Re: [PATCH net-next v2 2/4] net/sched: sch_cake: Add cake_mq qdisc for using cake on mq devices

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Toke Høiland-Jørgensen wrote:
> Add a cake_mq qdisc which installs cake instances on each hardware
> queue on a multi-queue device.
> 
> This is just a copy of sch_mq that installs cake instead of the default
> qdisc on each queue. Subsequent commits will add sharing of the config
> between cake instances, as well as a multi-queue aware shaper algorithm.
> 
> Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> ---
>  net/sched/sch_cake.c | 214 ++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 213 insertions(+), 1 deletion(-)

Is this code duplication unavoidable?

Could the same be achieved by either

extending the original sch_mq to have a variant that calls the
custom cake_mq_change.

Or avoid hanging the shared state off of parent mq entirely. Have the
cake instances share it directly. E.g., where all but the instance on
netdev_get_tx_queue(dev, 0) are opened in a special "shared" mode (a
bit like SO_REUSEPORT sockets) and lookup the state from that
instance.