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

[Luke Howard]

> On 19 Aug 2026, at 12:45 am, Jakub Kicinski <kuba@xxxxxxxxxx> 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.

MQPRIO can be implemented for mv88e6xxx, but it’s not a perfect fit, which is why I withdrew the patch [1].

[1] https://github.com/PADL/linux/commit/ecf7d2fe28d7a9459551dd28e96da06681446604