DPDK22 issue: Unable to set more than 4 queues in Azure

[Stephen Hemminger]

On Thu, 22 Jun 2023 22:06:10 +0530
Nageswara Rao <nagpen75 at gmail.com> wrote:

> Hi All,
> 
> We are observing the following issue with DPDK22.11. We didn’t find any
> upstream patches for this issue on the DPDK github. Is there any known
> issue, please let us know.
> 
> 
> 
> *Issue:*
> 
> On Azure platform, we are unable to configure more than 4 queues. When we
> try to configure more than 4 queues its failing with “EAL: Cannot send more
> than 8 FDs” error.
> 
> Here I am pasting the working and failing testpmd logs.
> 
> Please note that this issue is not observed in DPDK 21.11.
> 

You should be using the native netvsc PMD, not the vdev_netvsc,failsafe,tap kludge.

I don't work on Azure any more but I suspect the issue is that the default
in the kernel for TAP is for the number of queues == number of cores.

You aren't going to see any real benefit from having more queues than
the number of DPDK cores.