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

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

Hello Alexander,


On Mon, Jun 13, 2016 at 6:02 PM, Alexander Duyck <alexander.duyck@gmail.com>
wrote:

> On Mon, Jun 13, 2016 at 4:56 AM, Mauricio Vásquez
> <mauricio.vasquezbernal@studenti.polito.it> wrote:
> > 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?
>
> The datasheet should be referring to "VM pools".  The PF consumes one
> pool for any queues it is using.  As such VFs + 1 is the total number
> of pools in use if the PF is active.
>
> > One extra thing that I am not understanding, in the case I assign the
> > maximum number of possible VFs, the PF remains without queues?
>
> The device can support at most 64 pools.  So if you are allocating 64
> VFs then there are no resources left for the PF to allocate queues
> from.
>
> I hope this helps to make it a bit clearer.
>

This made everything clear for me, thanks.


>
> - Alex
>

Mauricio V,