netdev - Re: net-shapers plan

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Message-ID: <a3e8c008-384f-413e-bfa0-6e4568770213@nvidia.com>
Date: Tue, 1 Apr 2025 11:35:56 +0300
From: Carolina Jubran <cjubran@...dia.com>
To: Jakub Kicinski <kuba@...nel.org>, Cosmin Ratiu <cratiu@...dia.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 "horms@...nel.org" <horms@...nel.org>,
 "andrew+netdev@...n.ch" <andrew+netdev@...n.ch>,
 "davem@...emloft.net" <davem@...emloft.net>, Tariq Toukan
 <tariqt@...dia.com>, Gal Pressman <gal@...dia.com>,
 "jiri@...nulli.us" <jiri@...nulli.us>, Leon Romanovsky <leonro@...dia.com>,
 "edumazet@...gle.com" <edumazet@...gle.com>,
 Saeed Mahameed <saeedm@...dia.com>, "pabeni@...hat.com" <pabeni@...hat.com>
Subject: Re: net-shapers plan



On 28/03/2025 15:13, Jakub Kicinski wrote:
> On Thu, 6 Mar 2025 14:03:54 +0000 Cosmin Ratiu wrote:
>> It is not important which entity (kernel or hw) classifies packets as
>> long as the condition that a given txq only sends traffic for a single
>> traffic class holds.
> 
>> Furthermore, this cannot be done by simply grouping txqs for a given TC
>> with NET_SHAPER_SCOPE_NODE, because the TC for a txq is not always
>> known to the kernel and might only be known to the driver or the NIC.
>> With the new roots, net-shapers can relay the intent to shape traffic
>> for a particular TC to the driver without having knowledge of which
>> txqs service a TC. The association between txqs and TCs they service
>> doesn't need to be known to the kernel.
> 
> As mentioned in Zagreb the part of HW reclassifying traffic does not
> make sense to me. Is this a real user scenario you have or more of
> an attempt to "maximize flexibility"?

I don't believe there's a specific real-world scenario. It's really 
about maximizing flexibility. Essentially, if a user sets things up in a 
less-than-optimal way, the hardware can ensure that traffic is 
classified and managed properly.

Carolina