Subject: Re: [Intel-wired-lan] [PATCH iwl-next v4 4/5] ice: Add tx_scheduling_layers devlink param

From: Jiri Pirko <[email-masked]>
Date: Mon, 19 Feb 2024 18:15:13 +0100

Mon, Feb 19, 2024 at 02:33:54PM CET, [email-masked] wrote:
>On 2/19/24 13:37, Jiri Pirko wrote:
>> Mon, Feb 19, 2024 at 11:05:57AM CET, [email-masked] wrote:
>> > From: Lukasz Czapnik <[email-masked]>
>> > 
>> > It was observed that Tx performance was inconsistent across all queues
>> > and/or VSIs and that it was directly connected to existing 9-layer
>> > topology of the Tx scheduler.
>> > 
>> > Introduce new private devlink param - tx_scheduling_layers. This parameter
>> > gives user flexibility to choose the 5-layer transmit scheduler topology
>> > which helps to smooth out the transmit performance.
>> > 
>> > Allowed parameter values are 5 and 9.
>> > 
>> > Example usage:
>> > 
>> > Show:
>> > devlink dev param show pci/0000:4b:00.0 name tx_scheduling_layers
>> > pci/0000:4b:00.0:
>> >   name tx_scheduling_layers type driver-specific
>> >     values:
>> >       cmode permanent value 9
>> > 
>> > Set:
>> > devlink dev param set pci/0000:4b:00.0 name tx_scheduling_layers value 5
>> > cmode permanent
>> 
>> This is kind of proprietary param similar to number of which were shot
>
>not sure if this is the same kind of param, but for sure proprietary one
>
>> down for mlx5 in past. Jakub?
>
>I'm not that familiar with the history/ies around mlx5, but this case is
>somewhat different, at least for me:
>we have a performance fix for the tree inside the FW/HW, while you
>(IIRC) were about to introduce some nice and general abstraction layer,
>which could be used by other HW vendors too, but instead it was mlx-only

Nope. Same thing. Vendor/device specific FW/HW knob. Nothing to
abstract.

>
>> 
>> Also, given this is apparently nvconfig configuration, there could be
>> probably more suitable to use some provisioning tool.
>
>TBH, we will want to add some other NVM related params, but that does
>not justify yet another tool to configure PF. (And then there would be
>a big debate if FW update should be moved there too for consistency).
>
>> This is related to the mlx5 misc driver.
>> 
>> Until be figure out the plan, this has my nack:
>> 
>> NAcked-by: Jiri Pirko <[email-masked]>
>
>IMO this is an easy case, but would like to hear from netdev maintainers
>
>