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>
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index ba13b09..52ea418 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -682,22 +682,33 @@
static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
{
struct net *net = sock_net(skb->sk);
- int idx;
- int s_idx = cb->args[0];
+ int h, s_h;
+ int idx = 0, s_idx;
struct net_device *dev;
+ struct hlist_head *head;
+ struct hlist_node *node;
- idx = 0;
- for_each_netdev(net, dev) {
- if (idx < s_idx)
- goto cont;
- if (rtnl_fill_ifinfo(skb, dev, RTM_NEWLINK,
- NETLINK_CB(cb->skb).pid,
- cb->nlh->nlmsg_seq, 0, NLM_F_MULTI) <= 0)
- break;
+ s_h = cb->args[0];
+ s_idx = cb->args[1];
+
+ for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
+ idx = 0;
+ head = &net->dev_index_head[h];
+ hlist_for_each_entry(dev, node, head, index_hlist) {
+ if (idx < s_idx)
+ goto cont;
+ if (rtnl_fill_ifinfo(skb, dev, RTM_NEWLINK,
+ NETLINK_CB(cb->skb).pid,
+ cb->nlh->nlmsg_seq, 0,
+ NLM_F_MULTI) <= 0)
+ goto out;
cont:
- idx++;
+ idx++;
+ }
}
- cb->args[0] = idx;
+out:
+ cb->args[1] = idx;
+ cb->args[0] = h;
return skb->len;
}