rtnetlink: speedup rtnl_dump_ifinfo()

When handling large number of netdevice, rtnl_dump_ifinfo()
is very slow because it has O(N^2) complexity.

Instead of scanning one single list, we can use the 256 sub lists
of the dev_index hash table.

This considerably speedups "ip link" operations

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

1 files changed, 4 insertions, 0 deletions

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 699410142bfa..0addd45038ac 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -28,6 +28,10 @@ struct ctl_table_header;
 struct net_generic;
 struct sock;
 
+
+#define NETDEV_HASHBITS    8
+#define NETDEV_HASHENTRIES (1 << NETDEV_HASHBITS)
+
 struct net {
         atomic_t                count;          /* To decided when the network
                                                  *  namespace should be freed.