netdev - Re: [PATCH net v4 0/3] Fix large frames in the Gemini ethernet driver

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Date: Thu, 9 Nov 2023 12:50:37 +0200
From: Vladimir Oltean <olteanv@...il.com>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: Hans Ulli Kroll <ulli.kroll@...glemail.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Michał Mirosław <mirq-linux@...e.qmqm.pl>,
	Andrew Lunn <andrew@...n.ch>, linux-arm-kernel@...ts.infradead.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v4 0/3] Fix large frames in the Gemini ethernet driver

On Thu, Nov 09, 2023 at 10:03:11AM +0100, Linus Walleij wrote:
> This is the result of a bug hunt for a problem with the
> RTL8366RB DSA switch leading me wrong all over the place.
> 
> I am indebted to Vladimir Oltean who as usual pointed
> out where the real problem was, many thanks!
> 
> Tryig to actually use big ("jumbo") frames on this
> hardware uncovered the real bugs. Then I tested it on
> the DSA switch and it indeed fixes the issue.
> 
> To make sure it also works fine with big frames on
> non-DSA devices I also copied a large video file over
> scp to a device with maximum frame size, the data
> was transported in large TCP packets ending up in
> 0x7ff sized frames using software checksumming at
> ~2.0 MB/s.
> 
> If I set down the MTU to the standard 1500 bytes so
> that hardware checksumming is used, the scp transfer
> of the same file was slightly lower, ~1.8-1.9 MB/s.
> 
> Despite this not being the best test it shows that
> we can now stress the hardware with large frames
> and that software checksum works fine.
> 
> Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
> ---

Thanks for being persistent with this! I hope we didn't miss today's
"net" pull request :)