Re: [net-next v1 1/2] net: sched: use queue_mapping to pick tx queue

On Tue, 7 Dec 2021 10:10:22 +0800 Tonghao Zhang wrote:

quoted

In general recording the decision in the skb seems a little heavy
handed. We just need to carry the information from the egress hook
to the queue selection a few lines below. Or in fact maybe egress  

Yes, we can refactor netdev_core_pick_tx to
1. select queue_index and invoke skb_set_queue_mapping, but don't
return the txq.
2. after egress hook, use skb_get_queue_mapping/netdev_get_tx_queue to get txq.

I'm not sure that's what I meant, I meant the information you need to
store does not need to be stored in the skb, you can pass a pointer to
a stack variable to both egress handling and pick_tx.

quoted

hook shouldn't be used for this in the first place, and we need
a more appropriate root qdisc than simple mq?  

I have no idea about mq, I think clsact may make the things more flexible.
and act_bpf can also support to change sk queue_mapping. queue_mapping
was included in __sk_buff.

Qdiscs can run a classifier to select a sub-queue. The advantage of
the classifier run by the Qdisc is that it runs after pick_tx.