netdev - Re: [PATCH v3 02/12] netlink: spec: add shaper YAML spec

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Message-ID: <Zqy5zhZ-Q9mPv2sZ@nanopsycho.orion>
Date: Fri, 2 Aug 2024 12:49:50 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
	Madhu Chittim <madhu.chittim@...el.com>,
	Sridhar Samudrala <sridhar.samudrala@...el.com>,
	Simon Horman <horms@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Sunil Kovvuri Goutham <sgoutham@...vell.com>,
	Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [PATCH v3 02/12] netlink: spec: add shaper YAML spec

Thu, Aug 01, 2024 at 05:12:01PM CEST, pabeni@...hat.com wrote:
>On 8/1/24 15:10, Jiri Pirko wrote:
>> Tue, Jul 30, 2024 at 10:39:45PM CEST, pabeni@...hat.com wrote:
>> > +    type: enum
>> > +    name: scope
>> > +    doc: the different scopes where a shaper can be attached
>> > +    render-max: true
>> > +    entries:
>> > +      - name: unspec
>> > +        doc: The scope is not specified
>> > +      -
>> > +        name: port
>> > +        doc: The root for the whole H/W
>> 
>> What is this "port"?
>
>~ a wire plug.

What's "wire plug"? What of existing kernel objects this relates to? Is
it a devlink port?


>
>> > +      -
>> > +        name: netdev
>> > +        doc: The main shaper for the given network device.
>> > +      -
>> > +        name: queue
>> > +        doc: The shaper is attached to the given device queue.
>> > +      -
>> > +        name: detached
>> > +        doc: |
>> > +             The shaper is not attached to any user-visible network
>> > +             device component and allows nesting and grouping of
>> > +             queues or others detached shapers.
>> 
>> What is the purpose of the "detached" thing?
>
>I fear I can't escape reusing most of the wording above. 'detached' nodes
>goal is to create groups of other shapers. i.e. queue groups,
>allowing multiple levels nesting, i.e. to implement this kind of hierarchy:
>
>q1 ----- \
>q2 - \SP / RR ------
>q3 - /    	    \
>	q4 - \ SP -> (netdev)
>	q5 - /	    /
>                   /
>	q6 - \ RR
>	q7 - /
>
>where q1..q7 are queue-level shapers and all the SP/RR are 'detached' one.
>The conf. does not necessary make any functional sense, just to describe the
>things.

Can you "attach" the "detached" ones? They are "detached" from what?


>
>> > +    -
>> > +      name: group
>> > +      doc: |
>> > +        Group the specified input shapers under the specified
>> > +        output shaper, eventually creating the latter, if needed.
>> > +        Input shapers scope must be either @queue or @detached.
>> > +        Output shaper scope must be either @detached or @netdev.
>> > +        When using an output @detached scope shaper, if the
>> > +        @handle @id is not specified, a new shaper of such scope
>> > +        is created and, otherwise the specified output shaper
>> > +        must be already existing.
>> 
>> I'm lost. Could this designt be described in details in the doc I asked
>> in the cover letter? :/ Please.
>
>I'm unsure if the context information here and in the previous replies helped
>somehow.
>
>The group operation creates and configure a scheduling group, i.e. this
>
>q1 ----- \
>q2 - \SP / RR ------
>q3 - /    	    \
>	q4 - \ SP -> (netdev)
>	q5 - /	    /
>                   /
>	q6 - \ RR
>	q7 - /
>
>can be create with:
>
>group(inputs:[q6, q7], output:[detached,parent:netdev])
>group(inputs:[q4, q5], output:[detached,parent:netdev])
>group(inputs:[q1], output:[detached,parent:netdev])
>group(inputs:[q2,q3], output:[detached,parent:<the detached shaper create
>above>])

So by "inputs" and "output" you are basically building a tree. In
devlink rate, we have leaf and node, which is in sync with standard tree
terminology.

If what you are building is tree, why don't you use the same
terminology? If you are building tree, you just need to have the link to
upper noded (output in your terminology). Why you have "inputs"? Isn't
that redundant?

If this is not tree, what's that? Can for example q6 be input of 2
different groups? How is that supposed to work?


>
>I'm unsure if this the kind of info you are looking for?

I'm trying to understand the design. Have to say I'm just confused :/


>
>Thanks,
>
>Paolo
>