[Openstack] dnsmasq and ipv6 causing high load on network nodes with many fluctuates between D and S states.

Brian Haley brian.haley at hpe.com
Wed Nov 18 14:58:02 UTC 2015

On 11/18/2015 07:33 AM, kevin parrikar wrote:
> i am trying Juno *without *DVR and there are around 500 sub nets in each network
> node.
> Network nodes have 500+ dnsmasq process which are configured to give ipv6,ipv4
> addresses out of this some fluctuates between D and S state while others are in
> continuous S state.Probably because of too many processes in D state with
> "rtnetlink_rcv" in "wchan" its showing very high load average.
> functions in stack when in D state:
> [<ffffffff816360a9>] rtnetlink_rcv+0x19/0x30
> [<ffffffff81653e25>] netlink_unicast+0xd5/0x1b0
> [<ffffffff8165420e>] netlink_sendmsg+0x30e/0x680
> [<ffffffff8160e32b>] sock_sendmsg+0x8b/0xc0
> [<ffffffff8160e871>] SYSC_sendto+0x121/0x1c0
> [<ffffffff8160f25e>] SyS_sendto+0xe/0x10
> [<ffffffff817342dd>] system_call_fastpath+0x1a/0x1f
> [<ffffffffffffffff>] 0xffffffffffffffff
> but in couple of seconds it changes to S state with this in stack,all idle
> process have this in stack.
> [<ffffffff811d20d9>] poll_schedule_timeout+0x49/0x70
> [<ffffffff811d2ac6>] do_select+0x5b6/0x780
> [<ffffffff811d2e5c>] core_sys_select+0x1cc/0x2e0
> [<ffffffff811d301b>] SyS_select+0xab/0x100
> [<ffffffff817342dd>] system_call_fastpath+0x1a/0x1f
> [<ffffffffffffffff>] 0xffffffffffffffff
> interface in which dnsmasq is listening has " tentative dadfailed" in  "scope
> global" for ipv6 for all the dnsmasq process that are in D state.
> i don't understand why duplicate ipv6 issue is coming when there are vlan tags
> to separate each sub net.For ipv4 duplicate IP issue is not coming for same subnet.

DAD failure is fatal for the address, as it won't be tried again without 
bouncing the interface or tweaking the disable_ipv6 sysctl on the interface. 
The "tentative" flag is just showing it is still in that state (i.e. waiting for 
DAD to complete).  Figuring out why this is happening will most likely solve 
your problem, but there isn't enough here to go on.

The fact that you don't see an IPv4 'duplicate' message is that it's not going 
to typically do it, so you could have a duplicate there and just not know it.

I'd say to try Kilo or Liberty, but it's unclear if this is a Neutron issue or 
something more basic with your setup.


> Not able to understand why dnsmasq that are connected to interfaces that have
> "tentative dadfailed " continuously changes between S and D state while others
> are idle.
> attached is the strace while dnsmasq is in D state.
> Any idea about this issue?
> _______________________________________________
> Mailing list: http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack
> Post to     : openstack at lists.openstack.org
> Unsubscribe : http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack

More information about the Openstack mailing list