netdev - RE: [PATCH v2 0/2] devlink: Support setting max_io

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Message-ID:
 <PH0PR12MB5481F29AC423C4723F57318BDC042@PH0PR12MB5481.namprd12.prod.outlook.com>
Date: Fri, 12 Apr 2024 03:31:53 +0000
From: Parav Pandit <parav@...dia.com>
To: David Ahern <dsahern@...nel.org>, "Samudrala, Sridhar"
	<sridhar.samudrala@...el.com>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "stephen@...workplumber.org"
	<stephen@...workplumber.org>
CC: Jiri Pirko <jiri@...dia.com>, Shay Drori <shayd@...dia.com>
Subject: RE: [PATCH v2 0/2] devlink: Support setting max_io_eqs

Hi David, Sridhar,

> From: David Ahern <dsahern@...nel.org>
> Sent: Friday, April 12, 2024 7:36 AM
> 
> On 4/11/24 5:03 PM, Samudrala, Sridhar wrote:
> >
> >
> > On 4/10/2024 9:32 PM, Parav Pandit wrote:
> >> Hi Sridhar,
> >>
> >>> From: Samudrala, Sridhar <sridhar.samudrala@...el.com>
> >>> Sent: Thursday, April 11, 2024 4:53 AM
> >>>
> >>>
> >>> On 4/10/2024 6:58 AM, Parav Pandit wrote:
> >>>> Devices send event notifications for the IO queues, such as tx and
> >>>> rx queues, through event queues.
> >>>>
> >>>> Enable a privileged owner, such as a hypervisor PF, to set the
> >>>> number of IO event queues for the VF and SF during the provisioning
> stage.
> >>>
> >>> How do you provision tx/rx queues for VFs & SFs?
> >>> Don't you need similar mechanism to setup max tx/rx queues too?
> >>
> >> Currently we don’t. They are derived from the IO event queues.
> >> As you know, sometimes more txqs than IO event queues needed for XDP,
> >> timestamp, multiple TCs.
> >> If needed, probably additional knob for txq, rxq can be added to
> >> restrict device resources.
> >
> > Rather than deriving tx and rx queues from IO event queues, isn't it
> > more user friendly to do the other way. Let the host admin set the max
> > number of tx and rx queues allowed and the driver derive the number of
> > ioevent queues based on those values. This will be consistent with
> > what ethtool reports as pre-set maximum values for the corresponding
> VF/SF.
> >
> 
> I agree with this point: IO EQ seems to be a mlx5 thing (or maybe I have not
> reviewed enough of the other drivers).

IO EQs are used by hns3, mana, mlx5, mlxsw, be2net. They might not yet have the need to provision them.

> Rx and Tx queues are already part of
> the ethtool API. This devlink feature is allowing resource limits to be
> configured, and a consistent API across tools would be better for users.

IO Eqs of a function are utilized by the non netdev stack as well for a multi-functionality function like rdma completion vectors.
Txq and rxq are yet another separate resource, so it is not mutually exclusive with IO EQs.

I can additionally add txq and rxq provisioning knob too if this is useful, yes?

Sridhar,
I didn’t lately check other drivers how usable is it, will you also implement the txq, rxq callbacks?
Please let me know I can start the work later next week for those additional knobs.