netdev - Re: [PATCH net-next 11/15] net/mlx5e: SHAMPO, Add no-split ethtool counters for header/data split

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Date: Mon, 3 Jun 2024 12:46:35 +0000
From: Dragos Tatulea <dtatulea@...dia.com>
To: "kuba@...nel.org" <kuba@...nel.org>, "saeed@...nel.org" <saeed@...nel.org>
CC: "davem@...emloft.net" <davem@...emloft.net>, Tariq Toukan
	<tariqt@...dia.com>, Gal Pressman <gal@...dia.com>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "pabeni@...hat.com" <pabeni@...hat.com>,
	"edumazet@...gle.com" <edumazet@...gle.com>, Saeed Mahameed
	<saeedm@...dia.com>, Leon Romanovsky <leonro@...dia.com>
Subject: Re: [PATCH net-next 11/15] net/mlx5e: SHAMPO, Add no-split ethtool
 counters for header/data split

On Thu, 2024-05-30 at 08:31 -0700, Jakub Kicinski wrote:
> On Wed, 29 May 2024 20:32:23 -0700 Saeed Mahameed wrote:
> > On 29 May 18:22, Jakub Kicinski wrote:
> > > On Tue, 28 May 2024 17:28:03 +0300 Tariq Toukan wrote:  
> > > > +   * - `rx[i]_hds_nosplit_packets`
> > > > +     - Number of packets that were not split in modes that do header/data split
> > > > +       [#accel]_.
> > > > +     - Informative
> > > > +
> > > > +   * - `rx[i]_hds_nosplit_bytes`
> > > > +     - Number of bytes that were not split in modes that do header/data split
> > > > +       [#accel]_.
> > > > +     - Informative  
> > > 
> > > This is too vague. The ethtool HDS feature is for TCP only.
> > > What does this count? Non-TCP packets basically?
> > 
> > But this is not the ethtool HDS, this is the mlx5 HW GRO hds.
> 
> Okay, but you need to put more detail into the description.
> "not split in modes which do split" is going to immediately 
> make the reader ask themselves "but why?".
> 
We discussed internally and decided to drop this counter and patch for now. This
will be added back in the HDS series so that we have more time to converge on a
the documentation part.

> > On the sane note, are we planning to have different control knobs/stats for
> > tcp/udp/ip HDS? ConnectX supports both TCP and UDP on the same queue, 
> > the driver has no control on which protocol gets HDS and which doesn't.
> 
> No plans at this stage. The ethtool HDS is specifically there
> to tell user space whether it should bother trying to use TCP mmap.
> 
> > > Given this is a HW-GRO series, are HDS packets == HW-GRO eligible
> > > packets?
> > 
> > No, UDP will also get header data split or other TCP packets that don't
> > belong to any aggregation context in the HW.
> 
> I see.

Thanks,
Dragos