On Mon, Jan 13, 2020 at 10:11 AM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> 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:
>
> 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)
John, since you commented on v1 please review this v2. Thanks!
