Re: [PATCH bpf-next v3 0/3] xdp: Introduce bulking for non-map XDP_REDIRECT

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

On Thu, Jan 16, 2020 at 7:14 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>
> 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:
>
> v3:
>   - Switch two more fields to avoid a list_head spanning two cache lines
>   - Include Jesper's tracepoint patch
>   - Also rename xdp_do_flush_map()
>   - Fix a few nits from Maciej

Applied. Thanks