netdev - Re: [PATCH net-next V6 02/13] net/mlx5: Implement cqe_compress

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Message-ID: <20250709195300.6d393e90@kernel.org>
Date: Wed, 9 Jul 2025 19:53:00 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Saeed Mahameed <saeed@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>, Paolo Abeni
 <pabeni@...hat.com>, Eric Dumazet <edumazet@...gle.com>, Saeed Mahameed
 <saeedm@...dia.com>, netdev@...r.kernel.org, Tariq Toukan
 <tariqt@...dia.com>, Gal Pressman <gal@...dia.com>, Leon Romanovsky
 <leonro@...dia.com>, Jiri Pirko <jiri@...dia.com>, Simon Horman
 <horms@...nel.org>
Subject: Re: [PATCH net-next V6 02/13] net/mlx5: Implement cqe_compress_type
 via devlink params

On Tue,  8 Jul 2025 20:04:44 -0700 Saeed Mahameed wrote:
> Selects which algorithm should be used by the NIC in order to decide rate of
> CQE compression dependeng on PCIe bus conditions.
> 
> Supported values:
> 
> 1) balanced, merges fewer CQEs, resulting in a moderate compression ratio
>    but maintaining a balance between bandwidth savings and performance
> 2) aggressive, merges more CQEs into a single entry, achieving a higher
>    compression rate and maximizing performance, particularly under high
>    traffic loads.

This description sounds like 'aggressive' always  wins. Higher
compression rate and higher performance. You gotta describe the trade
offs for the knobs.

> diff --git a/Documentation/networking/devlink/mlx5.rst b/Documentation/networking/devlink/mlx5.rst
> index 7febe0aecd53..417e5cdcd35d 100644
> --- a/Documentation/networking/devlink/mlx5.rst
> +++ b/Documentation/networking/devlink/mlx5.rst
> @@ -117,6 +117,15 @@ parameters.
>       - driverinit
>       - Control the size (in packets) of the hairpin queues.
>  
> +   * - ``cqe_compress_type``
> +     - string
> +     - permanent
> +     - Configure which algorithm should be used by the NIC in order to decide
> +       rate of CQE compression dependeng on PCIe bus conditions.
> +
> +       * ``balanced`` : Merges fewer CQEs, resulting in a moderate compression ratio but maintaining a balance between bandwidth savings and performance
> +       * ``aggressive`` : Merges more CQEs into a single entry, achieving a higher compression rate and maximizing performance, particularly under high traffic loads

Line wrap please.

You already have a rx_cqe_compress ethtool priv flag.
Why is this needed and how it differs.
Is it just the default value for the ethtool setting?
-- 
pw-bot: cr