netdev - Re: Offloading Priority Tables for queue classification

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Date:   Mon, 25 Apr 2022 15:37:24 +0200
From:   Maxime Chevallier <maxime.chevallier@...tlin.com>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        "Allan.Nielsen@...rochip.com" <Allan.Nielsen@...rochip.com>
Subject: Re: Offloading Priority Tables for queue classification

Hi Vladimir !

On Fri, 15 Apr 2022 15:42:29 +0000
Vladimir Oltean <vladimir.oltean@....com> wrote:

> Hi Maxime!
> 
> On Fri, Apr 15, 2022 at 05:37:18PM +0200, Maxime Chevallier wrote:
> > So in the end, my question would be : Is it OK to mix all of these
> > together ? Using the dcb layer to configure the internal mapping of
> > traffic -> priority, then using mqprio to configure the priority ->
> > queue mapping, and then either TC again or ethtool do configure the
> > behaviour of the queues themselves ? Or is there some other way that
> > we've missed ?  
> 
> I think it's ok to mix all of those together. At least the
> ocelot/felix DSA switches do support both advance QoS classification
> using tc-flower
> + skbedit priority action, and basic QoS classification (port-based or
> IP DSCP based) using the dcbnl application table. In short, at the end
> of the QoS classification process, a traffic class for the packet is
> selected. Then, the frame preemption would operate on the packet's
> traffic class.

Thank you very much for that answer, it helps a lot. TBH when digging
into classification, especially with TC, it's a bit overwhelming and it
gets difficult pretty quickly to get what's the right approach.

> Do you have any particular concerns?

My concerns were mainly about not reinventing the wheel, but also
making sure that I have the correct understanding on these
classification steps. I'll make sure to CC you when I have a first
series implementing that.

Best regards,

Maxime