veth: reduce stat overhead

veth stats are a bit bloated. There is no need to account transmit
and receive stats, since they are absolutely symmetric.

Also use a per device atomic64_t for the dropped counter, as it
should never be used in fast path.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 95814d9747ef1988657ccd72bc01d56501bc7b37..c048f8d27bbf7e43a6ecd0148d1803cdb1515429 100644 (file)
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -25,18 +25,15 @@
 #define MIN_MTU 68             /* Min L3 MTU */
 #define MAX_MTU 65535          /* Max L3 MTU (arbitrary) */
 
-struct veth_net_stats {
-       u64                     rx_packets;
-       u64                     rx_bytes;
-       u64                     tx_packets;
-       u64                     tx_bytes;
-       u64                     rx_dropped;
+struct pcpu_vstats {
+       u64                     packets;
+       u64                     bytes;
        struct u64_stats_sync   syncp;
 };
 
 struct veth_priv {
-       struct net_device *peer;
-       struct veth_net_stats __percpu *stats;
+       struct net_device       *peer;
+       atomic64_t              dropped;
 };
 
 /*
@@ -107,50 +104,30 @@ static const struct ethtool_ops veth_ethtool_ops = {
        .get_ethtool_stats      = veth_get_ethtool_stats,
 };
 
-/*
- * xmit
- */
-
 static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
 {
-       struct net_device *rcv = NULL;
-       struct veth_priv *priv, *rcv_priv;
-       struct veth_net_stats *stats, *rcv_stats;
-       int length;
-
-       priv = netdev_priv(dev);
-       rcv = priv->peer;
-       rcv_priv = netdev_priv(rcv);
-
-       stats = this_cpu_ptr(priv->stats);
-       rcv_stats = this_cpu_ptr(rcv_priv->stats);
+       struct veth_priv *priv = netdev_priv(dev);
+       struct net_device *rcv = priv->peer;
+       int length = skb->len;
 
        /* don't change ip_summed == CHECKSUM_PARTIAL, as that
-          will cause bad checksum on forwarded packets */
+        * will cause bad checksum on forwarded packets
+        */
        if (skb->ip_summed == CHECKSUM_NONE &&
            rcv->features & NETIF_F_RXCSUM)
                skb->ip_summed = CHECKSUM_UNNECESSARY;
 
-       length = skb->len;
-       if (dev_forward_skb(rcv, skb) != NET_RX_SUCCESS)
-               goto rx_drop;
-
-       u64_stats_update_begin(&stats->syncp);
-       stats->tx_bytes += length;
-       stats->tx_packets++;
-       u64_stats_update_end(&stats->syncp);
+       if (likely(dev_forward_skb(rcv, skb) == NET_RX_SUCCESS)) {
+               struct pcpu_vstats *stats = this_cpu_ptr(dev->vstats);
 
-       u64_stats_update_begin(&rcv_stats->syncp);
-       rcv_stats->rx_bytes += length;
-       rcv_stats->rx_packets++;
-       u64_stats_update_end(&rcv_stats->syncp);
-
-       return NETDEV_TX_OK;
+               u64_stats_update_begin(&stats->syncp);
+               stats->bytes += length;
+               stats->packets++;
+               u64_stats_update_end(&stats->syncp);
+       } else {
+               atomic64_inc(&priv->dropped);
+       }
 
-rx_drop:
-       u64_stats_update_begin(&rcv_stats->syncp);
-       rcv_stats->rx_dropped++;
-       u64_stats_update_end(&rcv_stats->syncp);
        return NETDEV_TX_OK;
 }
 
@@ -158,32 +135,42 @@ rx_drop:
  * general routines
  */
 
-static struct rtnl_link_stats64 *veth_get_stats64(struct net_device *dev,
-                                                 struct rtnl_link_stats64 *tot)
+static u64 veth_stats_one(struct pcpu_vstats *result, struct net_device *dev)
 {
        struct veth_priv *priv = netdev_priv(dev);
        int cpu;
 
+       result->packets = 0;
+       result->bytes = 0;
        for_each_possible_cpu(cpu) {
-               struct veth_net_stats *stats = per_cpu_ptr(priv->stats, cpu);
-               u64 rx_packets, rx_bytes, rx_dropped;
-               u64 tx_packets, tx_bytes;
+               struct pcpu_vstats *stats = per_cpu_ptr(dev->vstats, cpu);
+               u64 packets, bytes;
                unsigned int start;
 
                do {
                        start = u64_stats_fetch_begin_bh(&stats->syncp);
-                       rx_packets = stats->rx_packets;
-                       tx_packets = stats->tx_packets;
-                       rx_bytes = stats->rx_bytes;
-                       tx_bytes = stats->tx_bytes;
-                       rx_dropped = stats->rx_dropped;
+                       packets = stats->packets;
+                       bytes = stats->bytes;
                } while (u64_stats_fetch_retry_bh(&stats->syncp, start));
-               tot->rx_packets += rx_packets;
-               tot->tx_packets += tx_packets;
-               tot->rx_bytes   += rx_bytes;
-               tot->tx_bytes   += tx_bytes;
-               tot->rx_dropped += rx_dropped;
+               result->packets += packets;
+               result->bytes += bytes;
        }
+       return atomic64_read(&priv->dropped);
+}
+
+static struct rtnl_link_stats64 *veth_get_stats64(struct net_device *dev,
+                                                 struct rtnl_link_stats64 *tot)
+{
+       struct veth_priv *priv = netdev_priv(dev);
+       struct pcpu_vstats one;
+
+       tot->tx_dropped = veth_stats_one(&one, dev);
+       tot->tx_bytes = one.bytes;
+       tot->tx_packets = one.packets;
+
+       tot->rx_dropped = veth_stats_one(&one, priv->peer);
+       tot->rx_bytes = one.bytes;
+       tot->rx_packets = one.packets;
 
        return tot;
 }
@@ -228,24 +215,16 @@ static int veth_change_mtu(struct net_device *dev, int new_mtu)
 
 static int veth_dev_init(struct net_device *dev)
 {
-       struct veth_net_stats __percpu *stats;
-       struct veth_priv *priv;
-
-       stats = alloc_percpu(struct veth_net_stats);
-       if (stats == NULL)
+       dev->vstats = alloc_percpu(struct pcpu_vstats);
+       if (!dev->vstats)
                return -ENOMEM;
 
-       priv = netdev_priv(dev);
-       priv->stats = stats;
        return 0;
 }
 
 static void veth_dev_free(struct net_device *dev)
 {
-       struct veth_priv *priv;
-
-       priv = netdev_priv(dev);
-       free_percpu(priv->stats);
+       free_percpu(dev->vstats);
        free_netdev(dev);
 }
 

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 0e1b92a0c1ec2e2e2e9adb38366600f06b5ab417..6835b5837f9324f91e5f1dd2400303198f982ff1 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1284,6 +1284,7 @@ struct net_device {
                struct pcpu_lstats __percpu     *lstats; /* loopback stats */
                struct pcpu_tstats __percpu     *tstats; /* tunnel stats */
                struct pcpu_dstats __percpu     *dstats; /* dummy stats */
+               struct pcpu_vstats __percpu     *vstats; /* veth stats */
        };
        /* GARP */
        struct garp_port __rcu  *garp_port;