Xenial, ethtool hangs while enabling MQ and consumes 100% if executed after OVS+DPDK startup

[Martinx - ジェームズ]

On 13 April 2016 at 17:01, Christian Ehrhardt <
christian.ehrhardt at canonical.com> wrote:

>
> On Wed, Apr 13, 2016 at 9:28 PM, Martinx - ジェームズ <
> thiagocmartinsc at gmail.com> wrote:
> [...]
> I couldn't exactly follow all of your setup, but since it is working lets
> assume that was fine.
>
>
>>  1- Reboot the VM and try to run ethtool again:
>>
>
> To confirm after the reboot the device should have 1 of X queues enabled
> as it is not persistent across reboots.
> But OVS-DPDK is starting, likely trying to create X queues as you
> configured but can't get them.
>
>
>>  ethtool -L ens6 combined 4
>>
>  # FAIL! It hangs, consuming 100% of guest's CPU...
>>
>
> Hmm, I'll need to reproduce that tomorrow.
> I mean you switch queues underneath OVS-DPDK using one of them, which
> isn't nice - but it shouldn't totally block.
>
>
>>  So, is this the right procedure? I mean, I believe that ethtool settings
>> doesn't survive across reboots, but, OVS settings are on its DB... Question
>> is, do we need to run ethtool on each reboot before starting OVS+DPDK with
>> VirtIO again?
>>
>>
> I agree your issue is that ethtool combined queues is not persistent while
> starting OVS and its config are.
> You will have to get the queues persistent before OVS-DPDK gets to start.
> It is not really a task for DPDK, nor OVS - more like sysctl but for
> network config.
> I haven't looked into that yet - let me know if you found a nice way -
> otherwise I'll start on it tomorrow together with analyzing what/why hangs
> on changing #queues.
>

Awesome! Thanks for your reply!

Looks like that this isn't an ethtool problem!

I'm seeing the very same behavior, while running:

---
# ip link set dev ens4 up
^Z^Z^Z^Z
^C^C^C^C
---

 Frozen! Where ens4 is a black-listed PCI in
/etc/default/openvswitch-switch!

 So, apparently, after starting a DPDK App in a VM with VirtIO NICs, both
ethtool and ip commands hangs up while trying to mange back-listed vNICs.

Best,
Thiago
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