Re: [dpdk-dev] queue to VF assigment in SR-IOV

["Mauricio Vásquez" <mauricio.vasquezbernal@studenti.polito.it>]

Hello Alexander,

On Tue, Jun 7, 2016 at 11:31 PM, Alexander Duyck <alexander.duyck@gmail.com>
wrote:

> On Tue, Jun 7, 2016 at 1:49 PM, Mauricio Vásquez
> <mauricio.vasquezbernal@studenti.polito.it> wrote:
> > Dear All,
> >
> > I implemented a program that uses flow director to forward packets to a
> > specific virtual function, however I faced the problem that I did not
> know
> > which queue belongs to a VF. I found in [1] that in the case of Intel
> > 82599, queues 0-7 belongs to VF0, 8-15 to VF1 and so on, I tested it but
> it
> > did not work, using the trial and error method I found that queue 0 is in
> > VF0, queue 4 in VF1 and so on.
> >
> > My question is: is there a standard way to know which queues belong to a
> > specific VF?
> >
> > Thanks in advance
> >
> > Mauricio V,
> >
> > [1]
> >
> http://www.intel.it/content/dam/www/public/us/en/documents/datasheets/82599-10-gbe-controller-datasheet.pdf
> ,
> > Table 7-72
>
> If you are using the kernel driver the way the queues are laid out
> depends on the number of VFs allocated and what features are enabled
> in the kernel.


I forgot to mention that I am using the DPDK ixgbe PMD.


> Assuming you are not using DCB you should be able to
> figure out how many queues are being allocated via VF by looking at
> the output of "ethtool -l <iface>".  The upper limit on RSS is t he
> number of queues each pool is allocated.
>
> So for example if you only enable up to 31 VFs then the PF driver
> allocates 4 queues per VF so you would have queues 0 - 3 allocated to
> VF0, queues 4-7 allocated to VF1, etc all the way through to the PF
> occupying (num_vfs * 4) to 127.  If you enable 32 or more VFs then the
> number of queues drops to 2 per VF and RSS on the PF will be limited
> to the 2 queues following the block reserved for the VFs.
>
>
I found that the behavior of the DPDK PMD is almost the same you described:
1 - 15 VFs -> 8 queues per VF
16 - 31 VFs -> 4 queues per VF
>= 32 VFs -> 2 queues per VF

But, according to the datasheet it should be
16 VFs -> 8 queues per VF
32 VFs -> 4 queues per VF
64 VFs -> 2 queues per VF

Am I missing something?

One extra thing that I am not understanding, in the case I assign the
maximum number of possible VFs, the PF remains without queues?

There are a few other configurations such as if DCB is enabled I
> believe it is possible to get 8 queues per VF if less than 16 VFs are
> allocated but in such a case you would not have access to RSS.  In
> this case if the maximum combined queue count reported is 1 you would
> need to check to see how many TCs are being supported by the PF in
> order to determine if the queue count is 4 or 8 per VF.
>
> - Alex
>

Thank you very much,

Mauricio V,