linux-kernel - Re: [PATCH 2/3] net: mana: Add sched HTB offload support

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Message-ID: <20250424093816.GD3042781@horms.kernel.org>
Date: Thu, 24 Apr 2025 10:38:16 +0100
From: Simon Horman <horms@...nel.org>
To: Erni Sri Satya Vennela <ernis@...ux.microsoft.com>
Cc: Jakub Kicinski <kuba@...nel.org>,
	Stephen Hemminger <stephen@...workplumber.org>, kys@...rosoft.com,
	haiyangz@...rosoft.com, wei.liu@...nel.org, decui@...rosoft.com,
	andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
	pabeni@...hat.com, longli@...rosoft.com, kotaranov@...rosoft.com,
	kent.overstreet@...ux.dev, brett.creeley@....com,
	schakrabarti@...ux.microsoft.com, shradhagupta@...ux.microsoft.com,
	ssengar@...ux.microsoft.com, rosenp@...il.com,
	paulros@...rosoft.com, linux-hyperv@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-rdma@...r.kernel.org
Subject: Re: [PATCH 2/3] net: mana: Add sched HTB offload support

On Fri, Apr 18, 2025 at 09:53:24AM -0700, Erni Sri Satya Vennela wrote:
> On Thu, Apr 17, 2025 at 05:00:52PM -0700, Jakub Kicinski wrote:
> > On Thu, 17 Apr 2025 12:47:27 -0700 Erni Sri Satya Vennela wrote:
> > > > A single leaf is just Token Bucket Filter (TBF).
> > > > Are you just trying to support some vendor config?  
> > > TBF does not support hardware offloading.
> > 
> > Did you take a look at net_shapers? Will it not let you set a global
> > config the way you intend?
> Yes, Jakub. I have reviewed net-shapers and noted that it is not
> integrated into the kernel like tc. I mean there isn't a standard,
> general-purpose command for net-shaper in Linux. It is used by other
> tools or potentially device-specific drivers that want to leverage the
> NIC's hardware shaping capabilities.
> 
> To configure shaping with net-shapers, users would need to execute a
> command similar to:
> 
> ./tools/net/ynl/cli.py --spec Documentation/netlink/specs/shaper.yaml
> --do set --json '{"ifindex":'$IFINDEX', 
> 		  "shaper": {"handle": 
> 			    {"scope": "node", "id":'$NODEID' },
> 		  "bw-max": 2000000}}'
> 
> Ref: https://lore.kernel.org/all/cover.1722357745.git.pabeni@redhat.com/
> 
> Given the simplicity of code implementation and ease of use for users in
> writing commands, I opted for tc-htb.

Hi Erni,

As someone who was involved with the design of net-shapers, I think it is
reasonable to instead use the Kernel API which appears to have been
designed specifically for this purpose: to control HW TX rate limiting.

If tooling isn't intuitive or otherwise doesn't meet user's needs
then that is something that can be addressed. But it's not a Kernel issue.