Re: [PATCH net-next v3 6/8] bpf: cpumap: switch to napi_skb_cache_get_bulk()

["Toke Høiland-Jørgensen" <toke@redhat.com>]

Alexander Lobakin <aleksander.lobakin@intel.com> writes:

> Now that cpumap uses GRO, which drops unused skb heads to the NAPI
> cache, use napi_skb_cache_get_bulk() to try to reuse cached entries
> and lower MM layer pressure. Always disable the BH before checking and
> running the cpumap-pinned XDP prog and don't re-enable it in between
> that and allocating an skb bulk, as we can access the NAPI caches only
> from the BH context.
> The better GRO aggregates packets, the less new skbs will be allocated.
> If an aggregated skb contains 16 frags, this means 15 skbs were returned
> to the cache, so next 15 skbs will be built without allocating anything.
>
> The same trafficgen UDP GRO test now shows:
>
>                 GRO off   GRO on
> threaded GRO    2.3       4         Mpps
> thr bulk GRO    2.4       4.7       Mpps
> diff            +4        +17       %
>
> Comparing to the baseline cpumap:
>
> baseline        2.7       N/A       Mpps
> thr bulk GRO    2.4       4.7       Mpps
> diff            -11       +74       %
>
> Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
> Tested-by: Daniel Xu <dxu@dxuuu.xyz>

Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>