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

[Martinx - ジェームズ]

Filled a bug report about this:

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1570195

I think that this is a Linux issue, but I'm not 100% sure...

On 14 April 2016 at 01:35, Martinx - ジェームズ <thiagocmartinsc at gmail.com>
wrote:

>
>
> 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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