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

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Message-ID: <20240530083158.02ecfa5c@kernel.org>
Date: Thu, 30 May 2024 08:31:58 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Saeed Mahameed <saeed@...nel.org>
Cc: Tariq Toukan <tariqt@...dia.com>, "David S. Miller"
 <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, Eric Dumazet
 <edumazet@...gle.com>, netdev@...r.kernel.org, Saeed Mahameed
 <saeedm@...dia.com>, Gal Pressman <gal@...dia.com>, Leon Romanovsky
 <leonro@...dia.com>, Dragos Tatulea <dtatulea@...dia.com>
Subject: Re: [PATCH net-next 11/15] net/mlx5e: SHAMPO, Add no-split ethtool
 counters for header/data split

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?".

> 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.