vlan: Precise RX stats accounting

With multi queue devices, its possible that several cpus call
vlan RX routines simultaneously for the same vlan device.

We update RX stats counter without any locking, so we can
get slightly wrong counters.

One possible fix is to use percpu counters, to get precise
accounting and also get guarantee of no cache line ping pongs
between cpus.

Note: this adds 16 bytes (32 bytes on 64bit arches) of percpu
data per vlan device.

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

1 files changed, 17 insertions, 0 deletions

diff --git a/net/8021q/vlan.h b/net/8021q/vlan.h
index 68f9290e6837..5685296017e9 100644
--- a/net/8021q/vlan.h
+++ b/net/8021q/vlan.h
@@ -16,6 +16,21 @@ struct vlan_priority_tci_mapping {
         struct vlan_priority_tci_mapping        *next;
 };
 
+
+/**
+ *      struct vlan_rx_stats - VLAN percpu rx stats
+ *      @rx_packets: number of received packets
+ *      @rx_bytes: number of received bytes
+ *      @multicast: number of received multicast packets
+ *      @rx_errors: number of errors
+ */
+struct vlan_rx_stats {
+        unsigned long rx_packets;
+        unsigned long rx_bytes;
+        unsigned long multicast;
+        unsigned long rx_errors;
+};
+
 /**
  *      struct vlan_dev_info - VLAN private device data
  *      @nr_ingress_mappings: number of ingress priority mappings
@@ -29,6 +44,7 @@ struct vlan_priority_tci_mapping {
  *      @dent: proc dir entry
  *      @cnt_inc_headroom_on_tx: statistic - number of skb expansions on TX
  *      @cnt_encap_on_xmit: statistic - number of skb encapsulations on TX
+ *      @vlan_rx_stats: ptr to percpu rx stats
  */
 struct vlan_dev_info {
         unsigned int                            nr_ingress_mappings;
@@ -45,6 +61,7 @@ struct vlan_dev_info {
         struct proc_dir_entry                   *dent;
         unsigned long                           cnt_inc_headroom_on_tx;
         unsigned long                           cnt_encap_on_xmit;
+        struct vlan_rx_stats                    *vlan_rx_stats;
 };
 
 static inline struct vlan_dev_info *vlan_dev_info(const struct net_device *dev)