Re: [Xen-devel] xen + i40e: transmit queue timeout

["Andreas Kinzler" <hfp@xxxxxxxxx>]

On Fri, 06 Jul 2018 14:03:00 +0200, Jan Beulich <JBeulich@xxxxxxxx> wrote:
> > I am currently researching a transmit queue timeout with Xen 4.8.2 and
> > Intel X722 (i40e driver). The problem occurs with various linux versions
> > (4.8.17, 4.13.16, SLES 15 port of i40e). The problem seems to be related
> > to heavy forwarding/bridging as I am running a heavy network stress test
> > in a domU (linux/pvm 4.13.16). It seems that if I run the same test
> > without Xen, it works (not sure).
> The log fragment below of course tells about nothing on why this
> is happening. Couple of questions therefore:
Thanks for suggesting helpful further steps.

> - Are interrupts still arriving for this device at the point of the
>   reported timeout?
> - Are interrupts distributed reasonably evenly between (v)CPUs?
> - Is the overall interrupt rate not higher than what the system
>   can reasonably handle (the lower handling overhead means
>   without Xen a higher rate would still be acceptable)?
> - Is the same heavy forwarding/bridging in effect when trying this
>   without Xen?
> - Does running the same stress test in Dom0 work?
> I take it that there are no other relevant messages in any of the
> logs, or else you would have provided them right away.
Actually, it seems that the driver is the problem which it quite  
counterintuitive because the driver is quite old (started in 2013) and you  
would expect it to be very mature.
For a test I used the 2.4.10 version from  
https://sourceforge.net/projects/e1000/files/i40e%20stable/ and all the  
problems went away. I am writing this here so that others with the same  
problem have a possible solution to try.
Regards Andreas

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