netdev - RE: [Intel-wired-lan] [PATCH iwl-next v1] ice: Add support for devlink loopback param.

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Date: Mon, 26 Feb 2024 09:40:03 +0000
From: "Romanowski, Rafal" <rafal.romanowski@...el.com>
To: "Kaminski, Pawel" <pawel.kaminski@...el.com>, Jakub Kicinski
	<kuba@...nel.org>
CC: "Kitszel, Przemyslaw" <przemyslaw.kitszel@...el.com>,
	"intel-wired-lan@...osl.org" <intel-wired-lan@...osl.org>, "Wilczynski,
 Michal" <michal.wilczynski@...el.com>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>
Subject: RE: [Intel-wired-lan] [PATCH iwl-next v1] ice: Add support for
 devlink loopback param.

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@...osl.org> On Behalf Of
> Kaminski, Pawel
> Sent: Thursday, December 7, 2023 1:26 AM
> To: Jakub Kicinski <kuba@...nel.org>
> Cc: Kitszel, Przemyslaw <przemyslaw.kitszel@...el.com>; intel-wired-
> lan@...osl.org; Wilczynski, Michal <michal.wilczynski@...el.com>;
> netdev@...r.kernel.org
> Subject: Re: [Intel-wired-lan] [PATCH iwl-next v1] ice: Add support for devlink
> loopback param.
> 
> On 2023-12-01 20:37, Jakub Kicinski wrote:
> > On Fri,  1 Dec 2023 15:59:49 -0800 Pawel Kaminski wrote:
> >> Add support for devlink loopback param. Supported values are
> >> "enabled", "disabled" and "prioritized". Default configuration is set to
> "enabled.
> >>
> >> By default loopback traffic BW is locked to PF configured BW.
> >
> > First off - hairpin-bandwidth or some such would be a much better name.
> > Second - you must explain every devlink param in Documentation/
> >
> > Also admission ctrl vs prioritizing sounds like different knobs.
> 
> While at certain abstraction level I agree, in my opinion it is not worth here to
> divide this to separate knobs, since underlying logic (FW) doesn't follow that
> anyways. It is driver specific and extremely unlikely to change in the future.
> Hopefully next gen card will not need this knob at all.
> 
> >> HW is
> >> capable of higher speeds on loopback traffic. Loopback param set to
> >> "prioritized" enables HW BW prioritization for VF to VF traffic,
> >> effectively increasing BW between VFs. Applicable to 8x10G and 4x25G
> >> cards.
> >
> > Not very clear what this means...
> > So the VFs are Tx bandwidth limited to link speed.
> > How does the device know it can admit extra traffic?
> > Presumably this doesn't affect rates set by devlink rate?
> 
> I will rewrite the description and explanation in v2 and include documentation
> change.
> 
> Thank you,
> PK
> _______________________________________________
> Intel-wired-lan mailing list
> Intel-wired-lan@...osl.org
> https://lists.osuosl.org/mailman/listinfo/intel-wired-lan


Tested-by: Rafal Romanowski <rafal.romanowski@...el.com>

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