linux-kernel - Re: [PATCH net-next V10 1/6] devlink: Extend devlink rate API with traffic classes bandwidth management

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Message-ID: <20250527162815.7c73d945@kernel.org>
Date: Tue, 27 May 2025 16:28:15 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Carolina Jubran <cjubran@...dia.com>
Cc: Tariq Toukan <tariqt@...dia.com>, "David S. Miller"
 <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, Eric Dumazet
 <edumazet@...gle.com>, Andrew Lunn <andrew+netdev@...n.ch>, Jiri Pirko
 <jiri@...dia.com>, Gal Pressman <gal@...dia.com>, Leon Romanovsky
 <leonro@...dia.com>, Donald Hunter <donald.hunter@...il.com>, Jiri Pirko
 <jiri@...nulli.us>, Jonathan Corbet <corbet@....net>, Saeed Mahameed
 <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, Shuah Khan
 <shuah@...nel.org>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-rdma@...r.kernel.org,
 linux-kselftest@...r.kernel.org, Moshe Shemesh <moshe@...dia.com>, Mark
 Bloch <mbloch@...dia.com>, Cosmin Ratiu <cratiu@...dia.com>
Subject: Re: [PATCH net-next V10 1/6] devlink: Extend devlink rate API with
 traffic classes bandwidth management

On Sun, 25 May 2025 17:57:28 +0300 Carolina Jubran wrote:
> >> +      -
> >> +        name: rate-tc-bw
> >> +        type: u32
> >> +        doc: |
> >> +             Specifies the bandwidth allocation for the Traffic Class as a
> >> +             percentage.
> >> +        checks:
> >> +          min: 0
> >> +          max: 100  
> > 
> > Why in percentage? I don't think any existing param in devlink rate
> > or net shapers is in percentage right? Not according to what i can
> > grok about the uAPI.
> >   
> 
> I thought percentage might fit better here because it lets users clearly 
> set the bandwidth share for each traffic class. While this isn’t the 
> same as tx_weight in devlink-rate, the idea is related since both use 
> relative values. If there isn’t a strong reason against it, I’d like to 
> keep using percentages here.

The existing APIs use absolute values for b/w limits.
If you want to diverge please provide clear and realistic use cases.