Message-ID: <07bae4f7-4450-4ec5-a2fe-37b563f6105d@redhat.com>
Date: Thu, 1 Aug 2024 16:31:04 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Donald Hunter <donald.hunter@...il.com>
Cc: netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
 Jiri Pirko <jiri@...nulli.us>, 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

On 7/31/24 23:13, Donald Hunter wrote:
> Paolo Abeni <pabeni@...hat.com> writes:
> 
>> diff --git a/Documentation/netlink/specs/shaper.yaml b/Documentation/netlink/specs/shaper.yaml
>> new file mode 100644
>> index 000000000000..7327f5596fdb
>> --- /dev/null
>> +++ b/Documentation/netlink/specs/shaper.yaml
> 
> It's probably more user-friendly to use the same filename as the spec
> name, so net-shaper.yaml

No big objection on my side, but if we enforce 'Name:' to be $(basename 
$file .yaml), the 'Name' field becomes redundant.

[...]
>> +    render-max: true
>> +    entries:
>> +      - name: unspec
>> +        doc: The scope is not specified
> 
> What are the semantics of 'unspec' ? When can it be used?

I guess at this point it can be dropped. It was introduced in a previous 
incarnation to represent the port parent - the port does not have a 
parent, being the root of the hierarchy.

>> +      -
>> +        name: port
>> +        doc: The root for the whole H/W
>> +      -
>> +        name: netdev
>> +        doc: The main shaper for the given network device.
> 
> What are the semantic differences between netdev and port?

netdev == Linux network device
port == wire plug

>> +      -
>> +        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.
> 
> I assume that shapers are always owned by the netdev regardless of
> attach status?

If you mean that it's up to the netdev clean them up on (netdev) 
removal, yes.

>> +>> +      -
>> +        name: inputs
>> +        type: nest
>> +        multi-attr: true
>> +        nested-attributes: ns-info
>> +        doc: |
>> +           Describes a set of inputs shapers for a @group operation
> 
> The @group renders exactly as-is in the generated htmldocs. There may be
> a more .rst friendly markup you can use that will render better.

Uhm... AFAICS the problem is the target (e.g. 'group') is outside the 
htmldoc section itself, I can't find any existing markup to serve this 
purpose well. What about sticking to quotes '' everywhere?

FTR, I used @ following the kdoc style.

[...]
>> +    -
>> +      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.
> 
> It says above that you cannot create a detached shaper, so how do you
> create one to use as an input shaper here? Is this group op more like a
> multi-create op?

The group operation has the main goal of configuring a single WRR or SP 
scheduling group atomically. It can creates the needed shapers as 
needed, see below.

The need for such operation sparks from some H/W constraints:

https://lore.kernel.org/netdev/9dd818dc-1fef-4633-b388-6ce7272f9cb4@lunn.ch/

>> +        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.
>> +        The operation is atomic, on failures the extack is set
>> +        accordingly and no change is applied to the device
>> +        shaping configuration, otherwise the output shaper
>> +        handle is provided as reply.
>> +      attribute-set: net-shaper
>> +      flags: [ admin-perm ]
> 
> Does there need to be a reciprocal 'ungroup' operation? Without it,
> create / group / delete seems like they will have ambiguous semantics.

I guess we need a better description. Can you please tell where/how the 
current one is ambiguous?

Thanks,

Paolo

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