netmap/vale periodic deadlock

[Harry Schmalzbauer]

Bezüglich Vincenzo Maffione's Nachricht vom 22.11.2017 09:04 (localtime):
> 
> 
> 2017-11-21 21:48 GMT+01:00 Harry Schmalzbauer <freebsd at omnilan.de
> <mailto:freebsd at omnilan.de>>:
> 
>     Bezüglich Vincenzo Maffione's Nachricht vom 21.11.2017 09:39
>     (localtime):
>     …
>     >
>     > If this is the case, although you are allowed to do that, I don't think
>     > it's a convenient way to use netmap.
>     > Since VLAN interfaces like vlan0 do not have (and cannot have) native
>     > netmap support, you are falling back to emulated netmap adapters (which
>     > are probably buggy on FreeBSD, specially when combined with VALE).
>     > Apart from bugs I think that with this setup you can't get decent
>     > performance that would justify using netmap rather than the standard
>     > kernel bridge and TAP devices.
> 
>     Hello,
> 
>     lockup happened earlier than expected.
>     This time 'vale-ctl' still reported (-l) the configuration.
>     One guest, using if_vtnet(4)-virtio-net#vale2:korso, showed:
>     dmz: watchdog timeout on queue 0
>     (dmz is the renamed if_vtnet(4))
> 
>     I could attach tcpdump to the uplink interface and also to all vlan
>     children.
>     Complete silence everywhere.  So it seems the nic stopped processing
>     anything.
> 
>     Do you think that symptom could be caused by my special vale
>     integration, so that bugs in netmap emulation could crash the NIC?
>     Or is it unlikely that this is related.
> 
>     I hadn't prepared a debug kernel for the host, so the machine rebooted
>     without again.
>     I think I'll have to start with replacing vale first, to narrow down
>     possible causes.  Today I was lucky, the lockup happend after business
>     hours, but I won't rely on that.
>     At least I know if I really need to look for a debug netmap kernel, or
>     possibly there's something else...
> 
>     Thanks,
> 
>     -harry
> 
> 
> 
> I can't really say anything without a stack trace or meaningful logs.
> There is a thing that you may do to see if the bug comes out of a bad
> interaction between
> emulated netmap and VALE.
> Instead of attaching the vlan interfaces to VALE you can connect VALE to
> the vlan interface
> through the "bridge" program. In this way nothing changes from the
> functional point of view,
> but you are not attaching anymore the VLAN interface to VALE (and you
> are using an additional process).
> 
> So instead of
> 
>   # vale-ctl vale0:vlan0
> 
> you would have
> 
>   # bridge netmap:vlan0 vale0:vv  # "vv" can be anything

Hello Vincenzo,

thank you very much for that interesting hint.
I prepared a netgraph setup yesterday evening, but I'll try your
suggestion first.  Unfortunately I don't have time to prepare a debug
kernel until next reboot (today evening), but maybe the result of this
config is interesting/meaningful using the same kernel.

Will keep you informed, thanks,

-harry