quoted

#2: You have allocations on the XDP fast-path.

The REAL secret behind the XDP performance is to avoid allocations on
the fast-path.  While I just told you to use the page-allocator and
order-0 pages, this will actually kill performance.  Thus, to make this
fast, you need a driver local recycle scheme that avoids going through
the page allocator, which makes XDP_DROP and XDP_TX extremely fast.
For the XDP_REDIRECT action (which you seems to be interested in, as
this is needed for AF_XDP), there is a xdp_return_frame() API that can
make this fast.

I had an initial implementation that did exactly that (that's why you the
dma_sync_single_for_cpu() -> dma_unmap_single_attrs() is there). In the case 
of AF_XDP isn't that introducing a 'bottleneck' though? I mean you'll feed fresh
buffers back to the hardware only when your packets have been processed from
your userspace application

Just a clarification here. This is the case if ZC is implemented. In my case
the buffers will be 'ok' to be passed back to the hardware once the use
userspace payload has been copied by xdp_do_redirect()

/Ilias