Current state of Intel XL710 40G NIC ixl performance

[K. Macy]

> On a single-client basis the fastest rates we see are around 5 Gbps.
> Hitting this server from multiple boxes we see peaks of 20 Gbps at the very
> highest.  More frequently things top off around 13 Gbps.  These numbers are
> coming from iperf tests.  We are seeing similar numbers with direct
> point-to-point as well as switched topologies.
>
> These threads from 2015 describe similar issues but fizzled out:
> https://lists.freebsd.org/pipermail/freebsd-net/2015-May/042273.html
> https://lists.freebsd.org/pipermail/freebsd-net/2015-October/043584.html
>
> Is there very particular tuning required to get these cards working at
> proper speed?  Any insights?

This is unfortunate. The iflib version of the ixl driver performed
quite well under NFLX load several years ago. I even saw 39Gbps single
stream with v6. Fortunately, Intel will eventually be pushing the
iflib version to HEAD.

-M