linux-kernel - Re: [PATCH V4 0/5] mlx5 ConnectX control misc driver

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Date: Fri, 5 Apr 2024 08:38:27 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Edward Cree <ecree.xilinx@...il.com>, David Ahern <dsahern@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Christoph Hellwig
 <hch@...radead.org>, Saeed Mahameed <saeed@...nel.org>, Arnd Bergmann
 <arnd@...db.de>, Leon Romanovsky <leonro@...dia.com>, Jiri Pirko
 <jiri@...dia.com>, Leonid Bloch <lbloch@...dia.com>, Itay Avraham
 <itayavr@...dia.com>, Saeed Mahameed <saeedm@...dia.com>, Aron Silverton
 <aron.silverton@...cle.com>, linux-kernel@...r.kernel.org,
 "netdev@...r.kernel.org" <netdev@...r.kernel.org>, Andy Gospodarek
 <andrew.gospodarek@...adcom.com>
Subject: Re: [PATCH V4 0/5] mlx5 ConnectX control misc driver

On Fri, 5 Apr 2024 08:13:06 -0300 Jason Gunthorpe wrote:
> As I answered to Anderew, a lot is functional behavior not so much
> "tunables". The same way many BIOS settings are not all tunables but
> have functional impacts to the machine. Like enable SRIOV, for
> instance.

Thanks, SRIOV is a great example:
https://docs.kernel.org/next/networking/devlink/devlink-params.html#id2
Literally the first devlink param on the list.

"We will flash it for you" seems to be what vendors like to offer.

> Even for dataplane tunables - you know there are micro-architectural
> performance tunables set in the special Meta NICs that are wired just
> for Meta's special use case? Apparently that is actually perfectly
> workable.

The only "tunables" I'm aware of were for the OCP Yosemite platform,
which is an interesting beast with 4 hosts plugged into one NIC,
and constrained PCIe BW. Which is why I said the "tunables" are really
about the server platform not being off the shelf. Updating NIC FW
to fix server compatibility is hardly unusual.

> It is really strange to hear you act like "Meta doesn't need
> provisioning or tuning" when the NIC Meta uses is *highly* customized
> specifically for Meta to the point it is an entirely different
> product. Of course you don't need provisioning, alot of other people
> did alot of hard work to make it that way.

:) When you say *highly* I think I know what you mean :)
It'd be unprofessional for us to discuss here, and I really doubt 
you actually want to air that laundry publicly :) :)

> So please don't use that as a justification to pull up the ladder so
> nobody else can enjoy even a semi-customized device.

So in this thread I'm pulling up the ladder and in the fbnic one I'm
not (as I hope you'd agree)? One could hopefully be forgiven for
wondering to what extent your assessment of my intentions is colored
by whether they align with your particular goals :(