[Cake] [PATCH net-next] net_sched: sch_cake: Add drop reasons

[Eric Dumazet]

On Mon, Dec 9, 2024 at 1:02 PM Toke Høiland-Jørgensen <toke at redhat.com> wrote:
>
> Add three qdisc-specific drop reasons for sch_cake:
>
>  1) SKB_DROP_REASON_CAKE_CONGESTED
>     Whenever a packet is dropped by the CAKE AQM algorithm because
>     congestion is detected.
>
>  2) SKB_DROP_REASON_CAKE_FLOOD
>     Whenever a packet is dropped by the flood protection part of the
>     CAKE AQM algorithm (BLUE).
>
>  3) SKB_DROP_REASON_CAKE_OVERLIMIT
>     Whenever the total queue limit for a CAKE instance is exceeded and a
>     packet is dropped to make room.
>
> Also use the existing SKB_DROP_REASON_QUEUE_PURGE in cake_clear_tin().
>
> Reasons show up as:
>
> perf record -a -e skb:kfree_skb sleep 1; perf script
>
>           iperf3     665 [005]   848.656964: skb:kfree_skb: skbaddr=0xffff98168a333500 rx_sk=(nil) protocol=34525 location=__dev_queue_xmit+0x10f0 reason: CAKE_OVERLIMIT
>          swapper       0 [001]   909.166055: skb:kfree_skb: skbaddr=0xffff98168280cee0 rx_sk=(nil) protocol=34525 location=cake_dequeue+0x5ef reason: CAKE_CONGESTED
>
> Signed-off-by: Toke Høiland-Jørgensen <toke at redhat.com>

Reviewed-by: Eric Dumazet <edumazet at google.com>