netdev - Re: "TCP: eth0: Driver has suspect GRO implementation, TCP performance may be compromised." message with "ethtool -K eth0 gro off"

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Message-ID: <20170206211226.GC3413@localhost.localdomain>
Date:   Mon, 6 Feb 2017 19:12:26 -0200
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Markus Trippelsdorf <markus@...ppelsdorf.de>,
        netdev@...r.kernel.org
Subject: Re: "TCP: eth0: Driver has suspect GRO implementation, TCP
 performance may be compromised." message with "ethtool -K eth0 gro off"

On Fri, Feb 03, 2017 at 06:47:33AM -0800, Eric Dumazet wrote:
> On Fri, 2017-02-03 at 12:28 -0200, Marcelo Ricardo Leitner wrote:
> 
> > Aren't you mixing the endpoints here? MSS is the largest amount of data
> > that the peer can receive in a single segment, and not how much it will
> > send. For the sending part, that depends on what the other peer
> > announced, and we can have 2 different MSS in a single connection, one
> > for each peer.
> > 
> > If a peer later wants to send larger segments, it can, but it must
> > respect the mss advertised by the other peer during handshake.
> > 
> 
> I am not mixing endpoints, you are.
> 
> If you need to be convinced, please grab :
> https://patchwork.ozlabs.org/patch/723028/
> 
> And just watch "ss -temoi ..." 

I still don't get it, but I also hit the warning on my laptop, using
iwlwifi. Not sure what I did in order to trigger it, it was by accident.

  Marcelo