netdev - Re: [PATCH RFC v3 0/5] Support fraglist GRO/GSO

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Date:   Thu, 19 Sep 2019 13:36:40 +0200
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     David Miller <davem@...emloft.net>
CC:     <marcelo.leitner@...il.com>, <willemdebruijn.kernel@...il.com>,
        <netdev@...r.kernel.org>, <pabeni@...hat.com>
Subject: Re: [PATCH RFC v3 0/5] Support fraglist GRO/GSO

On Thu, Sep 19, 2019 at 01:18:16PM +0200, David Miller wrote:
> From: Steffen Klassert <steffen.klassert@...unet.com>
> Date: Thu, 19 Sep 2019 13:01:25 +0200
> 
> > If the packet data of all the fraglist GRO skbs are backed by a
> > page fragment then we could just do the same by iterating with
> > skb_walk_frags(). I'm not a driver expert and might be misstaken,
> > but it looks like that could be done with existing hardware that
> > supports segmentation offload.
> 
> Having to add frag list as well as page frag iterating in a driver is
> quite a bit of logic, and added complexity.
> 
> If the frag list SKBs are indeed backed by a page, you could just as
> easily coalesce everything into the page frag array of the first SKB.

That is true indeed. Fraglist GRO is more optimized to the case
where we still need the skb arround the packet data. I.e. if it 
can't be offloaded.