Re: [PATCH net-next] sfc: reduce the number of requested xdp ev queues

On 16/12/2020 08:45, Jesper Dangaard Brouer wrote:

So, what I hear is that this fix is just pampering over the real issue.

Yes, it is, but it's better than nothing in the meantime while we work
 out the complete fix.

I suggest that you/we detect the situation, and have a code path that
will take a lock (per 16 packets bulk) and solve the issue.

Imho that would _also_ paper over the issue, because it would mean the
 system degraded to a lower performance mode of operation, while still
 appearing to support XDP_TX.  I think that that in general should not
 happen unless there is a way for the user to determine at runtime
 whether it has/should happen.  Perhaps Marek's new XDP feature flags
 could include a "tx-lockless" flag to indicate this?

-ed