netdev - [bpf-next V5 PATCH 0/8] xdp: introduce bulking for ndo_xdp

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Date:   Thu, 24 May 2018 16:45:41 +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:     Christoph Hellwig <hch@...radead.org>,
        BjörnTöpel <bjorn.topel@...el.com>,
        John Fastabend <john.fastabend@...il.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        makita.toshiaki@....ntt.co.jp
Subject: [bpf-next V5 PATCH 0/8] xdp: introduce bulking for ndo_xdp_xmit API

This patchset change ndo_xdp_xmit API to take a bulk of xdp frames.

When kernel is compiled with CONFIG_RETPOLINE, every indirect function
pointer (branch) call hurts performance. For XDP this have a huge
negative performance impact.

This patchset reduce the needed (indirect) calls to ndo_xdp_xmit, but
also prepares for further optimizations.  The DMA APIs use of indirect
function pointer calls is the primary source the regression.  It is
left for a followup patchset, to use bulking calls towards the DMA API
(via the scatter-gatter calls).

The other advantage of this API change is that drivers can easier
amortize the cost of any sync/locking scheme, over the bulk of
packets.  The assumption of the current API is that the driver
implemementing the NDO will also allocate a dedicated XDP TX queue for
every CPU in the system.  Which is not always possible or practical to
configure. E.g. ixgbe cannot load an XDP program on a machine with
more than 96 CPUs, due to limited hardware TX queues.  E.g. virtio_net
is hard to configure as it requires manually increasing the
queues. E.g. tun driver chooses to use a per XDP frame producer lock
modulo smp_processor_id over avail queues.

I'm considered adding 'flags' to ndo_xdp_xmit, but it's not part of
this patchset.  This will be a followup patchset, once we know if this
will be needed (e.g. for non-map xdp_redirect flush-flag, and if
AF_XDP chooses to use ndo_xdp_xmit for TX).

---
V5: Fixed up issues spotted by Daniel and John

V4: Splitout the patches from 4 to 8 patches.  I cannot split the
driver changes from the NDO change, but I've tried to isolated the NDO
change together with the driver change as much as possible.

Jesper Dangaard Brouer (8):
      bpf: devmap introduce dev_map_enqueue
      bpf: devmap prepare xdp frames for bulking
      xdp: add tracepoint for devmap like cpumap have
      samples/bpf: xdp_monitor use tracepoint xdp:xdp_devmap_xmit
      xdp: introduce xdp_return_frame_rx_napi
      xdp: change ndo_xdp_xmit API to support bulking
      xdp/trace: extend tracepoint in devmap with an err
      samples/bpf: xdp_monitor use err code from tracepoint xdp:xdp_devmap_xmit

 drivers/net/ethernet/intel/i40e/i40e_txrx.c   |   26 ++++-
 drivers/net/ethernet/intel/i40e/i40e_txrx.h   |    2 
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |   21 +++-
 drivers/net/tun.c                             |   37 +++++--
 drivers/net/virtio_net.c                      |   66 +++++++++----
 include/linux/bpf.h                           |   18 +++
 include/linux/netdevice.h                     |   14 ++-
 include/net/page_pool.h                       |    5 +
 include/net/xdp.h                             |    1 
 include/trace/events/xdp.h                    |   50 +++++++++-
 kernel/bpf/cpumap.c                           |    2 
 kernel/bpf/devmap.c                           |  131 +++++++++++++++++++++++--
 net/core/filter.c                             |   23 +---
 net/core/xdp.c                                |   20 +++-
 samples/bpf/xdp_monitor_kern.c                |   49 +++++++++
 samples/bpf/xdp_monitor_user.c                |   69 +++++++++++++
 16 files changed, 448 insertions(+), 86 deletions(-)

--
Jesper Dangaard Brouer