*cake.qos: support unlimited bandwidth

[intelfx]

No description provided.

[moeller0]

Quick note, did anyone test what this does with with fq_codel as selected qdisc?

[tohojo]

Erm, what's the point of supporting "unlimited" bandwidth? The whole point of sqm-scripts is to setup traffic shaping, without that you could just install a root qdisc, why do you need the complexity of sqm-scripts for this use case?

[intelfx]

The whole point of sqm-scripts is to setup traffic shaping, without that you could just install a root qdisc, why do you need the complexity of sqm-scripts for this use case?

@tohojo Because this tool is a common abstraction that simplifies management of the tc subsystem for both cases. As I understand, at least CAKE is explicitly designed with support for running it without the shaping part:

IF you want to run at line rate for your device, relying instead on backpressure from the ethernet driver (and hopefully BQL) don’t specify the bandwidth.

[tohojo]

Sure, cake can run in unlimited mode just fine, but I'm not sure how much of a 'simplification' it is? I mean, there's literally a single sysctl you can set to select default qdisc for the system, which has the added benefit of also correctly installing an mq qdisc on multi-queue devices, with the selected qdisc as the sub-qdisc for each HW queue.

What's the full config you are using with 'unlimited' bandwidth? Are you setting any other cake parameters?

In any case, if we support this, we should also support this for non-cake qdiscs. Meaning that for fq_codel et al, we should skip the HTB/TBF setup and just install the qdisc on the root interface.