netdev - Re: [PATCH net-next 6/6] ice: Document tx_scheduling

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Date: Wed, 24 Apr 2024 11:54:09 +0200
From: Mateusz Polchlopek <mateusz.polchlopek@...el.com>
To: Bagas Sanjaya <bagasdotme@...il.com>, Tony Nguyen
	<anthony.l.nguyen@...el.com>, <davem@...emloft.net>, <kuba@...nel.org>,
	<pabeni@...hat.com>, <edumazet@...gle.com>, <netdev@...r.kernel.org>
CC: Michal Wilczynski <michal.wilczynski@...el.com>, <corbet@....net>,
	<linux-doc@...r.kernel.org>, Jiri Pirko <jiri@...dia.com>, Przemek Kitszel
	<przemyslaw.kitszel@...el.com>
Subject: Re: [PATCH net-next 6/6] ice: Document tx_scheduling_layers parameter



On 4/23/2024 2:37 PM, Bagas Sanjaya wrote:
> On Mon, Apr 22, 2024 at 01:39:11PM -0700, Tony Nguyen wrote:
>> +       The default 9-layer tree topology was deemed best for most workloads,
>> +       as it gives an optimal ratio of performance to configurability. However,
>> +       for some specific cases, this 9-layer topology might not be desired.
>> +       One example would be sending traffic to queues that are not a multiple
>> +       of 8. Because the maximum radix is limited to 8 in 9-layer topology,
>> +       the 9th queue has a different parent than the rest, and it's given
>> +       more bandwidth credits. This causes a problem when the system is
>> +       sending traffic to 9 queues:
>> +
>> +       | tx_queue_0_packets: 24163396
>> +       | tx_queue_1_packets: 24164623
>> +       | tx_queue_2_packets: 24163188
>> +       | tx_queue_3_packets: 24163701
>> +       | tx_queue_4_packets: 24163683
>> +       | tx_queue_5_packets: 24164668
>> +       | tx_queue_6_packets: 23327200
>> +       | tx_queue_7_packets: 24163853
>> +       | tx_queue_8_packets: 91101417 < Too much traffic is sent from 9th
>> +
>> <snipped>...
>> +       To verify that value has been set:
>> +       $ devlink dev param show pci/0000:16:00.0 name tx_scheduling_layers
>>   
> 
> For consistency with other code blocks, format above as such:
> 
> ---- >8 ----
> diff --git a/Documentation/networking/devlink/ice.rst b/Documentation/networking/devlink/ice.rst
> index 830c04354222f8..0039ca45782400 100644
> --- a/Documentation/networking/devlink/ice.rst
> +++ b/Documentation/networking/devlink/ice.rst
> @@ -41,15 +41,17 @@ Parameters
>          more bandwidth credits. This causes a problem when the system is
>          sending traffic to 9 queues:
>   
> -       | tx_queue_0_packets: 24163396
> -       | tx_queue_1_packets: 24164623
> -       | tx_queue_2_packets: 24163188
> -       | tx_queue_3_packets: 24163701
> -       | tx_queue_4_packets: 24163683
> -       | tx_queue_5_packets: 24164668
> -       | tx_queue_6_packets: 23327200
> -       | tx_queue_7_packets: 24163853
> -       | tx_queue_8_packets: 91101417 < Too much traffic is sent from 9th
> +       .. code-block:: shell
> +
> +         tx_queue_0_packets: 24163396
> +         tx_queue_1_packets: 24164623
> +         tx_queue_2_packets: 24163188
> +         tx_queue_3_packets: 24163701
> +         tx_queue_4_packets: 24163683
> +         tx_queue_5_packets: 24164668
> +         tx_queue_6_packets: 23327200
> +         tx_queue_7_packets: 24163853
> +         tx_queue_8_packets: 91101417 < Too much traffic is sent from 9th
>   
>          To address this need, you can switch to a 5-layer topology, which
>          changes the maximum topology radix to 512. With this enhancement,
> @@ -67,7 +69,10 @@ Parameters
>          You must do PCI slot powercycle for the selected topology to take effect.
>   
>          To verify that value has been set:
> -       $ devlink dev param show pci/0000:16:00.0 name tx_scheduling_layers
> +
> +       .. code-block:: shell
> +
> +         $ devlink dev param show pci/0000:16:00.0 name tx_scheduling_layers
>   
>   Info versions
>   =============
> 
> Thanks.
> 

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