Re: [PATCH net-next v8 2/3] net: dsa: mv88e6xxx: use the hw tx queues

[Cedric Jehasse]

On Tue, Aug 18, 2026 at 07:45:08AM -0700, Jakub Kicinski wrote:
> On Tue, 18 Aug 2026 10:59:35 +0200 Cedric Jehasse wrote:
> > > Pretending that a DSA device has multiple Tx queues _from the stack_
> > > makes no sense. You should be offloading PRIO as the root qdisc,
> > > like mlxsw does. Then the rate limiters should be attached as children
> > > of PRIO.  
> > 
> > This patch follows what the implementation i found in other dsa drivers.
> > mlxsw seems to be the only driver handling TC_SETUP_QDISC_PRIO.
> > Wouldn't that mean setting up cbs for a mv88e6xxx switch would use different
> > tc commands than setting it up for another dsa switch (prio vs mqprio)?
> > Is your comment specific to this driver, or for dsa drivers in general?
> 
> Maybe Vladimir can comment why he picked mqprio. He probably explained
> it to me and I forgot.
> 
> My mental model is that mqprio offload is for the host ("NIC", IOW host
> traffic egress). But if you're configuring a switch where most of the
> traffic is internally forwarded within the ASIC. We should have a way
> to report stats and offload status. There's no need to pretend we have
> multiple host queues and waste memory.

I've found a similar patch from Vladimir for sja1105, but did't find an
explanation for picking mqprio:
https://lore.kernel.org/netdev/20200527165527.1085151-1-olteanv@xxxxxxxxx/
Note: the tc commands in Vladimir's patch are similar to the ones in this
patch (no offload on mqprio, offload on cbs).