netdev - RE: [PATCH net v3 2/2] igc: Modify the tx-usecs coalesce setting

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Message-ID: <SJ1PR11MB6180AA0A71479F82C152CF03B8EFA@SJ1PR11MB6180.namprd11.prod.outlook.com>
Date: Wed, 6 Sep 2023 15:02:30 +0000
From: "Zulkifli, Muhammad Husaini" <muhammad.husaini.zulkifli@...el.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>, "davem@...emloft.net"
	<davem@...emloft.net>, "pabeni@...hat.com" <pabeni@...hat.com>,
	"edumazet@...gle.com" <edumazet@...gle.com>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "Neftin, Sasha" <sasha.neftin@...el.com>,
	"horms@...nel.org" <horms@...nel.org>, "bcreeley@....com" <bcreeley@....com>,
	Naama Meir <naamax.meir@...ux.intel.com>
Subject: RE: [PATCH net v3 2/2] igc: Modify the tx-usecs coalesce setting



> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Wednesday, 6 September, 2023 10:47 PM
> To: Zulkifli, Muhammad Husaini <muhammad.husaini.zulkifli@...el.com>
> Cc: Nguyen, Anthony L <anthony.l.nguyen@...el.com>; davem@...emloft.net;
> pabeni@...hat.com; edumazet@...gle.com; netdev@...r.kernel.org; Neftin,
> Sasha <sasha.neftin@...el.com>; horms@...nel.org; bcreeley@....com;
> Naama Meir <naamax.meir@...ux.intel.com>
> Subject: Re: [PATCH net v3 2/2] igc: Modify the tx-usecs coalesce setting
> 
> On Wed, 6 Sep 2023 02:52:30 +0000 Zulkifli, Muhammad Husaini wrote:
> > > In the ioctl uAPI we can't differentiate between params which were
> > > echoed back to us vs those user set via CLI to what they already were.
> > >
> > > Maybe we should extend the uAPI and add a "queue pair" IRQ moderation?
> >
> > Good advice. BTW, if queue pair setting is enabled in the driver, could we
> change the existing ".supported_coalesce_params" for driver specific?
> >
> > From:
> > ETHTOOL_COALESCE_USECS which support (ETHTOOL_COALESCE_RX_USECS
> |
> > ETHTOOL_COALESCE_TX_USECS)
> >
> > To (new define):
> > ETHTOOL_QUEUE_PAIR_COALESCE_USECS (ETHTOOL_COALESCE_RX_USECS)
> >
> > With this, I believe user cannot set tx-usecs and will return error of
> unsupported parameters.
> 
> Do you mean change the .supported_coalesce_params at runtime?
> I think so far we were expecting drivers to set flags for all types they may
> support and then reject the settings incompatible with current operation mode
> at the driver level.

It doesn't seem like a runtime. 
The queue pair parameters that I stated previously can be set as soon as we want to register the ethtool operations. 
Currently it was set to ETHTOOL_COALESCE_USECS which supporting both tx-usecs and rx-usecs.
Thus, by restricting to only supporting rx-usecs with the new define of ETHTOOL_QUEUE_PAIR_COALESCE_USECS
would be useful in this situation IMHO.

https://elixir.bootlin.com/linux/latest/source/drivers/net/ethernet/intel/igc/igc_ethtool.c#L1980
https://elixir.bootlin.com/linux/latest/source/drivers/net/ethernet/intel/igc/igc_ethtool.c#L1939