netdev - Re: [PATCH net-next mlxsw v2 00/10] Add a new Qdisc, ETS

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Message-Id: <20191218.151648.1742732216376608428.davem@davemloft.net>
Date:   Wed, 18 Dec 2019 15:16:48 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     petrm@...lanox.com
Cc:     netdev@...r.kernel.org, roopa@...ulusnetworks.com,
        jakub.kicinski@...ronome.com, mrv@...atatu.com,
        idosch@...lanox.com, jiri@...nulli.us
Subject: Re: [PATCH net-next mlxsw v2 00/10] Add a new Qdisc, ETS

From: Petr Machata <petrm@...lanox.com>
Date: Wed, 18 Dec 2019 14:55:06 +0000

> The IEEE standard 802.1Qaz (and 802.1Q-2014) specifies four principal
> transmission selection algorithms: strict priority, credit-based shaper,
> ETS (bandwidth sharing), and vendor-specific. All these have their
> corresponding knobs in DCB. But DCB does not have interfaces to configure
> RED and ECN, unlike Qdiscs.
> 
> In the Qdisc land, strict priority is implemented by PRIO. Credit-based
> transmission selection algorithm can then be modeled by having e.g. TBF or
> CBS Qdisc below some of the PRIO bands. ETS would then be modeled by
> placing a DRR Qdisc under the last PRIO band.
> 
> The problem with this approach is that DRR on its own, as well as the
> combination of PRIO and DRR, are tricky to configure and tricky to offload
> to 802.1Qaz-compliant hardware. This is due to several reasons:
 ...
> So instead, this patch set introduces a new Qdisc, which is based on
> 802.1Qaz wording. It is PRIO-like in how it is configured, meaning one
> needs to specify how many bands there are, how many are strict and how many
> are ETS, quanta for the latter, and priomap.
 ...

Series applied, thanks.