Merge branch 'AF_XDP-zerocopy-for-i40e'

Björn Töpel says:

====================
This patch set introduces zero-copy AF_XDP support for Intel's i40e
driver. In the first preparatory patch we also add support for
XDP_REDIRECT for zero-copy allocated frames so that XDP programs can
redirect them. This was a ToDo from the first AF_XDP zero-copy patch
set from early June. Special thanks to Alex Duyck and Jesper Dangaard
Brouer for reviewing earlier versions of this patch set.

The i40e zero-copy code is located in its own file i40e_xsk.[ch]. Note
that in the interest of time, to get an AF_XDP zero-copy implementation
out there for people to try, some code paths have been copied from the
XDP path to the zero-copy path. It is out goal to merge the two paths
in later patch sets.

In contrast to the implementation from beginning of June, this patch
set does not require any extra HW queues for AF_XDP zero-copy
TX. Instead, the XDP TX HW queue is used for both XDP_REDIRECT and
AF_XDP zero-copy TX.

Jeff, given that most of changes are in i40e, it is up to you how you
would like to route these patches. The set is tagged bpf-next, but
if taking it via the Intel driver tree is easier, let us know.

We have run some benchmarks on a dual socket system with two Broadwell
E5 2660 @ 2.0 GHz with hyperthreading turned off. Each socket has 14
cores which gives a total of 28, but only two cores are used in these
experiments. One for TR/RX and one for the user space application. The
memory is DDR4 @ 2133 MT/s (1067 MHz) and the size of each DIMM is
8192MB and with 8 of those DIMMs in the system we have 64 GB of total
memory. The compiler used is gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0. The
NIC is Intel I40E 40Gbit/s using the i40e driver.

Below are the results in Mpps of the I40E NIC benchmark runs for 64
and 1500 byte packets, generated by a commercial packet generator HW
outputing packets at full 40 Gbit/s line rate. The results are with
retpoline and all other spectre and meltdown fixes, so these results
are not comparable to the ones from the zero-copy patch set in June.

AF_XDP performance 64 byte packets.
Benchmark   XDP_SKB    XDP_DRV    XDP_DRV with zerocopy
rxdrop       2.6        8.2         15.0
txpush       2.2        -           21.9
l2fwd        1.7        2.3         11.3

AF_XDP performance 1500 byte packets:
Benchmark   XDP_SKB   XDP_DRV     XDP_DRV with zerocopy
rxdrop       2.0        3.3         3.3
l2fwd        1.3        1.7         3.1

XDP performance on our system as a base line:

64 byte packets:
XDP stats       CPU     pps         issue-pps
XDP-RX CPU      16      18.4M  0

1500 byte packets:
XDP stats       CPU     pps         issue-pps
XDP-RX CPU      16      3.3M    0

The structure of the patch set is as follows:

Patch 1: Add support for XDP_REDIRECT of zero-copy allocated frames
Patches 2-4: Preparatory patches to common xsk and net code
Patches 5-7: Preparatory patches to i40e driver code for RX
Patch 8: i40e zero-copy support for RX
Patch 9: Preparatory patch to i40e driver code for TX
Patch 10: i40e zero-copy support for TX
Patch 11: Add flags to sample application to force zero-copy/copy mode
====================

Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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