Re: [dpdk-dev] A Question about the necessity of DPDK VF for Ethernet PMDs

[Alejandro Lucero <alejandro.lucero@netronome.com>]

On Mon, Feb 4, 2019 at 10:44 AM Rami Rosen <ramirose@gmail.com> wrote:

> Hi Alejandro,
>
> >Your concern is related to this thread
>
> Thanks for your reply, I was aware of this thread.
>
OK


> Still, I am not sure, in current kernels and currently available Ethernet
> DPDK PMDs about the answer to my queries (I don't think this mail thread
> gives info about it), like about what are the benefits of providing DPDK
> VFs,  is it mandatory in some use cases, and are there any advantage for
> using a DPDK PF/DPDK VF combination over using Kernel VF?
>
> That is an interesting discussion. I know there is some interest in this
case from OVS people, exactly for running an OVS instance inside a VM.
I can see other reasons:
   - when SRIOV is used by VMs, the slow path will always be faster (and
with lower latency) with DPDK.
   - When more VMs/containers than VFs, DPDK will allow to use SRIOV (for
higher priority VMs/containers) and vhost-user (for low-priority), and with
the low-priority being faster than through the kernel.
   - If SRIOV is not used by VMs, DPDK forwarding path using vhost-user
along with VF PMDs is faster than through the kernel.
   - Having the PF managed by user space could potentially mean faster VM
migration.
   - PF flow management, inserting/deleting flow rules, faster in user
space.


Regards,
>
> Rami Rosen
>
>
>