netdev - Re: [Intel-wired-lan] [PATCH iwl-next v4 0/5] iavf: Add devlink and devlink rate support'

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Date: Thu, 14 Dec 2023 17:46:04 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Paolo Abeni <pabeni@...hat.com>
Cc: Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org,
 anthony.l.nguyen@...el.com, intel-wired-lan@...ts.osuosl.org,
 qi.z.zhang@...el.com, Wenjun Wu <wenjun1.wu@...el.com>,
 maxtram95@...il.com, "Chittim, Madhu" <madhu.chittim@...el.com>,
 "Samudrala, Sridhar" <sridhar.samudrala@...el.com>, Simon Horman
 <simon.horman@...hat.com>
Subject: Re: [Intel-wired-lan] [PATCH iwl-next v4 0/5] iavf: Add devlink and
 devlink rate support'

On Thu, 14 Dec 2023 21:29:51 +0100 Paolo Abeni wrote:
> Together with Simon, I spent some time on the above. We think the
> ndo_setup_tc(TC_SETUP_QDISC_TBF) hook could be used as common basis for
> this offloads, with some small extensions (adding a 'max_rate' param,
> too).

uAPI aside, why would we use ndo_setup_tc(TC_SETUP_QDISC_TBF)
to implement common basis?

Is it not cleaner to have a separate driver API, with its ops
and capabilities?

> The idea would be:
> - 'fixing' sch_btf so that the s/w path became a no-op when h/w offload
> is enabled
> - extend sch_btf to support max rate
> - do the relevant ice implementation
> - ndo_set_tx_maxrate could be replaced with the mentioned ndo call (the
> latter interface is a strict super-set of former)
> - ndo_set_vf_rate could also be replaced with the mentioned ndo call
> (with another small extension to the offload data)
> 
> I think mqprio deserves it's own separate offload interface, as it
> covers multiple tasks other than shaping (grouping queues and mapping
> priority to classes)
> 
> In the long run we could have a generic implementation of the
> ndo_setup_tc(TC_SETUP_QDISC_TBF) in term of devlink rate adding a
> generic way to fetch the devlink_port instance corresponding to the
> given netdev and mapping the TBF features to the devlink_rate API.
> 
> Not starting this due to what Jiri mentioned [1].

Jiri, AFAIU, is against using devlink rate *uAPI* to configure network
rate limiting. That's separate from the internal representation.