Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit eec4df98 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

ipv4: speedup inet_dump_ifaddr() 



Stephen Hemminger a écrit :
> On Thu, 12 Nov 2009 15:11:36 +0100
> Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
>> When handling large number of netdevices, inet_dump_ifaddr()
>> is very slow because it has O(N^2) complexity.
>>
>> Instead of scanning one single list, we can use the NETDEV_HASHENTRIES
>> sub lists of the dev_index hash table, and RCU lookups.
>>
>> Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
>
> You might be able to make RCU critical section smaller by moving
> it into loop.
>

Indeed. But we dump at most one skb (<= 8192 bytes ?), so rcu_read_lock
holding time is small, unless we meet many netdevices without
addresses. I wonder if its really common...

Thanks

[PATCH net-next-2.6] ipv4: speedup inet_dump_ifaddr()

When handling large number of netdevices, inet_dump_ifaddr()
is very slow because it has O(N2) complexity.

Instead of scanning one single list, we can use the NETDEV_HASHENTRIES
sub lists of the dev_index hash table, and RCU lookups.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Acked-by: default avatarStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 342bde1b

net/ipv4/devinet.c

+38 −23
Original line number Diff line number Diff line
@@ -1174,20 +1174,29 @@ static int inet_fill_ifaddr(struct sk_buff *skb, struct in_ifaddr *ifa, 
static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)

{

	struct net *net = sock_net(skb->sk);

	int idx, ip_idx;

	int h, s_h;

	int idx, s_idx;

	int ip_idx, s_ip_idx;

	struct net_device *dev;

	struct in_device *in_dev;

	struct in_ifaddr *ifa;

	int s_ip_idx, s_idx = cb->args[0];

	struct hlist_head *head;

	struct hlist_node *node;



	s_ip_idx = ip_idx = cb->args[1];

	s_h = cb->args[0];

	s_idx = idx = cb->args[1];

	s_ip_idx = ip_idx = cb->args[2];



	for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {

		idx = 0;

	for_each_netdev(net, dev) {

		head = &net->dev_index_head[h];

		rcu_read_lock();

		hlist_for_each_entry_rcu(dev, node, head, index_hlist) {

			if (idx < s_idx)

				goto cont;

			if (idx > s_idx)

				s_ip_idx = 0;

		in_dev = __in_dev_get_rtnl(dev);

			in_dev = __in_dev_get_rcu(dev);

			if (!in_dev)

				goto cont;
@@ -1195,18 +1204,24 @@ static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb) 
			     ifa = ifa->ifa_next, ip_idx++) {

				if (ip_idx < s_ip_idx)

					continue;

			if (inet_fill_ifaddr(skb, ifa, NETLINK_CB(cb->skb).pid,

				if (inet_fill_ifaddr(skb, ifa,

					     NETLINK_CB(cb->skb).pid,

					     cb->nlh->nlmsg_seq,

					     RTM_NEWADDR, NLM_F_MULTI) <= 0)

					     RTM_NEWADDR, NLM_F_MULTI) <= 0) {

					rcu_read_unlock();

					goto done;

				}

			}

cont:

			idx++;

		}

		rcu_read_unlock();

	}



done:

	cb->args[0] = idx;

	cb->args[1] = ip_idx;

	cb->args[0] = h;

	cb->args[1] = idx;

	cb->args[2] = ip_idx;



	return skb->len;

}