[Intel-wired-lan] [PATCH bpf-next 10/11] i40e: implement AF_XDP zero-copy support for Tx

[Björn Töpel]

Den tis 5 juni 2018 kl 14:44 skrev Jesper Dangaard Brouer <brouer at redhat.com>:
>
> On Mon,  4 Jun 2018 14:06:00 +0200
> Björn Töpel <bjorn.topel at gmail.com> wrote:
>
> > Here, ndo_xsk_async_xmit is implemented. As a shortcut, the existing
> > XDP Tx rings are used for zero-copy. This will result in other devices
> > doing XDP_REDIRECT to an AF_XDP enabled queue will have its packets
> > dropped.
>
> This behavior is problematic, because XDP Tx rings are smp_processor_id
> based, and several RX queues can (via proc smp_affinity settings) be
> assigned to the same CPU. Thus, other RX-queues (than the AF_XDP
> enabled queue) can experience packet drops.  And other devices doing
> redirect through i40e, which happen to run on a CPU which XDP Tx queue
> is "hijacked" will see dropped packets.
>
> Any plans to allocate/create a dedicated TX ring per AF_XDP socket?
>

Yes -- again this was a shortcut, and must be addressed (for all the
reasons above).

Björn

> --
> Best regards,
>   Jesper Dangaard Brouer
>   MSc.CS, Principal Kernel Engineer at Red Hat
>   LinkedIn: http://www.linkedin.com/in/brouer