Re: [PATCH net-next 5/7] bnxt_en: limit netmem TX frags to 32KB

[Mina Almasry]

On Mon, Nov 2, 2026 at 11:14 AM Stanislav Fomichev <sdf.kernel@xxxxxxxxx> wrote:
>
> The TX BD length field is 16 bits wide. Limit netmem TX frags to the
> largest power of 2 which fits, which keeps 4K aligned frags 4K aligned.
>
> With 64K pages this already applies to PAGE_SIZE net_iovs, whose 64KB
> frags would otherwise wrap the BD length to 0 with BIG TCP.
>
> Tested on a 50Gb/s NIC: devmem TX from a 2MB hugepage-backed udmabuf
> runs at line rate with 2-3 frags per 64KB skb, none above 32KB.
>
> kperf output (sender side, 1 flow):
>
>   client: == Source <sender>
>   client:   Tx 46.358 Gbps (174483046400 bytes in 30110590 usec)
>   client:   Rx  0.000 Gbps (0 bytes in 30110590 usec)
>   client:   TCP retrans reord rtt rttvar d_ce snd_wnd cwnd
>   client:           729   153 599     48    0 13893632 3147
>   client:   net CPU 71: usr: 0.03% sys: 0.06% idle:67.62% iow: 0.00% irq: 1.12% sirq:31.14%
>   client:   app CPU 72: usr: 0.16% sys: 6.01% idle:90.66% iow: 0.00% irq: 0.83% sirq: 2.32%
>
> Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxxx>

Acked-by: Mina Almasry <almasrymina@xxxxxxxxxx>


-- 
Thanks,
Mina