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

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Message-ID: <aG9TUPziunm1tRgR@x130>
Date: Wed, 9 Jul 2025 22:44:48 -0700
From: Saeed Mahameed <saeed@...nel.org>
To: Jakub Kicinski <kuba@...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 09 Jul 19:53, Jakub Kicinski wrote:
>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.

Right I will add few words on latency costs.

>
>> 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.

ack.

>
>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?

cqe compression can be enabled or disabled per queue,
the priv flag is to enable/disable it on the netdev queues.

This permanent devlink parameter selects the internal ASIC
mechanism/algorithm for compression which is global for
all the queues that enable compression.

>-- 
>pw-bot: cr