From: Andrew Lunn <andrew@lunn•ch>
To: "Russell King (Oracle)" <linux@armlinux•org.uk>
Cc: Stefan Chulski <stefanc@marvell•com>,
Marcin Wojtas <mw@semihalf•com>,
"netdev@vger•kernel.org" <netdev@vger•kernel.org>
Subject: Re: mvpp2: incorrect max mtu?
Date: Fri, 14 May 2021 16:35:12 +0200 [thread overview]
Message-ID: <YJ6KoBEoEDb0VC7a@lunn.ch> (raw)
In-Reply-To: <20210514130018.GC12395@shell.armlinux.org.uk>
On Fri, May 14, 2021 at 02:00:18PM +0100, Russell King (Oracle) wrote:
> Hi all,
>
> While testing out the 10G speeds on my Macchiatobin platforms, the first
> thing I notice is that they only manage about 1Gbps at a MTU of 1500.
> As expected, this increases when the MTU is increased - a MTU of 9000
> works, and gives a useful performance boost.
>
> Then comes the obvious question - what is the maximum MTU.
>
> #define MVPP2_BM_JUMBO_FRAME_SIZE 10432 /* frame size 9856 */
>
> So, one may assume that 9856 is the maximum. However:
>
> # ip li set dev eth0 mtu 9888
> # ip li set dev eth0 mtu 9889
> Error: mtu greater than device maximum.
Hi Russell
It all seems inconsistent:
https://elixir.bootlin.com/linux/latest/source/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c#L6879
/* MTU range: 68 - 9704 */
dev->min_mtu = ETH_MIN_MTU;
/* 9704 == 9728 - 20 and rounding to 8 */
dev->max_mtu = MVPP2_BM_JUMBO_PKT_SIZE;
Maybe this comment is correct, the code is now wrong, and the MAX MTU
should be 9704?
Andrew
next prev parent reply other threads:[~2021-05-14 14:35 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-14 13:00 mvpp2: incorrect max mtu? Russell King (Oracle)
2021-05-14 14:25 ` Marcin Wojtas
2021-05-14 17:19 ` Russell King (Oracle)
2021-05-14 14:35 ` Andrew Lunn [this message]
2021-05-14 17:21 ` Russell King (Oracle)
2021-05-18 6:09 ` [EXT] " Stefan Chulski
2021-05-18 9:41 ` Russell King (Oracle)
2021-05-18 10:25 ` Stefan Chulski
2021-05-23 10:54 ` Stefan Chulski
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