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Commit 7c28bd0b authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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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: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8d5b2c08

include/net/net_namespace.h

+4 −0
Original line number Diff line number Diff line
@@ -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.

net/core/dev.c

+2 −5
Original line number Diff line number Diff line
@@ -193,18 +193,15 @@ static struct list_head ptype_all __read_mostly; /* Taps */ 
DEFINE_RWLOCK(dev_base_lock);

EXPORT_SYMBOL(dev_base_lock);



#define NETDEV_HASHBITS	8

#define NETDEV_HASHENTRIES (1 << NETDEV_HASHBITS)



static inline struct hlist_head *dev_name_hash(struct net *net, const char *name)

{

	unsigned hash = full_name_hash(name, strnlen(name, IFNAMSIZ));

	return &net->dev_name_head[hash & ((1 << NETDEV_HASHBITS) - 1)];

	return &net->dev_name_head[hash & (NETDEV_HASHENTRIES - 1)];

}



static inline struct hlist_head *dev_index_hash(struct net *net, int ifindex)

{

	return &net->dev_index_head[ifindex & ((1 << NETDEV_HASHBITS) - 1)];

	return &net->dev_index_head[ifindex & (NETDEV_HASHENTRIES - 1)];

}



/* Device list insertion */

net/core/rtnetlink.c

+24 −13
Original line number Diff line number Diff line
@@ -682,22 +682,33 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev, 
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;



	s_h = cb->args[0];

	s_idx = cb->args[1];



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

		idx = 0;

	for_each_netdev(net, dev) {

		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)

			break;

					     cb->nlh->nlmsg_seq, 0,

					     NLM_F_MULTI) <= 0)

				goto out;

cont:

			idx++;

		}

	cb->args[0] = idx;

	}

out:

	cb->args[1] = idx;

	cb->args[0] = h;



	return skb->len;

}