bridge: per-cpu packet statistics (v3)

The shared packet statistics are a potential source of slow down
on bridged traffic. Convert to per-cpu array, but only keep those
statistics which change per-packet.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_device.c

@@ -26,11 +26,12 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 	const unsigned char *dest = skb->data;
 	struct net_bridge_fdb_entry *dst;
 	struct net_bridge_mdb_entry *mdst;
+	struct br_cpu_netstats *brstats = this_cpu_ptr(br->stats);
 
-	BR_INPUT_SKB_CB(skb)->brdev = dev;
+	brstats->tx_packets++;
+	brstats->tx_bytes += skb->len;
 
-	dev->stats.tx_packets++;
-	dev->stats.tx_bytes += skb->len;
+	BR_INPUT_SKB_CB(skb)->brdev = dev;
 
 	skb_reset_mac_header(skb);
 	skb_pull(skb, ETH_HLEN);
@@ -81,6 +82,31 @@ static int br_dev_stop(struct net_device *dev)
 	return 0;
 }
 
+static struct net_device_stats *br_get_stats(struct net_device *dev)
+{
+	struct net_bridge *br = netdev_priv(dev);
+	struct net_device_stats *stats = &dev->stats;
+	struct br_cpu_netstats sum = { 0 };
+	unsigned int cpu;
+
+	for_each_possible_cpu(cpu) {
+		const struct br_cpu_netstats *bstats
+			= per_cpu_ptr(br->stats, cpu);
+
+		sum.tx_bytes   += bstats->tx_bytes;
+		sum.tx_packets += bstats->tx_packets;
+		sum.rx_bytes   += bstats->rx_bytes;
+		sum.rx_packets += bstats->rx_packets;
+	}
+
+	stats->tx_bytes   = sum.tx_bytes;
+	stats->tx_packets = sum.tx_packets;
+	stats->rx_bytes   = sum.rx_bytes;
+	stats->rx_packets = sum.rx_packets;
+
+	return stats;
+}
+
 static int br_change_mtu(struct net_device *dev, int new_mtu)
 {
 	struct net_bridge *br = netdev_priv(dev);
@@ -180,19 +206,28 @@ static const struct net_device_ops br_netdev_ops = {
 	.ndo_open		 = br_dev_open,
 	.ndo_stop		 = br_dev_stop,
 	.ndo_start_xmit		 = br_dev_xmit,
+	.ndo_get_stats		 = br_get_stats,
 	.ndo_set_mac_address	 = br_set_mac_address,
 	.ndo_set_multicast_list	 = br_dev_set_multicast_list,
 	.ndo_change_mtu		 = br_change_mtu,
 	.ndo_do_ioctl		 = br_dev_ioctl,
 };
 
+static void br_dev_free(struct net_device *dev)
+{
+	struct net_bridge *br = netdev_priv(dev);
+
+	free_percpu(br->stats);
+	free_netdev(dev);
+}
+
 void br_dev_setup(struct net_device *dev)
 {
 	random_ether_addr(dev->dev_addr);
 	ether_setup(dev);
 
 	dev->netdev_ops = &br_netdev_ops;
-	dev->destructor = free_netdev;
+	dev->destructor = br_dev_free;
 	SET_ETHTOOL_OPS(dev, &br_ethtool_ops);
 	dev->tx_queue_len = 0;
 	dev->priv_flags = IFF_EBRIDGE;

net/bridge/br_if.c

@@ -185,6 +185,12 @@ static struct net_device *new_bridge_dev(struct net *net, const char *name)
 	br = netdev_priv(dev);
 	br->dev = dev;
 
+	br->stats = alloc_percpu(struct br_cpu_netstats);
+	if (!br->stats) {
+		free_netdev(dev);
+		return NULL;
+	}
+
 	spin_lock_init(&br->lock);
 	INIT_LIST_HEAD(&br->port_list);
 	spin_lock_init(&br->hash_lock);

net/bridge/br_input.c

@@ -23,9 +23,11 @@ const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
 static int br_pass_frame_up(struct sk_buff *skb)
 {
 	struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
+	struct net_bridge *br = netdev_priv(brdev);
+	struct br_cpu_netstats *brstats = this_cpu_ptr(br->stats);
 
-	brdev->stats.rx_packets++;
-	brdev->stats.rx_bytes += skb->len;
+	brstats->rx_packets++;
+	brstats->rx_bytes += skb->len;
 
 	indev = skb->dev;
 	skb->dev = brdev;

net/bridge/br_private.h

@@ -135,6 +135,14 @@ struct net_bridge
 	spinlock_t			lock;
 	struct list_head		port_list;
 	struct net_device		*dev;
+
+	struct br_cpu_netstats __percpu {
+		unsigned long	rx_packets;
+		unsigned long	rx_bytes;
+		unsigned long	tx_packets;
+		unsigned long	tx_bytes;
+	} *stats;
+
 	spinlock_t			hash_lock;
 	struct hlist_head		hash[BR_HASH_SIZE];
 	unsigned long			feature_mask;