[dpdk-dev] KNI alternatives

[Stephen Hemminger]

Controlling DPDK interfaces with KNI is known to be broken.  Kni calls
usepspace with network mutex held. The problem is not fixable.

The kernel does provide netlink and devlink API's but there is no generic
solution with DPDK.

On Wed, Jan 13, 2021, 11:54 AM Igor Ryzhov <iryzhov at nfware.com> wrote:

>
>
> On Wed, Jan 13, 2021 at 9:45 PM Thomas Monjalon <thomas at monjalon.net>
> wrote:
>
>> 13/01/2021 19:17, Igor Ryzhov:
>> > On Wed, Jan 13, 2021 at 8:10 PM Stephen Hemminger <
>> > stephen at networkplumber.org> wrote:
>> > > On Wed, Jan 13, 2021, 9:06 AM Thomas Monjalon <thomas at monjalon.net>
>> wrote:
>> > >
>> > > > Hi,
>> > > >
>> > > > As discussed today in the techboard meeting, KNI has probably
>> > > > better alternatives today without using an out-of-tree module.
>> > > > Virtio-user is a good candidate to replace KNI.
>> > > > What is the performance of TAP?
>> > > > Is there a way to leverage af_packet, af_xdp, or even pcap
>> interfaces?
>> > >
>> > > Last time I tried.
>> > > Virtio user was as fast as KNI and consumed less cpu. Was seeing
>> 10mpps
>> > > Tap was much slower. Like 1mpps.
>> >
>> > Performance is not the only question. The advantage of KNI we are
>> currently
>> > using is
>> > the ability to control the DPDK interfaces by the kernel.
>> > For example, to implement bonding in the DPDK application, it is
>> possible
>> > to create KNI
>> > pair for each physical interface, create a bond interface in Linux over
>> > those KNI interfaces
>> > and just pass LACP packets between the app and the kernel. The kernel
>> > itself will control
>> > MACs, MTU, etc. of underlying interfaces. AFAIK it's not possible with
>> > virtio-user or tap.
>> > Am I wrong?
>>
>> I see at least 2 alternatives for bonding with kernel management:
>>         - mlx5 bonding
>>         - af_xdp interface for most of NICs
>>
>
> Bonding is just an example. My point is that KNI allows changing MAC, MTU,
> rx mode and admin status of a NIC used by DPDK application - all using
> standard Linux utilities without any need for additional APIs provided by
> the app.
>
> Yes, Mellanox NICs also allow this but it's just one of many drivers
> supported by DPDK.
> I'll dig into af_xdp, thanks.
>