netdev - [PATCH bpf-next v2 0/2] xdp: Introduce bulking for non-map XDP

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Date:   Mon, 13 Jan 2020 19:10:54 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     netdev@...r.kernel.org
Cc:     bpf@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        David Miller <davem@...emloft.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Björn Töpel <bjorn.topel@...il.com>,
        John Fastabend <john.fastabend@...il.com>
Subject: [PATCH bpf-next v2 0/2] xdp: Introduce bulking for non-map
 XDP_REDIRECT

Since commit 96360004b862 ("xdp: Make devmap flush_list common for all map
instances"), devmap flushing is a global operation instead of tied to a
particular map. This means that with a bit of refactoring, we can finally fix
the performance delta between the bpf_redirect_map() and bpf_redirect() helper
functions, by introducing bulking for the latter as well.

This series makes this change by moving the data structure used for the bulking
into struct net_device itself, so we can access it even when there is not
devmap. Once this is done, moving the bpf_redirect() helper to use the bulking
mechanism becomes quite trivial, and brings bpf_redirect() up to the same as
bpf_redirect_map():

                       Before:   After:
1 CPU:
bpf_redirect_map:      8.4 Mpps  8.4 Mpps  (no change)
bpf_redirect:          5.0 Mpps  8.4 Mpps  (+68%)
2 CPUs:
bpf_redirect_map:     15.9 Mpps  16.1 Mpps  (+1% or ~no change)
bpf_redirect:          9.5 Mpps  15.9 Mpps  (+67%)

After this patch series, the only semantics different between the two variants
of the bpf() helper (apart from the absence of a map argument, obviously) is
that the _map() variant will return an error if passed an invalid map index,
whereas the bpf_redirect() helper will succeed, but drop packets on
xdp_do_redirect(). This is because the helper has no reference to the calling
netdev, so unfortunately we can't do the ifindex lookup directly in the helper.

Changelog:

v2:
  - Consolidate code paths and tracepoints for map and non-map redirect variants
    (Björn)
  - Add performance data for 2-CPU test (Jesper)
  - Move fields to avoid shifting cache lines in struct net_device (Eric)

---

Toke Høiland-Jørgensen (2):
      xdp: Move devmap bulk queue into struct net_device
      xdp: Use bulking for non-map XDP_REDIRECT and consolidate code paths

 include/linux/bpf.h        |   13 +++++-
 include/linux/netdevice.h  |   11 +++--
 include/trace/events/xdp.h |  104 +++++++++++++++++++-------------------------
 kernel/bpf/devmap.c        |   94 +++++++++++++++++++++-------------------
 net/core/dev.c             |    2 +
 net/core/filter.c          |   86 +++++++-----------------------------
 6 files changed, 132 insertions(+), 178 deletions(-)