netdev - Re: [RFC net-next 1/1] idpf: Don't hard code napi

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Message-ID: <Zvsjitl-SANM81Mk@LQ3V64L9R2>
Date: Mon, 30 Sep 2024 15:17:46 -0700
From: Joe Damato <jdamato@...tly.com>
To: Przemek Kitszel <przemyslaw.kitszel@...el.com>
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>,
	netdev@...r.kernel.org, Tony Nguyen <anthony.l.nguyen@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	"moderated list:INTEL ETHERNET DRIVERS" <intel-wired-lan@...ts.osuosl.org>,
	open list <linux-kernel@...r.kernel.org>,
	Simon Horman <horms@...nel.org>
Subject: Re: [RFC net-next 1/1] idpf: Don't hard code napi_struct size

On Mon, Sep 30, 2024 at 03:10:41PM +0200, Przemek Kitszel wrote:
> On 9/30/24 14:38, Alexander Lobakin wrote:
> > From: Alexander Lobakin <aleksander.lobakin@...el.com>
> > Date: Mon, 30 Sep 2024 14:33:45 +0200
> > 
> > > From: Joe Damato <jdamato@...tly.com>
> > > Date: Wed, 25 Sep 2024 18:00:17 +0000
> 
> > struct napi_struct doesn't have any such fields and doesn't depend on
> > the kernel configuration, that's why it's hardcoded.
> > Please don't change that, just adjust the hardcoded values when needed.
> 
> This is the crucial point, and I agree with Olek.
> 
> If you will find it more readable/future proof, feel free to add
> comments like /* napi_struct */ near their "400" part in the hardcode.
> 
> Side note: you could just run this as a part of your netdev series,
> given you will properly CC.

I've already sent the official patch because I didn't hear back on
this RFC.

Sorry, but I respectfully disagree with you both on this; I don't
think it makes sense to have code that will break if fields are
added to napi_struct thereby requiring anyone who works on the core
to update this code over and over again.

I understand that the sizeofs are "meaningless" because of your
desire to optimize cachelines, but IMHO and, again, respectfully, it
seems strange that any adjustments to core should require a change
to this code.

I really do not want to include a patch to change the size of
napi_struct in idpf as part of my RFC which is totally unrelated to
idpf and will detract from the review of my core changes.

Perhaps my change is unacceptable, but there should be a way to deal
with this that doesn't require everyone working on core networking
code to update idpf, right?

- Joe