[PATCH v2] net/mlx5: mitigate the Tx queue parameter adjustment

[Raslan Darawsheh]

Hi,


On 24/04/2025 4:31 PM, Viacheslav Ovsiienko wrote:
> he DPDK API rte_eth_tx_queue_setup() has a parameter nb_tx_desc
> specifying the desired queue capacity, measured in packets.
> 
> The ConnectX NIC series has a hardware-imposed queue size
> limit of 32K WQEs (packet hardware descriptors). Typically,
> one packet requires one WQE to be sent.
> 
> There is a special offload option, data-inlining, to improve
> performance for small packets. Also, NICs in some configurations
> require a minimum amount of inline data for the steering engine
> to operate correctly.
> 
> In the case of inline data, more than one WQEs might be required
> to send a single packet. The mlx5 PMD takes this into account
> and adjusts the number of queue WQEs accordingly.
> 
> If the requested queue capacity can't be satisfied due to
> the hardware queue size limit, the mlx5 PMD rejected the queue
> creation, causing unresolvable application failure.
> 
> The patch provides the following:
> 
> - fixes the calculation of the number of required WQEs
>    to send a single packet with inline data, making it more precise
>    and extending the painless operating range.
> 
> - If the requested queue capacity can't be satisfied due to WQE
>    number adjustment for inline data, it no longer causes a severe
>    error. Instead, a warning message is emitted, and the queue
>    is created with the maximum available size, with a reported success.
> 
>    Please note that the inline data size depends on many options
>    (NIC configuration, queue offload flags, packet offload flags,
>     packet size, etc.), so the actual queue capacity might not be
>     impacted at all.
> 
> Signed-off-by: Viacheslav Ovsiienko <viacheslavo at nvidia.com>
> Acked-by: Dariusz Sosnowski <dsosnowski at nvidia.com>
> Patch applied to next-net-mlx,

-- 
Kindest regards
Raslan Darawsheh