
+	struct mmu_update rx_mmu[NET_RX_RING_SIZE];
+};