On Wed, Mar 09, 2016 at 03:47:25PM -0500, David Miller wrote:
> From: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
> Date: Wed, 9 Mar 2016 23:41:58 +0300
>
> > On Wed, Mar 09, 2016 at 03:27:30PM -0500, David Miller wrote:
> >> >
> >> > Yes. I can drop it off for a while and run tests without it,
> >> > then turn it back and try again. Would you like to see such
> >> > numbers?
> >>
> >> That would be very helpful, yes.
> >
> > Just sent out. Take a look please. Indeed it sits inside get_next_corpse
> > a lot. And now I think I've to figure out where we can optimize it.
> > Continue tomorrow.
>
> The problem is that the masquerading code flushes the entire conntrack
> table once for _every_ address removed.
>
> The code path is:
>
> masq_device_event()
> if (event == NETDEV_DOWN) {
> /* Device was downed. Search entire table for
> * conntracks which were associated with that device,
> * and forget them.
> */
> NF_CT_ASSERT(dev->ifindex != 0);
>
> nf_ct_iterate_cleanup(net, device_cmp,
> (void *)(long)dev->ifindex, 0, 0);
>
> So if you have a million IP addresses, this flush happens a million times
> on inetdev destroy.
>
> Part of the problem is that we emit NETDEV_DOWN inetdev notifiers per
> address removed, instead of once per inetdev destroy.
>
> Maybe if we put some boolean state into the inetdev, we could make sure
> we did this flush only once time while inetdev->dead = 1.
Aha! So in your patch __inet_del_ifa bypass first blocking_notifier_call_chain
__inet_del_ifa
...
if (in_dev->dead)
goto no_promotions;
// First call to NETDEV_DOWN
...
no_promotions:
rtmsg_ifa(RTM_DELADDR, ifa1, nlh, portid);
blocking_notifier_call_chain(&inetaddr_chain, NETDEV_DOWN, ifa1);
and here we call for NETDEV_DOWN, which then hits masq_device_event
and go further to conntrack code.
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