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ipv4: speedup inet_dump_ifaddr()

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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: Eric 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: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2009-11-12 07:44:25 +00:00 committed by David S. Miller
parent 342bde1b70
commit eec4df9885
1 changed files with 38 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

61
net/ipv4/devinet.c
View File

@ -1174,39 +1174,54 @@ 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];
idx = 0;
for_each_netdev(net, dev) {
if (idx < s_idx)
goto cont;
if (idx > s_idx)
s_ip_idx = 0;
in_dev = __in_dev_get_rtnl(dev);
if (!in_dev)
goto cont;
s_h = cb->args[0];
s_idx = idx = cb->args[1];
s_ip_idx = ip_idx = cb->args[2];
for (ifa = in_dev->ifa_list, ip_idx = 0; ifa;
ifa = ifa->ifa_next, ip_idx++) {
if (ip_idx < s_ip_idx)
continue;
if (inet_fill_ifaddr(skb, ifa, NETLINK_CB(cb->skb).pid,
for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
idx = 0;
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_rcu(dev);
if (!in_dev)
goto cont;
for (ifa = in_dev->ifa_list, ip_idx = 0; ifa;
ifa = ifa->ifa_next, ip_idx++) {
if (ip_idx < s_ip_idx)
continue;
if (inet_fill_ifaddr(skb, ifa,
NETLINK_CB(cb->skb).pid,
cb->nlh->nlmsg_seq,
RTM_NEWADDR, NLM_F_MULTI) <= 0)
goto done;
}
RTM_NEWADDR, NLM_F_MULTI) <= 0) {
rcu_read_unlock();
goto done;
}
}
cont:
idx++;
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;
}