[bpf-next V4 PATCH 0/8] xdp: introduce bulking for ndo_xdp_xmit API

Jesper Dangaard Brouer
2018-05-18T13:34:36Z

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

In this V4 patchset, I've split-out 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.

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).

---

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 | 16 ++-
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 | 134 ++++++++++++++++++++++++-
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, 449 insertions(+), 86 deletions(-)