Re: [PATCH bpf-next v1 0/2] xdp: recycle Page Pool backed skbs built from XDP frames

Jesper Dangaard Brouer
2023-03-03T10:40:00Z

On 01/03/2023 17.03, Alexander Lobakin wrote:
> Yeah, I still remember that "Who needs cpumap nowadays" (c), but anyway.
>
> __xdp_build_skb_from_frame() missed the moment when the networking stack
> became able to recycle skb pages backed by a Page Pool. This was making
^^^^^^^^^
When talking about page_pool, can we write "page_pool" instead of
capitalized "Page Pool", please. I looked through the git log, and here
we all used "page_pool".

> e.g. cpumap redirect even less effective than simple %XDP_PASS. veth was
> also affected in some scenarios.

Thanks for working on closing this gap :-)

> A lot of drivers use skb_mark_for_recycle() already, it's been almost
> two years and seems like there are no issues in using it in the generic
> code too. {__,}xdp_release_frame() can be then removed as it losts its
> last user.
> Page Pool becomes then zero-alloc (or almost) in the abovementioned
> cases, too. Other memory type models (who needs them at this point)
> have no changes.
>
> Some numbers on 1 Xeon Platinum core bombed with 27 Mpps of 64-byte
> IPv6 UDP:

What NIC driver?

>
> Plain %XDP_PASS on baseline, Page Pool driver:
>
> src cpu Rx drops dst cpu Rx
> 2.1 Mpps N/A 2.1 Mpps
>
> cpumap redirect (w/o leaving its node) on baseline:
>
> 6.8 Mpps 5.0 Mpps 1.8 Mpps
>
> cpumap redirect with skb PP recycling:
>
> 7.9 Mpps 5.7 Mpps 2.2 Mpps +22%
>

It is of cause awesome, that cpumap SKBs are faster than normal SKB path.
I do wonder where the +22% number comes from?

> Alexander Lobakin (2):
> xdp: recycle Page Pool backed skbs built from XDP frames
> xdp: remove unused {__,}xdp_release_frame()
>
> include/net/xdp.h | 29 -----------------------------
> net/core/xdp.c | 19 ++-----------------
> 2 files changed, 2 insertions(+), 46 deletions(-)
>