Re: [PATCHv7 bpf-next 0/3] xdp: add a new helper for dev map multicast support

Hangbin Liu
2020-07-15T12:31:46Z

On Tue, Jul 14, 2020 at 11:53:20PM +0200, Toke Høiland-Jørgensen wrote:
> >David Ahern <dsahern@gmail.com> writes:
> >>> Version | Test | Native | Generic
> >>> 5.8 rc1 | xdp_redirect_map i40e->i40e | 10.0M | 1.9M
> >>> 5.8 rc1 | xdp_redirect_map i40e->veth | 12.7M | 1.6M
> >>> 5.8 rc1 + patch | xdp_redirect_map i40e->i40e | 10.0M | 1.9M
> >>> 5.8 rc1 + patch | xdp_redirect_map i40e->veth | 12.3M | 1.6M
> >>> 5.8 rc1 + patch | xdp_redirect_map_multi i40e->i40e | 7.2M | 1.5M
> >>> 5.8 rc1 + patch | xdp_redirect_map_multi i40e->veth | 8.5M | 1.3M
> >>> 5.8 rc1 + patch | xdp_redirect_map_multi i40e->i40e+veth | 3.0M | 0.98M
> >>>
> >>> The bpf_redirect_map_multi() is slower than bpf_redirect_map() as we loop
> >>> the arrays and do clone skb/xdpf. The native path is slower than generic
> >>> path as we send skbs by pktgen. So the result looks reasonable.
> >>>
> >>> Last but not least, thanks a lot to Jiri, Eelco, Toke and Jesper for
> >>> suggestions and help on implementation.
> >>>
> >>> [0] https://xdp-project.net/#Handling-multicast
> >>>
> >>> v7: Fix helper flag check
> >>> Limit the *ex_map* to use DEVMAP_HASH only and update function
> >>> dev_in_exclude_map() to get better performance.
> >>
> >> Did it help? The performance numbers in the table above are the same as
> >> in v6...
> >>
> >
> > If there is only 1 entry in the exclude map, then the numbers should be
> > about the same.
>
> I would still expect the lack of the calls to devmap_get_next_key() to
> at least provide a small speedup, no? That the numbers are completely
> unchanged looks a bit suspicious...

As I replied to David, I didn't re-run the test as I thought there should
no much difference as the exclude map on has 1 entry.

There should be a small speedup compared with previous patch. But as the
test system re-installed and rebooted, there will be some jitter to the
test result. It would be a little hard to observe the improvement.

Thanks
Hangbin