netdev - [bpf-next V2 PATCH 0/8] bpf/xdp: add flags argument to ndo_xdp

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Message-ID: <152775714013.24817.5067576840614810786.stgit@firesoul>
Date:   Thu, 31 May 2018 10:59:42 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     netdev@...r.kernel.org, Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     liu.song.a23@...il.com, songliubraving@...com,
        John Fastabend <john.fastabend@...il.com>
Subject: [bpf-next V2 PATCH 0/8] bpf/xdp: add flags argument to ndo_xdp_xmit
 and flag flush operation

As I mentioned in merge commit 10f678683e4 ("Merge branch 'xdp_xmit-bulking'")
I plan to change the API for ndo_xdp_xmit once more, by adding a flags
argument, which is done in this patchset.

I know it is late in the cycle (currently at rc7), but it would be
nice to avoid changing NDOs over several kernel releases, as it is
annoying to vendors and distro backporters, but it is not strictly
UAPI so it is allowed (according to Alexei).

The end-goal is getting rid of the ndo_xdp_flush operation, as it will
make it possible for drivers to implement a TXQ synchronization mechanism
that is not necessarily derived from the CPU id (smp_processor_id).

This patchset removes all callers of the ndo_xdp_flush operation, but
it doesn't take the last step of removing it from all drivers.  This
can be done later, or I can update the patchset on request.

Micro-benchmarks only show a very small performance improvement, for
map-redirect around ~2 ns, and for non-map redirect ~7 ns.  I've not
benchmarked this with CONFIG_RETPOLINE, but the performance benefit
should be more visible given we end-up removing an indirect call.

---
V2: Updated based on feedback from Song Liu <songliubraving@...com>

Jesper Dangaard Brouer (8):
      xdp: add flags argument to ndo_xdp_xmit API
      i40e: implement flush flag for ndo_xdp_xmit
      ixgbe: implement flush flag for ndo_xdp_xmit
      tun: implement flush flag for ndo_xdp_xmit
      virtio_net: implement flush flag for ndo_xdp_xmit
      xdp: done implementing ndo_xdp_xmit flush flag for all drivers
      bpf/xdp: non-map redirect can avoid calling ndo_xdp_flush
      bpf/xdp: devmap can avoid calling ndo_xdp_flush

 drivers/net/ethernet/intel/i40e/i40e_txrx.c   |   14 ++++++++++++--
 drivers/net/ethernet/intel/i40e/i40e_txrx.h   |    3 ++-
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |   23 +++++++++++++++++------
 drivers/net/tun.c                             |   25 ++++++++++++++++++-------
 drivers/net/virtio_net.c                      |    9 ++++++++-
 include/linux/netdevice.h                     |    7 ++++---
 include/net/xdp.h                             |    4 ++++
 kernel/bpf/devmap.c                           |   19 ++++++-------------
 net/core/filter.c                             |    3 +--
 9 files changed, 72 insertions(+), 35 deletions(-)

--